Three-year old Norway spruce [Picea abies (L.) Karst.] trees of clonal stock originating from med... more Three-year old Norway spruce [Picea abies (L.) Karst.] trees of clonal stock originating from medium altitude in southern Germany were transplanted in May 1986 into two acid brown-earth soils which differed particularly in the amounts of exchangeable Ca^^ and Mg'^^. During the summers of 1987 and 1988 trees were exposed in largescale fumigation chambers (solardomes) to ozone at 200 or 40 (control) fig m'^. Acid (pH 3-6) or control mist (pH 5-5) solution was applied daily to trees in each half of the solardomes. In late autumn (1988) the light response of COg exchange, and the chlorophyll and soluble carbohydrate contents of needles were determined. Ozone and/or acid mist treatment had only minor (< 10 %) effects on the light-saturated rate of photosynthesis which were not statistically significant in plants from either soil. Needles from trees raised on the richer soil and exposed to a combination of ozone and acid mist showed a significant increase in the apparent quantum yield of photosynthesis which was associated with an increase in chlorophyll content. Ozone (alone) stimulated the rate of dark respiration by 40 and 58 % for trees grown in richer and poorer soils, respectively, and this was associated with a decrease in ethanol-soluble carbohydrate content of needles. Where significant interactions between ozone and acid mist were found, they were generally antagonistic. The reduction in the ethanol-soluble carbohydrates would be expected to reduce frost hardiness, and may contribute to the increased sensitivity of ozone-treated needles to freezing, which has been reported in previous studies.
The global carbon cycle is highly sensitive to climate-driven fluctuations of precipitation, espe... more The global carbon cycle is highly sensitive to climate-driven fluctuations of precipitation, especially in the Southern Hemisphere. This was clearly manifested by a 20% increase of the global terrestrial C sink in 2011 during the strongest sustained La Niña since 1917. However, inconsistencies exist between El Niño/La Niña (ENSO) cycles and precipitation in the historical record; for example, significant ENSO-precipitation correlations were present in only 31% of the last 100 years, and often absent in wet years. To resolve these inconsistencies, we used an advanced temporal scaling method for identifying interactions amongst three key climate modes (El Niño, the Indian Ocean dipole, and the southern annular mode). When these climate modes synchronised (1999-2012), drought and extreme precipitation were observed across Australia. The interaction amongst these climate modes, more than the effect of any single mode, was associated with large fluctuations in precipitation and productivity. The long-term exposure of vegetation to this arid environment has favoured a resilient flora capable of large fluctuations in photosynthetic productivity and explains why Australia was a major contributor not only to the 2011 global C sink anomaly but also to global reductions in photosynthetic C uptake during the previous decade of drought.
ABSTRACT Australia&#39;s climate is extremely variable with inter annual rainfall at any loca... more ABSTRACT Australia&#39;s climate is extremely variable with inter annual rainfall at any location varying up to eight-fold. Understanding water and productivity relationships represent key issues in climate change models that aim to predict how carbon and water relationships will shift with projected changes in the frequency, timing, amount and intensity of rainfall. After a decadal long drought cycle, Australia has experienced one of the wettest periods of recorded rainfall. In this study we assessed cross-biome responses to extreme drought and wet periods across continental Australia through investigations of rainfall use efficiencies (RUE), defined as above-ground net primary production (ANPP) divided by annual rainfall. 12 years of annually integrated MODIS satellite enhanced vegetation index (iEVI) were used as proxies of ANPP and combined with rainfall data to assess large area spatial and temporal patterns in rainfall use efficiency (RUE). Positive curvilinear relationships were found between iEVI and annual rainfall with decreasing sensitivity of iEVI to additional rainfall at the more humid and energy-limited tropical savannas and forests. The driest years resulted in all biomes converging to a common and maximum RUE, or RUEmax with ANPP and precipitation relationships that became strongly linear. Standardized anomaly values showed significantly enhanced ANPP values during the 2010 and 2011 wet years, however, these values were less than encountered prior to the decade long drought, suggesting a significant loss in resilience in many Australian biomes.
Restoration of belowground ecology is seldom a priority in designing revegetation strategies for ... more Restoration of belowground ecology is seldom a priority in designing revegetation strategies for disturbed landscapes. We determined earthworm abundance and diversity in a 16-year old grass sward (grassland), a 6-year old (Plantation-04) and a 4-year old (Plantation-06) plantation, both of mixed woody species, on a reclaimed waste disposal site, and in nearby remnant woodland, in suburban Sydney, Australia. While no catches were made in autumn, more earthworms were found in spring (21 ± 8.6 m(-2)) than in winter (10.2 ± 5.9 m(-2)) or summer (14.4 ± 5.5 m(-2)). Earthworm abundance in spring was in the order grassland ≈ Plantation-04 (35.2 m(-2)) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; woodland (12.8 m(-2)) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; Plantation-06 (0.8 m(-2)). None of the revegetated covers had restored earthworm diversity to levels found in the woodland. Exotic species, mostly Microscolex dubius, dominated in the four vegetation covers at any time; the only two native species (Heteroporodrilus sp. and Megascoleceides sp.) found were in the woodland. We also assessed how quality of the evolving soils from the three revegetated covers, compared with that from the woodland, impacted viability of common exotic earthworm species. Both weight gain and cocoon production by the exotic earthworms were higher in the soil from Plantation-04 than in soils from the other vegetation covers, including the woodland; the two variables were positively correlated with the pH and mineral nutrient content (as indicated by electrical conductivity that was in turn correlated with clay content) of the soil. Age of vegetation rather than its composition explained differences in the level of earthworm recovery observed.
Quantifying water use of native vegetation is an important contribution to understanding landscap... more Quantifying water use of native vegetation is an important contribution to understanding landscape ecohydrology. Few studies provide long-term (more than one growing season) estimates of water use and even fewer quantify interseasonal and interannual variation in transpiration. Globally, changes in land use are significantly altering landscape ecohydrology, resulting in problems such as dryland salinity and excessive groundwater recharge. Estimating stand water use is complex in multispecies forests, due to the ...
... Soil water potential in the upper soil profile can decline from zero (wet season) to -3.5 MPa... more ... Soil water potential in the upper soil profile can decline from zero (wet season) to -3.5 MPa or lower (Goldstein et al., 1986; Holbrook et al., 1995; Franco et al., 1996) (see section III). ... 1. Four phenological guilds are recognized in Australian savannas (Williams et al., 1997). ...
(2002) Snowdon. Read by researchers in: 100% Environmental Sciences. Estimation of thebiomass and... more (2002) Snowdon. Read by researchers in: 100% Environmental Sciences. Estimation of thebiomass and carbon content of Australian forest and woodland ecosystems and its rate of change is an important goal of the National Carbon Accounting System. This protocol... ...
Increased woody plant density (woody encroachment or woody thickening) is a globally observed phe... more Increased woody plant density (woody encroachment or woody thickening) is a globally observed phenomenon. Similarly, increased atmospheric carbon dioxide concentrations and decreased pan evaporation rates are globally observed phenomena. In this paper, we propose that the former (increased woody plant density) is a product of the latter. We propose that decreased stomatal conductance and increased rates of carbon fixation arising from an enriched atmospheric carbon dioxide concentration, in conjunction with reduced rates of pan evaporation, result in increased woody plant density. We suggest that this is analogous to the increased woody plant density that is observed along rainfall gradients that span arid to mesic environments. From this conceptual model, we make three predictions, namely, that (a) long-term trends in tree water-use-efficiency should reveal increased values; (b) run-off data should show an increase where woody thickening is occurring; (c) enriched CO 2 experiments should reveal an enhanced plant water status. These three predictions are discussed and shown to be supported by experimental data.
Throughout Australia many groundwater dependent ecosystems have been adversely affected by unsymp... more Throughout Australia many groundwater dependent ecosystems have been adversely affected by unsympathetic water abstraction practices. In Western Australia, the largest single supply of drinking water for the city of Perth is a superficial aquifer known as the Gnangara Groundwater Mound, located over an area of approximately 2200 km2 within and to the north of the city on the coastal plain. The groundwater resource supplies 60% of Perth’s pubic drinking water supply and 85% of total water demand for all users. Much of the mound is overlain by phreatophytic Banksia woodland that is susceptible to drought stress and death if the root system is separated from the unconfined aquifer for prolonged periods over the hot, dry Mediterranean summer. Drought stress has been exacerbated by diminished rainfall due to a changing climate regime. The aim of this research is to develop guidelines for sustainable groundwater abstraction (timing and volume) that will maintain the long term integrity of the ecosystem and recover up to 5GL/yr from existing borefields. We seek to investigate whether a change in abstraction regime, from ‘peak demand’ summer pumping to winter pumping allows groundwater levels to recover sufficiently prior to summer, thereby maintaining a healthy vegetation system. Hydrological and plant water status parameters were monitored over two winters at research sites with an initial depth to groundwater of less than 5m. During winter and spring, groundwater abstraction at a reduced capacity resulted in a 0.75m drawdown. Operation of the bores did not adversely impact the water status of phreatophytic Banksia at the study sites relative to control sites. Analysis of plant water source partitioning indicated that plants exposed to the winter drawdown were sustained by unsaturated zone soil moisture storage replenished by winter rainfall. When pumping ceased, the water table rose rapidly and plants utilised more groundwater during late spring and summer as the soil water store became depleted. A simple water balance model combined with phreatophyte vulnerability assessment was employed to identify allowable magnitude and rate of drawdown, and duration of bore operation.
Transactions of the British Mycological Society, 1986
The influence of substratum water potential on the growth of Serpula lacrimans and Phallus impudi... more The influence of substratum water potential on the growth of Serpula lacrimans and Phallus impudicus was investigated. Two methods of adjusting the water potential of the substratum were used; both gave qualitatively similar results. Linear growth rate decreased with substratum water potential. The turgor potential at the mycelial front and linear growth rate were positively correlated in both species on both media. An experiment concerned with growth from a medium of high water potential to one oflower water potential and vice versa produced results consistent with those obtained for growth on a single medium.
Tropical forests hold large stores of carbon, yet uncertainty remains regarding their quantitativ... more Tropical forests hold large stores of carbon, yet uncertainty remains regarding their quantitative contribution to the global carbon cycle. One approach to quantifying carbon biomass stores consists in inferring changes from long-term forest inventory plots. Regression models are used to convert inventory data into an estimate of aboveground biomass (AGB). We provide a critical reassessment of the quality and the robustness of these models across tropical forest types, using a large dataset of 2,410 trees ‡ 5 cm diameter, directly harvested in 27 study sites across the tropics. Proportional relationships between aboveground biomass and the prod-uct of wood density, trunk cross-sectional area, and total height are constructed. We also develop a regression model involving wood density and stem diameter only. Our models were tested for secondary and oldgrowth forests, for dry, moist and wet forests, for lowland and montane forests, and for mangrove forests. The most important predictors of AGB of a tree were, in decreasing order of importance, its trunk diameter, wood specific gravity, total height, and forest type (dry, moist, or wet). Overestimates prevailed, giving a bias of 0.5-6.5% when errors were averaged across all stands. Our regression models can be used reliably to predict aboveground tree biomass across a broad range of tropical forests. Because they are based on an unprecedented dataset, these models should improve the quality Electronic Supplementary Material Supplementary material is available for this article at http://dx.of tropical biomass estimates, and bring consensus about the contribution of the tropical forest biome and tropical deforestation to the global carbon cycle.
Three-year old Norway spruce [Picea abies (L.) Karst.] trees of clonal stock originating from med... more Three-year old Norway spruce [Picea abies (L.) Karst.] trees of clonal stock originating from medium altitude in southern Germany were transplanted in May 1986 into two acid brown-earth soils which differed particularly in the amounts of exchangeable Ca^^ and Mg'^^. During the summers of 1987 and 1988 trees were exposed in largescale fumigation chambers (solardomes) to ozone at 200 or 40 (control) fig m'^. Acid (pH 3-6) or control mist (pH 5-5) solution was applied daily to trees in each half of the solardomes. In late autumn (1988) the light response of COg exchange, and the chlorophyll and soluble carbohydrate contents of needles were determined. Ozone and/or acid mist treatment had only minor (< 10 %) effects on the light-saturated rate of photosynthesis which were not statistically significant in plants from either soil. Needles from trees raised on the richer soil and exposed to a combination of ozone and acid mist showed a significant increase in the apparent quantum yield of photosynthesis which was associated with an increase in chlorophyll content. Ozone (alone) stimulated the rate of dark respiration by 40 and 58 % for trees grown in richer and poorer soils, respectively, and this was associated with a decrease in ethanol-soluble carbohydrate content of needles. Where significant interactions between ozone and acid mist were found, they were generally antagonistic. The reduction in the ethanol-soluble carbohydrates would be expected to reduce frost hardiness, and may contribute to the increased sensitivity of ozone-treated needles to freezing, which has been reported in previous studies.
The global carbon cycle is highly sensitive to climate-driven fluctuations of precipitation, espe... more The global carbon cycle is highly sensitive to climate-driven fluctuations of precipitation, especially in the Southern Hemisphere. This was clearly manifested by a 20% increase of the global terrestrial C sink in 2011 during the strongest sustained La Niña since 1917. However, inconsistencies exist between El Niño/La Niña (ENSO) cycles and precipitation in the historical record; for example, significant ENSO-precipitation correlations were present in only 31% of the last 100 years, and often absent in wet years. To resolve these inconsistencies, we used an advanced temporal scaling method for identifying interactions amongst three key climate modes (El Niño, the Indian Ocean dipole, and the southern annular mode). When these climate modes synchronised (1999-2012), drought and extreme precipitation were observed across Australia. The interaction amongst these climate modes, more than the effect of any single mode, was associated with large fluctuations in precipitation and productivity. The long-term exposure of vegetation to this arid environment has favoured a resilient flora capable of large fluctuations in photosynthetic productivity and explains why Australia was a major contributor not only to the 2011 global C sink anomaly but also to global reductions in photosynthetic C uptake during the previous decade of drought.
ABSTRACT Australia&#39;s climate is extremely variable with inter annual rainfall at any loca... more ABSTRACT Australia&#39;s climate is extremely variable with inter annual rainfall at any location varying up to eight-fold. Understanding water and productivity relationships represent key issues in climate change models that aim to predict how carbon and water relationships will shift with projected changes in the frequency, timing, amount and intensity of rainfall. After a decadal long drought cycle, Australia has experienced one of the wettest periods of recorded rainfall. In this study we assessed cross-biome responses to extreme drought and wet periods across continental Australia through investigations of rainfall use efficiencies (RUE), defined as above-ground net primary production (ANPP) divided by annual rainfall. 12 years of annually integrated MODIS satellite enhanced vegetation index (iEVI) were used as proxies of ANPP and combined with rainfall data to assess large area spatial and temporal patterns in rainfall use efficiency (RUE). Positive curvilinear relationships were found between iEVI and annual rainfall with decreasing sensitivity of iEVI to additional rainfall at the more humid and energy-limited tropical savannas and forests. The driest years resulted in all biomes converging to a common and maximum RUE, or RUEmax with ANPP and precipitation relationships that became strongly linear. Standardized anomaly values showed significantly enhanced ANPP values during the 2010 and 2011 wet years, however, these values were less than encountered prior to the decade long drought, suggesting a significant loss in resilience in many Australian biomes.
Restoration of belowground ecology is seldom a priority in designing revegetation strategies for ... more Restoration of belowground ecology is seldom a priority in designing revegetation strategies for disturbed landscapes. We determined earthworm abundance and diversity in a 16-year old grass sward (grassland), a 6-year old (Plantation-04) and a 4-year old (Plantation-06) plantation, both of mixed woody species, on a reclaimed waste disposal site, and in nearby remnant woodland, in suburban Sydney, Australia. While no catches were made in autumn, more earthworms were found in spring (21 ± 8.6 m(-2)) than in winter (10.2 ± 5.9 m(-2)) or summer (14.4 ± 5.5 m(-2)). Earthworm abundance in spring was in the order grassland ≈ Plantation-04 (35.2 m(-2)) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; woodland (12.8 m(-2)) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; Plantation-06 (0.8 m(-2)). None of the revegetated covers had restored earthworm diversity to levels found in the woodland. Exotic species, mostly Microscolex dubius, dominated in the four vegetation covers at any time; the only two native species (Heteroporodrilus sp. and Megascoleceides sp.) found were in the woodland. We also assessed how quality of the evolving soils from the three revegetated covers, compared with that from the woodland, impacted viability of common exotic earthworm species. Both weight gain and cocoon production by the exotic earthworms were higher in the soil from Plantation-04 than in soils from the other vegetation covers, including the woodland; the two variables were positively correlated with the pH and mineral nutrient content (as indicated by electrical conductivity that was in turn correlated with clay content) of the soil. Age of vegetation rather than its composition explained differences in the level of earthworm recovery observed.
Quantifying water use of native vegetation is an important contribution to understanding landscap... more Quantifying water use of native vegetation is an important contribution to understanding landscape ecohydrology. Few studies provide long-term (more than one growing season) estimates of water use and even fewer quantify interseasonal and interannual variation in transpiration. Globally, changes in land use are significantly altering landscape ecohydrology, resulting in problems such as dryland salinity and excessive groundwater recharge. Estimating stand water use is complex in multispecies forests, due to the ...
... Soil water potential in the upper soil profile can decline from zero (wet season) to -3.5 MPa... more ... Soil water potential in the upper soil profile can decline from zero (wet season) to -3.5 MPa or lower (Goldstein et al., 1986; Holbrook et al., 1995; Franco et al., 1996) (see section III). ... 1. Four phenological guilds are recognized in Australian savannas (Williams et al., 1997). ...
(2002) Snowdon. Read by researchers in: 100% Environmental Sciences. Estimation of thebiomass and... more (2002) Snowdon. Read by researchers in: 100% Environmental Sciences. Estimation of thebiomass and carbon content of Australian forest and woodland ecosystems and its rate of change is an important goal of the National Carbon Accounting System. This protocol... ...
Increased woody plant density (woody encroachment or woody thickening) is a globally observed phe... more Increased woody plant density (woody encroachment or woody thickening) is a globally observed phenomenon. Similarly, increased atmospheric carbon dioxide concentrations and decreased pan evaporation rates are globally observed phenomena. In this paper, we propose that the former (increased woody plant density) is a product of the latter. We propose that decreased stomatal conductance and increased rates of carbon fixation arising from an enriched atmospheric carbon dioxide concentration, in conjunction with reduced rates of pan evaporation, result in increased woody plant density. We suggest that this is analogous to the increased woody plant density that is observed along rainfall gradients that span arid to mesic environments. From this conceptual model, we make three predictions, namely, that (a) long-term trends in tree water-use-efficiency should reveal increased values; (b) run-off data should show an increase where woody thickening is occurring; (c) enriched CO 2 experiments should reveal an enhanced plant water status. These three predictions are discussed and shown to be supported by experimental data.
Throughout Australia many groundwater dependent ecosystems have been adversely affected by unsymp... more Throughout Australia many groundwater dependent ecosystems have been adversely affected by unsympathetic water abstraction practices. In Western Australia, the largest single supply of drinking water for the city of Perth is a superficial aquifer known as the Gnangara Groundwater Mound, located over an area of approximately 2200 km2 within and to the north of the city on the coastal plain. The groundwater resource supplies 60% of Perth’s pubic drinking water supply and 85% of total water demand for all users. Much of the mound is overlain by phreatophytic Banksia woodland that is susceptible to drought stress and death if the root system is separated from the unconfined aquifer for prolonged periods over the hot, dry Mediterranean summer. Drought stress has been exacerbated by diminished rainfall due to a changing climate regime. The aim of this research is to develop guidelines for sustainable groundwater abstraction (timing and volume) that will maintain the long term integrity of the ecosystem and recover up to 5GL/yr from existing borefields. We seek to investigate whether a change in abstraction regime, from ‘peak demand’ summer pumping to winter pumping allows groundwater levels to recover sufficiently prior to summer, thereby maintaining a healthy vegetation system. Hydrological and plant water status parameters were monitored over two winters at research sites with an initial depth to groundwater of less than 5m. During winter and spring, groundwater abstraction at a reduced capacity resulted in a 0.75m drawdown. Operation of the bores did not adversely impact the water status of phreatophytic Banksia at the study sites relative to control sites. Analysis of plant water source partitioning indicated that plants exposed to the winter drawdown were sustained by unsaturated zone soil moisture storage replenished by winter rainfall. When pumping ceased, the water table rose rapidly and plants utilised more groundwater during late spring and summer as the soil water store became depleted. A simple water balance model combined with phreatophyte vulnerability assessment was employed to identify allowable magnitude and rate of drawdown, and duration of bore operation.
Transactions of the British Mycological Society, 1986
The influence of substratum water potential on the growth of Serpula lacrimans and Phallus impudi... more The influence of substratum water potential on the growth of Serpula lacrimans and Phallus impudicus was investigated. Two methods of adjusting the water potential of the substratum were used; both gave qualitatively similar results. Linear growth rate decreased with substratum water potential. The turgor potential at the mycelial front and linear growth rate were positively correlated in both species on both media. An experiment concerned with growth from a medium of high water potential to one oflower water potential and vice versa produced results consistent with those obtained for growth on a single medium.
Tropical forests hold large stores of carbon, yet uncertainty remains regarding their quantitativ... more Tropical forests hold large stores of carbon, yet uncertainty remains regarding their quantitative contribution to the global carbon cycle. One approach to quantifying carbon biomass stores consists in inferring changes from long-term forest inventory plots. Regression models are used to convert inventory data into an estimate of aboveground biomass (AGB). We provide a critical reassessment of the quality and the robustness of these models across tropical forest types, using a large dataset of 2,410 trees ‡ 5 cm diameter, directly harvested in 27 study sites across the tropics. Proportional relationships between aboveground biomass and the prod-uct of wood density, trunk cross-sectional area, and total height are constructed. We also develop a regression model involving wood density and stem diameter only. Our models were tested for secondary and oldgrowth forests, for dry, moist and wet forests, for lowland and montane forests, and for mangrove forests. The most important predictors of AGB of a tree were, in decreasing order of importance, its trunk diameter, wood specific gravity, total height, and forest type (dry, moist, or wet). Overestimates prevailed, giving a bias of 0.5-6.5% when errors were averaged across all stands. Our regression models can be used reliably to predict aboveground tree biomass across a broad range of tropical forests. Because they are based on an unprecedented dataset, these models should improve the quality Electronic Supplementary Material Supplementary material is available for this article at http://dx.of tropical biomass estimates, and bring consensus about the contribution of the tropical forest biome and tropical deforestation to the global carbon cycle.
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Papers by Derek Eamus