The fire-prone shrublands of southwestern Australia are renowned for their high plant species div... more The fire-prone shrublands of southwestern Australia are renowned for their high plant species diversity and prominence of canopy seed storage (serotiny). We compared species richness, abundance, and life history attributes for soil and canopy seed banks in relation to extant vegetation among four sites with different substrate conditions and high species turnover (50-80%) to identify whether this unusual community-level organization of seed storage might contribute to maintenance of high species richness. Soil seed bank (SSB) densities were low to moderate (233-1435 seeds/m 2) compared with densities for other Mediterranean-type vegetation and were lowest for sites with highest canopy seed bank (CSB) species richness and lowest nutrient availability, but not richness or abundance of resprouters. Annuals were infrequent in the lowest nutrient sites, but there was no evidence that small SSB size was due to low seed inputs or a trade-off between seed production/storage and seed size in response to low nutrient availability. Sorensen's similarity between SSB and extant vegetation was 26-43% but increased to 54-57% when the CSB was included, representing levels higher than reported for most other ecosystems. Resprouting species were well represented in both the SSB and CSB, and there was no evidence for lower seed production in resprouters than in non-sprouters overall. The SSB and CSB held no species in common and were characterized by markedly different seed dispersal attributes, with winged or small seeds in the CSB and seeds dispersed by ants, birds, and wind (though none with wings) in the SSB. There was no evidence of spatial differentiation in the distribution of seeds of SSB species between vegetated and open microsites that might facilitate species coexistence, but most woody non-sprouters showed aggregation at scales of 1-2 m, implying limited seed dispersal. High similarity between overall seed bank (SSB þ CSB) and extant species composition, high number of resprouting species, and seed dispersal processes before (SSB) and after fire (CSB) leading to differential spatial aggregation of postfire recruits from the two seed bank types may buffer species composition against rapid change and provide a mechanism for maintaining species coexistence at the local scale.
Westcott V Enright N Miller B Fontaine J and Lamont B Defining a Minimum Fire Return Interval For the Northern Sandplain Shrublands Western Australia in Ecological Society of Australia 2011 Annual Conference 21 25 November Hobart Australia, 2011
Enright N Groeneveld J Lamont B and Perry G Why Can Fire Killed and Resprouting Shrub Species Co Exist in Mediterranean Type Metacommunities in 10th International Congress of Ecology 16 21 August Brisbane Australia, 2009
Vegetation and soil properties of an iron-rich canga (laterite) island on the largest outcrop of ... more Vegetation and soil properties of an iron-rich canga (laterite) island on the largest outcrop of banded-iron formation in Serra de Carajás (eastern Amazonia, Brazil) were studied along a topographic gradient (738-762 m asl), and analyzed to test the hypothesis that soil chemical and physical attributes play a key role in the structure and floristic composition of these plant communities. Soil and vegetation were sampled in eight replicate plots within each of the four vegetation types. Surface (0-10 cm) soil samples from each plot were analyzed for basic cations, N, P and plant species density for all species was recorded. CCA ordination analysis showed a strong separation between forest and non-forest sites on the first axis, and between herbaceous and shrubby campo rupestre on the second axis. The four vegetation types shared few plant species, which was attributed to their distinctive soil environments and filtering of their constituent species by chemical, physical and hydrologi...
Ecological Science at the Frontier: Celebrating ESA's Centennial Don't forget to renew your membe... more Ecological Science at the Frontier: Celebrating ESA's Centennial Don't forget to renew your membership for 2015 to receive reduced registration fees for this very special event! For more information visit: www.esa.org/baltimore
There are two species of Araucaria in New Guinea, A. cunninghamii D. Don and A. hunsteinii K. Sch... more There are two species of Araucaria in New Guinea, A. cunninghamii D. Don and A. hunsteinii K. Schumm. Forests containing these species are of great interest to biologists for several reasons. They are among the most ancient and phylogenetically primitive of the world’s surviving conifers, are held in special regard (e.g. superstitious and religious) by the indigenous people in many parts of New Guinea, and are an economically valuable source of timber. Their ecology is of particular interest as most gymnosperms, and most other members of this genus, are absent from wet lowland tropical environments. Competition between species in such areas is generally considered to be intense and one might expect the evolutionary more advanced angiosperms to be advantaged in the struggle for survival.
Global positioning system (GPS) technology for tracking wildlife continues to evolve at a remarka... more Global positioning system (GPS) technology for tracking wildlife continues to evolve at a remarkable pace. As animal movement is increasingly recognised as being critical for several ecological processes, advanced telemetry technology permits collection of a high volume of data across short time intervals that was previously unobtainable. Here we describe the use of GPS telemetry to track the movements of five tagged Emus (Dromaius novaehollandiae Latham) released within the Jarrah (Eucalyptus marginata Sm.) forests of southwestern Australia. The Emu plays a significant role as a seed disperser for many species. Describing the movement patterns of this species is a key requirement in refining the extent and significance of its contribution to seed dispersal, both locally and over long distances. We found that Emus followed a typical correlated random walk pattern and that each bird demonstrated a variable response to the landscape in terms of behaviour, extent of movement and habitat selection. From a methodological perspective, 50% of our devices detached before 30 days of GPS locations could be collected, reflecting a need for device refinement for future studies on large ratites. Nevertheless, our preliminary data provide useful insights into the movements of the Emu and potential impacts on seed dispersal within the Jarrah forests.
Questions: Translocation of topsoil and its seed bank for ecological restoration is increasingly ... more Questions: Translocation of topsoil and its seed bank for ecological restoration is increasingly popular. How representative is the soil seed bank of the extant vegetation at the source site? What influence does the transfer process have on germinant density, species and plant functional type composition? Does smoke and heat treatment of transferred topsoil enhance germination and potential for restoration success? Location: Banksia woodland of the Swan Coastal Plain, Western Australia. Methods: To assess the efficacy of topsoil transfer for return of native plant species, we measured topsoil seed bank characterisitcs in situ proir to vegetation clearing, and immediately after transfer of the topsoil to an adjacent, degraded mediterranean-type woodland in southwest Australia. Glasshouse germination of topsoil samples from 24 pre-and 24 post-transfer plots was used to quantify the effects of transfer and soil depth on germinant density, species richness, plant functional types and seed bank similarity to in situ vegetation. Application of germination cues (heat + smoke) was used to explore the impact of topsoil transfer on seed germination and emergence. Results: Topsoil transfer significantly reduced germinant densities (pre-transfer 1692-4239 germinantsÁm À2 , post-transfer 795-1016 germinantsÁm À2 ; t = 6.7, P < 0.001) and shifted community structure (MRPP: A = 0.13, P < 0.001), including a reduction of woody species density by 81%. For the majority of functional types, heat and smoke failed to stimulate additional germination post-transfer, suggesting soil transfer simulated the effect of fire-related germination cues. Conclusion: Although topsoil transfer translocated many viable native seeds, potential restoration success was hindered by reduced germinant densities. This was mostly attributable to a dilution effect associated with mixing of transferred topsoil, so that many seeds were buried too deep to emerge. However, total reductions were greater than expected based on dilution alone, suggesting some seed mortality during the transfer process. Transfer shifted composition towards dominance by annual species, suggesting the need for topsoil transfer to be supplemented by other restoration techniques.
Podocarp species and genus richness is higher in the Malesian region than anywhere else on earth,... more Podocarp species and genus richness is higher in the Malesian region than anywhere else on earth, with maximum genus richness in New Guinea and New Caledonia and maximum species richness in New Guinea and Borneo. Members of the Podocarpaceae occur across the whole geographic and altitudinal range occupied by forests and shrublands in the region. There is a strong tendency for podocarp dominance of vegetation to be restricted either to highaltitude sites close to the limit of tree growth or to other sites that might restrict plant growth in terms of water relations and nutrient supply (e.g., skeletal soils on steep slopes and ridges, heath forests, ultramafic parent material). Although some species are widespread in lowland forests, they are generally present at very low density, raising questions concerning their regeneration ecology and competitive ability relative to co-occurring angiosperm tree species. A number of species in the region are narrowly distributed, being restricted to single islands or mountain tops, and are of conservation concern. Our current understanding of the distribution and ecology of Malesian podocarps is reviewed in this chapter, and areas for further research are identified.
Inflorescence and seed production was traced over seven consecutive years for the nikau palm, Rho... more Inflorescence and seed production was traced over seven consecutive years for the nikau palm, Rhopalostylis sapida, growing in temperate forests of northern New Zealand. Palms reach reproductive maturity when stems exceed a height of about 2.2 m, have about 60 frond scars, and are estimated to be approximately 90 years of age. However, inflorescences on young-mature palms usually aborted, and seed set was low for palms <3 m in height. Both the frequency of fruiting and the size of annual seed crops increased with increasing palm height to a maximum in the 6-8 m height class. However, the pattern of seed production in relation to number of frond scars (a better index of age) suggested declining seed production in old palms.Seed production varied up to three-fold between years and between sites. Seed production palm yr correlated positively with rates of frond fall (= frond production), inflorescences palm, and seeds inflorescence. Reproductive effort rarely exceeded 50%, possibly because of constraints in palm architecture which closely link seed production to frond and stem production.Mature palms in shaded locations produced less seeds than did palms in more open sites. Lianes also reduced seed production by interfering with frond fall and causing inflorescences to abort.
Disturbance regime is a fundamental driver of plant community composition and structure, and of s... more Disturbance regime is a fundamental driver of plant community composition and structure, and of species coexistence. Fire is one of the most common causes of recurrent landscape scale disturbance, and has shaped evolution and adaptation in many taxa globally (Bond & Keeley 2005). Altered fire regimes are a significant component of global environmental change and have been implicated in species losses and invasions. Climate change is predicted to result in decreased precipitation and increased temperature across many fire-prone regions, resulting in longer fire seasons and increased fire likelihood, while reduced productivity may lead to increased fuel limitation and less fire in other situations (Moritz et al. 2012).
The southwest of Australia is a global biodiversity hotspot with high levels of plant species ric... more The southwest of Australia is a global biodiversity hotspot with high levels of plant species richness and endemism. Kwongan vegetation makes up part of this high diversity area and is dominated by woody shrub species. The focus of previous research on kwongan is dominated by fire, examining the role of fire in species lifecycles and the effect of differing fire regimes. However, little has been done thus far to investigate the potential effects of a changing climate on kwongan. This study aims to examine the effects of changing climate on the northern sandplain kwongan of southwest Australia, specifically, the effects of changes in rainfall and temperature on the demography of key sandplain shrub species. To achieve this, rainout shelters have been established to create a drought treatment by reducing rainfall, and this intercepted rainfall is being used to then create an increased rainfall treatment using gravity fed irrigation. Open top temperature chambers are being used to create an increased temperature treatment. The treatments are being applied to contrasting topo-edaphic locations: dune tops and swales, in newly burnt and unburnt sites, allowing comparison of effect between mature phase and regeneration phase vegetation.
Background/questions/methods: The main urban areas of Western Australia (WA) are located on the S... more Background/questions/methods: The main urban areas of Western Australia (WA) are located on the Swan Coastal Plain - the 400 km long sandy landform between the Indian Ocean and Darling Scarp that encompasses the main habitat for endangered Banksia woodland. This floristically rich but poorly understood Mediterranean-type ecosystem is being rapidly destroyed by urban, horticultural and industrial development. In order to partially ameliorate the damage being inflicted on Banksia woodland vegetation WA land developers have been required to purchase offsets of, often degraded, land to where topsoil from construction sites can be moved to help rehabilitate the damaged areas. The aim of this project is to restore Banksia woodlands by optimising germination and survival of native species from the soil seed bank contained within transferred topsoil. The project is a part of an offset program associated with the development of the Jandakot Airport 25 km south of Perth city. In the first year, key research questions are focused on enhancing germination by varying depth of returned topsoil, ripping, fencing, weed control and experimental additions of smoke. Subsequent work will examine the survival and persistence of germinants including treatments such as provision of artificial shade. Assessing the efficacy of a spectrum of novel restoration technologies will provide new insights for environmental management of endangered plant communities. Results/conclusions: Preliminary results will be presented at the conference.
ABSTRACT Background/Question/Methods Tree populations in mesic (&gt;650 mm ppt yr–1) savannas... more ABSTRACT Background/Question/Methods Tree populations in mesic (&gt;650 mm ppt yr–1) savannas of the world have strong demographic bottlenecks to the transition of sub-adults to the canopy layer. Such bottlenecks are a major determinant of savanna physiognomy, yet factors that allow sub-adults to traverse the bottleneck are little studied. A conceptual framework was developed, linking landscape-scale variables in savannas (eg, seasonal fires) to the probability of a sub-adult tree reaching the canopy, considering local environments (eg, understorey) and tree attributes (eg, size, seasonal phenology which varies with life history stage). In a 32,400 m2 field experiment, 2,405 juveniles (&lt;150 cm height) and saplings (150–499 cm) of the eucalypt canopy species were individually marked and measured the year prior to fires set in 3 different seasons and again at the end of the following growing season (without fires) and assessed for survival, resprouting, and height growth. All fire treatments were repeated in plots dominated by the most common understorey, a native annual grass (sorghum) and in plots dominated by perennial native species; these produce different fuels for fires and vary in seasonal phenologies and competitive regimes. Trees in unburnt plots served as controls, as did wet season fires which naturally eliminate sorghum. Results/Conclusions Fires topkilled most juveniles, but almost all were persistent and few genets died. Genet mortality of juveniles depended on fire season and of saplings to understorey. Fire season x understorey interactions were important for growth of large juveniles and the transition of juveniles to sapling stages. After early dry-season fires, large juveniles and small saplings grew faster, especially those in sorghum. After late dry or wet season fires, however, all of the small saplings (&lt;299 cm height) were reduced to “juveniles” and did not recover pre-fire heights but, produced many new basal (coppice) stems. Initial size was an important explanatory variable for all demographic and growth responses by juveniles and small saplings, generally positively, but not for large saplings. For example, after late dry-season fires, &gt;80% of large saplings (300–499 cm) were reduced to juvenile size in sorghum understorey, whereas in non-sorghum understorey, 60% of large saplings grew to poles (500–999 cm). Unburnt large saplings were more likely to die and transition probabilities to larger sizes decreased, the larger their size, especially in non-sorghum. The key to understanding and managing sustainable woody cover in mesic savannas lies in the complex interactions of sub-adult trees with local environments.
The fire-prone shrublands of southwestern Australia are renowned for their high plant species div... more The fire-prone shrublands of southwestern Australia are renowned for their high plant species diversity and prominence of canopy seed storage (serotiny). We compared species richness, abundance, and life history attributes for soil and canopy seed banks in relation to extant vegetation among four sites with different substrate conditions and high species turnover (50-80%) to identify whether this unusual community-level organization of seed storage might contribute to maintenance of high species richness. Soil seed bank (SSB) densities were low to moderate (233-1435 seeds/m 2) compared with densities for other Mediterranean-type vegetation and were lowest for sites with highest canopy seed bank (CSB) species richness and lowest nutrient availability, but not richness or abundance of resprouters. Annuals were infrequent in the lowest nutrient sites, but there was no evidence that small SSB size was due to low seed inputs or a trade-off between seed production/storage and seed size in response to low nutrient availability. Sorensen's similarity between SSB and extant vegetation was 26-43% but increased to 54-57% when the CSB was included, representing levels higher than reported for most other ecosystems. Resprouting species were well represented in both the SSB and CSB, and there was no evidence for lower seed production in resprouters than in non-sprouters overall. The SSB and CSB held no species in common and were characterized by markedly different seed dispersal attributes, with winged or small seeds in the CSB and seeds dispersed by ants, birds, and wind (though none with wings) in the SSB. There was no evidence of spatial differentiation in the distribution of seeds of SSB species between vegetated and open microsites that might facilitate species coexistence, but most woody non-sprouters showed aggregation at scales of 1-2 m, implying limited seed dispersal. High similarity between overall seed bank (SSB þ CSB) and extant species composition, high number of resprouting species, and seed dispersal processes before (SSB) and after fire (CSB) leading to differential spatial aggregation of postfire recruits from the two seed bank types may buffer species composition against rapid change and provide a mechanism for maintaining species coexistence at the local scale.
Westcott V Enright N Miller B Fontaine J and Lamont B Defining a Minimum Fire Return Interval For the Northern Sandplain Shrublands Western Australia in Ecological Society of Australia 2011 Annual Conference 21 25 November Hobart Australia, 2011
Enright N Groeneveld J Lamont B and Perry G Why Can Fire Killed and Resprouting Shrub Species Co Exist in Mediterranean Type Metacommunities in 10th International Congress of Ecology 16 21 August Brisbane Australia, 2009
Vegetation and soil properties of an iron-rich canga (laterite) island on the largest outcrop of ... more Vegetation and soil properties of an iron-rich canga (laterite) island on the largest outcrop of banded-iron formation in Serra de Carajás (eastern Amazonia, Brazil) were studied along a topographic gradient (738-762 m asl), and analyzed to test the hypothesis that soil chemical and physical attributes play a key role in the structure and floristic composition of these plant communities. Soil and vegetation were sampled in eight replicate plots within each of the four vegetation types. Surface (0-10 cm) soil samples from each plot were analyzed for basic cations, N, P and plant species density for all species was recorded. CCA ordination analysis showed a strong separation between forest and non-forest sites on the first axis, and between herbaceous and shrubby campo rupestre on the second axis. The four vegetation types shared few plant species, which was attributed to their distinctive soil environments and filtering of their constituent species by chemical, physical and hydrologi...
Ecological Science at the Frontier: Celebrating ESA's Centennial Don't forget to renew your membe... more Ecological Science at the Frontier: Celebrating ESA's Centennial Don't forget to renew your membership for 2015 to receive reduced registration fees for this very special event! For more information visit: www.esa.org/baltimore
There are two species of Araucaria in New Guinea, A. cunninghamii D. Don and A. hunsteinii K. Sch... more There are two species of Araucaria in New Guinea, A. cunninghamii D. Don and A. hunsteinii K. Schumm. Forests containing these species are of great interest to biologists for several reasons. They are among the most ancient and phylogenetically primitive of the world’s surviving conifers, are held in special regard (e.g. superstitious and religious) by the indigenous people in many parts of New Guinea, and are an economically valuable source of timber. Their ecology is of particular interest as most gymnosperms, and most other members of this genus, are absent from wet lowland tropical environments. Competition between species in such areas is generally considered to be intense and one might expect the evolutionary more advanced angiosperms to be advantaged in the struggle for survival.
Global positioning system (GPS) technology for tracking wildlife continues to evolve at a remarka... more Global positioning system (GPS) technology for tracking wildlife continues to evolve at a remarkable pace. As animal movement is increasingly recognised as being critical for several ecological processes, advanced telemetry technology permits collection of a high volume of data across short time intervals that was previously unobtainable. Here we describe the use of GPS telemetry to track the movements of five tagged Emus (Dromaius novaehollandiae Latham) released within the Jarrah (Eucalyptus marginata Sm.) forests of southwestern Australia. The Emu plays a significant role as a seed disperser for many species. Describing the movement patterns of this species is a key requirement in refining the extent and significance of its contribution to seed dispersal, both locally and over long distances. We found that Emus followed a typical correlated random walk pattern and that each bird demonstrated a variable response to the landscape in terms of behaviour, extent of movement and habitat selection. From a methodological perspective, 50% of our devices detached before 30 days of GPS locations could be collected, reflecting a need for device refinement for future studies on large ratites. Nevertheless, our preliminary data provide useful insights into the movements of the Emu and potential impacts on seed dispersal within the Jarrah forests.
Questions: Translocation of topsoil and its seed bank for ecological restoration is increasingly ... more Questions: Translocation of topsoil and its seed bank for ecological restoration is increasingly popular. How representative is the soil seed bank of the extant vegetation at the source site? What influence does the transfer process have on germinant density, species and plant functional type composition? Does smoke and heat treatment of transferred topsoil enhance germination and potential for restoration success? Location: Banksia woodland of the Swan Coastal Plain, Western Australia. Methods: To assess the efficacy of topsoil transfer for return of native plant species, we measured topsoil seed bank characterisitcs in situ proir to vegetation clearing, and immediately after transfer of the topsoil to an adjacent, degraded mediterranean-type woodland in southwest Australia. Glasshouse germination of topsoil samples from 24 pre-and 24 post-transfer plots was used to quantify the effects of transfer and soil depth on germinant density, species richness, plant functional types and seed bank similarity to in situ vegetation. Application of germination cues (heat + smoke) was used to explore the impact of topsoil transfer on seed germination and emergence. Results: Topsoil transfer significantly reduced germinant densities (pre-transfer 1692-4239 germinantsÁm À2 , post-transfer 795-1016 germinantsÁm À2 ; t = 6.7, P < 0.001) and shifted community structure (MRPP: A = 0.13, P < 0.001), including a reduction of woody species density by 81%. For the majority of functional types, heat and smoke failed to stimulate additional germination post-transfer, suggesting soil transfer simulated the effect of fire-related germination cues. Conclusion: Although topsoil transfer translocated many viable native seeds, potential restoration success was hindered by reduced germinant densities. This was mostly attributable to a dilution effect associated with mixing of transferred topsoil, so that many seeds were buried too deep to emerge. However, total reductions were greater than expected based on dilution alone, suggesting some seed mortality during the transfer process. Transfer shifted composition towards dominance by annual species, suggesting the need for topsoil transfer to be supplemented by other restoration techniques.
Podocarp species and genus richness is higher in the Malesian region than anywhere else on earth,... more Podocarp species and genus richness is higher in the Malesian region than anywhere else on earth, with maximum genus richness in New Guinea and New Caledonia and maximum species richness in New Guinea and Borneo. Members of the Podocarpaceae occur across the whole geographic and altitudinal range occupied by forests and shrublands in the region. There is a strong tendency for podocarp dominance of vegetation to be restricted either to highaltitude sites close to the limit of tree growth or to other sites that might restrict plant growth in terms of water relations and nutrient supply (e.g., skeletal soils on steep slopes and ridges, heath forests, ultramafic parent material). Although some species are widespread in lowland forests, they are generally present at very low density, raising questions concerning their regeneration ecology and competitive ability relative to co-occurring angiosperm tree species. A number of species in the region are narrowly distributed, being restricted to single islands or mountain tops, and are of conservation concern. Our current understanding of the distribution and ecology of Malesian podocarps is reviewed in this chapter, and areas for further research are identified.
Inflorescence and seed production was traced over seven consecutive years for the nikau palm, Rho... more Inflorescence and seed production was traced over seven consecutive years for the nikau palm, Rhopalostylis sapida, growing in temperate forests of northern New Zealand. Palms reach reproductive maturity when stems exceed a height of about 2.2 m, have about 60 frond scars, and are estimated to be approximately 90 years of age. However, inflorescences on young-mature palms usually aborted, and seed set was low for palms <3 m in height. Both the frequency of fruiting and the size of annual seed crops increased with increasing palm height to a maximum in the 6-8 m height class. However, the pattern of seed production in relation to number of frond scars (a better index of age) suggested declining seed production in old palms.Seed production varied up to three-fold between years and between sites. Seed production palm yr correlated positively with rates of frond fall (= frond production), inflorescences palm, and seeds inflorescence. Reproductive effort rarely exceeded 50%, possibly because of constraints in palm architecture which closely link seed production to frond and stem production.Mature palms in shaded locations produced less seeds than did palms in more open sites. Lianes also reduced seed production by interfering with frond fall and causing inflorescences to abort.
Disturbance regime is a fundamental driver of plant community composition and structure, and of s... more Disturbance regime is a fundamental driver of plant community composition and structure, and of species coexistence. Fire is one of the most common causes of recurrent landscape scale disturbance, and has shaped evolution and adaptation in many taxa globally (Bond & Keeley 2005). Altered fire regimes are a significant component of global environmental change and have been implicated in species losses and invasions. Climate change is predicted to result in decreased precipitation and increased temperature across many fire-prone regions, resulting in longer fire seasons and increased fire likelihood, while reduced productivity may lead to increased fuel limitation and less fire in other situations (Moritz et al. 2012).
The southwest of Australia is a global biodiversity hotspot with high levels of plant species ric... more The southwest of Australia is a global biodiversity hotspot with high levels of plant species richness and endemism. Kwongan vegetation makes up part of this high diversity area and is dominated by woody shrub species. The focus of previous research on kwongan is dominated by fire, examining the role of fire in species lifecycles and the effect of differing fire regimes. However, little has been done thus far to investigate the potential effects of a changing climate on kwongan. This study aims to examine the effects of changing climate on the northern sandplain kwongan of southwest Australia, specifically, the effects of changes in rainfall and temperature on the demography of key sandplain shrub species. To achieve this, rainout shelters have been established to create a drought treatment by reducing rainfall, and this intercepted rainfall is being used to then create an increased rainfall treatment using gravity fed irrigation. Open top temperature chambers are being used to create an increased temperature treatment. The treatments are being applied to contrasting topo-edaphic locations: dune tops and swales, in newly burnt and unburnt sites, allowing comparison of effect between mature phase and regeneration phase vegetation.
Background/questions/methods: The main urban areas of Western Australia (WA) are located on the S... more Background/questions/methods: The main urban areas of Western Australia (WA) are located on the Swan Coastal Plain - the 400 km long sandy landform between the Indian Ocean and Darling Scarp that encompasses the main habitat for endangered Banksia woodland. This floristically rich but poorly understood Mediterranean-type ecosystem is being rapidly destroyed by urban, horticultural and industrial development. In order to partially ameliorate the damage being inflicted on Banksia woodland vegetation WA land developers have been required to purchase offsets of, often degraded, land to where topsoil from construction sites can be moved to help rehabilitate the damaged areas. The aim of this project is to restore Banksia woodlands by optimising germination and survival of native species from the soil seed bank contained within transferred topsoil. The project is a part of an offset program associated with the development of the Jandakot Airport 25 km south of Perth city. In the first year, key research questions are focused on enhancing germination by varying depth of returned topsoil, ripping, fencing, weed control and experimental additions of smoke. Subsequent work will examine the survival and persistence of germinants including treatments such as provision of artificial shade. Assessing the efficacy of a spectrum of novel restoration technologies will provide new insights for environmental management of endangered plant communities. Results/conclusions: Preliminary results will be presented at the conference.
ABSTRACT Background/Question/Methods Tree populations in mesic (&gt;650 mm ppt yr–1) savannas... more ABSTRACT Background/Question/Methods Tree populations in mesic (&gt;650 mm ppt yr–1) savannas of the world have strong demographic bottlenecks to the transition of sub-adults to the canopy layer. Such bottlenecks are a major determinant of savanna physiognomy, yet factors that allow sub-adults to traverse the bottleneck are little studied. A conceptual framework was developed, linking landscape-scale variables in savannas (eg, seasonal fires) to the probability of a sub-adult tree reaching the canopy, considering local environments (eg, understorey) and tree attributes (eg, size, seasonal phenology which varies with life history stage). In a 32,400 m2 field experiment, 2,405 juveniles (&lt;150 cm height) and saplings (150–499 cm) of the eucalypt canopy species were individually marked and measured the year prior to fires set in 3 different seasons and again at the end of the following growing season (without fires) and assessed for survival, resprouting, and height growth. All fire treatments were repeated in plots dominated by the most common understorey, a native annual grass (sorghum) and in plots dominated by perennial native species; these produce different fuels for fires and vary in seasonal phenologies and competitive regimes. Trees in unburnt plots served as controls, as did wet season fires which naturally eliminate sorghum. Results/Conclusions Fires topkilled most juveniles, but almost all were persistent and few genets died. Genet mortality of juveniles depended on fire season and of saplings to understorey. Fire season x understorey interactions were important for growth of large juveniles and the transition of juveniles to sapling stages. After early dry-season fires, large juveniles and small saplings grew faster, especially those in sorghum. After late dry or wet season fires, however, all of the small saplings (&lt;299 cm height) were reduced to “juveniles” and did not recover pre-fire heights but, produced many new basal (coppice) stems. Initial size was an important explanatory variable for all demographic and growth responses by juveniles and small saplings, generally positively, but not for large saplings. For example, after late dry-season fires, &gt;80% of large saplings (300–499 cm) were reduced to juvenile size in sorghum understorey, whereas in non-sorghum understorey, 60% of large saplings grew to poles (500–999 cm). Unburnt large saplings were more likely to die and transition probabilities to larger sizes decreased, the larger their size, especially in non-sorghum. The key to understanding and managing sustainable woody cover in mesic savannas lies in the complex interactions of sub-adult trees with local environments.
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