62 research outputs found
Weekly pollen count data for for the University of Tasmania, Hobart
No full text<p>The datafile contains the composition and abundance of airborne pollen in the suburb of Sandy Bay (University of Tasmania), Hobart, Tasmania, Australia. The data was collected for the period between July 2007 to December 2010 as part of a large research program looking at atmospheric particles and human health and phenology of urban planted environments (see Tng, DYP, Hopf, F, Haberle, SG, Bowman, DMJS 2010, Seasonal pollen distribution in the atmosphere of Hobart, Tasmania: preliminary observations and congruence with flowering phenology. Australian Journal of Botany 58, 440–452).</p>
Output from Pyrogeography in Flux
No full textOutput accompanying the paper: CX Cunningham, G. Williamson, RH Nolan, L Teckentrup, MM Boer, DMJS. Bowman. (2024) Pyrogeography in flux: reorganisation of Australian fire regimes in a hotter world. Global Change BiologyOutputRaster (.tiff) and shapefile of Australia's pyroregions.</p
What controls the distribution of tropical forest and savanna?
No full textC1 - Journal Articles RefereedForest and savanna biomes dominate the tropics, yet factors controlling their distribution remain poorly understood. Climate is clearly important, but extensive savannas in some high rainfall areas suggest a decoupling of climate and vegetation. In some situations edaphic factors are important, with forest often associated with high nutrient availability. Fire also plays a key role in limiting forest, with fire exclusion often causing a switch from savanna to forest. These observations can be captured by a broad conceptual model with two components: (1) forest and savanna are alternative stable states, maintained by tree cover-fire feedbacks, (2) the interaction between tree growth rates and fire frequency limits forest development; any factor that increases growth (e.g. elevated availability of water, nutrients, CO(2)), or decreases fire frequency, will favour canopy closure. This model is consistent with the range of environmental variables correlated with forest distribution, and with the current trend of forest expansion, likely driven by increasing CO(2) concentrations. Resolving the drivers of forest and savanna distribution has moved beyond simple correlative studies that are unlikely to establish ultimate causation. Experiments using Dynamic Global Vegetation Models, parameterised with measurements from each continent, provide an important tool for understanding the controls of these systems
Data from Pyrogeography in Flux
No full textData associated with CX Cunningham, G. Williamson, RH Nolan, L Teckentrup, MM Boer, DMJS. Bowman. (2024) Pyrogeography in flux: reorganisation of Australian fire regimes in a hotter world. Global Change BiologyData:Data to run the analyses delineating Australia's pyroregions: "fireMetricStack_20230821.tiff", "npp_mean.tif", and "NDVI_diff.tif"Folder containing files used to define study area and grid resolution: "Grid templates"Historical climate data: "AUS_wc2.1_30s_bio.tif"Folder containing projected climate data under three scenarios: "Future climate protections"</p
Code from Pyrogeography in Flux
No full textCode accompanying the paper: CX Cunningham, G. Williamson, RH Nolan, L Teckentrup, MM Boer, DMJS. Bowman. (2024) Pyrogeography in flux: reorganisation of Australian fire regimes in a hotter world. Global Change BiologyCode:"Metrics of fire regimes.R" is used to create the variables contained in "fireMetricStack_20230821.tiff" - see archived data section."Cluster analysis delineating fire regimes.R" is the main script used to delineate Australia's pyroregions and evaluate the extent of climatic change in each region."Pyroregionalisation functions.R" is a collection of custom functions used in the other two scripts.</p
Clearfelling versus selective logging in uneven-aged eucalypt forests
No full textUneven-aged eucalypt forests used for pulpwood extraction are generally clearfelled. This method is not necessary to induce regeneration. Clearfelling may be less expensive in the short term, but will result in a medium-term loss of sawlog, may be unsuited to extreme sites, may not be a more productive system than selection, and is likely to have more severe edaphic, aesthetic and biotic impact than selection. There may be a greater potential loss of productivity to wild fire with clearfelling than with selective systems
Tree growth rates in north Australian savanna habitats: Seasonal patterns and correlations with leaf attributes
No full textWe demonstrate a significant relationship between leaf attributes and growth rates of mature trees under natural conditions in northern Australia, a pattern that has not been widely reported before in the literature. Increase in diameter at breast height (DBH) was measured every 3 months for 2 years for 21 tree species from four habitats near Darwin: Eucalyptus open forest, mixed woodland, Melaleuca swamp and dry monsoon rainforest. Assimilation rates and foliar chlorophyll, nitrogen and phosphorus concentrations were positively correlated with growth rate and negatively correlated with leaf mass per area. For most species, increases in DBH were confined to the wet-season (summer) period between November and May. Average annual increases in DBH were larger in the dry monsoon rainforest (0.87 cm) and the Melaleuca swamp (0.65 cm) than in the woodland (0.20 cm) and the open forest (0.16 cm), and were larger in non-Myrtaceous species (0.53 cm) than in Myrtaceous species (0.25 cm). These results are discussed in relation to the frequent fire regime prevailing over much of northern Australia which causes the marked contrast between the small pockets of fire-tender closed monsoon rainforest and the surrounding large expanses of fire-tolerant savanna
Establishment, suppression and growth of Eucalyptus delegatensis R. T. Baker in multi-aged forests. II. Sapling growth and its environmental correlates
No full textSeedling and sapling regrowth occupies gaps and includes part of the understorey in the multiaged Eucalyptus delegatensis dry forests of central Tasmania. This regrowth is even-aged for any particular area. Variation in sapling height is symmetrical across east to west sections of gaps, 20-50 m diam., but asymmetrical in the north to south sections, where the tallest seedlings are found to the south. Density, height, diameter and wet weight of E. delegatensis regrowth are highly positively correlated with the distance to the nearest tree but are only related to solar radiation in the gaps. Concentrations of most major plant nutrients in the surface soil, and soil moisture-holding capacity, have no strong relationship with the various growth measures. Thus, adult trees suppress sapling growth independent of incident solar radiation, while sapling growth outside the influence of adult trees increases with increasing incident solar radiation
Establishment, suppression and growth of Eucalyptus delegatensis R.T. Baker in multi-aged forests. I. The effects of fire on mortality and seedling establishment
No full textIn the dry uneven-aged eucalypt forests of central Tasmania the establishment of seedlings of Eucalyptus delegatensis requires a mitigation of the competition provided by the understorey, regeneration being observed to follow both fire and cultivation. Most of the adult trees of E. delegatensis survive even severe fires, although there can be considerable later mortality associated with mechanical failure of the base of the trunk. E. delegatensis dry forest usually has a distinctive sapling layer. Fire kills most of these saplings, the mortality rate being inversely related to their height and bark thickness
Intra-specific variation in leaf attributes of four savanna tree species across a rainfall gradient in tropical Australia
No full textLeaf attributes of four savanna tree species were measured along a rainfall gradient (1650-950 mm per annum) in the Australian monsoon tropics. As the mean annual rainfall decreased, leaf thickness increased for three of these four species. However, a corresponding decrease in leaf density for two species meant that leaf mass per area increased significantly only for one species. Physiological measurements were made during both the wet and dry seasons on comparable stands of vegetation near the extremes and middle of this gradient. Assimilation per unit mass was similar at all three sites but assimilation per leaf area was higher at the drier sites because leaves were thicker with higher mass per area. These results probably reflect reduced tree density and leaf area index at the drier sites, which offsets the lower rainfall, potentially allowing similar rates of assimilation per unit carbohydrate invested in leaves. © CSIRO 2005
- …
