E. viminalis - University of Melbourne

-------------------------------------------------------------------,THE DISTRIBUTION OF EUCALYPTUS VIMINALIS ANDEUCALYPTUS CAMALDULENSIS IN VICTORIAA Thesis submitted for the Degree of Master of Sciencein the University of MelbournebyMICHELE MARYBARSONMelbourne1978

DECLARAT IONI hereby declare that this thesis is my own work~except where specifically stated to the contrary~and that it is not substantially the same as anyother thesis which has already been sUbmitted toany other university.M 'c-he4e.-B

I IACKNOWLEDGEMENTSIt is a pleasure to acknowledge the assistance of the fol lowingpeople and organizations:My supervisors, Dr D.H. Ashton and Dr P.Y. Ladiges for guidance andencouragement;Dr D.M. Calder, School of Botany, University of Melbourne, forproviding facilities;The National Parks Service for provision of fencing and access to thestudy sites at WesterfoldsjAustral ian Glass Manufacturers Pty. Ltd. who donated acid-washed sandfor use in the sand culture experiments;Dr R.H.M. van der Graaffe and Mr P. Jefferies of the Soil ConservationAuthori ty;Mr C. Aeberl i who carefully tended my plants in the glasshouse;Robert Bartlett, Robert Marshal I and Geoff Hampton for technicalass i stance;Phillip Ladd, Chris Anderson, Neville Rosengren, Jane Lennon andBruce Moore -thank you.My mother, Mrs J. Cruise, and Marg Robertson for the typing;The Department of Geography, University of Melbourne, for a tutorshipwhich enabled me to carry out this work.

iiiCONTENTSPageDECLARATIONACKNOWLEDGEMENTSLIST OF FIGURESL I-ST OF TABLESLIST OF PLATESi ivvi iixI NTRO DUCT I ONCHAPTER 1: THE DISTRIBUTION OF E. VIMINALIS AND 4E. CAl1ALDULENSISAustralian Distribution 4Victorian Distribution 10CHAPTER 2: THE YARP.A 7ALLEY STUDY SITE 16eli mate 16Soi Is 18Vegetation 19Westerfolds Study Site 22CHAPTER 3: SEEDLING GROWTH RATE AND RESPONSE TO NUTRIENTS 26IntroductionSoi I CharacteristicsComparison of Seedling Growth RatesSeedling Growth in the FieldDiscussionSummary262833485256

IVCHAPTER 4:SEEDLING TOLEP.ANCE TO DROUGHTIntroductionMethodsResultsDiscussionSummary575758606466CHAPTER 5:THE P.ELATIVE TOLERANCES OF E. VIMIl'lALIS ANDE. CAMALDULEllSIS TO WATERLOGGING67Introduction 67The Effects of Waterlogging on Soils and Plants 67The Influence of Waterlogging on Plant Distribution 74Methods 76Results 77Discussion 80Summary 82CHAPTER 6: DISCUSSION AND SUMMARY 83BIBLIOGRAPHY 89

vLIST OF FIGURESFi g. No.Shortened titlesFacing pageThe distribution of E. viminaZis andE. camaZduZensis in Australia4la23Location map for Victoria 10The distribution of E. viminaZis in Victoria 10The distribution of E. camaZduZensis in 10Victoria45678910Average annual rainfall for VictoriaLocation of sites and average annual rainfallin the Yarra ValleyYarra Valley transectsWesterfolds geologyWesterfolds landformsWesterfolds eucalypt distributionpF values for four soils101620222324301112Height growth of E. viminalis and E. camaZduZensis 35in monoculture and mixed culture on two topsoilsShoot dry weights of E. viminalis and35E. camaZduZensis in monoculture and mixed cultureon two topsoils13Replacement diagrams for competition trials 3614Height growth of E. viminaZis and E. camaZduZensis 37on alluvial soils in monoculture and mixed culture15Shoot dry weights of E. viminaZis andE. camaZduZensis grown in monoculture and mixedculture on alluvial soils37

vii6Height growth of E. viminalis 'Westerfolds ' ,E. viminalis 'Eltham ' and E. camaldulensison alluvial soils in monoculture and mixedculture40171819Shoot dry weights of E. viminalis 'Westerfolds ' ,E. viminalis 'Eltham ' and E. camaldulensisgrown on alluvial soils in monoculture andmixed cultureEffect of increasing levels of phosphorus andnitrogen on the height growth of 2. viminalisand~.camaldulensisThe effect of increasing levels of phosphorusand nitrogen on the total dry weights, leafarea and root/shoot ratios of E. viminalis andE. camaldulensis41444720212223Height growth and percentage death of fieldtrialsVariations in percentage soil moisture over oneyear at the field trial sitesTranspiration rates of control and droughtedseedlingsHeight growth of control, half waterlogged andfully waterlogged seedlings4960627724Total dry weights of control, half waterlogged and 78fully waterlogged seedlings

vi iLIST OF TABLESNo.Shortened titlesPage234Description of soil profiles at WesterfoldsMean seedling heights for E. viminalis andE. camaldulensis grown in monoculture andcompet it i onSoil profiles at four field sitesResults of particle size analysis of soils atfour field sites2427282956789Percentage disaggregation of soils at four fieldsitesPercentage organic matter of soils at four fieldsitesChemical analyses of soils at four field sitesAnalysis of variance results for seedling growthAnalysis of variance results for seedling growthon alluvial soils in monoculture and mixed culture31313236381011Analysis of var:ance results for the growth of twopopulations of E. viminalis and E. camaldulensison alluvial soilsComposition of nutrient solutions414312131415Analysis of variance results of seedling growth at 45three levels of phosphorus and nitrogenAnalysis of variance results for field trials 50Analysis of variance results for transpiration data 61Leaf water potentials for droughted and control 62seedl i ngs

vi i i1617Leaf area, dry weights and root/shoot ratios ofdroughted seedlingsAnalysis of variance results for waterloggingexperiment637818Root dry weights and root/shoot ratios for control, 79half waterlogged and fully waterlogged seedlings

ixLI ST OF PLATESNo.Shortened TitleFaci ng Page1aThe forest form of E. viminalis111bThe woodland form of E. viminaZis11lcThe rough-barked form of E. viminalis112aThe forest form of E. camaldulensis132bThe plains form of E. camaldulensis133aE. viminalis and E. camaldulensis on thebanks of the Yarra at Westerfolds253bRiverbank understorey at Westerfolds254aField trials on the E. camalduZensis plot524bField trials on the E. viminaZis plot525The growth of E. camaZdulensis roots underfully waterlogged conditions80

INTRODUCTIONEucalyptus viminalis and Eucalyptus camaldulensis are closely relatedand widely distributed species which may at times occupy similar habitats.although they do not usually form mixed stands.Both species show considerablevariation throughout their total geographic range (Pryor 1955 •Karschon 1967. Larsen 1967. Pryor and Byrne 1969), and in Victoria severalforms of each species occur.Ladiges and Ashton (1974) have distinguishedforest and woodland forms of E. viminalis. the former generally occurringon more fertile soils of higher rainfall areas, the latter on drier sites.Forest forms of E. camaldulensis are generally found on floodplains, whilstwoodland forms commonly occupy rol ling open plains and the drier margins offloodplains.The boundaries of the two species are frequently contiguous.and within the ecotone each species usually occurs in discrete stands whichform patterns that are often related to topography.This study aims to describe the distribution of E. viminalis andE. camaldulensis in Victoria, and in particular to examine the habitatconditions which may account for their distribution in the riparianenvi ronment.The distribution of eucalypts is often controlled on a broad scaleby climatic factors. and locally by edaphic factors (MooreI959a).Theconcurrence of plant communities and soil types has been shown by Crocker(1944), Specht and Perry (1948), and Lang (1960). Florence (1965) demonstrateda consistent relationship between forest composition and variationin soil parent material and physical characteristics in south-eastQueensland (Qld).

2Specific chemicalproperties of soils have also been associated withthe distribution of particular communities.Beadle (1954, 1962) hasemphasized the role of phosphorus in delimiting plant communities nearSydney.Coaldrake and Haydock (1958) did not find a similar relationshipbetween topsoil phosphate content and vegetation distribution in southeastQueensland, but Beadle (1962) has suggested that their data supportshis contention that phosphorus levels determine the type of vegetation.Moore (1961) has related the distribution of ~ucaZyptusmelliodora andEucalyptus rossii on the Southern Tablelands of New South Wales (N.S.W.)to the degree of calcium saturation of the soil. Other properties whichhave been shown to influence the distribution of certain eucalypt speciesinclude sal inity (Parsons 1968a) and 1 ime chlorosis (Parsons and Specht 1967).The physical properties of soils which influence soil moisture characteristicsmay also be important in cantrall ing the distribution of eucalyptspecies.Specht and Perry (1948), Parsons (1969), Florence (1964), Lamband Florence (1973) and Ashton, Bond and Morris (1975) have suggestedrelationships between soil moisture status and species distribution.Moore (1959b, 1961) and Parsons (1969) have demonstrated theinfluence of interspecific competition on eucalypt distribution wherespecies tolerances to physiological factors in the environment are shownto overlap.McColl and Humphreys (1967) however found that pot trials ofinterspecific competition between Eucalyptus ~~fera and Eucalyptusmaculata for soil nutrients were inconclusive.Pryor (1959a)points out that "while some species are widespread intheir total geographic extent, the mosaic pattern characteristic of manyareas of Eucalyptus is not affected by the occurrence in that area of thewidespread species.In almost all cases, such a species, though widespread,is also tied closely to a circumscribed habitat in the particular limited

3area.This implies that the habitat factors which finally I imit a widespreadspecies evoke a different physiological response in the species, andare perhaps different from those which cause a species to change from siteto site in a restricted areal!.For E. viminalis and E. camalduZensis this may be interpreted to meanthat, although their abil ity to occupy a range of habitats with respect toclimatic, edaphic and topographic factors may be at least partly related tothe ecotypic variabil ity observed in each species throughout their range,it seems likely that local distributions may be related to the subtle changesin site factors such as drainage and shelter, and to competition betweenadjacent species.In the present study, the distribution of E. viminalis and E. camalduZensisin Victoria was mapped and correlated with broad environmental factors, andthe behaviour of seedl ings of both species from a riparian habitat atTemplestowe in the Yarra Valley was assessed by field trials and glasshouseexper i ments.Nomenclature is according to Willis (1972) unless otherwise stated.

fN&IiFig. 1The distribution ofE. camaidulmsis A ~ andE. viminalis J. L. B 0 inAustralia0 ... , __'_OOO___ 2000km \)BIr--._._._._._._._._._._._./'_ ........... \IIIIIIi""~'~i\..'"'.~.. I.I '",I . \J''-'" . ................._. No 100 200 300 400 500 km, ,Sourc:a; CIrtIr 1931. JICbIII _HtII It'" 1!J70. Sp.cIIt 1m

4CHAPTER 1THE DISTRIBUTION OF EUCALYPl'US VIMINALIS AND EUCALYPTUS CAMALDULENSISINTRODUCTIONThe natural distribution and morphological variation of E. viminalisand E. camaldulensis throughout Australia are examined briefly; theVictoridn distribution is mapped in some detail and related to broad topographic.climatic and edaphic patterns to gain insight into factors whichmay affect the distribution of these two species.EUCALYPTUS VIMINALISAustralian DistributionE. viminalis is widely distributed throughout south-eastern Australia(Fig. 1); it is found on the Tablelands and western slopes of N.S.W .• in theMt. Lofty Ranges and south-eastern South Australia (S.A.), in southernVictoria (Vic.), and in the north-west and eastern half of Tasmania (Tas.)(Hall. Johnston and Chippendale 1970).It has also been recorded on CapeBarren. Clarke, Flinders, Hunter, King and Three Hummock Islands in BassStrait.The species occurs over a wide topographic range, and reaches itsoptimum development as a tall ribbon-gum form in valleys in moist montaneareas.It is also found as a woodland form on plains and undulating terrain,on volcanic scoria cones, granite outcrops, and sometimes on sandy coastaldeposits.In southern states, it occurs from just above sealevel to analtitude of 1220 m; in N.S.W. it reaches altitudes of up to 1370 m (Hall,Johnston and Marryat 1963).

5cZimateE. vimina~is occurs predominantly within the marine west coast climaticzone (Cfb of Koppen) (Ladiges 1969), where the mean temperature of the warmestmonth is less than 22 0 C, and where for at least four months of the yeart h e temperature excee d s 1 OOC.The mean temperature of the coldest month isabove -3 0 C (Dick 1975).Frosts occur with greater frequency at higheraltitudes and at greater distances from the sea. Hobart, Tas., at 58 mexperiences up to seven frosts per year; Alexandra, Vic. (223 m) averages26. I, and Guyra, N.S.W. (1453 m) may have up to 67 frosts a year (Hall etaz' 1963).E. viminaZis is found over a wide range of rainfall regimes, with annualprecipitation ranging from 512 mm to 1500 mm. In the western sector of itsrange, winter rainfall predominates, but in eastern Vic. and parts of Tas.and N.S.W. rainfall is uniformly distributed.In northern N.S.W. rainfalloccurs chiefly in summer (Bureau of Meterology 1975).SoiZsThe edaphic range of E. viminaZis is also very great; it occurs onsoils of widely differing nutrient status and waterholding capacity (Ladigesand Ashton 1974).I-n N.S.W. it has been recorded principally from basaltderivedkrasnozems (Brough, McLuckie and Petrie 1924, Pidgeon 1937, Fraserand Vickery 1939), and on transitional alpine humus soils and brown podsolsof the Monaro Region (Costin 1954).South Australian occurrences are ongrey brown podsols in the Mt Lofty Ranges (Specht and Perry 1948). and sandsin the Lower South East (Crocker 1944).In Vic. E. viminaZis is found onkrasnozems, brown earths, podzols, yellow podzolic soi 15, rendzinas andterra rossas (Ladiges and Ashton 1974).In Tas. it occurs on soils derivedfrom granite, basalt (J.B. Kirkpatrick pers. comm.) , mudstone, sandstonesand dolerite (Jackson 1965, Martin 1940) as well as deeply leachedsil iceous sands (Bowden and Kirkpatrick 1974, Kirkpatrick 1975).

6Systematic Stab~and DistributionThroughout its range, E. viminaZis exhibits considerable variation incharacters such as habit, tree height, height of rough bark, and number offlower buds per inflorescence.This variation has resulted in a number oftaxonomic problems, some of which are yet to be solved (Pryor 1962).Thesystematic status of E. viminaZis and related populations has been discussedby Ladiges (1971).Their distribution appears to be as follows:New South WalesN.S.W. occurrences of E. viminaZis recorded by Byles (1932), Pigeon(1937), Fraser and Vickery (1939), Brough et al. (1924) and Costin (1954)indicate that the species is generally true to type here, that is smoothbarkedexcept at the base, and possessing exclusively three-floweredinflorescences and orposite, sessi le juvenile leaves.Occasional roughbarkedtrees are thought to be hybrids (Pryor 1955).South Austra 1 i aThere is considerable morphological variation in E. viminaZis andrelated populations described from S.A.Tall, smooth-barked E. viminalisis found in the wetter gullies of the Mt Lofty Ranges, and a similar, butmore spreading woodland form occurs along lower watercourses (Pryor 1962).More rough-barked populations which often have more than three flowers perinflorescence are found in the Mt Lofty Ranges, on Kangaroo Island and inthe Lower South East.These trees, known as Eucalyptus huberiana have beenreferred to as E. vimina~is ssp. viminalis (Pryor and Johnson 1971). Halland Brooker (1974) have since revived the name E. huberana for the roughbarkedpopulations of S.A. and south-west Vic.VictoriaLadiges and Ashton (1974) showed that considerable variation also occurswithin this species in Victoria. This study confirmed the recognition madeby Pryor (1962) of the tall, smooth-barked gully form and the more umbrageous

7woodland forms of E. viminalis.In higher rainfall areas tall open-forestpopulations of mature trees show similar maximum heights, girths and degreeof basal bark persistence.In the more diverse habitat of lower rainfallregions greater variation is observed and some populations could includeE. huherana.Populations of very rough-barked E. viminalis var. racemosa occurchiefly on sandy coastal deposits between Melbourne and Metung (Will is 1972).Inthe present study, all rough-barked forms have been mapped as thisvariety, although again some populations could be classified as E. huherana.TasmaniaThe distribution of E. viminalis has been mapped by Jackson (1965).It occurs in the eastern sector of the island, generally below 820 m,extending along the north coast with some isolated stands on the northwestcoast.Most populations are tall and smooth-barked, although there issome tendency for trees growing on poor acidic sands to have more roughbark.However, bark seldom constitutes more than 50% of the bole, and moreusually less than 20% (J.B. Kirkpatrick, pers. corrrn.).A specimen ofE. viminalis near Fingal is 89.92 m tall, making E. viminalis possibly thethird tallest species in the world (Anon. 1976).According to Penfold andWill is (1961), occurrences of rough-barked E. viminalis var. racemosa arevery restricted in Tas.EUCALYPTUS CAMALDULENSISAus tl'a lian Dis tl--ibutionEucalyptus camaldulensis is the most widely distributed eucalypt species(Fig. 1).It occurs as a network distribution across the whole of theAustralian continent, except on the coastal fringes of most of N.S.W.osouthern Qld •• eastern and western Vic. and southern W.A. (Hall et al. 1970).

8Throughout most of its range, E. camaldulensis is found along streamlinesand on adjacent flats. However, it forms extensive woodlands on thelower slopes of the Ht Lofty and Flinders Ranges in S.A. (Jacobs 1955), andon rolling plains in western Victoria.It is best developed in the HurrayRiver basin of south-eastern Austral ia where pure stands form forests withelite individuals up to 49 m tall (Dexter 1970).Although generally not found above altitudes of 390 m,it has beenrecorded at heights of up to 656 m (Hall et al. 1963); seepage of waterfrom higher slopes may allow E. camaldulensis to establish on such sites.ClimateE. camaIduIensis grows across a wide range of climatic types, but itgenerally occurs in areas that have warm summers. Surrrner rainfall ischaracteristic throughout much of its range, but mean annual rainfall(H.A.R.) varies from less than 100 mmin arid central Austral ia to 1400 mmin tropical northern Australia.In areas of low rainfall (100-350 mm),E. camalduZensis is dependent on seasonal flooding or the presence of ahigh water table for sufficient moisture (Hall et al. 1970).In the cooler,moister climates of south-eastern Australia, it is not generally found inareas which receive more than 1000 mm H.A.R.With the exception of some northern Austral ian coastal localities,frosts occur throughout the range of E. camaldulensis. with 5-20 frostsper annum being common (Hall et al. 1970).Edaphic RangeSince E. camaIduIenSis is riparian throughout much of its range, itusually grows on soils derived from alluvial materials. but is also foundon sandy plains where permanent subsoil moisture is available (Hall et al.1963). The red gum woodlands of south-eastern Australia occur on soilsderived from shales, siltstones, basalts, sands and clays, generally

9showing a preference for soils with some clay content.Specht and Perry(1948), Boomsma (1950) and Gi bbons and Downes (1964) have reported thatE. camaldulensis occurs on soils of relatively high fertility.Systematic Status and Geographic VariationThe systematic status of E. camaldulensis Dehnhardt has been discussedby Pryor and Byrne (1969).Morphological variation has led to the recognitionof two subspecies, E. camaldulensis spp. camaldulensis and E. camaldulensisspp. obtusa by Pryor and Johnson (1971).Geographic variation in E. camaldulensis sensu lato has been demonstratedby Larsen (1967), Karschon (1967) and Pryor and Byrne (1969).Onthe basis of population differences in 1 ignotuber frequency and seedl ingleaf characteristics, Karschon, and later Pryor and Byrne, recognisednorthern and southern ecotypes.Karschon also distinguished a WesternAustralian subgroup.Ecotypic variation is also indicated by provenancevariation in seedling growth rates and root/shoot ratios (Awe, Shepherd andFlorence 1976), differential frost resistance (Karschon 1971, Awe andShepherd 1975), differences in flooding and salinity tolerance (Karschonand Zohar 1975), by biochemical characteristics (Banks and Hill~s1969) andby leaf morphology (Burley, Wood and Hans 1971).Larsen (1967) distinguished three main groups of E. camaldulensis,found in the Murray River area, coastal W.A. and inland central Australia.He found that within these groups introgressive hybridization was takingplace with Eucalyptus rudis (southern W.A.), Eucalyptus alba (northernAustralia) and Eucalyptus tereticornis (eastern Australia).In Victoria, E. camaldulensis hybridizes with several species,including E. tereticornis (Willis 1972).On the East Gippsland Plains,where the ranges of these two groups overla~ it is difficult to make anymorphological distinction between them (Fell 1975).Laurie (1976) has

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10also shown that there are some genotypic differences between forest andwoodland forms of E. camaldulensis in the Barmah Forest, Vic.VICTORIAN DISTRIBUTION OF E. VIMINALIS AND E. CAMALDULENSISFigures 2 and 3 show the respective distribution of E. viminalis andE. camaZduZensis in Victoria. These maps were compiled from localityrecords made available by the National Herbarium of Victoria, the Herbariumof the Botany School, University of Melbourne, from published material,personal communications (D.H. Ashton and P.Y. Ladiges) and fieldwork.In an attempt to account for some of the natural variation within thesetwo species each was subdivided into types.For mapping purposes, three forms of E. viminaZis were differentiatedon the basis of stature and proportion of rough bark on the tree trunk.These are the tall, smooth-barked tree of gullies and highland areas, thesomewhat shorter woodland form with varying amounts of rough bark, andpopulations whose rough bark extends to the secondary branches, that isE. viminalis var. racemosaE. camaldulensis was categorised by habitat, a distinction made byBoomsma (1950).In riparian sites, under the influence of accessible watertablesand seasonal flooding, trees vary from tall forest to woodland form.On open plains, where moisture is derived from precipitation, trees areinvariably of woodland form.E. viminalisSmooth-Barked Forest FormThis form (Plate la) is common on the northern slopes of the Dividein the Eastern Highlands where M.A.R. exceeds 1000 mm (Fig. 4). Chieflyfound on brown earths and krasnozems, it occupies moist but well-drainedvalley sites and forms tall open-forests (after Specht 1970).

cBPLATE 1A. Smooth-barked forest formof E. viminaZis at Fernshawin the Upper Yarra Valley.B. The woodland form ofE. viminaZis on a Si lurianoutcrop near Morang, northwest of Melbourne.C. Rough-barked E. viminaZisvar. racemosa on podsolizedsoils near Frankston.A

11In the broader valleys below 300 m where average annual rainfall isless than 1000 mm, E. camaldulensis replaces E. viminalis as the dominantriparian species, with Eucalyptus camphora occupying poorly drained sites.E. viminalis occurs in tall open-forests with Eucalyptus obliqua andEucalyptus radiata between 400 and 1600 m, although it has occasionallybeen recorded from greater altitudes, such as on the Nunniong Plateau at1300 m (D.H. Ashton, pers. corrrn.).On the southern slopes of the Eastern Highlands, smooth-barkedE. viminalis also occupies riparian habitats (but at slightly lower altitudesthan on the northern slopes), where M.A.R. generally exceeds 700 rrrn, althoughit also occurs in lower rainfall areas in protected gullies. On moistsheltered slopes between 400 m and 1200 m,it forms tall open-forests withEucalyptus regnans and Eucalyptus nitens.In the Western Highlands smooth-barked E. viminalis is chiefly foundabove 500 m on basalt and granite outcrops where M.A.R. is more than 700 mm.It forms open-forests and sometimes tall open-forests with E. obliqua andE. radiata. In slightly drier areas this form of E. viminalis is confinedto steep gully sites.Other major occurrences are in relatively high rainfall (M.A.R. 1000 rrrn)highland areas such as the Otway Ranges and the South Gippsland Highlands.In the Otways, smooth-barked E. viminalis fringes streams and forms tallopen-forests. with Eucalyptus globulus, E. regr.ans and E. obZiqua on fertilebrown earths (Parsons, Kirkpatrick and Carr 1977) and is emergent overNothofagus closed-forest (Howard and Ashton 1973).In Western Victoria, isolated occurrences of smooth-barked E. viminalishave been noted in very sheltered valleys at Hall's Gap in the Grampians andon Moleside Creek east of Nelson, where average annual rainfall is 900 mm.

12Woodland FormThe woodland form of E. viminaZis (Plate 1b) is generally found in thewestern half of Victoria, where it may occur in areas which receive 600-300 mm H.A.R., but it is more common where H.A.R. is at least 700 mm. Itis generally found on relatively good loamy or clayey soils. Stands recordedin areas where H.A.R. exceeds 800 mm are generally growing on deep sandysoils. At localities near Geelong, E. viminaZis woodlands are known fromsites which receive little more than 500 mm M.A.R.In the Western Highlands, woodland E. viminaZis tends to be restrictedto basalt cappings and granite outcrops, where M.A.R. is rarely less than700 mm. Within these areas smooth-barked E. viminaZis also occurs insheltered gullies. To the south, on the Western District Volcanic Plains,E. viminaZis woodlands are found on the wetter margins of the plains, andare particularly extensive on stony rises along the southern extent of thebasalt. On coastal plains in south-western Victoria it occurs on sandysoils derived from calcareous materials (Ladiges and Ashton 1977); eastwardson the coastal plain which flanks the Otway Ranges,woodland E. viminaZiscommonly occurs on the Pliocene Hoorabool Viaduct formation.In eastern Victoria, woodland E. viminaZis occurs on coastal plainswest of Wilson1s Promontory, and occasionally on the East Gippsland coastalplains west of Bairnsdale.Rough-Barked Form (var. racemosa)Rough-barked populations of E. viminaZis (piate lc) are chiefly foundin coastal areas of eastern Victoria on the deep sandy podzols of Pleistocenesand sheets and recent dune deposits, where M.A.R. is 630-760 mm.Otherrough-barked populations are found near Torquay, and from Nelson inland tothe Grampians, generally on infertil~ acidic sands.

APLATE 2. '~Jo._, '-'.i#-__ fJ.~ ~A. The woodland formof E. camaldulensisgrowing on basaltderived soils nearMorang.B. The forest form ofE. camaZdulensis atBarmah on the MurrayRi ver.B

13E. CAMALDULENSISE. camaZduZensis occurs throughout Vic. except in the Eastern Highlandsand far East Gippsland.It usually forms woodland or open-woodland (Plate2a); however, in the Barmah and Gunbower areas along the Murray River, tallopen-forests (Plate 2b) are found on the best quality sites (Laurie 1976).North of the Dividing Range, on the Northern Plains where M.A.R. is380-635 mm, E. camalduZensis is restricted to riparian habitats, some ofwhich may be seasonally waterlogged.Eucalyptus ZargifZorens occupies theless frequently inundated sites, and both are replaced by EucaZyptus microcappaon the heavy clay soils of the Northern Plains.In north easternVic., E. camaZduZensis is found on the floodplains of the major rivers inareas which receive up to 1000 mm M.A.R.South of the Divide, E. camaZduZensis is generally regarded as beingabsent east of Dandenong. although there are sporadic occurrences on theEast Gippsland Plains.West of Dandenong it occurs in both riparian andplains habitats.Riparian E. camalduZensis occurs in areas where M.A.R. is500-700 mm; where M.A.R. is less than 500 mm it forms a thin, discontinuousfringe along streams.The woodland form is found on heavy clay soils of theDundas Tablelands, and on the wetter margins of the Western Volcanic Plains,where- M.A.R. is 600-700 mm.On heavy clay soils south of the Yarra Riverand near Dandenong. the woodland form of E. camaZduZensis occurs where M.A.R.is 700-1000 !TIn.ECOTONES OF E. VIMINALIS AND E. CAMALDULENSISIn Victoria, the ranges of these two widely distributed species overlapin both the plains and riparian habitats.However, within these recognizable,broad ecotones, each species tends to occupy a topographicallydistinct site.

14Plains Bounda~dWoodland forms of both species occur on plains in western Vic. southof the Dividing Range.E. camaldulensis commonly occupies the drier sites(600-700 mm) where soils are predominantly clayey. E. viminalis isgenerally found in somewhat wetter areas (M.A.R. > 700 mm)on well-drainedsoils. Where both species occur together, E. camaldulensis commonlyoccupies the wetter sites, whilst E. viminalis shows a distinct preferencefor better drained sites.Riparian BoundaryRiparian communities of E. viminalis and E. camaldulensis overlap atthree main regions in Victoria:(a)On the northern slopes of the Eastern Highlands smooth-barkedE. viminalis is found in upper valley tracts above 300 m, where M.A.R.exceeds 1000 mm.At lower altitudes, E. camaldulensis is the dominantspecies on the floodplains.(b)On the south-western flanks of the Eastern Highlands, E. viminalisextends almost down to sealevel along sheltered valleys where M.A.R. isequal to or greater than 700 mm.E. camaldulensis occurs along some watercourses on the adjacent coastal plains south-east of Melbourne. and on thebasalt plains north of Melbourne.The woodland form of E. viminalis mayalso be found here on slopes above the river valleys.(c)In the Western Highlands. smooth-barked E. viminalis occurs on northernand southern slopes, but is largely confined to the headwatersof streams,giving way to E. camaldulensis where stream valleys broaden and M.A.R.decreases.Both species show preferences for particular sites within the riparianhabitat. E. viminalis occupies moist but well-drained river flats andvalley slopes. E. camaldulensis grows along river banks often on heavy.poorly structured soils in areas which may be periodically flooded.

15SUMMARYDetailed mapping disclosed some of the relationships between the variousforms of E. viminalis, E. camaldulensis and environmental factors.Thehabitat requirements for some forms of these two species are very broadlysimilar; however, E. viminalis generally shows a preference for the higherrainfall but well-drained localities, whilst E. camaldulensis most commonlyoccurs in somewhat drier areas on heavy, frequently poorly drained soils.Where both species occur together, habitat preferences seem to be expressedfor particular soil moisture regimes, E. viminalis being found on the betterdrained sites.A study site was chosen at Templestowe in the Yarra Valley, where bothspecies occur, to investigate some of the local factors which may influencedistribution patterns in the riparian habitat.

Ng~8DO- isohyets (mOl.)catchment boundarytransectsA study sites• Westerfolds".- ...- , ...\\... , ,/II\,,-- \,---- /' ......" \" - ...' .....,_/ ...' _,-,\... ..... _-----,\,\\\, ,II- ,........ I'"'~I ... .1 "./Port PhillipBtlyAflef Mlrriott, 1915.L ~ 10 15 , 20 2S.m ,Fig. 5.The Yarra Valley showing the location of Westerfolds, study sites A, B, C and D, transect locationsand rainfall isohyets.

16CHAPTER 2THE YARRA VALLEY STUDYI NTRODUCT I ONSites within the Yarra Valley were chosen to examine the factorsaffecting the distribution of E. viminaZis and E. camaZduZensis in theriparian habitat. E. viminaZis fringes the upper tributaries of the Yarra,and is found as far downstream as Templestowe (Fig. 5 ); from this localityE. camaldulensis occurs along the river and adjacent gentle slopes to theriver mouth at Melbourne.Both species are present along the river for0.7 km between Bonds Road and Homestead Road; Westerfolds State Park waschosen as the primary study site. Both species are present there alongthe river, and as isolated stands on adjacent slopes.Fenced plots wereerected for field trials, and seed and topsoil samples were collectedthere for use in glasshouse trials.CLIMATE OF THE YARRA VALLEYThe Yarra Valley experiences considerable variation In rainfall,temperature and other climatic elements due to its location and topography.Mean annual rainfall increases markedly from west to east across thecatchment (Fig. 5), the mountainous upper tract receiving more than 1400 mm,and the western area less than 600 mm per annum.Rainfall is fairly evenlydistributed throughout the year, although SUmmer tends to be the driestseason.Seven major droughts have been experienced since settlement,although the region is not normally considered drought prone (CommonwealthBureau of Meteorology 1968).Frequent floods were common in the YarraValley, and five major floods have been recorded.However, the frequency

17and severity of floods has been mitigated in recent years by the constructionof reservoirs to augment Melbourne's water supply.Mean maximum temperatures range from about lSoC to 19 0 C east to westacross the catchment, and annual mean minimum temperatures from 5°C to 9°C.Mean maximum temperatures for January range from 25°C to 27°C, for Julyo 010 C to 13 C. Annual average evaporation ranges from 1000 mm over thelower areas of the catchment, decreasing to 750 mmin the upper catchment.There is considerable local and regional variation in the occurrenceof frosts, Melbourne averages nine a year; their frequency increases inthe central valley with Healesville experiencing 38 per year.In themountainous upper reaches as many as 100 may occur annually (Marriott 1975).PHYSIOGRAPHY AND GEOLOGYThe Yarra Valley catchment extends to the north and east of Melbourne,bounded by the southern slopes of the Great Dividing Range to the northand by the I ine of granite and granodiorite intrusions and acid lavas whichform the Dandenong Ranges and the Baw Baw Plateau (Gill 1949) to the south.To the west it includes part of the Newer Volcanics plains.The Yarra River has its source in mountainous terrain 48 km upstreamfrom Warburton (Marriott 1975) and flows in a westerly direction to emptyinto Port Phillip Bay at Melbourne.In its upper tracts the Yarra Valleyis cut into Silurian mudstones, sandstones and shales. The presence downstreamof acid lavas, a granodiorite intrusion, hornfels and a group ofacid dykes has resulted in the formation of an incised section fromMcMahon's Gorge to Warburton Gorge (Gill 1949).Below the WarrandyteGorge. the Yarra emerges into a broad alluviatedvalley with wide flats which are still subject to flooding.At Fairfield

18the valley narrows again due to partial infilling by Quaternary basaltswhich flowed down the ancestral valleys of the Darebin and Merri Creeks.Ponding by basalt here resulted in the development of the broad flatsupstream at Heidelberg and Templestowe.Below Fairfield, the Yarra is alateral stream cutting a winding valley on the eastern boundary of theQuaternary basalt against Silurian sediments.The valley widens betweenSouth Yarra and Princes Bridge where a narrow floodplain has developed.Below Princes Bridge the river winds across its delta to Hobson's Bay(Ne i I son 1967).SOILSSoils of the Yarra catchment upstream from Diamond Creek have beenmapped by the Soil Conservation Authority (1976).Major types includeyellow brown duplex soils which are most commonly found on Lower Devonianand Silurian siltstones, sandstones, mudstones and shales at altitudes ofup to 300 m where M.A.R. is 750-1200 mm.They also occur in the catchmentarea west of Diamond Creek and south of the Yarra to Gardiner's Creek(Grant 1972).At altitudes between 200-1600 mm, where M.A.R. exceeds 1000 mm,red,brown and occasionally reddish brown, yellowish brown and yellowish redgradational soils occur on a wide range of parent materials includinggranites, granodiorites, rhyodacites and rhyol ites, tertiary basalts andmetamorphosed sedimentary rocks.Soils developed on Recent alluvial sediments along the Yarra andits tributaries include uniform sandy soils on levee banks, loamy soilswith mottled subsoils on the occasionally flooded middle Yarra floodplains,and uniform cracking clay soils on the more frequently flooded areas ofthe middle and lower Yarra Valley.\.Jest of the Plenty River on theNewer Volcanics, soi Is are generally uniform heavy-textured clays (Grant 1972).

19VEGETATION OF THE YARRA CATCHMENTMuch of the vegetation of the Yarra catchment has been severelymodified by firing, clearing, agricultural practices and the introductionof exotic species since European settlement. The vegetation on publicland within the catchment has been mapped by the Land Conservation Councilof Victoria (L.C.C.V. Melbourne Study Area 1973).The mountainous and wetter areas of the catchment (M.A.R. > 1100 mm),which have remained comparatively undisturbed, support tall open-forestof E. regnans and E. deZegatensis, which may extend below 600 m on shelteredsites. E. regnans is usually dominant below 950 m, and is common in theheadwaters of the Yarra River.E. nitens frequently occurs at the junctionbetween these two species at 900-1000 m. E. ~dPeZZocarpa~ E. viminalis andE. obZiqua tall open-forest is common at lower altitudes. In very shelteredgullies, Nothoragus cunninghamii closed-forest is found.Open-forest of various eucalypt species occurs on drier sites andat lower elevations.On the lower slopes of the Kinglake Plateau,~. obZiqua~ E. dives and E. radiata form open-forest, sometimes withEucaZyptus rubida and Eucalyptus polyanthemos.E. dives and E. polyanthemosare found on the driest sites. West of the Donna Buang area, open-forestof E. dives and Eucalyptus goniocalyx occurs on the drier spurs.In theUpper Yarra Valley, E. obliqua and E. radiata form open-forest on the moreexposed sites, and Eucalyptus sieberi occurs variously with E. obZiqua,E. baxteri and E. radiata on ridges and steep northern slopes.Much of the catchment downstream from Healesville has been cleared.Undulating areas of Silurian and Lower Devonian siltstones and mudstonessupport open-forest or woodland of various species including E. obliqua~E. baxteri~ E. radiata~ E. dives~ E. macrorhyncha and E. goniocalyx.At the western end of the catchment, basalt-derived soils supported open

NNW Fernshaw 1193 mm. SSEErad EobEv Eov EvEcE camaldulmsisE9",£ goniocaLyxE! E. LeucoxylonEmac E macrorhynchaErne! E melliodomE ob" E. obLiquaEov E. ovataEp,E polyanlizemosE rad . E. radiataE reg £ regnansEv £ L/imlnalispastureWHealesville 1028 ml1l.EErne!EmacNWEvHurstbridge 740 mm.Erad Ev Ev EvEgEcEpSEEc~ AlluviumD ... .[§JNewer volcanics~ ;/.-: ... :.' Tertiary sands0,_-Devonian rhyodacit-Silurian sandstoneand mudstonepastureNTemplestowe 788mln.SErne!E!NNWKew 735 mm.SSEEcErne'EcN Richmond (reconstructed from remaining traes) 670 mm. sFig. 6. The landform, geology and eucalypt distribution across transectsthe Yarra Valley. Rainfall (rrm) is for nearest recording station.

20dry tussock grassland (Willis 1964) which have now largely been replacedby exotic species.The Distribution of E. viminalis and E. camaldulensis in the River TractA series of cross valley transects (Fig. 6) were drawn to examinethe distribution of riparian eucalypt species in the Yarra valley.Alongthe valleys of the Upper Yarra and its tributary streams such as the WattsRiver at Fernshaw, where M.A.R. Exceeds 1100 mm,the forest form ofE. viminalis occurs on alluvial flats and riverbanks, sometimes withE. regnans. At Fernshaw E. regnans is dominant on the well-structuredbrown loamy soils of the south facing valley slopes, whilst E. obliquaoccupies the somewhat drier north facing slopes.Forest-form E. viminalis fringes the Yarra downstream past Healesville,and was once more widely spread across the broad alluvial flats. Poorlydrained clayey depressions on the flats are occupied by E. ovata, whilstthe Silurian sandstone-derived soils on the valley slopes supportE. obliqua-E. radiata forest. At Hurstbridge on the Diamond Creek, whererainfall is considerably lower, the forest form of E. viminalis occurs onsilty sands along the creek. E. camaldulenais woodlands occur on theduplex soils of the lower valley slope beyond the floodplain.On theshallow rocky soils of the upper slope and slope crest E. camaldulenaisgives way to E. polyanthemos, E. goniocalyx and E. macrorhyncha woodland.A similar sequence occurs on the Yarra River upstream from Westerfolds.At Westerfolds both E. viminalia and E. camaldulensis occur onalluvial soils along the riverbank.Prior to clearing, E. camaldulenaisprobably extended across the lower alluvial terraces which are frequentlywaterlogged in winter. Now only small stands remain. E. camaldulensisalso grows on the duplex soils of the gentle Silurian slopes.Occasionalstands of E. viminalis also occur here.On the northern aspect where slopes

21are steep and soils shallow and rocky, E. radiata~E. goniocaZyx andE. rubida occur.Further downstream at Kew, where M.A.R. is slightly lower,E. camalduZensis occurs on alluvial terrace deposits and up the lowerslopes of the valley.The upper valley slopes on the east bank supportE. meZliodOra woodland, which grades into E. Zeucoxylon woodland on theTertiary sandy capping.steep, sheltered banks.E. viminaZis only occurs very sporadically onAt Richmond and further downstream,E. camaldulensis is the only naturally occuring riparian eucalypt, andthe woodland form of the species occurson undulating topography withE. melliodOra, and extends across onto the basalt. This latter specieswas once common in the area now occupied by the City of Melbourne.The Distribution of E. viminalis and E. camaldulensis ~nthe SurroundingRegionThe woodland form of both E. viminalis and E. camaldu4ensis occurson gently undulating terrain around Melbourne.E. camaZdulensis woodlandsgrow on relatively deep soils on Silurian topography east of Melbourne asfar as Burwood, the easternmost extent corresponding with the 800mm isohyet.South east of Melbourne, remnants of E. camaZdulensis woodland occur on lowlyingTertiary sands between St. Kilda and Cheltenham, where M.A.R. is600-700 mm, on peaty soils south east towards Frankston, and on heavy claysoils near Dandenong, where M.A.R. is 800 mm.E. camaldulensis also growson the basalt plains to the north and west of Melbourne where M.A.R.exceeds 500 mm; towards the Maribyrnong River the woodlands become sparser,further west stunted trees occur in depressions or fringe drainage lines.Stands of the woodland form of E. viminalis were probably not asextensive as those of E. camaldulensis, and tended to be restricted to

WESTERFOLDS - GEOLOGYNo o·s 1kmIi i i ~ ~ 11 Silurian mudstones, siltstones and sandstonesE::-a Quaternary alluvial terracesI: ..... :1 Quaternary alluvial flatsSource: Melbourne and SuiubI GIatovY. 1959Fig. 7

22well-drained sites, generally in slightly higher rainfall areas.Remnantsof E. viminaZis woodlands occur on Tertiary sandy cappings in the WattlePark-Ashburton area and on older basalt outcrops near Kangaroo Groundwhere M.A.R. exceeds 800 mm.WESTERFOLDS - THE STUDY SITEWesterfolds State Park is located at Templestowe on the Yarra River(see Fig. 5). The site was chosen for its accessibility and the presenceof ecotone riparian communities of E. viminaZis and E. camaZduZensis.Impending management of the property by the National Parks Service madeit a convenient place to establish field trials.Average annual rainfall for the nearest recording station at Doncaster(altitude 76 m) is 788 mm. Westerfolds which is 40-60 m above sealevelprobably receives slightly less rainfall. The nearest station for whichtemperature data are avai lable is Melbourne, which experiences a meanmaximum of 19.4 o c and a mean minimum of 9.S o C (Commonwealth Bureau ofMeteorology 1968).GeoZogy~Physiography and SoiZsThe bedrock of Silurian siltstones, sandstones and mudstones atWesterfolds is largely overlain by Quaterna~yalluvial deposits formingriver terraces and flats (Fig. 7). These broad river terraces which areconspicuous along the Yarra River upstream from Darebin Creek, originatedwhen lava flows down the Merri and Darebin Creeks dammed the old valleyof the Yarra (Neilson and Jenkin 1967).As the Yarra subsequently deepenedits bed, terraces were cut in the alluvial material.The Yarra River atWesterfolds consists of a series of meanders, with steep river cliffs upto 50 m high on the northern bank and a gently sloping spur with terrace

WESTERFOLDS • LANDFORMSNtIIIIIJ)E] ....IIill....D~B~,{:~IIsteep slopes and ridgesgentle crestsmoderate slopesupper terrace surfacesupper terrace slopeslower terraceleveebillabong, ! ! ' , ,o 100 200 300 400 !500 met,..BCE. camaidulensis field trial siteE. viminalis field trial siteFig. 8

23deposits on the southern side.Narrow alluvial flats fringe the Yarra.The meander on the western side of the river was cut off by floods inthe 1930 1 5 (Lennon 1974).The land forms have been mapped by Jeffery and Howe (1976).Theyhave recognised eight major categories, which include steep slopes andridges, gentle crests and moderate slopes on Silurian outcrops, upperterrace surfaces and slopes, lower terraces which border the Yarra andthe main creek, billabongs and levee banks (Fig. 8).Soils (Table 1) derived from Silurian mudstones, siltstones andsandstones and some terrace deposits are mottled, yellow and duplex(Oy 3.41 after Northcote 1965), with sandy loams overlying clays.On somelow terraces soils are deep, brown gradational clay loams (Gn 4). Weaklydifferentiated brown uniform profiles are found on levees and in billabongs,with sandy loams on levees (Uc 1.43) and clay loams (Um)inbillabongs (P. Jefferies, pers. comm.).VegetationFigure 9 shCPNSthe distribution of the major eucalypt species atWesterfolds.Most of the 122.2 ha consists of improved pastures, althoughsome native grass and herbaceous species are still present. The Yarrabanks support a narrow fringe of E. viminalis and E. camaldulensis forest(Plate 3a); E. camaldulensis is dominant downstream from the maintributary creek. t~ear Fitzsirrmons Lane E. viminalis is the dominantriparian species, and between these areas both species are present.Acacia me~oxylon~ Acacia dealbata~ Acacia mearnsii~ Hymenanthera dentata~Bursaria spinosa~ Olearia argophylla, Leptospermum lanigerum~ Leptospenmumphyliaoides, Callistemon paludOsus and Prostanthera lasianthos form a denseshrubby understorey (Plate 3b) along undisturbed sectors of the bank.Theexotic species Salix babyloniaa and Rubus frutiaosus are common, Salixis sometimes dominant along the lower river bank.

T b , .. '--,- - Po. - ' .,." ....a e .. .., ., ..... c,.. ...............___.. __ ·.....F .. V R' r . ! ... i4~a",,:-. ,-tL.-t,.U"&t ••':'I! __ _Mottled Yellow Duplex (Dy 3.41)*Brown Gradational (Gn 4)Brown Uniform (Uc 1 .~3)Hor i zon anddepth (em)DescriptionHor! zon anddepth (cm)DescriptionHor! zon anddepth (cm)DescriptionAl 20A2 35sandy loamfriable10 YR 4/21,pH 5.9sandy loamvery friable10 YR 6/2pH 6.5Al 15A2 30Al 45brownfine sandy loampH 5.0pale brownfine sandy loampH 5.5brown clay loampH 5.51550Fine sandy loam10 YR 3/3few brown mottlesfine sandy loam10 YR 4/3pH 5.5B 100clayfirmabundant yellowmottles10 YR 4/4pH 6.9A2 50B I 80pale brovJnclay loamyellow mottlespH 6.0brown light clayabundan t ye 110wmottlespH 6.8B2 100brownIi gh t clayabundant yellow mottlespH 7.8*Northcote (1965). P. Jefferies pers. comm.

WESTERFOLDS - EUCALYPT DISTRIBUTIONN,.. ,.....n~~~r.?m~c:JE. viminalisE. camaldulensisE. viminalis and E. camaldulensisE. melliodoraImproved pastureo 100 200 300 400 500 metres,Fi g. 9

24On the upper terraces and Silurian slopes scattered stands ofE. viminalis~ E. camaldulensis and E. melliodora form woodlands oropen woodlands, but this may be the result of partial clearing (Womersley1976). Although E. viminalis is generally found on the well-drained deepbrown gradational clay loams of the river banks and lower terraces,occasional stands occur on duplex soi Is of the Silurian slopes.E. camaldulensis is also found on both the gradational and duplex soils,but occurs more commonly than E. viminalis on the duplex soils of theSilurian slopes.Although neither species is restricted to one soil type,both E. viminalis and E. camaldulensis show some site preferences on eachsoil. Along the river bank E. viminalis tends to occupy the upper bank,whilst E. camaldulensis is able to grow closer to the river. On theduplex soils E. camaldulensis generally occurS upslope of E. viminalis,on the steeper drier slopes .In summary, throughout the Yarra Valley the forest form of E. viminalisoccupies moist but generally well-drained sites where M.A.R. exceeds 700 mm.Where M.A.R. is less than 700 mm, E. camaldulensis is the dominantriparian species, it fringes rivers and billabongs and is found on sitessubject to periodic inundation.E. camaldulensis also forms woodlands onthe relatively deep clay subsoils of the surrounding basalt and Siluriantopography, where it may be exposed to drought stress.Hence, E. camaldulensis appears to be tolerant of greater extremesin moisture supply, it may be subject to drought stress or flooding andsubsequent waterlogging.Climate, topography, soil texture and soilstructure will all interact to determine these conditions.Small changesin soil nutrient status may act as a more subtle differentiating factor.Pot trials were therefore established to assess the relative toleranceof seedlings of both species from the riparian habitat to the effects ofwaterlogging and drought.The role of soil nutrients was also examined

ABPLATE 3A. Riparian occurrences of E. viminaZis (v) andE. camaldulensis (c) at Westerfolds in the YarraVa lley.B. Typical shrubby riparian understorey at Westerfolds.

25by chemical analysis of soil samples, and the assessment of seedlinggrowth response to varying levels of phosphorus and nitrogen.Interspecificcompetition for nutrients was investigated by growing seedlingsin competition on soils from the field.Field trials were conducted toassess survival and growth rates of seedlings in the field.The possibility of population variation in E. viminalis within theYarra Valley was also examined, and seedlings were grown from seed ofsuspected E. viminaZis x E. camalduZensis hybrids, however the progenywere typical E. viminalis.

26CHAPTER 3SEEDLING GROWTH RATE AND RESPONSE TO NUTRIENTSI NTRODUCT I ONField observations on the distribution of eucalypt species alongthe Yarra River and its tributaries (Chapter 2) suggested that the forestform of E. viminalis occurs predominantly on better drained alluvial soilswhere M.A.R. exceeds 700 mm.In the drier areas of the Yarra Valley,E. camaldulensis is the dominant eucalypt on alluvial deposits, butwhere the ranges of the two species overlap, the latter tends to occupysites with heavy soi Is which may be subject to waterlogging, or is foundon drier gentle slopes, away from the river, which may be prone to drought.It is suggested that the forest form of E. viminalis may have a fastergrowth rate than E. camaldulensis on better drained alluvium in the higherrainfall areas of the Yarra Valley, and that competition between the twospecies may in part have determined their present distribution.A preliminary experiment carried out by D.H. Ashton (unpublished)suggested that interspecific competition may be an important factor inthe delimitation of these species. When E. viminalis seed collected fromEltham was germinated and grown for two years in drained two gallon plasticbuckets containing a well structured garden soil seedlings grew much tallerthan E. camaldulensis (seed source Heidelberg), both in monoculture andmixed culture (Table 2).Previous work with other eucalypt species has shown that the presenceof interspecific competition may influence the distribution of specieswhich generally occur in discrete stands although their edaphic rangesoverlap,Moore (1961), in an investigation of the factors delimitingE. melliodora and E. rossii communities on the Southern Tablelands of

27Table 2.Mean heights (cm) of seven two-year-old E. viminalis andE. camalduZensis seedlings grown on a friable garden soil mixture inmonoculture and mixed culture (D.H. Ashton, pers. comm.).SpeciesMonocultureMixed CultureE. viminalisE. camaZduZensis1883421061N.S.W., found that when the species were grown in competition, increasinglevels of exchangeable calcium favoured the growth of E. meZZiodora.Hesuggested that its success would result in its dominance in a naturalcommunity if soil calcium levels were high.Experimental work by Parsons and Specht (1967) has suggested that thedistribution of E. baxteri on siliceous coastal sands in the wetter areasof southern Australia is due to a faster growth rate, which may enable itto replace E. diversifolia and E. incrassata on sites where rainfall isadequate.The distributions of E. incrassata and E. socialis, whoseedaphic ranges overlap, have also been related to the competitive advantageof each species under different conditions of soil moisture and fertility(Parsons 1969).Chemical and physical analyses were carried out on soils collectedfrom E. viminaZis and E. camalduZensis stands to examine the possible roleof edaphic factors in influencing the species distribution. Seedlinggrowth rates were compared in monoculture and mixed culture on the twotopsoils and on riverbank soils and in sand cultures at various levels ofphosphorus and nitrogen in glasshouse trials, and field trials were

, .. '' J S 'If ........,~-"'..--"wc···~'''"'~ ...-·;$\I;)jl'&iL..,'

28n..~ established to investigate seedling behaviour at Westerfo1ds .~~- ••SOIL CHARACTERISTICS~~. ~~.~s -0~~.~~~~0 0~~w -G.~~ t~~n~~~~ ~ -~ ~0-~Co ~~ ~0 •.."MethodsSoil characteristics were described from the E. camaldulensis (site B)and E. viminaLis (site C) field trial plots at Westerfolds. Since thesesites were less than one km apart, it was decided to include data for adownstream site supporting only E. camaLduLensis (site A near the BanksiaSt. bridge, Heidelberg) and a site upstream near Healesvi 11e (site D)>~ ~dominated by E. viminaLis.~W %G~~ ~< ~ Five replicate samples were collected from sites Band C each month~.... ••~ ~....~ ~~~.~.5~between June 1976 and July 1977 for the gravimetric determination of soil~ moisture. In January 1977 five topsoil (0-10 cm) and five subsoil (50-60.~.... ~~~. ~~ ~s~~cm) samples were collected from each of the four sites, bulked and mixedthoroughly.Subsamp1es were used for particle size analysis: the clay andsilt fractions were determined using the plummet bulb hydrometer (Hutton~1955), and the sands by decantation of the fine fractions. Percentage~.. disaggregation (Downes and Leeper 1940) of the topsoi 1s and subsoils was..~~~measured, and pF (Leeper 1967) estimated.Analysis of the major nutrients,organic nitrogen (Kjeldah1 method), total phosphorus (Chapman and Pratt~~~ 1961) J available phosphorus (Colwell 1963) and determination of thes~.~ exchangeable bases, Ca, K (flame photometry) and Mg (atomic adsorption) J~-0 was carried out by Food Laboratories (Aust.) Pty. Ltd.rtmrt• ~~•~ Results~ Soil profile descriptions are given in Table 3. Two profiles are~0described for site B since soils within the field trial plot were derived-~~from two types of parent material, Silurian bedrock and alluvial terracedeposits.The particle size analysis (Table 4) indicated that all topsoils

29Table 4.Particle size analysis of soils at A:Heidelberg (E. camaZduZensis),B:E. camaZdulensis plot at Westerfolds, C:E. viminaZis plot at Westerfolds,~ Healesville (E. viminaZis).Site% Clay% Silt % Fine Sand % Course SandTextureA0-10 em14.520.55510loam50-60 em1724572loamB0-10 em8.522.55712loamy sand50-60 em2517.546.511clay loamC0-10 em6156811loamy sand50-60 em28.511.550.59.5clay loamD0-10 em14.527.5535s i I ty loam50-60 em18.529.5493s i I ty loam*-Values for soil derived from Silurian parent materials.

(a)6 A horizon6B horizona E. yiminalis• E. camlldullMis55pF 332...o10 20 30 40 5060Soil moisturl (%)(b)6 A horizon6B horizon5544pf 332210 20 30 40 5060 o10 20 30 5060Soil moisturl (")Fig. 10. pF curves for soils from (a) E. camaldulensis (Site B) andE. viminalis (Site C) field trial plots at Westerfolds, and (b)E. camaldulensis stand at Heidelberg (Site A) and E. viminalis standat Healesville (Site D). A, horizon 0-10 cm depth; B, 50-60 cm depth.PWP = permanent wilting point, Fe = field capacity (after Leeper 1967).

30contained a high proportion of fine sand, with varying amounts of clayand silt. For the levee bank sites at Heidelberg and Healesville therewas no marked texture change with depth, however for Westerfolds siteson Silurian bedrock, the B horizon, was generally a heavy clay loam.Table 5 provides some indication of soi 1 structure; topsoi 1 at Heidelberg(A) had a fine crumb structure, whilst at Westerfolds (sLtes B and C)itwas generally apedal.Percentage disaggregation values for Healesvi lIetopsoil were similarly high, but in the field the topsoil, which had ahigh organic content (Table 6) was quite friable.Subsoils were poorlystructured, the slightly lower values for Westerfolds \'Jere attributed tothe presence of false aggregation (baked clay lumps) in the samples.In order to separate all the fine material from the aggregates it wasnecessary to continue flushing the soil for up to one hour, three timesthe suggested period, and it is thought that the method did not provideentirely satisfactory results.Analyses for the major soil nutrients (Table 7) did not indicate anyconclusive differences in the fertility of the four sites. There was sometendency for the riverbank soils (sites A and D) to have higher levels oforganic nitrogen and total phosphorus.at site C which supports E. viminaZis.Avai lable phosphorus was highestCalcium levels were highest forsites A, Band C.The validity of these results as a basis for comparisonis somewhat uncertain, since site A has been uti lised for grazing, andsites Band C intensively grazed and probably top dressed.Site 0 isundisturbed.A comparison of the pF values (Fig. 10) for topsoils at Westerfoldssuggested that more water would be available at the E. aamaZduZensissite (8).There was little difference in the amount of moisture availablein the subsoils, however exact values were not estimated since these soils(and the E. aamaZduZensis topsoil) formed a slurry before field capacitywas reached.Examination of the percentage soil moistures for these two

31Table 5.Percentage disaggregation of soils at A: Heidelberg,B: E. aamaldulensis plot at Westerfolds, C: E. viminalis plot atWesterfolds, D: Healesville.Depth (em)ABCD0-105973747650-6098868990Table 6.Percentage organic matter of soils at A: Heidelberg,B: E. aamaldutensis plot at Westerfolds, C: E. viminatis plot atWesterfolds, D: Healesville.Depth (cm)ABCD0-105231260-504355

32i':Table 7. Soil analyses for field localities - site A: Heidelberg,B: E. ~amaZduZenais field trial plot at Westerfolds, C: E. viminaZisfield trial plot at Westerfolds, D: Healesvi lIe.SitepHCaMgmg/lKpAvail.pTotalN (%)A0-8 em5.572044050182880.248-1574039018422430.18606. 152068014171880.31B0-8 em5.510403604082000.228-154902502061110.12605.61203401221000.04C0-8 em5. 172080020321290.228-15267220815720.08605.8180160145400.04o0-8 em4.812042032102480.368-15603402271610.32605.51025063-1450.07*Oetermined by Food Laboratories (Aust.) Pty. Ltd., Carlton 3053.

33sites over a 12 month period show that the pF values are not a reliableindication of the amount of moisture available to plants throughout theyear.The E. viminalis site (C) is situated on a slow-draining terraceslope which is effectively waterlogged for part of the year.TheHeidelberg and Healesville sites (A and D)tended to have more avai lablewater in their topsoils than the Westerfolds sites, but less in the subsoilswhich contained a smaller clay fraction than the Westerfolds sites.The results of the soil moisture measurements are further discussed inChapter 4.COMPARISON OF SEEDLING GROWTH RATESSeedling Growth on Two TopsoilsMethodsSeed was collected from the Westerfolds study site at Templestoweand germinated in petri dishes under light in a constant temperature(23 0 C) room. Topsoils (0-10 em) collected from sites adjacent to theE. viminatis and E. camaZduZensis field trial plots were sieved coarselyand placed in 12.5 cm pots.Seedl ings were planted. out one week aftergermination, two seedlings of the same species per pot for the monoculturetreatment and one of each species for competition.Pots were arranged ina randomised block, 2 species x 2 soils x 9 replicates each for monocultureand mixed culture. Plants were grown under glasshouse conditions for 19weeks (October 1975 - March 1976).Shoot heights were measured and plantsharvested to record oven dry weights.Statistical analysesStatistical methods for the analysis of competition experiments wherespecies are grown in both monoculture and mixed culture trial includethose of Williams (1962). McGilchrist (1965) and Langer (1973).Thesemethods are based on a comparison of the absolute yields of species

34grown in monoculture with the yields achieved in mixed culture, andassume that these absolute increases and decreases are approximately thesame. The relative yield approach of de Wit and van den Bergh (1965).designed to allow for comparison of the relative reproductive rate ofspecies from a series of harvests when growth may have occurred underdifferent conditions, or when harvests were obtained at irregular intervals,is based on a comparison of the proportional changes in yields ofthe competing species.Van den Bergh (1968) has shown that arithmeticincreases and decreases, on which earlier analyses were based, are onlylikely to approach equality when the yields obtained in monoculture aresimilar.McGilchrist and Trenbath (1971) re-analysed the data obtainedby Wi lliams (1962) and compared it with the earljer approach of McGilchrist(1965). They reported that the data " are fj tted somewhat better by thepresent statistical model [but] experience has shown that this is nota 1 ways the case'i.In the present study, the yield data were analysed by a three wayanalysis of variance (species x soil treatment x competition treatment).Monoculture yields were halved for comparison with the competitionyields per species; height data were log transformed since variables wereproportional to means (see Williams 1962) and subjected to a split plotanalysis in time (Steel and Torrie 1960).would seem appropriate as a first approach.Such a straight forward analysisFurthermore the clear nonsignificanceof some effects (see results) did not warrant more refinedanalyses such as those outlined by Langer (1973) and HcGilchrist andTrenbath (1971).Replacement series diagrams (de Wit and van den Bergh 1965) wereconstructed for dry weight data using mean total shoot dry weight per potfor monocultures, and mean total shoot dry weight per species for mixedcultures. The relative yield totals were calculated using the formulagiven in Burdon and Pryor (1975).The occurrence of competitive inter-

c.I"45~iIIiI IIl'4Q~~ I:5. " 35 1.. IA!/j//!1 // /I / /..:l "" I / // /I I //d /III •/pr~" ""." "~~"~~..-"~..-..- "..-~'~1II I,. 40 1Ii" 35 l130~130 1/I / I/iiI" '//I12 14 16 18IiiiIBr:fIIIIIII"II20 12WeeksII///II14 16oE. vimlnali.• E. camaldillensi$- monoculture--- mlled tultull18I20Fig. 11. Height growth of E. viminalis and E. camaldulensis on twoin monoculture and mixed culture. (a) on E. camaldulensis topsoi I,E. viminalis topsoil. Confidence limits are not shown as few means aresignificantly different.2(bl(blo E. villin ....O...L...-'---E. ClIMldullnsis soil E. viminllis soilFig. 12. Shoot dry weights of E. viminalis and E. camaldulensis growntwo topsoils in (a) monoculture and (b) mixed culture. Vertical bar (confidence limits.) allows comparison of species and treatments (Scheftes t) .

35action was indicated by the slope of the lines in the replacements diagram.Where the slope exceeded 45 0competitive interaction between the two speciesresulted in suppression of the yield of one species and enhancement of theother (Etherington 1975).Resu ItsAnalysis of the height growth data (Table 8) showed that the significanceof the main effect, species, was time dependent, as was the speciesx soil interaction. The competition effect was not significant.Figure11 shows that E. viminalis was the taller of the two species on both soilsand for both monoculture and competition treatments immediately prior toharvest.Species differences were more pronounced after 20 weeks growthon the E. camaldulensis soil. However, shoot dry weights provide adifferent picture, being significantly larger for E. camaldulensis thanfor E. viminalis (Table 8, Fig. 12).Shoot dry weight production byE. viminalis tended to be greater in monoculture than in mixed cultureconditions; this trend was reversed for E. camaldulensis.Suppression ofE. viminalis growth in mixed culture suggests that competition withE. camaldulensis may have been taking place, however this effect was notstatistically significant.The replacement series diagrams (Fig. 13a,b) indicates that competitiondid not occur; the slope of the lines being close to 45°.The displacementof the E. camaldulensis slope above E. viminalis (Fig. 13) representsdifferent growth rates. The relative yield totals close to 1.0 indicatesthat there is no inhibition nor stimulation of growth when the two speciesare grown together.The preliminary experiment carried out by Ashton showed a more markedspecies difference in height growth, with E. viminalis suppressingE. camaldulensis. However, E. viminalis did not overtop E. camaldulensisuntil seedlings were twelve months old.It was suggested that a growing

aAoRYT-'-O' RYT -0-89v+C"~ _____ ~o-----~12V v+C C V Vw+C CBE~ AYT-'-Q4 RYT "1'058.~ ..~'iii~~Vl>--0c(1) VV+c c Va \fe+C CQ):212CRYT", "'3 RYT "0-89F5 12 ~. ___ _v V+C vFig. 13. Replacement diagrams for competition trials betweenE. viminaZis and E. camaZduZensis. A, yields from E. camaZduZensistopsoil; B, yields from E. viminaZis topsoil - experiment one.C, yields from alluvial soils - experiment two. D-F, yields fromE. viminaZis 'Westerfolds', E. viminaZis 'Eltham' andE. camaZduZensis grown on alluvial soils - experiment three.Relative yield total (RYT) values above diagrams relate to yieldsin mixed culture.

36Table 8.Analyses of variance of data from seedling growth on twotopsoils (Experiment 1).Source of Variation df MS Fp(a) Height, 10910 transformed.Split plot analysis in time.Species0.00581O. 12NSSoi Is0.040300.80NSSpp. x Soils0.022230.44NSCompetition0.002590.05NSSpp. x Competition0.010430.21NSSoils x Competition0.013110.26NSSpp. x Soils x Camp.0.015460.31NSRes i dua 1 a640.05037Time20.2214160.43Spp. x Time20.007545.46Soi Is x Time20.000890.64NSS pp. x So i 1 s x Time20.004943.58Camp. x Time20.002361. 71NSSpp. x Camp. x Time20.001461.06NSSoils x Camp. x Time20.0021. 45NSSpp. x Soils x C. x T.20.002241.62N5Residual b1280.00138(b) Shoot dry weightSpecies50 i 1 s3.690140.032949.100.08**NSSpp. x 50 i Is0.242670.60N5Competition0.051200.13NSSpp. x Camp.0.704091. 74N5Soils x Compo0.013890.03N5Spp. x Soils x Compo0.000360.001N5Residual640.40534*. :'::': ***, significant at p = 0.5, 0.1, 0.001 respectively;N5, not significant at p 0.5.

----------------------------',8-0---------0~--------'"I I(a) (b)1·0I/ II II I//fI1'1I II II/III•o E. viminllis• E. CIImlldulensismonoculturl----- mixed culturet6I8112116Weekst20124128Fig. 14. Height growth of E. viminalis and E. aamaldulensis in monoculturemixed culture. Vertical bars indicate 95% confidence limits, allowing compariof (a) anyone species/treatment combination over time, (b) species and treaat anyone time.(b)6-CD5.!: 4CD'w3:>- J.cC;.,g 2'"(8)(b)Iv v c cFig. 15. Shoot dry weights of E. viminaZis (V) and E. camaZduZensis (C)culture (a) and in mixed culture (b). Vertical bar allows comparison bespecies and treatments.

37period of 20 weeks may have been too short for any similar reversal ingrowth rates to occur.Direct comparison between the two experimentsis difficult since Ashton used soil of a different texture and ferti lity,and grew seedl ings in larger pots for a longer period.However a secondexperiment was established to examine this possibil ity.A Comparison of Seedling Growth Rates on Alluvial SoilMethodsTopsoi I of fine, loamy sand from the river bank where stands of bothE. viminalis and E. camaldulensis occur at Westerfolds was sieved coarselyand placed in 15.2 cm pots.Four pinches of seed (of one species for monoculture,two of each species for mixed culture) collected from Westerfoldswere germinated on the soil surface in the pots.After germination,seedlings were thinned to four per pot, and following four weeks growththe tallest two seedl ings were selected.Pots were randomised in a blockdesign with 2 species x 11replicates in monoculture and mixed culture.Pots were watered daily, heights were measured at regular intervals andgrowth continued in a heated glasshouse unti I July 1977.Harvesting wascarried out after 28 weeks as seedl ing height growth for both speciesappeared to have ceased.Shoots were oven-dried and weighed; height anddry weight data were anlysed as for the first experiment.ResultsAnalysis of the height data (Table 9) indicated a significantdifference between the species which was maintained over time.Figure14 shows that E. camaldulensis,which did equally well in monoculture andmixed culture, grew taller than E. viminalis. The competition effectwas not significant.There was also a significant species difference in dry weightproduction (Table 9), and the species x competition interaction wassignificant.Dry weight production by E. camaldulensis was significantly

38Table 9.Analyses of variance of data from seedling growth incompetition (Experiment 2).Source of Variance df MS Fp(a) Height, 10910 transformed.Split plot analysis in time.Spec i es0.112285.34*Competitiono .022111.05NSSpecies x Competition0.000180.01NSResidual a400.021008Time45.65103281 . 17Species x Time40.075523.76Competition x Time40.000540.03NSSpecies x Compo x Time40.017380.86NSRes i dua I b1600.020098(b) Shoot dry weightsSpecies52.4072820.32*.,,:*Competition0.36728O. 14NSSpecies x Competition14.547505.64*Residual402.57953* **. *** significant at p : 0.5,0.01,0.001 respectively;NS, not significant at p : 0.5.

39greater than that of E. vimiY'..o.lis (Fig. 15), and was largest under mixedculture conditions.Shoot dry weights \"lere smallest for E. viminalisseedlings growing in mixed culture, indicating that E. camaldulensiswas suppressing the growth of E. viminalis.The slope for E. camaldulensis on the replacement series diagram(Fig. 13c) is convex, whi 1st that for E. viminalis is concave, suggestingthat the growth of E. camaldulensis was enhanced in mixed culture, andthat of E. viminalis suppressed.Comvarative c Growth Rates of _ E. camaldulensis and Two Provenances ofE. vimina lisThe yield results for the first and second experiments suggestedthat growth for E. camaldulensis was greater than that for E. viminalis,and that in mixed culture the presence of E. camaldulensis may suppressE. viminaZis growth. In view of the results of the preliminary experiments,it was decided to investigate the possibility of ecotypic variation withinE. viminalis in the Yarra Valley. An experiment was established toexamine the growth rates of E. viminalis and E. camaldulensis fromWesterfolds and E. viminalis from Eltham (the seed source for the preliminaryexperiment).No seed was available for the Heidelberg provenanceof E. camaldulensis used in the preliminary experiment.MethodsE. viminalis and E. camaldulensis from Westerfolds, and E. viminalisseed collected from tall forest form E. viminalis growing along DiamondCreek, Eltham (hereafter called E. viminalis 'Eltham ' ), was germinatedas for the first experiment.Fine loamy sand topsoil was collected fromthe riverbank at Westerfolds, sieved. coarsely and placed into 15.5x15 emdrained plastic buckets.Seedlings were planted out, eight per bucket,in monoculture and mixed culture combinations two weeks after germination.Buckets were randomly assigned to blocks, the experimental design being

1·81·81·4A-.-----. -------- ... -- -----_.0- _ - ______ 0------0T: Ii 1la) Ibjo E v,m,nalis 'Westertolds"4 E .,m,nalos "Eltham"• E camaldulen ...,,2monocuJturemlud culrur~t '-8"6'·4B" II1/ "'I,,0 •!!p''"'-1I-,o'---''''''2-14''''---'1~--18'---2O'''''i -2"1"'2--"24--'28T1'81I.:.. 1'6~la)iiIb) IiI1-41WeeksI1'21: ,I,oiI"IIc~ I If I If'l/,//1/ ,- I II IId , /I.:l'-~,.------: -0___::Z:::::::::S::-:·::_:'A-IP--~/- -}/ ;:s./i i,i i I iTO 12 14 18 18 20 22 24 26I Itil) (bIFig. 16. Heights of E. viminaZis 'Westerfolds ' • E. viminalis 'Eltham ' andE. aamaldulensis grown in monoculture and mixed culture. Vertical barsrepresent 95% confidence limits for the comparison of (a) any species/treatmencombination over time. (b) species or treatments at anyone time_A. E. viminaZis 'Westerfolds ' x E. aamaldulensis.B. E. viminalis 'Eltham ' x E. aamaZdulensis.C. E. viminalis 'Westerfolds ' x E. viminalis 'Eltham'.

403 'species'x2 treatments x 3 replicates. Plants were grown under glasshouseconditions for 27 weeks (August 1977 -February 1978), and heightswere measured each month.Plants were harvested in February after bothspecies had developed purple tinged leaves, lower leaf abscission wasoccurring and height growth rates had slowed down.Shoots were oven-driedand weighed.experiments.Dry weights and heights were analysed as for the previousSeed sources or 'species' were analysed in pairs (hence threeanalyses).Resul tsThere were significant differences in height between E. viminaZis'Westerfolds' and E. camaldulensis (Table 10).After 11 weeks growthE. camaldulensis had overtopped E. viminalis 'Westerfolds' in both monocultureand mixed culture treatments (Fig. 16a); at 20 weeksE. camaldulensis was significantly taller (error bar (b)) than E. viminalis'Westerfolds'.However the competition effect was not significant.A comparison of the mean heights of E. viminalis 'Eltham' andE. camaldulensis indicates that the significance of this species differencewas dependent on time (Table 10), after 23 weeks E. camalduZensis wassignificantly taller (Fig. 16b).E. viminalis 'Eltham', like E. viminaZis'Westerfolds ' , showed reduced height growth when grown in competition withE. camaZduZensis, whose height growth was greatest in mixed cultures,although this competition effect again was not significant. There wereno significant differences between the mean heights of E. viminalis'Westerfolds ' and E. viminaZis 'Eltham ' , but treatment effects weresignificant (Table 10). Both populations showed reduced height growthin mixed culture (Fig. 16c).Shoot dry weights (Fig. 17) showed asimilar pattern to height growth, with E. camaldulensis having a greateryield than either E. viminalis populations.Although the competitioneffect was not statistically significant, E. camaZduZensis tended to havea greater yield in mixed culture than in monoculture.There were no

~ ~~l10~:;: t:·/~~:y"i ,.. 5 n, It(,~ I~S\f»., I.'iii"[",II~~1I 1 n~QI i 1 III t\;i\I ~~..."0.c I t,~';\ i tF§ 1 ' III !'"0II ~,(i:.~', .:.:.,....i ~~IIw C Vw~C II. e Vt' C IIw lit Vwxll.IIFig. 17. Shoot dry weights for E. viminalis 'Westerfolds ' (Vw),E. viminalis 'Eltham' (Ve) and E. camaldulensis (C) grown in monocultureand mixed culture (Vw x C. Ve x C. Vw x Ve). Vertical bars represent95% confidence limits.

41Table 10.Analyses of variance for growth trials with two populationsof E. viminalie and E. camaldulqnsis (Experiment 3).Source of Variation df MS F p(a) Height growth, 10910 transformed.Split plot analysis in time.1. E. viminalis Westerfolds x E. ccunaldulensisBlocks 7 0.16797 6.56 :,,**Species 0.46511 18. 17-;1:;':*Competition 0.01750 0.68 NSSpecies x Camp. 0.05622 2.2 NSResidual a 21 0.0255919Time 4 2.59252 277.34 ***Species x Time 4 0.11310 12. 1 *-1:*Competition x Time 4 0.00271 0.29 NSSpp. x Camp. x Time 4 0.00962 1.03 NSRes i dua 1 b 112 0.00934782. E. viminalis Eltham x E. camaldulensisBlocks 7 0.20965 3.02 *Species 0.21962 3.16 NSCompetition 0.04121 0.59 NSSpecies x Camp. 0.05135 0.74 NSResidual a 21 0.0694133Time 4 2.87576 642.71 :':::':'*Species x Time 4 0.08313 18.58 ;'c**Competition x Time 4 0.00101 0.22 NSSpp. x Camp. x Time 4 0.00864 1.93 NSResidual b 112 0.0044744----_..(cant. )

42Table 10 (cont.)3. E. viminalis Westerfolds x E. viminalis ElthamBlocksSpeciesCompetitionSpecies x Compo70.263430.002280.317670.0628210.00.0912.062.38***NS**NSResidual a210.0263371TimeSpecies x Time442.067870.00252547. 140.67***NSCompo x Time40.000820.22NSSpp. x Compo x Time40.001230.32NSRes i dua I b1120.0037794(b) Shoot dry weight.1. E. viminalis Westerfolds x E. camaldulensisBlocksSpeciesCompetition766.83777180.832651 .308153.158.530.06****NSSpp. x Competition31.343401.48NSResidual2121.2024552. E. viminalis Eltham x E. camaldulensisBlocksSpeciesCompetition755.13296249.035406.399253.7416.880.43*****NSSpp. x Competition37.476152.54NSResidual2114.7515773. E. viminalis Westerfolds x E. viminalis ElthamBlocksSpeci es737.82098O. 101253.880.01**NSCompetition3.367010.35NSSpp. x Competition2.226050.25NSResidual219.7392347*, **, ***, significant at p = 0.5, 0.01, 0.001 respectively;NS, not significant at p = 0.5.

PIN} P 1 N 2 P1N3 P2 N} P2 N 2 P2 N 3 P3 N I P3 N 2 P3 N 3;t~ B.O B.o B.oP as KH2P04 0.5 0.5 0.5 2.0 2.0 2.0N as NH4N03 3.0 12.0 48.0 3.0 12.0 4B.0 3.0 12.0 48.0K as KH2P04 + K2 S04 9.84 9.84 9.84 9.84 9.84 9.84 9.84 9.84 9.84Ca as CaCl2 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0Hg as HgS04 7H20 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0Hn as HnS04 H2 O O. 1 0.1 0.1 O. 1 O. 1 0.1 0.1 0.1 0.1Ho as Ho (NH1\)6 H07024 4H2 0 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05Zn as ZnS047H20 0.1 0.1 O. 1 0.1 0.1 0.1 0.1 0.1 0.1B as H3 BO 30.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2Cu as CUS04 5H20 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02Fe as Fe EDTA 2.0 2.8 2.8 2.B 2.B 2.B 2.8 2.8 2.8pH of solution 5.5 5. 1 5. 1 5.5 5. 1 5.0 4.B 4.9 4.9* Analytical grade reagents used.

43significant differences in the dry weight production of E. viminalis'Westerfolds ' and E. viminalis 'Eltham' (Table 10).The replacement series diagram for the E. viminalis 'Eltham 'xE. camaldulensis combination suggests that some competitive interactionmay have been taking place, as the slope deviates slightly from 45°, butthe major effect is the different growth rates of the two species.Therelative yield total of 0.89 for the E. viminalis 'Westerfolds ' xE. viminalis 'Eltham' suggests some inhibition of both forms when grownin mixed culture, the statistical analysis also indicated that thecompetition effect was significant.Growth at Various Phosphorus and Nitrogen LevelsThe experiment was established to examine the responses ofE. viminalis and E. camaldulensis over a range of nutrient conditions,and to assess the relative nutrient requirements of the species.MethodsE. viminalis and E. camaldulensis seed collected from Westerfoldswas germinated as for the first experiment.Two week old seedlings wereplanted out, four per pot, into 12.5 cm plastic pots containing a 2:1mixture of acid-washed sand and perlite, which was added to improve drainage.Pots were placed on saucers and arranged randomly in blocks, the experimentaldesign being 2 species x 9 treatments x 7 replicates. The treatmentsconsisted of three levels of phosphorus, each of which was applied at threelevels of nitrogen.The composition of the treatments and their nomenclatureis given in Table 11.Seedlings were watered daily with 100 mls of distilled water duringthe first week, followed by 50 mls 12.5% P1N 1 for one week.When seedlingswere four weeks old the strength of the solution was doubled, and at fiveweeks the amount increased to 100 mls.During the sixth week plants weregiven 100 mls of 50% P1Nl. at week seven full strength P1Nl solution was

AN,18l--AE ....E'Q; ""--==Q.... ""1-6H~IIl2l ..I1- 101-61-6,;L;/B/~' /.. J ........-' " -- /"• /// ,'P' /~/ //'fr,II/II'/jI I I12 14 16N Z,'T1Io E vlminalis• E. camaldulensis---Pi - - P z ------P JT114'·2,.,,,, ",·2'·0tH---,i-----ri------~I--12 14 16? LH----~I-------r-----~i--12 14 16WeeksFig. 18. Effect of increasing levels of phosphorus at three levels of nitrogenon height growth of E. viminaZis and E. camaZduZensis seedlings. Vertical barallows comparison of species or treatments at anyone time, and o.f anyonespecies/treatment combination over time. Arrow indicates commencement of fullstrength treatment.

44applied.Nine week old seedlings, which were at the four leaf pair stage,were thinned to three per pot prior to the commencement of full scaletreatment.Treatment solutions were appl ied at the rate of 100 mls dailyand once a week pots were watered with 100 mls of distilled water toprevent possible accumulations of salts.Seedling heights were measured and the experiment was harvestedafter a total of 16 weeks growth in the glasshouse.Leaves were detachedfrom all three plants in five pots of each species in each treatment, andleaf area was measured using a Paton Leaf Area Planimeter.estimated from regression equations for the remaining pots.Leaf area wasOven dryweights of roots and shoots were determined, seedling heights, leaf area,total dry weights and root/shoot ratios were subjected to analyses ofvariance.The heights and dry weights were log transformed prior toanalysis since variances appeared proportional to the means.The heightdata were subjected to a split plot analysis in time.Results1. HeightsAll single factors. species. phosphorus and nitrogen and theirinteractions were significant except for phosphorus x nitrogen; howeverthe phosphorus x nitrogen interaction was significant over time (Table 12).E. camaldulensis generally grew taller than E. viminalis; it showedan increased height growth in response to phosphorus at Nl (Fig. 18a),but for N2 and N3 treatment differences were time dependent, beinginsignificant at 14 and 16 weeks.For the highest level of N (N3, Fig.l8c) there was a trend for the rate of height growth to decline with thehighest level of phosphorus.E. viminalis showed a similar response tophosphorus at N3 (Fig. 18c), but at lower levels of nitrogen, the reactionof E. viminaZis to phosphorus was different from that of E. camaZduZensis.

45Table 12.Analyses of variance of data from seedling response to varyinglevels of phosphorus and nitrogen.Source of Variation df MS FP(a) Heights, 10910 transformed.Split plot analysis in time.Blocks60.026212.54SpeciesPhosphorus23.233575.96366313.33577.87***Species x Phosphorus20.2702126. 18NitrogenSpecies x NitrogenPhosphorus x Nitrogen2240.334130.069580.0241332.386.742.34*****NSSpecies x Phos. x Nit.40.028722.78Residual a1020.01032TimeSpecies x Time220.118270.045849.843.81***-:.Phosphorus x TimeSpecies x Phos. x Time440.051840.007654.310.64**NSNitrogen x TimeSpecies x Nit. x TimePhos. x Nit. x TimeSpp. x Phos. x Nit. x Time44880.050690.005220.040320.000934.220.433.350.08**NS**NSResidual b1920.012021(b) Dry we i ghts. log 10 transformed.Blocks60.025911.68NSSpeciesPhosphorus23.021720.53016195.5634.31******Species x Phosphorus20.101256.55NitrogenSpecies x NitrogenPhosphorus x NitrogenSpecies x Phos. x Nit.22440.205160.050860.040910.0050013.283.292.650.32*****NSResidual1020.015452(cont.)

46Table 12 (cont.)( c) Leaf areaBlocks 6 10.54073 3. 14Species 74.29018 22. 13Phosphorus 2 183.27744 54.60Species x Phosphorus 2 7.95721 2.37Nitrogen 2 101.99558 30.38Species x Nitrogen 2 16.32363 4.86Phosphorus x Nitrogen 4 6.05313 1.80Species x Phos. x Nit. 4 2.64994 0.79Residual 102 3.356729**'1:*'1:-;~*~r:NS**1.*"1,NSNS(d) Root/shoot rat i osBlocks 6 0.00907 1.28Speci es 0.07975 11 .21Phosphorus 2 0.25617 36.01Species x Phosphorus 2 0.03454 4.85Nitrogen 2 0.00408 0.57Speci es x Nitrogen 2 0.01582 2.22Phosphorus x Nitrogen 4 0.00927 1. 30Species x Phos. x Nit. 4 0.01201 1.69Residual 102 0.007114NS-h:****~':*NSNSNSNS*, **, *** significant at p = 0.5,0.01,0.001 respectively;NS, not significant at p = 0.5.

48it continued to increase in response to increased nitrogen supply evenwhen phosphorus levels were high (compare P3 NI. P3 N2. P3 N3).Bothspecies produced their maximum leaf areas at P3 N3.4. Root/shoot ratiosSpecies. phosphorus as main effects and their interaction significantlyaffected root/shoot ratios (Table 12).E. viminalis root/shoot ratiosgenerally decreased in response to increasing levels of phosphorus, whi 1stthose for E. camaldulensis were not so affected, and in fact at N3itsroot/shoot ratios increased with increasing levels of phosphorus.Seedling Growth in the FieldMethodA preliminary field trial was established in December 1975 as soonas fences were erected to exclude stock. E. camaldulensis seed1 ingswere grown from seed collected at Westerfolds, however the E. viminalisseed used was from Kyneton, as capsules collected at Westerfolds containedonly chaff that year.6y mid-January many of the E. viminalis and some ofthe E. camaldulensis seedlings had died of drought stress, by earlyFebruary almost all seedlings on both sites were dead.For the second field trial seed was collected from 8-10 maturespecimens of E. viminalis and E. camaldulensis at Westerfolds, germinatedin a constant temperature (23 0 C)room in petri dishes and planted out intosmall plastic pots (8 em diameter x 7 em depth) fi lIed with one part sand,one part krasnozem soil and growth continued in the glasshouse for a furtherfive weeks.After an eight week hardening off period outside the glasshouse,18 seedlings of each species were transplanted to each of the fieldsites (6 and C) at Westerfolds. Seedlings were planted in a random blockdesign 35 cm apart within 30x30 m wire, rabbit-proof enclosures.Duringthe following 12 months (June 1976-July 1977) seedl ing heights wererecorded every two months and measured again in April 1978; heights were

A100aE. vi.in,li,80• E. CI ..,ldu... i.--- E. villli.llis soil------ E. Clllllld_sis soil/,-,fJ"~,-",-",-,-,-",-,-,-"""~,O,-,-,-..." ....0II r20 30 40 50 60t t w..bJune 1978 Jlttuary 197770tJUI'II 1977809010011080B0E. villljnllil"#.60:I~40-S•c!20~E. Cllllliduflftlil0E. villliOliis soil E. CI"'lklu.sis soilFig. 20. A, Height growth rates of E. viminaZis and E. camaZduZensisfor field trials at E. viminaZis and E. camaldulensis sites atWesterfolds. Arrow indicates time at which most deaths (29.6%)occurred. B, Percentage death rate after 22 months of E. viminalisand E. camaldulensis field trials grown at E. viminalis andE. camaZdulensis sites.

49measured to the top of the growing shoot, and deaths were recorded.Hei,ght data were subjected to analyses of variance.Res ul tsA significant difference in height growth between the species wasevident (Table 13); Fig. 20a indicates that E. viminalis, taller thanE. camaldulensis when planted, grew better than E. camaldulensis on bothplots unti I the summer of 1977.Subsequently there was a high death rateamongst E. viminalis on the E. viminalis plot, and remaining seedlings grew.~slowly" E. viminalis on the E. camaldule~~is plot continued to grow muchfaster than any other group.The mean height growth of E. camaldulensiswas similar for both sites.Percentage death rate for E. viminalis on the E. viminalis plot was72% (Fig. 20b) , and most of these seedlings died from drought stress insummer.Twenty-eight percent of the E. camaldulensis seedlings on thisplot also died, the survivors tending to be the larger, better establishedplants.Only two E. viminaZis seedlings (11%) died on the E. camaldulensisplot, but 39% of the E. camaldulensis died, 28% during summer.By Apri I1978 E. viminalis seedlings were dominating the E. camaldulensis plot;although E. camaldulensis replicates were as tall as the E. viminalis,their dry weights and leaf areas would be much smaller (Plate 4a).Onthe E. viminaZis plot, less than 30% of the E. viminalis had survived, but-'."The decrease in height shown in Fig. 20 reflects the inclusion of deadseedl ings as zero height since a measure of the success of the specieswas required.The zero values did not affect the analysis greatly,since analysis of variance is somewhat robust and a non-parametric testshowed similar significant results (p,Y. Ladiges, pers. comm.).

50Table 13.Analyses of variance of height growth data for field trials.Source of Variation df MS F p(a) Ti me 1Species 1104.5 72.02~I:*"i':Treatment 6.72222 0.46 NSSpecies x Treatment 4.01389 0.27 NSResidual 68 14.72263(b) Time 2Species 1116.28125 49.37 ***Treatment 50.83681 2.25 NSSpecies x Treatment 12.92014 0.57 NSResidual 68 22.60927(c) Time 3Species 1196.42014 27.25 ***Treatment 129.33681 2.94 NSSpecies x Treatment 103.92014 2.37 NSResidual 68 43.90870(d) Time 4Species 1417.78125 14.23 ***Treatment 14]1.53125 14.77 ***Species x Treatment 452.50347 4.54 *Residual 68 99.61254(e) Time 5Species 589.38889 1.97 NSTreatment 5724.5 19.12,~fd.Species x Treatment 4802.0 16.04***Residual 68 299.38399(con t.)

51Tab 1 e 13 (con t. )( f) Time 6Species 220.5 0.44Treatment 6593.34722 13 .24Species x Treatment 5512.5 11 .07Residual 68 497.87214NS-h***-;'t-;I:;(g) Time 7Species 533.55556 0.77Treatment 9706.88889 14.0Species x Treatment 8320.5 12.0Residual 68 693.14216NS**-ir.'1:**(h) Time 8Species 180.5 0.10Treatment 18304.22222 10.0Sp-cies x Treatment 1 28163.55556 15.37Residual 68 1832.35784NS*******. **. ***. significant at p = 0.5. 0.01. 0.001 respectively;NS, not significant at p 0.5.

8PLATE 4A. Seedling growth on the E. camalduZensis field trialplot at Westerfolds, April 1978. Note greater sizeof E. viminalis seedlings.B. Seedling growth on, the E. viminalis field trial plotat Westerfolds, April 1978. Ranging pole indicates,scal~, each band is 30 em high.

52E. camaZdulensis height growth was slightly better here than on theE. camaldulensis plot. Seedlings of both species were subject to insectattack on the E. viminaZis plot, and plants appeared depauperate (Plate4b) .DISCUSSIONThe results of the four glasshouse trials indicated significantdifferences in the growth rates of E. viminalis and E. camaldulensis.Height growth (except in experiment one) and dry weight production wassignificantly greater for E. camaldulensis.The effects of competitionon the growth rates of the two species were not significant, except inthe second experiment where E. viminalis dry weights were significantlydepressed in mixed culture. There was a trend for the height growth andshoot dry weights of E. viminalis to be depressed in culture, whilstthose of E. camaldulensis tended to increase.The replacement seriesdiagrams provided a similar, but visual picture, of the results of theanalyses of variance.The response of E. viminalis and E. camaldulensis in both the monocultureand mixed cultures of experiments one, two and three were at variancewith those obtained in the preliminary experiment, even when similar seedsources (experiment three) were used.It is suggested that the structureof the soil used in these experiments is an important factor affectinggrowth.Topsoil collected from the riverbank at Westerfolds for use inexperiments two and three was very fine-textured; after several weeks ofdaily watering during the growth trials it set into solid blocks in thepots.Soils collected from the field trial sites for experiment onealso tended to compact in the pots to some extent.Beadle (1962) noted that the physical structure of the soil, whichaffects such properties as pore space, drainage, aeration and waterlogging,is destroyed when soils are collected and sieved.Thus where physical

53properties of the soil are influencing the distribution of species,extrapolation from pot trials to field conditions may be misleading.The ability of E. camaldulensis to grow in heavy soi Is has beennoted by Jacobs (1955). and is further discussed in Chapter 5.It issuggested that in the present study E. camaldulensis grew better becauseof the superior abi lity of its root system to grow in heavy soils, andits higher root/shoot ratio which enabled it to exploit the restrictedvolume of the pot quickly.Height growth of E. viminaZis was greater thanthat of E. camaldulensis in both monoculture and mixed culture when thespecies were grown in well-structured garden soil used in the preliminaryexperiment by Ashton. and in the field trials planted on alluvial depositsof the E. camaldulensis field trial plot.I t is suggested that thephysical structure of the soil may be an important factor influencingthe distribution of the two species.Field observations support this hypothesis, but the results of thepercentage disaggregation analysis (Table 5) show that soils at site A,which support E. camaldulensis, had a slightly better structure than soilsat the other sites. However the method employed was not entirely satisfactory.The structure of the complete profile appears to be an importantfactor, particularly in controlling drainage, and in a floodplain environmentwhere depositional lenses of material may occur sporadically in theprofi Ie, two samples at 0-10 cm and 50-60 cm are unlikely to be sufficientlyrepresentative.The results of the field trials indicated that E. viminaZis was ableto grow faster than E. camaldulensis on well-drained, comparatively wellstructuredsoils.It is thought that the slow growth rate and death ofmany E. viminalis seedlings in the E. viminalis field trial plot was theresult of winter waterlogging of the soil. Waterlogging may havedifferentially affected the development of E. viminalis and E. camaldulensisroot systems, so that poorly establ ished E. viminalis seedlings were highly

54susceptible to drought stress when the topsoil dried out during summer.The effect of waterlogging on the root systems of E. viminalis andE. eamaldulensis is further discussed in Chapter 5.The glasshouse results were often difficult to correlate with fieldobservations, and it is felt that pot experiments (as competitionexperiments) may not give a real istic view.The present study has shownthat when the physical structure of the soil affects seedling growth, itis particularly difficult to relate the performance of species in pottrials to their behaviour in the field, and it is suggested that thelimited volume of soil avai lable for exploitation in the pots used mayfurther decrease the validity of such pot trials. The high root/shootratio of E. eamaldulensis may have allowed it to rapidly exploit theI imited volume of the pots to the detriment of E. viminalis. \.Jhere soi 1volumes are less limiting, as in field situations, E. eamaldulensis maynot gain such an initial advantage.Harper (1977) has also pointed outthat in competition experiments it is difficult to know whether theinteraction between plants is taking place above or below ground.E. camaldulensis overall grew faster than E. viminaZis in sandculture but responses to phosphorus and nitrogen differed. The root/shootratios of E. viminalis declined with increasing levels of nutrients, whilstthose for E. eamaZdulensis increased.Ladiges (197~) found that root/shoot ratios of E. viminaZis seedlings from five populations generallydecreased as nutrient levels were increased, and suggested that as aresult E. viminaZis may be more susceptible to drought on fertile sites.E. viminaZis continued to respond to increased applications of nitrogen(N2 to N3) and may have a higher optimum for some nutrients thanE. camaZdulensis. It is suggested that the levels of phosphorus applied(0.5, 2, 8 mg/l) may have been too low to el icit optimum responses fromboth species, since dry weights continued to increase as nutrient levelsincreased.However, these values are realistic in terms of available

phosphorus levels measured for soi Is.Upper values of 50 mg/l used byothers (eg. Attiwill 1964) seem high, although it is still difficult todetermine rates of appl ication for sarod culture experiments.As in the present study, and that of Attiwill (1964), Parsons (1968b)was unable to establish optimum levels of response for three malleeeucalypts to phosphorus over a range of levels, 0-15 mg/l whilst nitrogenwas varied concurrently (5-300 mg/l), although the highest nutrientapplication apparently represented higher nitrogen and phosphorus levelsthan those found in the soils supporting the species.Studies by Moore and Keraitis (1971) on the effect of nitrogen sourceon the growth of eucalypts in sand culture have shown that the form ofnitrogen suppl ied affects the growth rates of eucalypt species, and thusmay mask the effects of factors being tested. Woodland species tested mademaximum growth where ammonium did not exceed one half of the total nitrogentreatment, whilst forest species behaved quite differently.However therewere some differences within these groupings, and it was not possible topredict the preferred nitrogen source for a eucalypt species from itstaxonomic classification or ecological habitat.In the present studynitrogen was supplied as ammonium nitrate, but it was difficult to be surethat the optimum forms or concentrations for E. viminaZis andE. camaZduZensis were suppl ied.Limited studies of the soil nutrient status carried out at the fourfield localities provided no conclusive evidence for any differences insoil fertility which could have influenced the distribution of the twospecies in the Yarra Valley.In addition, there was no significantdifference in the growth rate of each species on the topsoils collectedfrom beneath E. viminaZis abd E. camaZduZensis stands at Westerfolds(experiment one).However grazing and top dressing at sites A, Band Cmay have substantially altered the soil fertility.

56Mueller-Dombois and Ellenberg (1974) have emphasized that thecompetitive capacity of a species varies with habitat factors.In thepresent study the competitive abi lity of E. viminalis andE. camaldulensis appears to be dependent on the physical structure ofthe soil, which may thus influence the distribution of the two species.Further experimental work will be carried out to examine this possibility.SUMMARYThe results of the pot trials indicated that E. camaldulensis has afaster growth rate than E. viminalis in both monoculture and mixed culture.However field trials Support the hypothesis that E. viminalis is able toout-compete E. camaldulensis on well-drained, well-structured soils. Fromthe limited soil analysis undertaken it appears that soi 1 fertil ity is notan important factor in determining the distribution of the two species.It is suggested that the physical characteristics of the soi I mayinfluence local distribution.

57CHAPTER 4SEEDLING TOLERANCE TO DROUGHTINTRODUCTIONIn the Yarra Valley area the forest form of E. viminalis is generallyriparian, and extends from the foothi 11s zone of the Great Dividing Rangeto about the 700 mm isohyet. Woodland forms of this species may also occuron the duplex and gradational soils of Teriary sandy cappings, and onkrasnozem basalt soils where M.A.R. is between 700 and 800 mm.E. aamaldulensis dominates the riparian environment where rainfall is lessthan 700 mm per annum.It extends onto undulating Silurian topography, andonto the heavy soils of the basalt plains where-M.A.R. is 550-700 mm.AtWesterfo1ds the two species cohabit on the alluvial flats and are found toa limited extent on Silurian mudstone topography.The death of six-month-01d, hardened seedlings planted out as a fieldtrial at Westerfo1ds (Chapter 3) suggested that seedling tolerance tolimiting soil moisture conditions may be an important factor in the establishmentof trees, and may confine E. viminalis to soils which are relativelywell drained, yet have a high water holding capacity.The influence of limiting soil moisture conditions on the distributionof eucalypt species has been studied by a number of workers.Specht andPerry (1948) correlated the distribution of some tree species in the Mt.Lofty Ranges of S.A. with the water retaining capacities of soils. Hollandand Moore (1962) related the distribution of some species in the BollonDistrict (Qld.) to soil moisture status, and Florence (1964) has suggestedthat the vegetational pattern in Australian east coast forests is influencedby physical properties of the soil, including soil moisture availability.Pook, Costin and Moore (1966) correlated observed drought damage of eucalypt

58species with soil texture and depth and resultant differences in moisturestorage, suggesting that occasional severe droughts may be a contributoryfactor in the distribution of eucalypt communities.Lamb and Florence(1973) have shown that the distribution of E. fas~igata in the A.C.T. maybe delimited by smal I variations in soil properties influencing root movementand penetration of light summer rainfall. Ashton, Bond and Morris(1975) related the distribution of dominant species along a moisture gradientto their relative tolerance to droughted conditions.Parsons (1969) hasshown that competition for water under I imiting soil moisture conditionsmay influence the distribution of E. socialis and E. incrassata, andKirkpatrick (1970) has suggested that the distribution of E. sideroxyZonand E. gZobulus x bicostata in the Otways region may be related to competitionand the relative drought tolerance of these two species.In the present study pot trials were established to compare thebehaviour of E. viminalis and E. camaldulensis seedlings under droughtstress. Habitat differences were examined by the description of soilprofiles and measurement of soil moisture conditions over a 12 month period.HETHODSSoil Moisture CharacteristicsSoil samples were collected from the E. viminaZis field trial ploton an upperslope and from the E. camaZduZensis site located on lowerterrace deposits at Westerfolds for the gravimetric determination of soilmoisture from June 1976 to July 1977.Five replicates were collected fromeach site at depths of 0-10 em and 50-60 em.Seedling Behaviour under Drought StressSeed of E. viminaZis and E. camaZdulensis collected at Westerfoldsin the Yarra Valley was germinated in petri dishes in a constant temperature

59room.Due to fungal attack additional seed was germinated six days later,and seedl ings from both germinations were initially established in si liceoussand to which was added a full nutrient solution (Aquasol. at the rate of50 mls of 0.125 g/Aquasol/l, then 50 mls of 1 9 Aquasol/l). After fourweeks growth seedlings were pricked out and transferred to plastic pots of12.5 cm diameter, containing a 1:1 mixture of loam and sand. Growth inthe glasshouse continued for a further three months, during which seedlingswere thinned to one per pot.Pots were then moved outside to harden offfor five weeks.Twenty seedlings (aged five months) of each species were returned tothe glasshouse and watered until the soil was near field capacity. Thepots were then sealed to prevent direct waterloss from the soil, and placedinside larger earthenware pots to prevent overheating of the soil (Ladiges1974). Each species was divided into two groups: water was withheld fromthose to be droughted, whilst the control pots received as much water dailyas was necessary to maintain their initial weight.The daily transpirationrate of each plant was measured over six days by weighing the pots eachmorning at 7 am, measurements were expressed as waterloss in g/24 hours/dm 2leaf area.Regression equations for leaf area/weight relationships werecalculated for five seedlings of each species and each treatment separately.This enabled leaf area estimates to be made for the remaining plants,particularly severely drought damaged plants whose dead leaves were difficultto measure directly. Daily transpiration rates were subjected to an analysisof variance.Leaf water potentials were estimated on days four and six of theexperiment, using the Wescor Model C-51 Sample Chamber combined with theDew Point Microvoltmeter (Campbell. Campbell and Barlow 1973).Five tosix plants per population x treatment unit were sampled.With this methodreduction in leaf area during transpiration measurements was minimal, since

A2°1 E. vimlnaiis soilIE. camaldulensis soilIII15,10"';5--////T/...I( II ITI1(a) IIII---XIIr1.l-I1 !ITrIIf ,I f ...rfi I I"" \ T T 1!IIbl ~ V.- .-JI , "'"\1 .... .- .-I ...... :I "-... ' TrT r \.\. ..---..I,.. II .... - , II , ... I...r .I- T '\, .I..I. ... 1.I-"- ! I, , ...'-*Cll'-~.....'"aE'0en°2°11510J J A S 0 N 0 J F M A M J J1976 1977B r IrT1r1II(a)iI1I1/IIr! I/\'T If ,f I I5 / T \'\ f I r/....- I "- / \ I.... .- "- /, I I;/ \ I"- r-- ~-.-~~.-/\ I I"- I / \ II -J.'-' I\._--- \ !(bl I T r r , I I.... rr..L I I T :::: .L II I .L..L J..L :::-'-"TI/III/ T/////T....,//IIIIIJ J A S 0 N 0 J F M A M J J1976 1977Fig. 21. Percentage soil moisture for soils from E. viminaZis (Site C) andE. camaZduZensis (Site B) field trial plots at \~esterfolds. At 0-10 em depth;S, 50-60 em depth. Bars indicate ± standard error. Where there are no errorbars fewer than five replicates were used.

60only one disc ( 0.8 cm diameter) was removed from anyone plant.After the sixth day of treatment all plants were rewatered and leftto recover for three days.The shoots of each plant were harvested, andthe leaves cut into dead and alive areas, oven dried and weighed.Droughtdamage was estimated by calculating the percentage of dead leaf material.Percentages were subjected to a T test, normality and homogeneity of thevariance being assumed.RESULTSSoil Moisture CharacteristicsDescriptions of soil profiles at the Westerfolds E. viminalis andE. camaldulensis plots are given in Table 1 (see Chapter 3). Soil moisturecontents throughout the year were generally higher at the E. viminalis site(Fig. 21), although differences in the topsoi 1 were not as marked as thoseat 50-60 cm depth.Examination of the percentage soil moisture values forthe field trial sites over a 12 month period (Fig. 21) indicated thatboth the topsoil (except in spring 1976) and subsoil of theE. viminalissite generally contained more moisture than the soils of the E. camaldulensissite. The high variability in subsoil replicates is attributed to changesin the depth and distribution of clay across the study sites. The pF values(Fig. 10 , Chapter 3)indicated that the slightly sandier E. viminalis topsoilwould contain less available water than the topsoi 1 of theE. camaldulensis site, however the E. viminalis plot is situated'on aslowdraining 'slope and is waterlogged during winter. The nature of thesubsoil at the E. camaldulensis site is very variable; the alluvial soilsalthough deep are sandy, whilst the clay subsoils derived from Silurianparent material are comparatively shallow.Both subsoils at this sitewould have less available water than the E. viminalis subsoil, and probablydry out more rapidly in summer.

61Table 14.Analyses of variance of transpiration data.Day Source of Variance df MS F P

20A1816,... ,.EI..........14 ,. 0~:!-- --,..''"..Iff:.".....IN--- -"-...d~ .........12... ... ..... '0"'....•~ 10:!. g~ 8.Q.~ 6oE. viminllil• E. Clmllduleflsiscontrol pllnts,.,-drought.d pllntl,. ,4202 3 5 630B...•. ,..... ." ..•.. ' ..•....... -............ . m8JlimumrnHn daily............... _-- minimumt54-____ ~---~-~~~~-~-~~~-~-~-r~--~~--~2 3 4 5 690"l/I.XC 70C:" _-----.. mean daily.......-~.50 minimum2 3 4 5 6Fig. 22. A. Transpiration rates for control and droughted plants ofE. viminaZi8 and E. camaZduZensis; B, air temperature; C, relativehumidity of glasshouse.

62Seedling BehaviourNo significant differences were observed in the transpiration ratesof E. viminalis and E. camaldulensis (Table 14, Fig. 22 ). On day one ofthe experiment, the transpiration rates of the droughted plants of bothspecies were higher than those for the controls (possibly a samplingeffect), but thereafter they decreased abruptly.The more rapid decreasein the transpiration rates of droughted E. camaldulensis suggests that itwas able to more quickly control transpiration by stomatal closure.Increases in the rates of transpiration of the controls occurred afterday four, paralleling increases in glasshouse temperature.This increasedrate of water loss was also reflected in the decrease in the leaf waterpotential of control plants (Table 15) observed between days four and six.Table 15.Leaf water potential (bars) for droughted and freely wateredplants on days 4 and 6 of experiment.Values for day 4 are calculatedfrom 5 replicates, those for day 6 on 6 replicates.Day 4 I Day 6IE. viminalis (control) -17.3 -23.2E. v imina lis (droughted) -37.9 -43.5E. camaldulensis (control) -15.5 -25.0E. camaldulensis (droughted) -39.2 -46.0Droughtedreplicates of both species began to show signs of wiltingon the second day, the onset of wilting appeared to be related to plantsize. By the fourth day all the droughted E. camaldulensis and somedroughted E. viminalis were wilted, and by the sixth day all droughtedplants of both species were wilted.Plants wilted from the tips initially,

63however tissue death was more extensive In the lower leaves.Death of thelower leaves was more marked in Z. camaldulensis, and leaf abscission hadbegun by the sixth day. Measurements of leaf water potential (Table 15)suggest that droughted E. camaZdulensis may have been subject to greaterwater stress, however with the limitation of only one sample chamberinsufficient replicates were sampled for these measurements to be statisticallysignificant.Table 16 shows that the root/shoot ratio, total dry weight, total leafarea and percentage leaf death of droughted seedl ings was significantlygreater for E. camaZduZensis than for E. viminalis.Since E. camaZdulensisseedlings were 66% larger and had a greater transpirational area, yet weregrown in the same sized pots, they were therefore probably subject toearlier drought stress than the E. viminaZis seedlings.The lower leafwater potentials recorded for E. camalduZensis give some indication of this.Table 16.Means and standard errors (parenthesis) of leaf area, dryweight and root/shoot ratios for droughted seedlings.Means significantlydifferent at p '" 0.5 (*), .001 ('b·~"'~).Root/Shoot Total Dry Total Leaf % DeadRatio Wt. (g) Area (dm 2 ) LeavesE . viminaZis 0.33 5.48 3.76 51.0(0.04) (0.63) (0.61) (9.70)E. camaZduZensis 0.41 9. 11 5.68 71.8***,'d~* ...':-;':-/- "1:

DISCUSSIONThe transpiration responses of the droughted seedlings are in agreementwith those reported by Lubrano and Tarsia (1973).When water waswithheld successively from groups of potted E. viminalis and E. camaldulensisseedlings aged 1t, 3t, 5. 6t, 7t and 10 months, no significant speciesdifferences in transpi ration rates, water saturation deficits or plantmoisture contents were observed.As reported for the present study, Quraishi and Kramer (1970) foundthat E. camalduZensis when droughted, suffered severe injury.In acomparison of the effects of soil water stress on potted seedlings ofE. rostrata (E. camaZdulensis)~ E. polyanthemos and E. sideroxylon, theyfound that E. camaldulensis which had a relatively high transpiration rateunder non-limiting moisture conditions, depleted soil moisture reservesmore quickly than the other species when water was withheld.They attributedthe greater injury suffered by E. camaldulensis to its later stomatalclosure and higher rate of cuticular transpiration.In the present study,the rate of decrease in transpiration losses indicated that stomatal closureprobably occurred earlier in E. camaldulensis, and that cuticular transpirationwas slightly lower than for E. viminaZis.Pot experimentsinvestigating the water relations of E. camaldulensis and E. globulus(Pereira and Kozlowski 1976) indicated that E. camaZdulensis was lessdrought resistant than E. globulus,a species which throughout itsrange would occasionally be subject to moderate summer drought, but ingeneral occurs in higher rainfall zones.Under droughted conditions plantwater stress increased more rapidly in E. camaZduZensis, its higher transpirationrate was associated with larger numbers of stomata on both leafsurfaces.Extensive development of the E. camaldulensis root system inthe restricted volume of soil in the pots also induced greater waterdeficits than developed in E. globulus.However, when seedlings of bothspecies were grown in long plastic tubes with an unrestricted soil volume,

65water stress did not develop more rapidly in Z. camalduZensis than inE. giobulus, indicating that a major factor in the drought avoidance ofE. camaZdulensis was the capacity to produce a deep, extensive rootsystem capable of obtaining water from deep soil layers after the topsoilhas dried out.The development of a deep root system probably enables E. camaldulensisto survive prolonged periods of drought in the field.Levitt (1972) hassuggested that certain species are able to avoid drought in spite of hightranspiration rates "by extracting larger quantities of water from the soilper unit time and leaf surface".A high root/shoot ratio provides a highratio of water absorbing to water evaporating surface, and may enableexploitation of deeper water reserves in the soil.Zimmer and Grose (1958) have correlated the possession of high root/shoot ratios in eucalypts with certain habitat factors; species with highroot/shoot ratios generally occur in dry areas where summer temperaturesare very high.Furthermore, Parsons (1969) has suggested that the largerroot/shoot ratio of E. socialis may be a consistent genotypic differencewhich can be expected to confer superior drought avoidance. Jacobs (1955)has suggested that the high root/shoot ratio typical of E. camaldulensispermits the development of a deep, foraging root system before the shootbecomes too large. and Awe et al. (1976) have demonstrated that the abilityof E. camaldulensis to establish successfully in a drying soil profile islargely dependent on its capacity to produce a massive root system veryquickly.Additionally, the -abscission of the lower leaves observed inE. camaldulensis under droughted conditions by Pereira and Kozlowski (1976),and in the present study in the glasshouse and field trials. may indicatean adaptive response.The ability of a plant to survive drought may beenhanced by a reduction in surface area (Levitt 1972).Field trial observ-

66ations indicate that E. camaldulensis is able to p~oducenew foliagequickly once soil is rewetted.The greater damage suffered by E. camaldulensis in the present studyresulted from mo~erapid depletion of soil moisture by its larger rootsystem and transpi~ationlosses from its significantly larger leaf area.In the field the higher ~oot/shootratio of E. camaldulensis should enableit to tolerate limiting soil moisture conditions more readily thanE. viminalis. At the Westerfo1ds field trial site the extensive rootsystem of E. camaldulensis would assist in the establ ishment and survivalof seed1 ings on the sandier soil profiles where subsoil moisture reservesare smaller during the summer period.Comparison of species is also complicated by population variation.Population differences in the drought resistance of forest and woodlandforms of E. viminalis have been demonstrated by Ladiges (1974, 1975, 1976);the most tolerant population occurring in a low rainfall area on a shallowsoil with poor available water storage.In the Yarra Valley, since theforest form of E. viminalis is essentially riparian, it may be more susceptibleto drought under field conditions in drier sites, particularly ifthere is competition with E. camaldulensis for scarce moisture resources.SUMMARYPot trials indicated no significant difference in the transpirationrates of droughted E. viminalis and S. camaldulensis, and limiting soilmoisture conditions induced greater injury in E. camaldulensis.It isconcluded that the purported advantage of E. camaldulensis over E. viminalis,to produce an extensive root system able to maintain water supply underdroughted conditions, was obscured by the use of pots in which the soilvolume was limited.In the field it is expected that the high root/shootratio of E. camaldulensis would result in superior drought avoidance.

67CHAPTER 5THE RELATIVE TOLERANCES OF E. VIMINALIS ANDE. CAMALDULENSIS TO WATERLOGGINGINTRODUCTIONAs indicated in Chapter 1, E. viminaZis and E. camaZduZensis occurover a wide range of soil and rainfall conditions.However, each speciesshows habitat preferences - most forms of E. viminaZis occur on moist welldrainedsites, whilst E. camaZduZensis is usually found on heavy soi Issubject to periodic waterlogging.In the riparian environment of theYarra Val ley, E. camaZduZensis tends to occur in localities which by virtueof their topography and/or soil structure tend to be more frequently waterlogged.The hypothesis that E. camaZduZensis is more tolerant thanE. viminaZis of such soil conditions was tested in a pot experiment. Theeffects of waterlogging on soil conditions and plant distribution arereviewed.THE EFFECTS OF WATERLOGGING ONSOILS AND PLANTSThe extent to which plants are able to tolerate waterlogged soilconditions is dependent on the relative tolerance of the species or localpopulation, on edaphic factors, and on the timing, depth and duration offlooding.Changes in SoiZ ConditionsChanges in soi 1 conditions associated with the onset of flooding orwaterlogging may result in a habitat which can only be occupied by plantstolerant of these conditions.Waterlogging may result from inundation ofthe soil by flood waters, poor soil permeability. the presence of an

68impervious layer in the profile, or a high water table (Ponnamperuma 1972).An excess of water in the soil displaces air from the non-capillarypore space, and slows down the rate of gaseous diffusion between the soiland the atmosphere, which results in the onset of anaerobic conditions.Within a few hours, soil micro-organisms reduce almost all the molecularoxygen present (Ponnamperuma 1972).Soil microbes capable of anaerobicrespiration now reduce combined forms of oxygen or other electron acceptors,often producing substances toxic to plants. According to Russell (1973),the principal inorganic reductions are nitrate to nitrite, manganic saltsand manganese dioxide to manganous ions, ferric hydroxide to ferrous ions,hydrogen ions to hydrogen gas and sulphates to sulphites and sulphides.Inthe early stages of flooding, anaerobic decomposition of organic matterresults in the production of nitrogen and nitrous oxide, hydrogen gas and arange of low molecular weight hydrocarbons, including methane and ethylene.Toxic substances formed in waterlogged soils include methane, methylcompounds and complex aldehydes; ferrous ions, nitrites, sulphides andmanganous ions may also accumulate to toxic levels (Kramer and Kozlowski1960). Ethylene production also increases, and many plant responses toflooding have been attributed to its accumulation (Russell 1973, Kawase 1974,Jackson and Campbell 1975, 1976).Edaphic factors which may influence plant responses to waterlogginginclude soil textures, structure and the supply of decomposable organicmatter.Heavy soils with limited pore space normally have low rates ofoxygen diffusion, so that soils with a high clay content are likely to havea greater degree of root anaerobiosis.Accumulation of toxic products alsotends to be more acute in heavy textured soi Is (Gill 1970).The presence ofhardpans or impermeable layers in soils also impedes the diffusion of gasesand prevents water from draining out of the soil surface layers (Kramer andKozlowski 1960).The nature and content of soil organic matter has some

69influence on the course, rate and degree of reduction (Ponnamperuma 1972),the effects of waterlogging being more marked in soils with a high organicmatter content, since greater microbial activity is possible (Russell 1973).Smith and Dowdell (1974) have suggested that under some conditions theavailabil ity of substrates for microbial activity may be the limitingfactor controlling the production of ethylene.Plant ResponsesInterspecific differences in the waterlogging tolerance of maturewoody species have been reported by Green (1947). Parker (1950) and Hosner(1958, 1959. 1960); and for seedl ings of woody species by Boden (1963),Bannister (1964). Ladiges and Kelso (1977) and Pereira and Kozlowski (1977).Significant differences in tolerance have also been observed between populationsof a single species (Karschon and Zohar 1972, 1975; Ladiges andKelso 1977).Reasons for such observed differences are thought to berelated to structural differences which result in a better oxygen supply tothe roots of some species, or to physiological differences in cell tolerationof the products of anaerobic respiration or a combination of these (Kramer1969) .The timing of the onset of waterlogged conditions influences theresponse of some plants.Many conifers and deciduous species are relativelyinsensitive to waterlogging during their dormant season (Gill 1970).Plantsalso differ in their ability to tolerate varying degrees of waterlogging,from soil saturation, partial inundation of the shoot to total submergence.Demaree (1932) reported that total submergence of Taxodium seedlings resultedin death; however,seedlings half submerged in the cotyledon stage were ableto produce leaves.Dexter (1967) found that differential survival of floodedE. camalduZensis seedlings was related to seedling height, and depth andduration of flooding.The duration of waterlogging has also been shown toaffect seedling survival (Karschon and Zohar 1972); Hosner (1958) hasrecorded differential species survival dependent on the duration of sub-

70mergence.Kawase (1974) has established a quantitative relationshipbetween degrees of flood damage symptoms and duration of flooding.Initial reactions of the plant to poor soil aeration include decreasedabsorption capacity of the root, due to a reduction in its permeability towater because of oxygen deficiency or carbon dioxide excess (Kramer 1969).Decreased absorption results in water deficits, wilting, decreased nutrientuptake, a reduced transpiration rate (Parker 1950, Kramer 1951, Bannister 1964),and a decrease in photosynthesis (Regehr, Bazzaz and Boggess 1975).The Effects of Waterlogging on Root SystemsThe long term effects of inadequate aeration on root systems isreduction in size (Parsons 1968) or even death (Kramer 1969).Changes inroot distribution of plants under waterlogged conditions have also beenobserved (Parsons 1968, Wample and Reid 1975), including a strong developmentof surface rooting systems (Williams and Barber 1961, Boden 1963), and negativegeotropism of surface roots (Clucas 1977, Pereira and Kozlowski 1977).The formation of adventitious roots, usually from the stem, is a commonresponse to flooding recorded for a wide variety of species (Kramer 1951,Boden 1963, Kawase 1974, Jackson and Campbell 1975, Clemens and Pearson1977, Ladiges and Kelso 1977). It is thought that adventitious root formationmay be an adaptive characteristic, providing the plant with an auxilIaryroot system in a relatively aerobic zone where they can respire and sofulfill their absorptive functions (Gill 1970).Resumption of shoot growthin waterlogged tomatoes has been recorded following the development ofadventitious roots (Kramer 1951).However, Gill (1975) was unable todemonstrate any overriding importance of adventitious roots to the floodingtolerance of Al.nus gl.utinosa, and Pereira and Kozlowski (1977) found 1 ittlecorrelation between the capacity for adventitious root production andtolerance to flooding.Kramer (1969) has suggested that blockage of downwardtranslocation of carbohydrate and auxins stimulat~thegrowth of

71adventitious roots, whilst Abeles (1973) and Kawase (1974) suggest thatethylene production also stimulates such development.Uptake by roots of toxic substances including divalent iron andmanganese from waterlogged soils has been recorded by Jones and Etherington(1970) and Jones (19 72a), a 1 though a decrease in manganese was noted byLadiges and Kelso (1977).However, Somers and Shive (1942) considered thatthe relative proportions of these ions were likely to be more significantthan absolute concentrations.Studies of plants growing under waterloggedconditions have indicated a greater concentration of iron in the rootsystems than in the shoot, suggesting that there is some immobilisation ofthis substance in the former.Increase was particularly marked in the rootsof plants which do not normally grow on waterlogged sites (Jones andEtherington 1970, Jones 1972a).Precipitation of iron in the intercellularspaces (Armstrong and Boatman 1967) and cell walls (Green and Etherington1977) has been noted in some flood tolerant species.Plants tolerant of waterlogged soils must be able to maintain sufficientroot oxygen supplies for metabolic functioning and to prevent the accumulationof toxic substances from the soil. Diffusion of atmospheric oxygen from theshoots down to the roots and out into the rhizosphere (Armstrong 1964)results in an oxygen sheath which surrounds the roots.The larger oxygensheaths of flood tolerant species afford better protection against toxicsubstances which must pass through this oxidising zone to reach the rootsurface (Armstrong 1970).The presence of an enzymatic component in additionto the diffused oxygen is thought to account for the high root oxidisingactivities observed in some bog species (Armstrong 1967a).The presence of aerenchymatous tissue in roots has been correlated withthe ability of roots to survive in poorly aerated environments (Cannon 1940)and of some species to grow under waterlogged conditions (Martin 1968).Martin (1968) has suggested that although the development of extensive

72intercellular air spaces in roots may be superfluous in supplying oxygen fornormal respiration (Williams and Barber 1961), it may be regarded as anadaptation to provide for an oxidising environment around the root, asdescribed by Armstrong (1970).The development of intercellular air spacesreduces the amount of tissue requiring oxygen in the root. and allowsoxygen diffusion into the rhizosphere, enabling oxidation of toxic reducedsubstances.Aerenchyma is also thought to act as an oxygen reservoir duringperiods of prolonged stomatal closure (Conway 1937 • Armstrong 1967b).The Effects of Waterlogging on the ShootMorphological responses of the shoot system to waterlogging includedownward roll ing of leaf laminae (Jackson and Campbel I 1975) which maypreceed petiole epinasty (Kramer 1951, Kramer and Jackson 1954, Kawase 1974,Jackson and Campbell 1975, 1976; Clemens and Pearson 1977) and leaf chlorosis(Kramer 1951, Kramer and Jackson 1954, Kawase 1974, Clemens and Pearson 1977),which may be followed by abscission of flowers, fruits and leaves, particularlyof the lower leaves (Kramer 1951. Parsons 1968, El-Beltagy and Hall 1974.Clemens and Pearson 1977. Ladiges and Kelso 1977. Pereira and Kozlowski 1977).The appearance of these symptoms may be followed by accelerated senescence.The development of basal stem hypertrophy. enlargement of the corticalcells and intercellular spaces soon after the onset of waterlogged conditionshas also been recorded for a variety of species (Kramer 1951. Boden 1963,Kawase 1974, Clemens and Pearson 1977. Clucas 1977. Ladiges and Kelso 1977).Retardation in shoot growth rates is also common (Kramer and Jackson 1954,Boden 1963, EI-Beltagy and Hall 1974, Kawase 1974. Clemens and Pearson 1977,Ladiges and Kelso 1977).Increased synthesis of ethanol, abscissic acidand ethylene, and reduced levels of giberellins and cytokinins have beenimplicated in the production of morphological changes in the shoots offlooded plants (Wample and Reid 1975 and references therein).

73ihus morphological changes in waterlogged plants seem to be induced bya complex set of interactions between the soi 1 environment and various planthormones. These changes have been classified by Wample and Reid (1975):dwarfing, leaf chlorosis and petiole epinasty result from root anaerobiosis,but stem hypertrophy and adventitious root development are induced merely byan excess of water around the roots and hypocotyl.Although some authorshave correlated certain morphological responses, such as the developmentsof adventitious roots, with tolerance to waterlogging (Boden 1963, Gill1970), it is not clear which responses have adaptive significance.Intolerant species often display the same symptoms as those shown by plantstolerant of waterlogging, but these are indicative of senescence (Clucas1977) .Metabolic Responses to WaterloggingUnder anaerobic conditions, the rate of glycolysis in plants sensitiveto waterlogging is accelerated when pyruvate is decarboxylated to producecarbon dioxide and acetaldehyde. The acetaldehyde is reduced directly to..ethanol by the enzyme alcohol dehydrogenase. McManmon and Crawford (1971)found a highly significant correlation between alcohol dehydrogenase activityand plant sensitivity to waterlogging.Plants intolerant of flooding areunable to control the rate of glycolysis which increases with the onset ofanaerobiosis, and results in the accumulation of toxic products includingcarbon dioxide, ethanol and acetaldehyde (Crawford 1966).Flood tolerantspecies are able to avoid such an acceleration, producing a wide range ofnon-toxic end products.Accumulation of organic acids including malate (Crawford and Tyler 1969)and succinate (Crawford 1967) have been noted in some waterlogged plants.Other organic acids such as shikimic may be produced as intermediate metab-01 ites (Boulter, Coult and Henshaw 1963). Tolerant species may undergo ametabo Ii c swi tch from ethano I to ma 1 ate product i on (C rawford and Ty 1 er 1969).

74Waterlogging also induces the degradation of protein, resulting in anincrease in the concentration of free amino acids in roots and shoots(van der Heide, de Boer-Bolt and van der Raalte 1963).Garcia-Nova andCrawford (1973) suggest that this response may be an adaptation to suchconditions.Associated changes in the nitrate metabolism of flood tolerantspecies result in the provision of alternative electron acceptors and a meansfor disposal of hydrogen ions -increasing the capacity of the plant to withstandwaterlogged conditions.THE INFLUENCE OF WATERLOGGING ON PLANT DISTRIBUTIONThe local distribution of certain species has been correlated withthe presence of anaerobic conditions, and the subsequent accumulation ofelements in toxic concentrations which results from waterlogging of the soil(Bannister 1964, Crawford 1966, Armstrong and Boatman 1967, Martin 1968).High levels of ferrous ions (Martin 1968, Jones and Etherington 1970,Jones 1972a) and manganous ions (Jones 1972b) have been shown to exclude somespecies from waterlogged sites. Some species tolerant of periodic waterloggingwhich results in reduced growth rate, show better growth on freelydraining soils (Boden 1963, Parsons 1968, Clucas 1977, Ladiges and Kelso1977). This suggests that interspecific competition may be an importantfacto'r in influencing the distribution of species under waterloggedconditions (Boden 1963, Bannister 1964).Eucalypts are typically species of well-drained sites, with only asmall percentage occurring in areas subject to waterlogging for long periods.Eucalyptus robusta (Clemens and Pearson 1977) and E. camphora, species knownto be tolerant of flooding, are largely confined as adult trees to swampyareas which are waterlogged for most of the year (Boden 1963).Comparativelyfew studies have been carried out on the role of waterlogging in influencingthe distribution of eucalypt species.Boden (1963) related the performance

75of z. ~~~nora and ~. daZrumpZeana under waterlogged conditions to observedfield distributions; however, Parsons (1~68a)obtained no conclusive evidencethat waterlogging was important in control 1 ing the distribution of threesouth-east Austral ian mal lee eucalypts.Species able to grow On sites subject to seasonal waterlogging includeE. aggregata~ E. camaZduZensis~ E. incrassata~ E. ovata~ E. rodwayi~ E. rudis~E. steZZuZata and Z. yarraensis. However, these species are not necessarilyconfined to such sites, and may be found on well-drained soils (Clucas1977). Other species generally confined to well-drained sites tolerateoccasional waterlogging, and these include E. blakeZyi~E. rubida andE. viminalis (Boden 1963). Ecotypic variation in the tolerance of eucalyptsto waterlogging also occurs (Karschon and lohar 1972, 1975; Ladiges andKelso 1977).THE DISTRIBUTION OF E. VIMINALIS AND E. CAMALDULENSIS WITH REFERENCETO WATERLOGGINGPrevious workers (Patton 1930, Gibbons and Downes 1964) have describedE. viminalis as a species of well-drained sites. According to Boden (1963),it may occur on sites subject to occasional waterlogging for short periods.Populations have been recorded on seasonally waterlogged soils at a numberof sites, and intraspecific variation in tolerances to such conditions hasbeen observed (Karschon and lohar 1972, Ladiges and Kelso 1977).E. camalduZensis commonly occurs on sites which may be subject to periodicwaterlogging for a prolonged time (Boden 1963). as the result of flooding orpoor permeability of heavy soils, and seedlings are even able to tolerateperiods of total immersion (Dexter 1967).Karschon and lohar (1975) havereported differences in the flooding tolerance of various provenances ofE. camaZduZensis, which they related to contrasting ecological conditionsat the seed source.

76Since field observations in the Yarra Valley had suggested that waterloggingmay be a discriminating factor in the distribution of E. viminaZisand E. camaldulensis, pot trials were established to investigate the effectsof waterlogging on the growth of seedlings from the local populations underconsideration in the Yarra Valley.METHODSSeed was collected from six trees of E. vi~:nalisand E. camaldulensisat Templestowe (Westerfolds), and germinated (in mid-September 1976) inopetri dishes under 1 ight at a constant temperature of 25 C.Seedlings wereplanted in 60 pots (13 cm diameter) containing topsoil (0-10 em)fromWesterfolds which had been passed through a 1 cm sieve.Drainage holes inthe pots were plugged with foam rubber in an attempt to prevent root growthoutside the pots.After four weeks growth in the glasshouse (during which seedlings werethinned to two per pot), the seedlings were hardened off outside for twoweeks, then randomly placed in plastic-lined wooden troughs for waterloggingin the glasshouse.The experimental treatments used were the same as those of Parsons (1968a)and Ladiges and Kelso (1977).Ten pots of each species were fully waterloggedwith the water level maintained just above the soil surface, andanother ten pots were half waterlogged, the water level being kept atapproximately half pot height.The remainder were used as controls andwatered daily.Seedling heights were measured throughout the treatmentperiod, which began in October, and was continued until May 1977 when allplants were harvested for dry weight estimation.

A2- 0 11SjI ,;:~I;1-0 I•rSpecies0-----0 E vlmlnalls-----. E. camaldulensis" treatment commenced0-5~oi5 10 15 20 25 30 35Eu~='

77Statis-c~caZ~4nc:.:ysesData were subject to analyses of variance.Root/shoot ratios werearcsine transformed prior to analysis since a wide range of values hadbeen recorded.The height measurements were log transformed since thevariances were proportional to the means (Sokal and Rohlf 1969, p.369),and subject to a spl it plot analysis in time (Steel and Torrie 1960).RESULTSHeightThe height data indicated that there was a significant differencebetween the two species (Table 17).Interactions between treatment andtime, and species, treatment and time were highly significant. Threeweeks after treatment began, E. camaldulensis had reached a greater heightthan E. viminalis in all treatments.E. camalduZensis was not affected bythe waterlogging treatment but height growth in E. viminalis was reduced(Fig. 23).Dry WeightOne of the seedlings in two pots of E. viminalis and E. camaZduler$isunder fully waterlogged conditions died during the experiment.Yield wasrecorded as total dry weight per pot, irrespective of whether one or twoplants survived.The species and treatment effects on yield were significant,as was the species x treatment interaction (Table 17). Yield for E. viminaZiswas severely decreased by the fully waterlogged treatment; E. camaldulensistended to grow best under half waterlogged conditions, althought thedifference was not statistically significant, and performed equally wellunder waterlogged as under control conditions (Fig. 24).

15E. viminalis15E. c ..... ldulenli.I10100o:t........m~Q;>= 55Wltlrlogging treatment0""----cwFi g. 24.Yields of seedl ings subjected to control (c), half waterlogged(tw) and fully waterlogged (w) conditions.Vertical barsrepresent 95% confidence limits for comparison of treatments.

78Table 17.Analyses of variance of data from waterlogging experiment.Source of va ria t ion df MS FP(a) He i gh t, 10910 trans formed. Sp 1 i t plot analysis in timeSpecies 1 0.13891 6.85Treatment 2 0.00589 0.29Species x Treatment 2 0.00008 0.004}~NSNSResidual a 54 0.02029Time 6 1.51682 238.64Species x Time 6 0.14236 0.0004Treatment x Time 12 2.02903 319.23Species x Treatment x Time 12 0.15258 24.011': ":,I~-:::.NS";,'~.}:';,I:~I:*;I:Res i dua 1 b 324 0.006356(b)Dry weightSpecies 1 360.83633 40.04Treatment 2 61.34809 6.81Species x Treatment 2 32.45305 3.6*i~i'~**0'

79~oot/ShootRatioRoot/shoot ratios were very variable in both species, but a significantinteraction between species and treatment was noted (Table 17).E. camaZduZensis had a larger root/shoot ratio in al I treatments, and theratio increased, as the total root weight increased in response to waterlogging(Table 18). The root/shoot ratios of ~. viminaZis did not differsignificantly between treatments (Table 18), but that for fully waterloggedplants was lower than for E. camaZduZensis.Table 18.Mean oven dry weights of roots (g) and the calculated root/shoot ratios (R/S)'~'Control Half Waterlogged Fully WaterloggedRoots R/S Roots R/S Roots R/SE. viminaZis 3.60 0.50 3.66 0.54 1.92 0.46 CE. camaZduZensis 4.59 0.54 A 5.64 0.59 6 I 5.71 0.78ABC*back transformed meansMeans with same superscript are significantly different at p < 0.5(S che ffes tes t) .MorphoZogyBoth species showed similar morphological responses to waterlogging inthe development of surficial root systems and basal stem hypertrophy.Surficial roots occurred occasionally in half waterlogged pots, and frequentlyin fully waterlogged pots.Some root death WaS observed in waterlogged potsof both species, but was more extensive in E. viminaZis.Stem hypertrophywas common in both species under fully waterlogged conditions.

PLATE 5The effect of waterlogging on the roots ofE. camaldulensis seedl ings.

80However, the extent of root development under fully waterloggedconditions was very different for the t\-JO species. Root growth in mostof the fully waterlogged E. viminalis was confined to the top 9 cm of thepot, whereas almost all other replicates were pot-bound at the conclusionof the experiment.In spite of the foam rubber packing in drainage holes.roots of fully waterlogged E. camaldulensis grew out of the pots and up to..the surface in the troughs (Plate 5 ) less than 8 weeks after treatmentbegan.These extra-pot roots were subsequently harvested and included indry weight measurements, but similar root systems grew again.Extra-potroots developed in one repl icate of fully waterlogged E. viminalis, but werevery short. Two fully waterlogged E. camaldulensis seedlings also developedsmall adventitious roots arising from their stems.DISCUSSIONThe results indicate that E. camaldulensis is more tolerant of waterloggedconditions than E. viminalis. Waterlogging induced some similarmorphological responses in both species; however, the different responsesof the root systems may account for the observed interspecific differences.The growth of E. camaldulensis roots through the drainage holes of the potsmay have provided a pathway for the absorption of some oxygen directly fromthe surrounding water, thus mitigating to some extent the effects of waterlogging.The abil ity of E. camaldulensis to produce massive root systemsquickly has been noted by Awe et al. (1976), and Karschon and Zohar (1975)reported strong development of floating adventitious roots following diebackof the main taproot in some more flood sensitive provenances ofE. camaldulensis.High root/shoot ratios have also been reported for E. camaldulensis(Jacobs 1955, Zirrrner and Grose 1958), and Jacobs (1955) suggested that theyassist E. camaldulensis to penetrate heavy, unaerated floodplain soils and

~ ____ _81reach better-aerated soils below.Significantly greater root/shoot ratioswere recorded for fully waterlogged E. camaldulensis in the present studyindicating the abil ity of seedling root systems to penetrate waterloggedsoils.It is thoughtthat the difference in root/shoot ratios was inducedby treatment.Although there were significant differences in the growth rates ofwaterlogged E. viminalis and E. camaldulensis. they were not as large asmight be expected.Measurements of oxygen flux and redox potential madein a similar experiment (Ladiges and Kelso 1977). suggested that substantiallyless oxygen was available to fully waterlogged plants than to freely drainingcontrols; however, some oxygenation may have taken place during thefrequent topping up of water levels. This may have reduced root anaerobiosisfor both species to some extent.Experimental evidence (Karschon and Zohar 1972. Ladiges and Kelso 1977)suggests that seedlings of some populations of E. viminalis can survivewaterlogging for up to 220 days when flooded to just above the soil surface.However, under these conditions growth rates are reduced.In a competitivesituation not only survival but the degree of growth rate retardation maybe critical. The effect of total or partial submergence of the shoot onthe survival of E. viminalis seedlings has not been examined.E. viminalismay prove more sensitive to shoot submergence than E. camaldulensis.The development of stem-borne adventitious roots has been reported forE. camaldulensis (Jacobs 1955) and other eucalypts (Boden 1963), althoughnot for E. viminalis.In the field they appear to be restricted toinundated sections of trunks or stems.In the present study, two waterloggedE. camaldulensis produced these structures, although stems were not submerged.In a flooding environment, adventitious roots may be important insurvival where sedimentation is taking place around the butts of trees.

82In the Yarra Valley, ~.viminalis generally occurs on well-drainedsites, a I though occas i ona I stan ds occu r on some s 10\oJ d ra i n i ng te rraces andslopes where the water table may only be 15 cm below the soil surface duringwinter.Most sites occupied by E. camaldulensis are probably not subjectto prolonged waterlogging, since catchment management has changed theflooding regime of the river.Floods now usually recede after several days.Most of the floodplain has been cleared of trees, and stands ofE. camaldulensis are now largely restricted to areas which drain fairlyquickly, such as the banks of rivers and bi llabongs.However, swampydepressions on the floodplain probably supported E. camaldulensis prior toclearing.E. camaldulensis was found to be more tolerant of experimentallyinduced waterlogged conditions than E. viminaZis.Growth rate retardationoccurred in both species subjected to waterlogging, but was significantlygreater in E. vi~nalis.It is suggested that this difference may bereflected in the competitive abil ity of these species on waterlogged sites.

83CHAPTER 6DISCUSSION AND CONCLUSIONSThe distributions of E. viminalis and E. camaldulensis in Victoriaoverlap in the region of the 1000 mmisohyet in the north east and atthe 700 mm isohyet south of the Divide and in western Victoria. It issuggested that the occurrence of the ecotone between the two species atdifferent mean annual rainfalls north and south of the Divide is theresult of the effectiveness of the rainfall in these areas.The variation in form observed in E. camaldulensis in Victoria,from tall forest to woodland. appears to be related to soil moisturegradients. The occurrence of various forms in E. viminalis has beenrelated to both soil moisture and soil nutrient status.In the north east and on the northern slopes of the Divide. ecotonesbetween the smooth-barked forest form of E. viminalis and the riparianform of E. camaldulensis occur on streambank and floodplain sites wherefloodplains interdigitate with spurs of the north east highlands.Southof the Divide riparian ecotones between the two species occur at the700 mm isohyet. Ecotones also occur between the woodland forms of thesespecies in the region south of the Divide and including the WesternDistrict of Victoria in the 600-700 mmrainfall belt on undulatingtopography where the soil nutrient status is fair to good.HereE. viminalis generally occurs on the better drained sites. In the lowerrainfall region south of the Divide E. viminalis has been able to exploita wide range of soil types, including acid and calcareous sands (Ladigesand Ashton 1977), whilst E. oamaldulensis tends to be confined to heavycl ay so i 1 s.

;84It appears that the geographic extent of E. viminaZis andE. camaZduZensis in Victoria is strongly influenced by mean annualrainfall, and that E. viminaZis has a preferece for higher rainfallI oca lit i es .A survey of the Australian distribution of E. viminaZis andE. camaZduZensis in Chapter 1 indicated that both species occupy acomparatively wide range of habitats with respect to altitude, topography.rainfall and soil type, although E. viminaZis is largely restricted toone climatic zone (Cfb - humid mild-winter climate of Koppen) whilstE. camaZduZensis,because it is riparian and depends on flooding or thewatertable for moisture, occurs across a range of climatic types, fromhumid tropical through semi-arid climates of inland Australia to thehumid mild-winter climates of south eastern Australia.Ladiges and Ashton (1974) suggested that the ability of E. viminaZisto occupy such a variety of habitats may be related to the occurrence ofecotypic variation within the species.Genetic differences betweenpopulations growing in central Victoria have been demonstrated by fieldtransplants and pot trials. They included differences in seedlingestablishment and growth rate, tolerance to drought (Ladiges and Ashton1974, Ladiges 1974a, 1974b) and tolerance of waterlogged conditions(Ladiges and Kelso 1977).Population differences in growth rate anddrought tolerance have been related to differences in edaphic factors,and it has been suggested that differential selection pressures haveprimarily been responsible for the establishment of such populationdifferences (Ladiges 1976).Some ecotypic variation has also been demonstrated forE. camaZduZensis in pot trial comparisons of tropical and subtropic~lpopulations.Such population differences have been recorded in seedling

85height (Pryor and Byrne 1969), response to lOW temperatures (Pryor andByrne 1969. Karschon 1971, Awe and Shepherd 1975) and tolerance toflooding and salinity (Karschon and Zohar 1975).In Victorian populationsthere is some morphological variation, but variation of the scaledemonstrated by E. viminalis has not been observed, nor extensivelystudied, although Laurie (1976) has suggested that there are genotypicdifferences in the seedling growth rate and rate of root penetration offorest and woodland forms of E. camalduZensis growing under differentflooding regimes in the Barmah Forest.At the junctions between the species ranges in Victoria, E. viminalisand E. camaldulensis, like most species capable of interbreeding. rarelyform mixed stands (Pryor 1953).Where the species occur in closeproximity they tend to occupy separate habitats, with both the woodlandand forest forms of E. viminalis on the better drained sites. Howeversome hybridization between the species has been recorded (Pryor 1955,Penfold and Willis 1961, Willis 1972), and intermediates have been notedat Westerfolds and near Eildon.The distribution of E. viminaZis and E. camaldulensis in the YarraValley mirrors the patterns observed throughout Victoria, the tall smoothbarkedform of E. viminalis occurring as tal I open-forest in the uppercatchment where M.A.R. exceeds 1000 mm and fringing the Yarra and itstributaries downstream to the 700 mmisohyet, where it gives way toE. camaldulensis. The woodlal;d form of E. viminalis occurs on Tertiarybasalts and flat sites on sandy cappings towards the drier limits ofthe E. viminaZis range, whilst woodland E. camaldulensis occupies heavyclay soils on the gently undulating topography of Silurian slopes andQuaternary basalt plains down to the 500 mmisohyet.

86?ryor (1959a, 1959b) has suggested that the factors which controlthe local distribution of wide ranging eucalypt species are I ikely tobe different from those which restrict them at their geographic limits.He thought that competition. nutrition and the effects of microclimatemay be, factors contributing to the observed local distributions.Inthe present study evidence suggests that in the Yarra Valley where M.A.R.exceeds 700 mm and soils are well-drained and comparatively wellstructured.the faster growth rates of the forest form of E. viminaZismay result in the exclusion of E. camaldulensis from such sites bycompetition.In addition. floods favor the downstream dispersal ofE. viminalis which has occasionally been noted growing amongstE. camaZduZensis on steep. sheltered south facing banks as far downstreamas Richmond.At the upper limits of its range in the Yarra catchment (eg.Hurstbridge and upstream from Westerfolds) • E. camaZdulensis occurs onflood plain margins. but does not extend far up the valley slope wheresoils tend to be shallow and often very stony!It does not occupyE. viminaZis sites closer to the river. The woodland form ofE. camaldulensis which occurs on undulating topography away from theriver banks and floodplain may prove to be a more drought tolerantecotype of E. camaZduZensis.However, it is suggested that soil volumemay be a critical factor in the tolerance of E. camalduZensis to drought;soils derived from basalt and Silurian bedrock near Melbourne arerelatively deep and frequently have a clay subsoil which tends to havea high moisture retaining capacity.Field observations and some experimental results indicate thatunder certain conditions E. viminalis is able to grow faster thanE. camaldulensis and that E. camaldulensis is more tolerant of waterloggingand limiting soil mositure conditions.Differences between the

87two species which may influence their gr~vthrates and success in theYarra Valley habitats include seed size and root/shoot ratios.E. viminalis seeds are typically larger than those ofE. camaldulensis (Grose and Zimmer 1958 ) and it is suggested that thismay give E. viminalis an advantage over E. camaldulensis providinggermination rates do not differ markedly, and providing soil structureand nutrient levels are favorable to the growth of E. viminalis.In the present study the root/shoot ratios of E. camalduZensis wereconsistently higher than those of E. viminaZis, and it was suggestedthat they may confer greater drought avoidance on E. camalduZensis.Previous studies have shown that there is a correlation between theroot/shoot ratios of eucalypts and site water availabil ity, and bothinterspecific and intraspecific comparisons have demonstrated a decreasefrom high to low root/shoot ratios with increasing wetness of provenancesite (Zimmer and Grose 1953, Hopkins 1964, Parsons 1968b).Consequentlyit has been suggested that a high root/shoot ratio represents anadaptation to drought conditions (Zimmer and Grose 1958), although lownutrient levels may also be a selective factor (eg. Ladiges and Ashton1977) .There was also a differential species response of root/shoot ratiosto increasing levels of phosphorus and nitrogen, the root/shoot ratioof E. viminalis tended to decrease when nutrient levels were increased,whilst root/shoot ratios of E. camaldulensis showed little change.Theseresults suggest that on more fertile soils in lower rainfall areas someecotypes of E. viminalis may be more susceptible to drought stress.Parsons (1968c) has suggested that there may be a positive correlationbetween soil fertility and drought susceptibility, and Ladiges (1974a)noted that lower root/shoot ratios were a feature of tall forestpopulations of E. viminalis found on wetter sites.

38It is not known what role the very high root/shoot ratio observedin the fully waterlogged plants of E. camaldulensis (Chapter 5) mayplay in the waterlogging tolerance of this species, however Jacobs (1955)has suggested that, on the heavy floodplain soils of the Murray Riversystem, the high root/shoot ratio of E. camaldulensis helps penetrationof heavy gley layers of soils to reach better aerated layers beneath.SUMMARYIt is concluded that,while average annual rainfall stronglyinfluences the geographic extent of E. viminalis and E. camaldulensis,at the local level the effects of competition interacting with soilmoisture and soil structural properties determine the distribution ofthe two species.Interpretation of distribution patterns is complicatedby intraspecific variation, particularly in E. viminalis.

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