Download Full PDF - 28.09 MB - The Society of Irish Foresters
Download Full PDF - 28.09 MB - The Society of Irish Foresters Download Full PDF - 28.09 MB - The Society of Irish Foresters
Crop Structure and Productivity for Unthinned Sitka Spruce 49Vo I to 8cm topdiam./ha.m380600400/'" '" /'""'"'"//200- survey- - - BFC[1971]4 8 12 16Top Height m}'ig. 5. Calculated productivity classes for unthinned Sitka spruce: comparedwith production classes of the Forest Management Tables(1971).20'24bands (al, b\ c l ) derived from the curves shown in figure 2 arecompared with bands shown in the Forest management tables(a, b, c). The "b l ", band runs along the "a" band for most of itslength except in the 16-20m. top height area. Beyond 16m. topheight data become scarce so that the rest of the band must not begiven undue importance. The few measured plots over 16m. topheight occur both ,over and under the average production curveso it is not really 'possible to conclude if beyond this top heightthe average production is similaa- to the average of that in theForest Management Tables, or if it remains above it. It is evident,however, that in young unthinned stands average production issome 60m 3 per ha. greater for top height than shown in the tablesof Hamilton and Christie. Though very high relative productionfor top height can be found in young unthinned stands they tendto approach standards in the Forest Management Tables (1971) as
50 ' - Irish Forestrythey grow older. The average production however, ("b I " band) hereremains a little higher than the Tables, in the order of 20-40m. 3 /ha.Arising from the exercise in constructing yield classes fromthe unthinned spruce stands it would seem that classes well over24m 3 /ha./annum might be obtained. The evidence for this figurelS the rate of M.A.!. at early stages and the similarity in shape:between the height/age curves got from plots and those fromHamilton and Christie (1971) (fig. 3). The increments within thesecategories have been obtained from the volume/top height curve(fig. 3 Equation 1) so again the question as to the validity of thiscurve at top heights over 16m. must be cons~dered. Two possibilitiesarise here: (1) If the volume curve falls back to the ManagementTable (1971) curve or below it, the possibility of shorter rotationsfor approximately the same yield classes might be entertained; (2)but on the indications of the sparse data above 16m. top heightrotations might be longer but yield h:gher. The only way to verifythis will be to moniter permanent plots to 45 years or over. Anotherpoint to be considered is whether the reduction in volumeincrement for top height at 16m. is related to growth potential orto stand condition. More open stocking m:ght achieve betterproduction at this point and the increase of mortality for topheights between 12-16m. will be of interest here.SUMMARY OF MAIN CONCLUSIONS(1) Crop structure pattern for top height in terms of one variable,volume, basal area or top diameter can be determined by curvesand the areas within which 95 % of samples fall. Best volumepredictions can be made through equations including both topheight and basal area.(2) There is likelyto'be a wide variation in volume productivityfor top height which can be as much as ± 100m3/ha. This isreflected in basal area arid dominant diameter.(3) Average production for top height in all young unthinnedstands is likely to be higher than indicated in the Forest ManagementTables (1971). Average production of lower yield class&lands is likely to be higher in both young and and older stands .. (4) Sampled stands suggest yield classes up to over 24m 3 /ha./annum with each yield class having a range of at least ± 2m. 3 •Height age curves approximate the Forest Management Tablescurves (1971).(5) The volume/top height relationships suggest some reductionin productivity at 14-16m. top height due possibly to limitations indata or to crop conditions. This has some implications:
- Page 8 and 9: McCULLOCHWorlds best-selling CHAIN
- Page 10 and 11: IRISH FORESTRY:CONTENTS(A uthors al
- Page 12 and 13: IRISH FORESTRYVolume 29 1972 No.2Ed
- Page 14 and 15: Some Forestry Problems in the Europ
- Page 16 and 17: Some Forestry Problems in the Europ
- Page 18 and 19: Some Forestry Problems in the Europ
- Page 20 and 21: Some Forestry Problems in the Europ
- Page 22 and 23: Some Forestry Problems in the Europ
- Page 24 and 25: The Response of Sitka Spruce to Sul
- Page 26 and 27: The R esponse of Sitka Spruce to Su
- Page 28 and 29: The R esponse of Sitka Spruce to Su
- Page 30 and 31: The R esponse of Sitka Spruce to Su
- Page 32 and 33: The R esponse of Sitka Spruce to Su
- Page 34 and 35: The R esponse of Sitka Spruce to Su
- Page 36 and 37: The Response 0 fSitka Spruce to Sul
- Page 38 and 39: Labour Cost Trends in ForestNurseri
- Page 40 and 41: Labour Cost Trends in Forest Nurser
- Page 42 and 43: SOJ?e Patterns in Crop Structureand
- Page 44 and 45: Crop Structure and Productivity for
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- Page 62 and 63: Trees Woods and Literature- · 7A w
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- Page 72 and 73: Reviews 63includes an Appendix VI b
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Crop Structure and Productivity for Unthinned Sitka Spruce 49Vo I to 8cm topdiam./ha.m380600400/'" '" /'""'"'"//200- survey- - - BFC[1971]4 8 12 16Top Height m}'ig. 5. Calculated productivity classes for unthinned Sitka spruce: comparedwith production classes <strong>of</strong> the Forest Management Tables(1971).20'24bands (al, b\ c l ) derived from the curves shown in figure 2 arecompared with bands shown in the Forest management tables(a, b, c). <strong>The</strong> "b l ", band runs along the "a" band for most <strong>of</strong> itslength except in the 16-20m. top height area. Beyond 16m. topheight data become scarce so that the rest <strong>of</strong> the band must not begiven undue importance. <strong>The</strong> few measured plots over 16m. topheight occur both ,over and under the average production curveso it is not really 'possible to conclude if beyond this top heightthe average production is similaa- to the average <strong>of</strong> that in theForest Management Tables, or if it remains above it. It is evident,however, that in young unthinned stands average production issome 60m 3 per ha. greater for top height than shown in the tables<strong>of</strong> Hamilton and Christie. Though very high relative productionfor top height can be found in young unthinned stands they tendto approach standards in the Forest Management Tables (1971) as
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