OFR 151.pdf - CRC LEME
OFR 151.pdf - CRC LEME OFR 151.pdf - CRC LEME
scale. Replacement communities are usually more diverse or structurally complex than the communities they succeed (secondary succession). In rare instances, e.g. following volcanic eruptions, major landslips, severe flooding and hot fires, the succession will be primary in that the pioneer plants have to colonise bare rock surfaces or mineral soils. 1.3.6 Ecology and ecophysiology Fox (1999) has reviewed environmental influences on the Australian vegetation. The only information available on the ecological preferences of most plant species is empirical, i.e. is based on their distribution along known gradients in precipitation, temperature and soil fertility, e.g. Jackson (1968, 1999). In exceptional cases, objective techniques such as BIOCLIM, which use trend surface analysis of plant distribution data (Nix 1982, 1991), have been used to estimate climatic envelopes. Examples are Nothofagus (Busby 1986) and some Miocene floras (Kershaw 1995). This technique is not particularly successful in predicting species distributions in mountainous terrain, where microclimates can vary rapidly over short vertical and horizontal distances. As noted for some Eucalyptus spp. on the Southeastern Highlands of New South Wales (M. Austin pers. comm.), thriving stands do not always occupy sites having the optimal climatic regime and this can make it difficult to determine the relative importance of the presumed environmental controls. A more reliable method is to study the physiological response(s) of phytosociologically important species to controlled variations in the environment, particularly light intensity, water-stress and low temperatures. For example, Read and Hill (1985), Hill et al. (1988), Read and Hope (1989), Read (1990) and Read and Francis (1992) have prepared ecophysiological profiles for several canopy dominants in lowland rainforest. Brodribb and Hill (1997, 1998, 1999) have studied the physiological adaptations and responses of selected Southern Hemisphere gymnosperms to low light intensities and water-stress. Eamus (1999) has analysed the ecophysiological traits of evergreen trees with 100% (deciduous), >50% (semi-deciduous) and
Accordingly, only at sites with exceptional resolution will short-term changes be preserved in the fossil record. Australian examples are rhythmites at Lemonthyme Creek, north-west Tasmania (Early Oligocene), and Yallalie, south-west Western Australia (mid Pliocene). High levels of biodiversity seem to be restored by ~10 million years after major extinction events (cf. Erwin 1998, 2000; Gaston 2000). 1.3.8 Fire and soil fertility Over shorter periods of time, the role of climate becomes more ambiguous whilst the influence of other factors such as soil drainage, soil fertility and the frequency/intensity of wildfires and other disturbances become more pronounced on the local to regional scale (references in Fox 1999 for mainland Australia, Jackson 1968, 1999, Macphail 1979, 1980 for Tasmania, Ogden et al. 1996 for New Zealand, Read and Hope 1996 for New Guinea and New Caledonia, Peres 1999 for South-East Asia, and Veblen et al. 1996 for South America). Hill (1998a, 1998b) has restated the distinction between the morphological response of plants to low levels of soil nutrient such as phosphorus (scleromorphy), and low soil moisture levels (xeromorphy), but notes that these forcing factors and wildfires have 'genuinely overlapped' in Australia since Late Eocene times and scleromorphic and xeromorphic plants are well adapted to the ubiquitous presence of fire in the modern landscape (‘fire-requiring and promoting’ species). Low intensity wildfires may help increase regional rainfall in that low concentrations of smoke particles help water droplets form. However, recent forest fires over South-East Asia have confirmed that very dense smoke haze 'turns off' normal tropical rainfall due to oversaturation of the atmosphere with small particles (Adler 1999). For this reason, anthropogenic wildfires are suggested to be partly responsible for the decline in rainfall seen in the tropics over the past century. Periods of intense volcanic activity and/or meteor impact almost certainly will have had similar consequences on the local to regional scale (Kerr 2000). 1.3.9 Vagility and vicariance Plants differ greatly in their ability to disperse propagules such as spores and seeds into the surrounding landscape (vagility). The relatively high levels of endemism (vicariance) in Australasian rainforest floras is attributed to the low vagility of many rainforest species (Barlow 1981, Dawson 1986, Hartley 1986, Morat et al. 1986, Thorne 1986, Webb et al. 1986, Whiffen and Hyland 1986). Nevertheless, fruits, seeds and seedlings of mangroves and other strand plants are routinely found on the beaches on cays in the south Coral Sea, confirming that plant propagules can drift from as far away as Fiji, Vanuatu and New Caledonia to Australia (Smith 1992). Similarly, palynostratigraphic evidence confirms that many woody and some herbaceous plants have been able to cross wide ocean gaps, including to New Zealand and Ninetyeast Ridge in the Indian Ocean (Kemp and Harris 1977, Macphail et al. 1994). These data demonstrate that chance dispersal events, many of which are of intrinsically very low probability due to the low vagility of the species concerned, have occurred during Early Tertiary when Australia was surrounded by wide oceans. Conversely during the Late Tertiary when Australia has been close to South-East Asia, only limited floristic interchange has taken place due to the lack of suitable ‘target’ habitats in northern Australia (Macphail 2000). 42
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- Page 3 and 4: Electronic copies of the publicatio
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- Page 9 and 10: Table A (cont.) Basin and related s
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- Page 22 and 23: EXECUTIVE SUMMARY This review prese
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- Page 28 and 29: INTRODUCTION Mineral resources, whe
- Page 30 and 31: Professor B. Balme (Geology Departm
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- Page 37 and 38: 1.3 Flora, vegetation and climate 1
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scale. Replacement communities are usually more diverse or structurally complex than the<br />
communities they succeed (secondary succession). In rare instances, e.g. following volcanic<br />
eruptions, major landslips, severe flooding and hot fires, the succession will be primary in<br />
that the pioneer plants have to colonise bare rock surfaces or mineral soils.<br />
1.3.6 Ecology and ecophysiology<br />
Fox (1999) has reviewed environmental influences on the Australian vegetation. The only<br />
information available on the ecological preferences of most plant species is empirical, i.e. is<br />
based on their distribution along known gradients in precipitation, temperature and soil<br />
fertility, e.g. Jackson (1968, 1999). In exceptional cases, objective techniques such as<br />
BIOCLIM, which use trend surface analysis of plant distribution data (Nix 1982, 1991), have<br />
been used to estimate climatic envelopes. Examples are Nothofagus (Busby 1986) and some<br />
Miocene floras (Kershaw 1995). This technique is not particularly successful in predicting<br />
species distributions in mountainous terrain, where microclimates can vary rapidly over short<br />
vertical and horizontal distances. As noted for some Eucalyptus spp. on the Southeastern<br />
Highlands of New South Wales (M. Austin pers. comm.), thriving stands do not always<br />
occupy sites having the optimal climatic regime and this can make it difficult to determine the<br />
relative importance of the presumed environmental controls.<br />
A more reliable method is to study the physiological response(s) of phytosociologically<br />
important species to controlled variations in the environment, particularly light intensity,<br />
water-stress and low temperatures. For example, Read and Hill (1985), Hill et al. (1988),<br />
Read and Hope (1989), Read (1990) and Read and Francis (1992) have prepared<br />
ecophysiological profiles for several canopy dominants in lowland rainforest. Brodribb and<br />
Hill (1997, 1998, 1999) have studied the physiological adaptations and responses of selected<br />
Southern Hemisphere gymnosperms to low light intensities and water-stress. Eamus (1999)<br />
has analysed the ecophysiological traits of evergreen trees with 100% (deciduous), >50%<br />
(semi-deciduous) and
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