russell fairfax - Academia.edu (original) (raw)
Papers by russell fairfax
Australian Geographical Studies, 2002
Landscape Ecology, 2009
There is circumstantial evidence that grasslands on the Bunya Mountains were once maintained by A... more There is circumstantial evidence that grasslands on the Bunya Mountains were once maintained by Aboriginal burning, and with lack of fire under European management are being colonised by trees. To assess the efficacy of burning for maintaining grasslands, 119 fires were lit between 1996 and 2006. The total area of unburnt grasslands decreased by 27%, while grasslands burnt at least once decreased by 1%. The density of invading trees was recorded from fixed plots on 23 grasslands burnt between one and six times. Cassinia was virtually eliminated and the density of the Rainforest species guild slowly but continually declined. Acacia irrorata exhibited a humped response, with initial increases resulting from vegetative resprouting and gradual decline with persistent burning. Phyllodinous Acacia and Woodland trees were the least fire sensitive guilds, having stable or increased density with repeated burning. Multi-factor regression modelling detected no significant relationships between changes in woody plant density and the interval between fires, fire intensity, the initial density of large trees, an index of soil moisture, or the cumulative number of fires for any species guild. The survivorship of both Cassinia and Rainforest guilds was significantly lower with summer burning than winter burning, but a seasonal effect of burning was not evident for other guilds. The findings suggest that regardless of fire conditions, frequent burning will reduce the number of adult trees, maintain resprouts in an immature state, facilitate further fire and reduce the rate of grassland loss. Woodland species are especially resilient to fire, and burning to maintain grassy ecosystems will be most successful where the main colonisers are rainforest species and burning is conducted in summer. The findings suggest that the montane grasslands of the Bunya Mountains were maintained by anthropogenic burning and active fire management will prolong their existence.
Wetlands Ecology and Management, 2003
The Great Artesian Basin is an aquifer system that underlies a large area of north-eastern Austra... more The Great Artesian Basin is an aquifer system that underlies a large area of north-eastern Australia. The spring wetlands in the Great Artesian Basin are of conservation significance because they provide habitat for endemic species including fish, invertebrates and plants. Since European settlement massive quantities of water have been artificially extracted through bores, reducing spring-flows. Records of the springs of the Queensland section of the Great Artesian Basin (excluding Cape York Peninsula) were compiled from a range of historical sources. Most remaining active springs were visited and surveyed, the physical attributes of the springs described and their current status determined. Recharge springs occur in areas where the evidence suggests the basin is recharged by rainfall and 93% of the original 245 spring-groups in these areas are still active. Discharge springs occur in sections of the Basin down-gradient of the recharge areas and only 36% of the original 300 spring-groups in these areas have at least some springs that are still active. The capping of bores could provide a partial restoration of artesian pressure and enhance spring flows. Of the active spring-groups surveyed 26% have suffered major or total damage as a result of excavation of the wetlands. An emerging threat is the use of exotic grasses as ponded pastures, which have the ability to dominate the habitat of spring wetlands. The potential impacts of other threats including those associated with stock, exotic animals and fire are also discussed. Mitigating these threats requires a conservation strategy that seeks to protect remaining springs with high conservation values.
Global Change Biology, 2009
Increasing densities of woody plants in savannas has been attributed to both elevated atmospheric... more Increasing densities of woody plants in savannas has been attributed to both elevated atmospheric CO2 and reduced burning with grazing management, such that the biome could represent a substantial carbon sink. However, we show that extreme droughts (less than two-thirds expected rainfall over 3 years) occur in the drier half of the savanna biome and can cause substantial tree death. An Australian case study reveals that a net increase in tree cover over five decades of above-average rainfall was offset by sudden tree death during drought. The relationship between woody cover change and rainfall is moderated by competition with growth being facilitated by low woody cover and drought-induced death more likely as the woody component of savanna increases. The results are not supportive of a sustained increase in the woody component of xeric savannas resulting from CO2 fertilization or land management. Extensive tree death in savanna regions will become a stark consequence of climate change if predictions of increasing severity and frequency of drought are realized.
Journal of Environmental Management, 2003
Features of the land management history over a 125,755 km(2) area of central Queensland, Australi... more Features of the land management history over a 125,755 km(2) area of central Queensland, Australia were determined from a variety of sources. A random sample of 205 site locations provided the basis for determining trends in land use. Trends in vegetation clearing were determined using sequential aerial photography for the sample sites, revealing a steady rate averaging nearly 1% of the region per annum over 41 years. This measure of sustained clearing over a large region is higher than recently published clearing rates from South America. Land types have been selectively cleared with over 90% of the Acacia on clay land type having been cleared. A land-holder questionnaire pertaining to the random sites yielded a response rate of 71% and provided information on vegetation clearing, ploughing, tree killing (ring-barking or tree poisoning), and fire frequency, season and intensity. The land-holder responses were compared with independent data sources where possible and revealed no mis-information. However, land-holders may have been marginally less likely to respond if the sample area had been cleared, although this effect was not statistically significant. Ploughing and tree killing are variable depending on land type, but the former has affected about 40% of the Acacia on clay land type, effectively eliminating options for natural regrowth. The proportion of decade-site combinations that were reported as having no fires increased from 22% in the 1950s to an average of 42% for subsequent decades, although the reporting of more than one fire per decade has been relatively constant through the study period. The reporting of at least one fire per decade varies from 46% for the Acacia on sand land type to 77% for the Eucalypt on sand land type for decade-site combinations. Fires are more intense when associated with clearing than in uncleared vegetation, but the proportion of cool and hot fires is relatively constant between land types in uncleared vegetation. Nearly all fires reported were either in spring or summer and this seasonally restricted regime is probably at variance with Aboriginal fire regimes. This study describes the rapid transformation of central Queensland. This has yielded substantially increased agricultural production but may also result in a range of negative impacts and these are discussed.
Austral Ecology, 2006
Abstract: Eucalyptus tereticornis seedlings occurring on the edges of grassy balds on the Bunya M... more Abstract: Eucalyptus tereticornis seedlings occurring on the edges of grassy balds on the Bunya Mountains were burnt by four separate fires. From the results, a logistic model demonstrated that lignotuber size was positively related and fire temperature negatively related to survivorship. While mortality was high for young seedlings there was no mortality of 5-year old survivors from these trials subject to repeat burning. The model predicted that burning every 2 years will not substantially limit seedling establishment. This prediction was strengthened by results verifying that management fires on the grassy balds are generally of low intensity. Fire intensity is weakly related to a Fire Danger Index, indicating that the timing of burning in relation to weather conditions will not substantially enhance opportunities for more intense fires. Thus, even with biennial burning under optimal conditions eucalypt forest will replace grassy balds where they adjoin. Regular burning by aborigines may have maintained grassy bald-rainforest boundaries, but not boundaries with eucalypt forest. Seed dispersal and migration barriers may have limited the expansion of eucalypt forest. It is concluded that under current conditions the long-term preservation of the grassy balds is only possible where they are entirely surrounded by rainforest and are regularly burnt.
Journal of Biogeography, 2003
Aim This study documents the effects of multiple fires and drought on the woody structure of a no... more Aim This study documents the effects of multiple fires and drought on the woody structure of a north Australian savanna never grazed by domestic stock.Location The study was conducted in a 500 ha pocket of Eucalyptus-dominated savanna surrounded by a late Quaternary lava flow. The flow is known as the Great Basalt Wall, located c. 50 km northeast of Charters Towers in semi-arid north-eastern Australia. This region was exposed to the largest 5-year rainfall deficit on record between 1992 and 1996.Methods All individual woody plants were tagged within a 1.56 ha plot. Species were segregated into their habitat affinities (rain forest, ecotone, savanna) and regeneration strategy (resprouter, seeder). The survivorship of plants within these categories was analysed in relation to fire intensity from the first fire, and to each of four fires lit between 1996 and 2001.Results Before the first fire, the plot contained thirty-one tree species including twenty-one typical of the surrounding dry rain forest. These rain forest species were represented by small individuals and constituted <1% of the total basal area of woody plants. The basal area of savanna trees was 7.5 m2 ha−1 at the commencement of monitoring, although 31% had recently died and others had major crown damage. Further death of the drought debilitated savanna trees was substantial during the first year of monitoring and the basal area of live savanna trees declined to 1.1 m2 ha−1 after 5 years. Most species from both rain forest and savanna were classified as resprouters and are capable of regenerating from underground organs after fire. Species without this ability (rain forest seeders and ecotone seeders) were mostly eliminated after the first two consecutive fires. Among resprouters, survivorship declined as fire intensity increased and this was more pronounced for rain forest than for savanna species. Repeated burning produced a cumulative effect of decreasing survivorship for rain forest resprouters relative to savanna resprouters.Main conclusions The study provides evidence that savanna and rain forest trees differ in fire susceptibility and that recurrent fire can explain the restricted distribution of rain forest in the seasonally arid Australian tropics. The time of death of the savanna trees is consistent with the regional pattern after severe drought, and highlights the importance of medium term climate cycles for the population dynamics of savanna tree species and structure of Australian savannas.
Journal of Vegetation Science, 2010
Questions: The following hypotheses of neighbourhood effects on drought-induced mortality are eva... more Questions: The following hypotheses of neighbourhood effects on drought-induced mortality are evaluated: (A) drought-induced stem death is randomly distributed in space, (B) stems are predisposed to drought-induced death through negative density-dependent effects and (C) stems are predisposed to drought-induced death due to local deficits in plant available resources.Location: Central Queensland, Australia.Methods: Recent mass mortality of woody stems was surveyed and mapped in three 1.21-ha quadrats within Eucalyptus melanophloia-dominated savanna. A multi-faceted analytical approach was adopted including spatial pattern analyses, two logistic regressions of neighbourhood density effects on survival and spatial autocorrelation analyses of model residuals.Results: Mortality was concentrated in stems ≤15-cm diameter at breast height (DBH). Survival was aggregated or random in quadrats 1 and 3 and random o regular in quadrat 2. Small neighbour density had a negative effect on survival in all quadrats. In addition, the second model identified a positive relationship between survival and living neighbour density in quadrat 3 (indicating a resource patch effect), but a negative relationship in quadrat 2 (density effect). Analysis of model residuals showed that neighbour density explained mortality equally well across quadrat 2, but not across quadrats 1 and 3.Conclusions: There was evidence in support of hypotheses B (neighbour density) and C (resource heterogeneity). We found strong support for an interaction between microsite quality and neighbourhood stem densities, and suggest that this interaction is driven by plant available water.
International Journal of Remote Sensing, 2002
Cover of vegetation understorey and overstorey was determined from aerial photography at 1:25000 ... more Cover of vegetation understorey and overstorey was determined from aerial photography at 1:25000 and 1:40000 scales by a grid sampling technique. Models were developed relating values of aerial cover to éeld cover as determined by intensive é eld measurement. The inè uence of photo-scale, photo colour, the angle of the image, shadow, the hiatus between aerial and é eld sampling,
Australian Journal of Botany, 2004
Biological Conservation, 2000
Australian Journal of Botany, 1996
Journal of Vegetation Science, 2007
Ecological Management and Restoration, 2003
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2010
Focusing on woody vegetation in Queensland, Australia, the study aimed to establish whether the r... more Focusing on woody vegetation in Queensland, Australia, the study aimed to establish whether the relationship between Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) HH and HV backscattering coefficients and above ground biomass (AGB) was consistent within and between structural formations (forests, woodlands and open woodlands, including scrub). Across these formations, 2781 plot-based measurements (from 1139 sites) of tree diameters by species were collated, from which AGB was estimated using generic allometric equations. For Queensland, PALSAR fine beam dual (FBD) 50 m strip data for 2007 were provided through the Japanese Space Exploration Agency's (JAXA) Kyoto and Carbon (K&C) Initiative, with up to 3 acquisitions available for each Reference System for Planning (RSP) paths. When individual strips acquired over Queensland were combined, `banding' was evident within the resulting mosaics, with this attributed to enhanced L-band backscatter following rainfall events in some areas. Reference to Advanced Microwave Scanning Radiometer-EOS (AMSR-E) data indicated that strips with enhanced L-band backscatter corresponded to areas with increased effective vegetation water content (kg m-2) and, to a lesser extent, soil moisture (g cm-3). Regardless of moisture conditions, L-band HV topographically normalized backscattering intensities backscatter (σfo) increased asymptotically with AGB, with the saturation level being greatest for forests and least for open woodlands. However, under conditions of relative maximum surface moisture, L-band HV and HH σfo was enhanced by as much as 2.5 and 4.0 dB respectively, particularly for forests of lower AGB, with this resulting in an overall reduction in dynamic range. The saturation level also reduced at L-band HH for forests and woodlands but remained similar for open woodlands. Differences in the rate of increase in bo- - th L-band HH and HV σfo with AGB were observed between forests and the woodland categories (for both relatively wet and dry conditions) with these attributed, in part, to differences in the size class distribution and stem density between non-remnant (secondary) forests and remnant woodlands of lower AGB. The study concludes that PALSAR data acquired when surface moisture and rainfall are minimal allow better estimation of the AGB of woody vegetation and that retrieval algorithms ideally need to consider differences in surface moisture conditions and vegetation structure.
Australian Journal of Botany, 2004
Biological Conservation, 2008
Commercial grazing is possible over much of arid Australia due to a high density of artificial wa... more Commercial grazing is possible over much of arid Australia due to a high density of artificial watering points. The broadscale supplementation of drinking water has not only enhanced densities of sheep (Ovies aries), cattle (Bos taurus, Bos indicus) and goats (Capra hircus), ...
Journal of Environmental Management, 2003
Australian Geographical Studies, 2002
Landscape Ecology, 2009
There is circumstantial evidence that grasslands on the Bunya Mountains were once maintained by A... more There is circumstantial evidence that grasslands on the Bunya Mountains were once maintained by Aboriginal burning, and with lack of fire under European management are being colonised by trees. To assess the efficacy of burning for maintaining grasslands, 119 fires were lit between 1996 and 2006. The total area of unburnt grasslands decreased by 27%, while grasslands burnt at least once decreased by 1%. The density of invading trees was recorded from fixed plots on 23 grasslands burnt between one and six times. Cassinia was virtually eliminated and the density of the Rainforest species guild slowly but continually declined. Acacia irrorata exhibited a humped response, with initial increases resulting from vegetative resprouting and gradual decline with persistent burning. Phyllodinous Acacia and Woodland trees were the least fire sensitive guilds, having stable or increased density with repeated burning. Multi-factor regression modelling detected no significant relationships between changes in woody plant density and the interval between fires, fire intensity, the initial density of large trees, an index of soil moisture, or the cumulative number of fires for any species guild. The survivorship of both Cassinia and Rainforest guilds was significantly lower with summer burning than winter burning, but a seasonal effect of burning was not evident for other guilds. The findings suggest that regardless of fire conditions, frequent burning will reduce the number of adult trees, maintain resprouts in an immature state, facilitate further fire and reduce the rate of grassland loss. Woodland species are especially resilient to fire, and burning to maintain grassy ecosystems will be most successful where the main colonisers are rainforest species and burning is conducted in summer. The findings suggest that the montane grasslands of the Bunya Mountains were maintained by anthropogenic burning and active fire management will prolong their existence.
Wetlands Ecology and Management, 2003
The Great Artesian Basin is an aquifer system that underlies a large area of north-eastern Austra... more The Great Artesian Basin is an aquifer system that underlies a large area of north-eastern Australia. The spring wetlands in the Great Artesian Basin are of conservation significance because they provide habitat for endemic species including fish, invertebrates and plants. Since European settlement massive quantities of water have been artificially extracted through bores, reducing spring-flows. Records of the springs of the Queensland section of the Great Artesian Basin (excluding Cape York Peninsula) were compiled from a range of historical sources. Most remaining active springs were visited and surveyed, the physical attributes of the springs described and their current status determined. Recharge springs occur in areas where the evidence suggests the basin is recharged by rainfall and 93% of the original 245 spring-groups in these areas are still active. Discharge springs occur in sections of the Basin down-gradient of the recharge areas and only 36% of the original 300 spring-groups in these areas have at least some springs that are still active. The capping of bores could provide a partial restoration of artesian pressure and enhance spring flows. Of the active spring-groups surveyed 26% have suffered major or total damage as a result of excavation of the wetlands. An emerging threat is the use of exotic grasses as ponded pastures, which have the ability to dominate the habitat of spring wetlands. The potential impacts of other threats including those associated with stock, exotic animals and fire are also discussed. Mitigating these threats requires a conservation strategy that seeks to protect remaining springs with high conservation values.
Global Change Biology, 2009
Increasing densities of woody plants in savannas has been attributed to both elevated atmospheric... more Increasing densities of woody plants in savannas has been attributed to both elevated atmospheric CO2 and reduced burning with grazing management, such that the biome could represent a substantial carbon sink. However, we show that extreme droughts (less than two-thirds expected rainfall over 3 years) occur in the drier half of the savanna biome and can cause substantial tree death. An Australian case study reveals that a net increase in tree cover over five decades of above-average rainfall was offset by sudden tree death during drought. The relationship between woody cover change and rainfall is moderated by competition with growth being facilitated by low woody cover and drought-induced death more likely as the woody component of savanna increases. The results are not supportive of a sustained increase in the woody component of xeric savannas resulting from CO2 fertilization or land management. Extensive tree death in savanna regions will become a stark consequence of climate change if predictions of increasing severity and frequency of drought are realized.
Journal of Environmental Management, 2003
Features of the land management history over a 125,755 km(2) area of central Queensland, Australi... more Features of the land management history over a 125,755 km(2) area of central Queensland, Australia were determined from a variety of sources. A random sample of 205 site locations provided the basis for determining trends in land use. Trends in vegetation clearing were determined using sequential aerial photography for the sample sites, revealing a steady rate averaging nearly 1% of the region per annum over 41 years. This measure of sustained clearing over a large region is higher than recently published clearing rates from South America. Land types have been selectively cleared with over 90% of the Acacia on clay land type having been cleared. A land-holder questionnaire pertaining to the random sites yielded a response rate of 71% and provided information on vegetation clearing, ploughing, tree killing (ring-barking or tree poisoning), and fire frequency, season and intensity. The land-holder responses were compared with independent data sources where possible and revealed no mis-information. However, land-holders may have been marginally less likely to respond if the sample area had been cleared, although this effect was not statistically significant. Ploughing and tree killing are variable depending on land type, but the former has affected about 40% of the Acacia on clay land type, effectively eliminating options for natural regrowth. The proportion of decade-site combinations that were reported as having no fires increased from 22% in the 1950s to an average of 42% for subsequent decades, although the reporting of more than one fire per decade has been relatively constant through the study period. The reporting of at least one fire per decade varies from 46% for the Acacia on sand land type to 77% for the Eucalypt on sand land type for decade-site combinations. Fires are more intense when associated with clearing than in uncleared vegetation, but the proportion of cool and hot fires is relatively constant between land types in uncleared vegetation. Nearly all fires reported were either in spring or summer and this seasonally restricted regime is probably at variance with Aboriginal fire regimes. This study describes the rapid transformation of central Queensland. This has yielded substantially increased agricultural production but may also result in a range of negative impacts and these are discussed.
Austral Ecology, 2006
Abstract: Eucalyptus tereticornis seedlings occurring on the edges of grassy balds on the Bunya M... more Abstract: Eucalyptus tereticornis seedlings occurring on the edges of grassy balds on the Bunya Mountains were burnt by four separate fires. From the results, a logistic model demonstrated that lignotuber size was positively related and fire temperature negatively related to survivorship. While mortality was high for young seedlings there was no mortality of 5-year old survivors from these trials subject to repeat burning. The model predicted that burning every 2 years will not substantially limit seedling establishment. This prediction was strengthened by results verifying that management fires on the grassy balds are generally of low intensity. Fire intensity is weakly related to a Fire Danger Index, indicating that the timing of burning in relation to weather conditions will not substantially enhance opportunities for more intense fires. Thus, even with biennial burning under optimal conditions eucalypt forest will replace grassy balds where they adjoin. Regular burning by aborigines may have maintained grassy bald-rainforest boundaries, but not boundaries with eucalypt forest. Seed dispersal and migration barriers may have limited the expansion of eucalypt forest. It is concluded that under current conditions the long-term preservation of the grassy balds is only possible where they are entirely surrounded by rainforest and are regularly burnt.
Journal of Biogeography, 2003
Aim This study documents the effects of multiple fires and drought on the woody structure of a no... more Aim This study documents the effects of multiple fires and drought on the woody structure of a north Australian savanna never grazed by domestic stock.Location The study was conducted in a 500 ha pocket of Eucalyptus-dominated savanna surrounded by a late Quaternary lava flow. The flow is known as the Great Basalt Wall, located c. 50 km northeast of Charters Towers in semi-arid north-eastern Australia. This region was exposed to the largest 5-year rainfall deficit on record between 1992 and 1996.Methods All individual woody plants were tagged within a 1.56 ha plot. Species were segregated into their habitat affinities (rain forest, ecotone, savanna) and regeneration strategy (resprouter, seeder). The survivorship of plants within these categories was analysed in relation to fire intensity from the first fire, and to each of four fires lit between 1996 and 2001.Results Before the first fire, the plot contained thirty-one tree species including twenty-one typical of the surrounding dry rain forest. These rain forest species were represented by small individuals and constituted <1% of the total basal area of woody plants. The basal area of savanna trees was 7.5 m2 ha−1 at the commencement of monitoring, although 31% had recently died and others had major crown damage. Further death of the drought debilitated savanna trees was substantial during the first year of monitoring and the basal area of live savanna trees declined to 1.1 m2 ha−1 after 5 years. Most species from both rain forest and savanna were classified as resprouters and are capable of regenerating from underground organs after fire. Species without this ability (rain forest seeders and ecotone seeders) were mostly eliminated after the first two consecutive fires. Among resprouters, survivorship declined as fire intensity increased and this was more pronounced for rain forest than for savanna species. Repeated burning produced a cumulative effect of decreasing survivorship for rain forest resprouters relative to savanna resprouters.Main conclusions The study provides evidence that savanna and rain forest trees differ in fire susceptibility and that recurrent fire can explain the restricted distribution of rain forest in the seasonally arid Australian tropics. The time of death of the savanna trees is consistent with the regional pattern after severe drought, and highlights the importance of medium term climate cycles for the population dynamics of savanna tree species and structure of Australian savannas.
Journal of Vegetation Science, 2010
Questions: The following hypotheses of neighbourhood effects on drought-induced mortality are eva... more Questions: The following hypotheses of neighbourhood effects on drought-induced mortality are evaluated: (A) drought-induced stem death is randomly distributed in space, (B) stems are predisposed to drought-induced death through negative density-dependent effects and (C) stems are predisposed to drought-induced death due to local deficits in plant available resources.Location: Central Queensland, Australia.Methods: Recent mass mortality of woody stems was surveyed and mapped in three 1.21-ha quadrats within Eucalyptus melanophloia-dominated savanna. A multi-faceted analytical approach was adopted including spatial pattern analyses, two logistic regressions of neighbourhood density effects on survival and spatial autocorrelation analyses of model residuals.Results: Mortality was concentrated in stems ≤15-cm diameter at breast height (DBH). Survival was aggregated or random in quadrats 1 and 3 and random o regular in quadrat 2. Small neighbour density had a negative effect on survival in all quadrats. In addition, the second model identified a positive relationship between survival and living neighbour density in quadrat 3 (indicating a resource patch effect), but a negative relationship in quadrat 2 (density effect). Analysis of model residuals showed that neighbour density explained mortality equally well across quadrat 2, but not across quadrats 1 and 3.Conclusions: There was evidence in support of hypotheses B (neighbour density) and C (resource heterogeneity). We found strong support for an interaction between microsite quality and neighbourhood stem densities, and suggest that this interaction is driven by plant available water.
International Journal of Remote Sensing, 2002
Cover of vegetation understorey and overstorey was determined from aerial photography at 1:25000 ... more Cover of vegetation understorey and overstorey was determined from aerial photography at 1:25000 and 1:40000 scales by a grid sampling technique. Models were developed relating values of aerial cover to éeld cover as determined by intensive é eld measurement. The inè uence of photo-scale, photo colour, the angle of the image, shadow, the hiatus between aerial and é eld sampling,
Australian Journal of Botany, 2004
Biological Conservation, 2000
Australian Journal of Botany, 1996
Journal of Vegetation Science, 2007
Ecological Management and Restoration, 2003
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2010
Focusing on woody vegetation in Queensland, Australia, the study aimed to establish whether the r... more Focusing on woody vegetation in Queensland, Australia, the study aimed to establish whether the relationship between Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) HH and HV backscattering coefficients and above ground biomass (AGB) was consistent within and between structural formations (forests, woodlands and open woodlands, including scrub). Across these formations, 2781 plot-based measurements (from 1139 sites) of tree diameters by species were collated, from which AGB was estimated using generic allometric equations. For Queensland, PALSAR fine beam dual (FBD) 50 m strip data for 2007 were provided through the Japanese Space Exploration Agency's (JAXA) Kyoto and Carbon (K&C) Initiative, with up to 3 acquisitions available for each Reference System for Planning (RSP) paths. When individual strips acquired over Queensland were combined, `banding' was evident within the resulting mosaics, with this attributed to enhanced L-band backscatter following rainfall events in some areas. Reference to Advanced Microwave Scanning Radiometer-EOS (AMSR-E) data indicated that strips with enhanced L-band backscatter corresponded to areas with increased effective vegetation water content (kg m-2) and, to a lesser extent, soil moisture (g cm-3). Regardless of moisture conditions, L-band HV topographically normalized backscattering intensities backscatter (σfo) increased asymptotically with AGB, with the saturation level being greatest for forests and least for open woodlands. However, under conditions of relative maximum surface moisture, L-band HV and HH σfo was enhanced by as much as 2.5 and 4.0 dB respectively, particularly for forests of lower AGB, with this resulting in an overall reduction in dynamic range. The saturation level also reduced at L-band HH for forests and woodlands but remained similar for open woodlands. Differences in the rate of increase in bo- - th L-band HH and HV σfo with AGB were observed between forests and the woodland categories (for both relatively wet and dry conditions) with these attributed, in part, to differences in the size class distribution and stem density between non-remnant (secondary) forests and remnant woodlands of lower AGB. The study concludes that PALSAR data acquired when surface moisture and rainfall are minimal allow better estimation of the AGB of woody vegetation and that retrieval algorithms ideally need to consider differences in surface moisture conditions and vegetation structure.
Australian Journal of Botany, 2004
Biological Conservation, 2008
Commercial grazing is possible over much of arid Australia due to a high density of artificial wa... more Commercial grazing is possible over much of arid Australia due to a high density of artificial watering points. The broadscale supplementation of drinking water has not only enhanced densities of sheep (Ovies aries), cattle (Bos taurus, Bos indicus) and goats (Capra hircus), ...
Journal of Environmental Management, 2003