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On the western rivers and plains of southern New South Wales, relatively small areas of forests remain in a semi-natural condition and conservation reserves are lacking. Severe drought stress in recent decades after two centuries of European management has raised issues about how best to manage these forests and, if necessary, restore them. The region was explored between 1817 and 1836. Settlers, foresters and ecologists described changes as Aboriginal culture was displaced, domestic stock, feral animals and exotic plants were introduced, rabbits were controlled, rivers were regulated, and grazing was reduced. The Aboriginal ecosystems were different to the new red gum ( Eucalyptus camaldulensis ) and white cypress ( Callitris columellaris ) forests which lack resilience. Trees, saplings, fallen timber, shrubs and parasitic plants have accumulated in recently ‘undisturbed’ sites and these features are now promoted as benchmarks for conservation. However, human activity including watering, thinning, firewood collection, grazing and/or burning may aid restoration whereas non-intervention may allow continuing degradation. This historical ecology and recent palaeoecology provide insights to conserving grassy woodlands globally.

In the Eden area in NSW, Australia, low fertility granitic surface soils were sampled from 156 sites and analysed for pH, organic C, total N, total P, available P, exchangeable bases and exchangeable Al. Fifty eight of these sites were also sampled to a depth of 40 cm. Time since fire ranged from 1 to 39 years and was used in the analysis as a surrogate for fire frequency. No information was available on fire intensity. No significant relationships were found between time since fire and P or base cations. However, the quantities of organic matter and total N (kg ha−1), and the C/N ratio were significantly related to both time since fire alone and to the combination of time since fire and soil total P. Based on these relationships, it was estimated that there were average net increases of between 11 and 21 kg N ha−1 year−1 in surface soil, the actual quantity depending on the level of soil total P. There was little change in N in the initial 10 years after fire and there was a peak in N accumulation about 24 years after fire. The C/N ratio and surface soil pH decreased with time since fire. Accumulation of N and reductions in pH and C/N ratio were studied further in a small scale paired plot analysis. The repeatedly burnt plots had lower levels of both litter and understorey and the overstorey trees generally had healthier crowns than in the unburnt plots. The differences between the repeatedly burnt and the unburnt plots matched the models developed from the general survey. There were no significant changes in the C/N ratio, but the unburnt sites had higher levels of extractable mineral N and the relationships between the mineral N and the C/N ratio for burnt and unburnt sites were statistically significant. The quantities of extractable mineral N in the unburnt soils (2.3 kg N ha−1) were about twice the levels in the burnt soils (1.2 kg N ha−1). The pH of the surface soil (4.4 in 1:1 water) in the regularly burnt area was higher than in the unburnt area (pH 4.1) and the exchangeable aluminium also differed (0.62 c mol−1 in the burnt area and 1.3 c mol−1 in the unburnt). The combined data indicate that changes occur in forest soils when there is a long period of exclusion of fire. It is suggested that these changes generally lead to secondary changes, such as in pH and availability of other elements such as aluminium. The study highlights a number of issues including the rates of inputs of N to the system and the question of N saturation and its long term interaction with plant species. It is hypothesised that reduced burning leads to increased N availability and other soil changes which negatively impact on tree health.

Summary Eucalypt dieback is widespread throughout Australia and affects an increasing range of species. In addition to salt, a 1993 study listed 13 types of insects, five types of fungi, five kinds of vertebrate animals, four climatic perturbations and a parasitic plant that had been implicated as major agents of dieback in southeastern Australia. Repeated defoliation by insects has usually been identified as a major factor in rural and forest diebacks, while mesic understorey development is often an important feature of forest diebacks. Different mechanisms of initiation and reinforcement have been proposed to account for many different forms of dieback. High rates of folivory leading to both rural and forest diebacks, have been related either to high resource availability and tree vigour or to low resource availability and tree stress. A simple model of eucalypt dieback is proposed to account for both rural and forest dieback, including an increasing range of ‘susceptible’ species and sites. It associat...

Summary Height and diameter equations were developed using the Chapman-Richards function for 30 species in the regrowth forests of southeast New South Wales. These species included all commercial species of eucalypts and non-commercial small tree species of acacia and allocasuarina in the region. To improve prediction accuracy, the mean height and mean diameter of 50 largest regrowth trees/ha were incorporated in a modified Chapman-Richards function: where H and D represent total tree height in m and diameter at breast height in cm, H50 and D50 are the mean height and mean diameter of 50 largest trees/ha in m and cm respectively, a, b, c and d are parameters. Detailed evaluation of prediction accuracy through resampling showed that the incorporation lead to unbiased and more precise prediction for tree height and stem volume of most species and for stand volume of the regrowth forests. The common practice of calibrating height prediction from species-specific individual tree height-diameter equations agai...

Summary Old tree retention during logging results in irregular regrowth forests, for which growth and yield information are urgently required by forest managers in Australia. Using data obtained from 30 stands through random sampling in regrowth Eucalyptus fastigata forests on the south-east tablelands of New South Wales, equations were developed to determine the yield of the regrowth stands in relation to old tree density. The predicted regrowth stand volume for stands without any old trees increased from 253m3ha1 at age 20 to 623m3ha−1 at age 80 for the most productive site, from 253m3ha1 to 339m3ha−1 for the average site and from 84m3ha−1 to 206m3ha−1 for the least productive site. As old tree density increases from 0 to 100 trees ha−1 the percentage reduction in regrowth stand volume increases from 0 to 66%. As a result of past fire and logging disturbances, the old trees had a wide range of crown conditions, with many having a small and sparse crown, but not a large healthy primary crown. A clear und...

Summary Two studies of foraging preference of the smoky mouse at the same site in south-eastern NSW reached distinctly different conclusions. The first found that the smoky mouse foraged on relatively bare exposed slopes but not in heath. The second study concluded that the smoky mouse foraged and nested in heath. This article examines the sampling strategies and results in terms of vegetation patterns and nest locations. It concludes that the results of the second study reflected the placement of traps in relation to nests rather than foraging preferences. It also questions another conclusion of the second study, that it may be necessary to reserve large areas of undisturbed vegetation to conserve the smoky mouse. This conclusion was not supported by the data presented.