Eucalypt Forests Of Australia Research Articles

Size fractionation as a tool for separating charcoal of different fuel source and recalcitrance in the wildfire ash layer

Charcoal is a heterogeneous material exhibiting a diverse range of properties. This variability represents a serious challenge in studies that use the properties of natural charcoal for reconstructing wildfires history in terrestrial ecosystems. In this study, we tested the hypothesis that particle size is a sufficiently robust indicator for separating forest wildfire combustion products into fractions with distinct properties. For this purpose, we examined two different forest environments affected by contrasting wildfires in terms of severity: an eucalypt forest in Australia, which experienced an extremely severe wildfire, and a Mediterranean pine forest in Italy, which burned to moderate severity. We fractionated the ash/charcoal layers collected on the ground into four size fractions (>2, 2–1, 1–0.5, <0.5mm) and analysed them for mineral ash content, elemental composition, chemical structure (by IR spectroscopy), fuel source and charcoal reflectance (by reflected-light microscopy), and chemical/thermal recalcitrance (by chemical and thermal oxidation).At both sites, the finest fraction (<0.5mm) had, by far, the greatest mass. The C concentration and C/N ratio decreased with decreasing size fraction, while pH and the mineral ash content followed the opposite trend. The coarser fractions showed higher contribution of amorphous carbon and stronger recalcitrance. We also observed that certain fuel types were preferentially represented by particular size fractions. We conclude that the differences between ash/charcoal size fractions were most likely primarily imposed by fuel source and secondarily by burning conditions. Size fractionation can therefore serve as a valuable tool to characterise the forest wildfire combustion products, as each fraction displays a narrower range of properties than the whole sample. We propose the mineral ash content of the fractions as criterion for selecting the appropriate number of fractions to analyse.

Visual assessments of fuel loads are poorly related to destructively sampled fuel loads in eucalypt forests

Fire managers around the world commonly use visual assessment of forest fuels to aid prediction of fire behaviour and plan for hazard reduction burning. In Australia, fuel hazard assessment guides also allow conversion of visual assessments to indicative fuel loads, which is essential for some rate of spread models and calculation of fireline intensity or emissions. The strength of correlation between fuel hazard and destructively sampled (directly measured) fuel load was tested using a comprehensive dataset of &gt;500 points from across a range of eucalypt forests in Australia. Overall, there was poor correlation between the assigned fuel hazard rating and measured biomass for surface, near-surface and elevated fuel components, with a clear tendency for these systems to under-predict fuel load at low hazard ratings, and over-predict it at high hazard ratings. Visual assessment of surface fuels was not statistically different from a random allocation of hazard level. The considerable overlap in fuel load between hazard ratings at higher ranges suggests the need to reduce the number of hazard classes to provide clearer differentiation of fuel hazard. To accurately assess forest fuel condition, improvements in fuel hazard descriptions and calibration of visual assessment with destructively measured fuels is essential.

Patterns of soil water repellency in response to coarse woody debris and fire: implications for eucalypt regeneration in dry forests

The severity of soil water repellency (WR) is affected by fire in dry eucalypt forests in Australia. This study aimed to investigate the variability of soil WR and moisture in and around typical seedling microsites after fire: in ashbeds near coarse woody debris (CWD). Values of soil WR severity and moisture content were measured adjacent to and at multiple distances from CWD in ashbeds and in unburnt soils. Soils were measured at depths of 0 to 5 cm in 1 cm increments for 8 individual CWD samples in ashbeds. Data were analysed to determine whether WR varied significantly among soil depths and distances from CWD. In microsites subjected to a severe burn, WR differed significantly among depths but not distance from CWD. Next to CWD, soil was wettable for 1–2 cm below the surface and this wettable layer was underlain by a severely water repellent layer of at least 1 cm thickness with less repellent soil below that. In areas of less severe and no burn, surface layers were moderately to extremely water repellent. The interaction between fire and CWD and the resultant severe burn, leads to spatially restricted regions where surface soil WR is reduced, moisture accumulates and seedling establishment is promoted.

Long-term repeated burning reduces Lantana camara regeneration in a dry eucalypt forest

Previous short-term studies predict that the use of fire to manage lantana (Lantana camara) may promote its abundance. We tested this prediction by examining long-term recruitment patterns of lantana in a dry eucalypt forest in Australia from 1959 to 2007 in three fire frequency treatments: repeated annual burning, repeated triennial burning and long unburnt. The dataset was divided into two periods (1959–1972, 1974–2007) due to logging that occurred at the study site between 1972 and 1974 and the establishment of the triennial burn treatment in 1973. Our results showed that repeated burning decreased lantana regeneration under an annual burn regime in the pre- and post-logging periods and maintained low levels of regeneration in the triennial burn compartment during the post-logging period. In the absence of fire, lantana recruitment exhibited a dome-shaped response over time, with the total population peaking in 1982 before declining to 2007. In addition to fire regime, soil pH and carbon to nitrogen ratio, the density of taller conspecifics and the interaction between rainfall and fire regime were found to influence lantana regeneration change over time. The results suggest that the reported positive association between fire disturbance and abundance of lantana does not hold for all forest types and that fire should be considered as part of an integrated weed management strategy for lantana in more fire-tolerant ecosystems.

Projecting canopy cover change in Tasmanian eucalypt forests using dynamically downscaled regional climate models

Loss of forest cover is a likely consequence of climate change in many parts of the world. To test the vulnerability of eucalypt forests in Australia’s island state of Tasmania, we modelled tree canopy cover in the period 2070–2099 under a high-emission scenario using the current climate–canopy cover relationship in conjunction with output from a dynamically downscaled regional climate model. The current climate–canopy cover relationship was quantified using Random Forest modelling, and the future climate projections were provided by three dynamically downscaled general circulation model (GCM) simulations. Three GCMs were used to show a range of projections for the selected scenario. We also explored the sensitivity of key endemic and non-endemic Tasmanian eucalypts to climate change. All GCMs suggested that canopy cover should remain stable (proportional cover change <10 %) across ~70 % of the Tasmanian eucalypt forests. However, there were geographic areas where all models projected a decline in canopy cover due to increased summer temperatures and lower precipitation, and in addition, all models projected an increase in canopy cover in the coldest part of the state. The model projections differed substantially for other areas. Tasmanian endemic species appear vulnerable to climate change, but species that also occur on the mainland are likely to be less affected. Given these changes, restoration and carbon sequestration plantings must consider the species and provenances most suitable for future, rather than present, climates.

TIDA: an algorithm for the delineation of tree crowns in high spatial resolution remotely sensed imagery

The sustainable management of forests for multiple uses requires fine-scale resource information for a range of attributes. Remotely sensed imagery, if appropriately interpreted, can provide detailed, quantitative data for deriving forest information. This paper describes the tree identification and delineation algorithm (TIDA), an image analysis tool designed to delineate tree crowns automatically in high spatial resolution digital imagery. The (local) radiometric maxima and minima are the primary image features used for the crown delineation process, being indicative of crown centroids and boundaries, respectively. TIDA was developed for application to imagery of native Eucalypt forests in Australia, and uses a ‘top–down’ spatial clustering approach involving key steps designed to reduce the effects of crown segmentation. The assumptions and fundamental processes of the algorithm are described, examples of the output and performance considerations are given, and possible limitations are discussed.

Decomposition of Slash Residues in Thinned Regrowth Eucalpt Forest in Western Australia

1. Stand thinning is being used increasingly by forest managers to maximize wood production from regrowth eucalypt forests in Australia. Many of the ecological effects of this intensive method of management, including changes in nutrient cycling and the susceptibility of sites to fire due to addition of slash residues to the forest floor, are not well understood. 2. Decomposition of slash residues was studied at one site in regrowth karri (Eucalyptus diversicolor) forest, a tall, open forest growing in south-western Australia. 3. Thinning reduced tree density from 4000 to 380 stems ha -1 , reduced tree basal area from 32 to 17m 2 ha -1 and removed 2000 stems ha -1 of understorey plants. Approximately 78 t ha -1 slash residues from the thinning operation were added to the existing 40 t ha -1 of forest floor litter. 4. Rates of decomposition of 27 components of slash were determined during a 2-year period, following thinning using the mesh bag technique. Components studied consisted of 5 leaf fractions from the overstorey and main understorey species, 15 twig and stem components from the understorey, 6 twig and stem components from the overstorey and bark from the overstorey. 5. The rate of weight loss of each slash fraction was assessed using single and double exponential decay models. The single exponential model adequately described the decay of karri stem and twig wood, and of understorey stem wood. Decay of leaf fractions, bark and small-diameter understorey wood were best described by the double exponential model. 6. Fractions of labile components in leaf, bark and small understorey wood were lost rapidly during the initial decay phase (half-lives 1-6 weeks); thereafter decomposition proceeded more linearly and was dominated by the rate of decay of the resistant fraction of each slash component. Model predictions of the fraction of each slash residue present as labile compounds were significantly related (r 2 = 0.94) to the amounts determined in laboratory extractions of the residues. 7. The decay rate of wood components was slower than for leaf fractions and was dependent on the size of the wood and its source. Rate of decay decreased with wood diameter and was more rapid for understorey wood than overstorey wood. 8. Half-lives of leaf components of slash ranged from a few weeks up to about 18 months, whereas half-lives of wood in the slash residues were much greater and exceeded 30 years for the largest diameter overstorey wood fraction. 9. Fire control and nutrient conservation are critical considerations in formulating strategies for management of thinning residues in eucalypt forests. Thinning residues deposited on the forest floor increase the risk of fire. However, where this hazard can be tolerated for limited periods, a delay in fuel-reduction burning for up to 2 years following thinning will allow time for much of the leaf material to decompose. This will reduce the fire risk and enhance conservation of the nutrient capital.

Ecological disturbance and the conservative management of eucalypt forests in Australia

Ecological disturbance and the conservative management of eucalypt forests in Australia

The Earth in transition: patterns and processes of biotic impoverishment

Preface Acknowledgements List of contributors Part I. Global Change and the Patterns of Impoverishment: 1. The earth under stress: a transition to climatic instability raises questions about patterns of impoverishment George M. Woodwell 2. The experimental impoverishment of natural communities: effects of ionizing radiation on plant communities, 1961-1976 George M. Woodwell and Richard A. Houghton 3. Air pollution and temperate forests: creeping degradation F. Herbert Bormann 4. The long-term effects of air pollutants on lichen communities in Europe and North America D. L. Hawksworth 5. Biotic impoverishment in Northern Peatlands Eville Gorham 6. Climatic change and the survival of forest species Margaret Bryan Davis 7. The atmosphere and the future of the biosphere: points of interactive disturbance Michael Oppenheimer Part II. Chronic Disturbance and Natural Ecosystems: Forests: 8. The restoration of Nonsuch Island as a living museum of Bermuda's precolonial terrestrial biome David B. Wingate 9. Patterns of impoverishment in natural communities: case history studies in forest ecosystems - New Zealand A. F. Mark and G. D. McSweeney 10. Changes in the eucalypt forests of Australia as a result of human disturbance R. L. Specht 11. Impoverishment in Pacific Island forests Dieter Mueller-Dombois 12. Deforestation in Brazilian Amazonia Philip M. Fearnside 13. Incentives for sustainable forest management Robert Repetto Part III. Chronic Disturbance and Natural Ecosystems: Woodlands, Grasslands and Tundra: 14. Changes in the Mediterranean vegetation of Israel in response to human habitation and land use Zev Naveh and Pua Kutiel 15. Bromus tectorum, a biotic cause of ecosystem impoverishment in the Great Basin W. D. Billings 16. Detecting early signs of regional air-pollution injury to coastal sage scrub Walter E. Westman 17. Arctic ecosystems: patterns of change in response to disturbance L. C. Bliss Part IV. Chronic Disturbance and Natural Ecosystems: Aquatic and Emergent Ecosystems Section A. Marine Systems: 18. Changes in a Red Sea coral community structure: a long-term case history study Y. Loya 19. Are deep-sea communities resilient? J. Frederick Grassle, Nancy J. Maciolek and James A. Blake 20. Species dominance-diversity patterns in Oceanic communities John A. McGowan Section B. Freshwater Systems: 21. Natural and anthropogenically imposed limitations to biotic richness in fresh waters David W. Schindler 22. Human impacts on the South Florida Wetlands: the Everglades and Big Cypress Swamp William A. Niering 23. The impoverishment of aquatic communities by Smelter activities near Sudbury, Canada N. D. Yan and P. M. Welbourn 24. Biotic impoverishment: effects of anthropogenic stress John Cairns Jr and James R. Pratt Part V. Conclusion: Steps Toward a World that Runs Itself: 25. Steps toward sustainability J. Gustave Speth 26. A reaction from a multitude Donella H. Meadows Name index Subject index.

Determination of Fire-Residence Time, and Its Role in the Survival of Eucalypts After a Bushfire

Bushfires occur frequently in drought-prone eucalypt forests of Australia, and their intensity can vary within very wide limits. Permanent damage is caused when a tree's vascular cambium layer is heated above 60°C, but this may be prevented in eucalypts by a thick layer of bark. It can take several minutes of flaming combustion during a bushfire for sufficient heat to penetrate the bark and kill the cambium. By heating some small sections of wood or bark in an oven to temperatures between 300°C and 600°C, then grinding and polishing a transverse section, reflectance measurements have been made in vertical incident light through a microscope fitted with a photomultiplier. These readings show a linear correlation between the logarithm of reflectance and temperature. Using this correlation, some maximum temperature profiles were obtained across transverse bark sections cut from trees subjected to a low-intensity bushfire. These have been compared with some graphs which relate the maximum temperatures reached within bark to the distance from the outer surface after progressively longer periods. By using reflectance measurements made on sections of charred bark or, more simply, by measuring the thickness of the black outer layer of charred bark an estimate of the fire residence time of a bushfire can be obtained.

Is insect defoliation in eucalypt forests greater than that in other temperate forests?

AbstractClaims have been made in the past that insect defoliation in eucalypt forests of Australia is both chronically high and greater than defoliation levels in northern temperate forests. Recent published data, however, indicate that some eucalypt forests may sustain low level defoliation. Careful reexamination of the literature on defoliation in eucalypt forests indicates that there are not enough data available to quantify defoliation on an Australian‐wide basis. Therefore it cannot be claimed that insect defoliation in eucalypt forests is greater than that in other temperate forests. There are also insufficient data to claim that insects are a major factor responsible for the growth differential between indigenous and overseas plantation‐grown eucalypts. The ecological impact of herbivorous insects in eucalypt and northern temperate forests is also discussed.

The Economics of Modifying Eucalypt Forests

SUMMARY The multiple demands made by society on the eucalypt forests of Australia are increasing and changing in emphasis. Choice between alternative forms of modification and use of these forests must aim to provide the greatest net benefit to society and hence evaluation is needed within an economic framework. Some of the major issues relating to environmental modification of eucalypt forests are examined within such a framework. Choices between preservation and development, between single and multiple use, and between clearcutting and selection systems, are discussed for a eucalypt forest of relatively limited area. Deficencies in the data required for a definitive evaluation of these issues are outlined. Some of the dangers inherent in attempting to generalise results to other localities and larger areas of forest are discussed.

TERMITES AS FOREST PESTS

SUMMARY The attack toy termites on indigenous eucalypt forests in Australia results in a serious loss of timber. Porotermes adamsoni is the most serious pest of alpine forests in New South Wales, Tasmania, and Victoria; and two species of Coptotermes (C. acinaciformis and C. frenchi) are very serious pests of trees in coastal forests and savannah woodland areas. Healthy trees in plantations of exotic pines are not attacked. It is possible that the attack by P. adamsoni can be reduced considerably by a sound regeneration program involving the removal of veteran trees and good silvicultural treatment of all trees before they reach the veteran stage. Such programs are being carried out in Australia. In contrast to P. adamsoni the damage to highly developed coastal eucalypt forests by the two Coptotermes spp. remains severe. Trees are often attacked well before they reach mill log size. Studies of tile gallery systems of C. acinaciformis have shown that the termites from a colony within one living tree can at...