Eucalypt Forest In South-eastern Australia Research Articles

Hollow selection by vertebrate fauna in forests of southeastern Australia and implications for forest management

We examined the types of hollows, and types of hollow-bearing trees, occupied by vertebrate fauna in temperate eucalypt forests in southeastern Australia. Hollow-bearing trees are selected for retention in wood production forests to mitigate the effects of logging on hole-nesting fauna. A total of 471 hollows was examined in 228 trees felled as part of routine logging operations. Fauna had occupied 43% of all hollows (⩾2cm minimum entrance width; ⩾5cm depth). Hollows with small (2–5cm), medium (6–10cm) and large (>10cm) minimum entrance widths had occupancy rates of 29, 44 and 62%, respectively. The internal dimensions of hollows, especially hollow depth, were the best predictors of hollow occupancy, even when variables measured at the tree and site levels were considered. Fauna occupied 57% of all hollow-bearing trees. In a Poisson regression model, the number of hollows in trees that contained evidence of occupancy was positively associated with: (1) the total number of hollows visible in the tree; (2) the proportion of the tree's crown that contained dead branches; and (3) tree diameter. The number of different vertebrate species that occupied trees was positively associated with the same explanatory variables except tree diameter. Thus, our results suggest that trees with multiple hollows and dead branches in the crown should be preferentially selected for occupancy by hollow-using fauna. Our results suggest that trees with the largest diameter are not the most suitable for retention. Possibly because they contain proportionally fewer hollows with small entrances, which are favoured by some vertebrate species.

A simple landscape‐scale test of a spatially explicit population model: patch occupancy in fragmented south‐eastern Australian forests

The results of a landscape‐scale test of ALEX, a widely used metapopulation model for Population Viability Analysis (PVA), are described. ALEX was used to predict patch occupancy by the laughing kookkaburra and the sacred kingfisher in patches of eucalypt forest in south‐eastern Australia. These predictions were compared to field surveys to determine the accuracy of the model. Predictions also were compared to a “naïve” null model assuming no fragmentation effects. The naïve null model significantly over‐predicted the number of eucalypt patches occupied by the sacred kingfisher, but the observed patch occupancy was not significantly different from that predicted using ALEX. ALEX produced a better fit to the field data than the naïve null model for the number of patches occupied by the laughing kookaburra. Nevertheless, ALEX still significantly over‐predicted the number of occupied patches, particularly remnants dominated by certain forest types – ribbon gum and narrow‐leaved peppermint. The predictions remained significantly different from observations, even when the habitat quality of these patches was reduced to zero. Changing the rate of dispersal improved overall predicted patch occupancy, but occupancy rates for the different forest types remained significantly different from the field observations. The lack of congruence between field data and model predictions could have arisen because the laughing kookaburra may move between an array of patches to access spatially separated food and nesting resources in response to fragmentation. Alternatively, inter‐specific competition may be heightened in a fragmented habitat. These types of responses to fragmentation are not incorporated as part of traditionally applied metapopulation models. Assessments of predictions from PVA models are rare but important because they can reveal the types of species for which forecasts are accurate and those for which they are not. This can assist the collection of additional empirical data to identify important factors affecting population dynamics.

The influence of habitat disturbance on reptiles in a Box-Ironbark eucalypt forest of south-eastern Australia

Understanding how habitat disturbance affects the occurrence of fauna is an important issue in the effective management of habitat and conservation of biodiversity. In this study, 11 paired sites were established around the periphery of Rushworth State Forest in central Victoria, south-eastern Australia, to examine the influence of disturbance to structural complexity in the ground strata on the occurrence of reptiles. Study sites were paired on the basis of proximity, physiognomic and vegetational characteristics – each pair was established in the same vegetation 'type' (Ecological Vegetation Class) and was dominated by the overstorey species of Red Ironbark Eucalyptus tricarpa and Grey Box E. microcarpa, or Bull Mallee E. behriana and Grey Box. They were also paired on the basis that they had experienced different degrees of disturbance to the ground strata. Sites within each pair differed substantially in their ground-layer structure (e.g. number of stumps, total number of shrubs, litter depth), but were virtually indistinguishable in their overstorey characteristics (e.g. basal area, canopy cover, cover of tall shrubs). Surveys over two summer seasons using area-constrained active searches yielded ten species of reptiles from five families. Despite the repeated search effort, both the number of reptile species and individuals recorded per site were low (≤4 species, ≤17 individuals), suggesting the possibility of historical impoverishment. Reptiles were generally 2.4 times more abundant on 'undisturbed' than 'disturbed' sites. The disparity was also reflected in the number of species per site, which was significantly greater on the 'undisturbed' sites. The greater species richness and abundance of reptiles recorded for 'undisturbed' sites are attributed to the greater structural complexity of the ground strata on these sites. Effective management for reptiles, therefore, should aim to create, retain or increase the structural heterogeneity of a site, particularly in the ground-layers.

Comparison of a forest process model (3-PG) with growth and yield models to predict productivity at Bago State Forest, NSW

Summary In this paper predictions from a process model, based on the Physiological Principel Predicting Growth (3-PG) model, are compared with those of two conventional growth and yield models. A number of forest growth variables are compared including the standing volume, mean diameter at breast height (DBH), and stocking over 50 000 ha of native eucalypt forest in south-eastern Australia. Stand variable predictions at 22 permanent plot locations, using a locally calibrated empirical growth model and 3-PG were highly correlated with field estimates derived from plot data. 3-PG predictions of standing volume, diameter at breast height (DBH) and stocking explained 86%, 59% and 89% of the variance respectively, compared to the local empirical model which explained 84%, 59% and 78% of the variance in predictions of the same variables. A generic forest growth model explained only 6% of the variance in standing volume predictions. A number of methods of estimating maximum potential standing volume across the landscape were also compared. The estimates over an 80-year rotation varied by as much as 24% for a forest stratum, and by as much as 40% at the stand level. Results suggest that significant improvements in local and regional prediction of forest growth may be gained by augmenting information derived from aerial photography and limited field inventory, with predictions made from process models such as 3-PG. The utility of process models to predict forest growth variables at specific stand ages, and their capacity to be extrapolated across the landscape using geographic information system (GIS) technology, now offer operational potential for use in routine forest management and planning.

Nutrient Movement Due to Overland Flow in Managed Native Eucalyptus Forests, Southeastern Australia

A rainfall simulator study of total nutrient movement due to overland flow on forest skid trails and general harvesting areas (GHA) in the native eucalypt forests of southeastern Australia, confirmed that the disturbed and compacted areas were the dominant sources of sediment-bound pollutants. Low runoff production and low sediment availability on the rough surfaces of the GHA reduced total nutrient yields. On the more recently disturbed and burnt sites, the solution pathway may have been more dominant due to runoff coming in contact with surface ash and charcoal. We also recorded significant reductions in the total nutrient yields as runoff from the skid trail was delivered to the adjacent hillslope via a cross bank (water bar). This was due primarily to coarse-grained sediment deposition at the base of the banks. Nutrient concentrations in the eroded sediment at the cross bank outlets, however, remained 9 times higher than the in-situ surface soils, due to the preferential delivery of fine aggregate material to the adjacent hillslope. Further reductions in total nutrient yields occurred as overland flow passed through the GHA, illustrating the effectiveness of vegetative filtering in reducing runoff volumes and sediment fluxes. Temporal trends in the data highlighted significant reductions in total nutrient movement on both areas of disturbance as sites regenerated over a period of ∼ 5 years. Water pollution abatement practices in these environments should aim to locate skid trails to maximise the redistribution of runoff and sediment from highly disturbed areas to more vegetated parts of the hillslope, and by appropriate cross bank spacing, reduce the volume of overland flow carrying sediment and nutrients.

Conservation of the greater glider (Petauroides volans) in remnant native vegetation within exotic plantation forest

AbstractA field‐validated metapopulation model of patch occupancy was used to examine the persistence of greater gliders (Petauroides volans) in patches of remnant native eucalypt forest in south‐eastern Australia. The model was based on a system of eucalypt patches embedded within a plantation forest of exotic radiata pine (Pinus radiata) at Buccleuch State Forest, New South Wales. The probability of local extinction in occupied patches was a function of patch size. The probability of colonization of empty patches was a function of the size and proximity of occupied patches. The results of the simulations suggested that suitable habitat should occupy approximately 10% (or more) of the total landscape to ensure the persistence of greater gliders. Rates of patch occupancy were maximized when suitable habitat was clustered into larger patches. Patches <3 ha in area were predicted to be of limited value as habitat for greater gliders. The predictions of the model are consistent with the observed persistence of greater gliders in the eucalypt patch system. The system of unlogged eucalypt patches within the pine plantation is a useful model of a network of small to medium‐sized conservation reserves. Principles of reserve design can have value even in somewhat degraded and highly modified landscapes. The results demonstrate that reserved patches of native forest embedded within intensively logged forest can have significant conservation value, with important implications for the design and establishment of new softwood plantations.

Conservation of the greater glider (Petauroides volans) in remnant native vegetation within exotic plantation forest

A field-validated metapopulation model of patch occupancy was used to examine the persistence of greater gliders (Petauroides volans) in patches of remnant native eucalypt forest in south-eastern Australia. The model was based on a system of eucalypt patches embedded within a plantation forest of exotic radiata pine (Pinus radiata) at Buccleuch State Forest, New South Wales. The probability of local extinction in occupied patches was a function of patch size. The probability of colonization of empty patches was a function of the size and proximity of occupied patches. The results of the simulations suggested that suitable habitat should occupy approximately 10% (or more) of the total landscape to ensure the persistence of greater gliders. Rates of patch occupancy were maximized when suitable habitat was clustered into larger patches. Patches <3 ha in area were predicted to be of limited value as habitat for greater gliders. The predictions of the model are consistent with the observed persistence of greater gliders in the eucalypt patch system. The system of unlogged eucalypt patches within the pine plantation is a useful model of a network of small to medium-sized conservation reserves. Principles of reserve design can have value even in somewhat degraded and highly modified landscapes. The results demonstrate that reserved patches of native forest embedded within intensively logged forest can have significant conservation value, with important implications for the design and establishment of new softwood plantations.

Prediction of the distribution and abundance of small mammals in the eucalypt forests of south-eastern Australia from airborne videography

The relationship between forest structure or habitat complexity and distribution and abundance has been demonstrated for a variety of mammalian species in the southern forests of Australia. Recently, studies that utilise airborne videography data have predicted forest structure across forested landscapes. This paper unites these two fields of research. Existing models of species abundance were applied to spatial estimates of habitat complexity to produce predictions of the distribution and abundance of two small ground-dwelling mammals commonly found in eucalypt forests. The spatial estimates of habitat complexity were extrapolated across the landscape from videography at 2-m spatial resolution on four 1-km 2 study areas. To examine the accuracy of the abundance predictions, trapping grids for the two species were established across a range of abundances. Linear regression showed a strong positive relationship between the predicted distribution and abundance from the videography and the recorded distribution and abundance for the species.

Molecular diversity of rhizobia occurring on native shrubby legumes in southeastern australia

The structure of rhizobial communities nodulating native shrubby legumes in open eucalypt forest of southeastern Australia was investigated by a molecular approach. Twenty-one genomic species were characterized by small-subunit ribosomal DNA PCR-restriction fragment length polymorphism and phylogenetic analyses, among 745 rhizobial strains isolated from nodules sampled on 32 different legume host species at 12 sites. Among these rhizobial genomic species, 16 belonged to the Bradyrhizobium subgroup, 2 to the Rhizobium leguminosarum subgroup, and 3 to the Mesorhizobium subgroup. Only one genomic species corresponded to a known species (Rhizobium tropici). The distribution of the various genomic species was highly unbalanced among the 745 isolates, legume hosts, and sites. Bradyrhizobium species were by far the most abundant, and Rhizobium tropici dominated among the Rhizobium and Mesorhizobium isolates in the generally acid soils where nodules were collected. Although a statistically significant association occurred between the eight most common genomic species and the 32 hosts, there was sufficient overlap in distributions that no clear specificity between rhizobial genomic species and legume taxa was observed. However, for three legume species, some preference for particular genomic species was suggested. Similarly, no geographical partitioning was found.

Modelling distributions of arboreal and ground-dwelling mammals in relation to climate, nutrients, plant chemical defences and vegetation structure in the eucalypt forests of southeastern Australia

Numerous studies over the past 15 years have investigated relationships between the distributions of arboreal and ground-dwelling mammals and environmental, structural and leaf compositional variables in the temperate Eucalyptus forests of southeastern and northeastern New South Wales, Australia. This paper draws together the general trends emerging from these studies and identifies some clear messages for the future modelling of regional biodiversity in these forests. The studies on arboreal mammals (all are marsupials in these forests) reviewed here generally fall into two broad categories: those that conclude that the nutrient status of forests is the prime determinant of habitat quality for arboreal marsupials and those that put equal or greater emphasis on variables related to structural characteristics of forests. Recent studies suggest a hierarchical model that is consistent with both of these emphases. They postulate that a proportion of temperature eucalypt forests, regardless of their climatic or structural characteristics, cannot support permanent populations of arboreal marsupials, especially leaf-eating species, due to low food quality and/or high phytochemical toxicity. Above a postulated nutritional or phytotoxicological ‘threshold’, food quality is adequate and other variables, including climatic and structural ones, apparently interact to determine habitat quality. Hence, differences in the extent to which different studies sample regional environmental variability, the range of nutrient status and forest structure, are likely to greatly affect which variables appear most significant in models of habitat requirements. Structural characteristics (measured as habitat complexity) of the forest have emerged as explanatory variables for the ground-living mammals also. Variables such as nutrients, lithology, terrain and climate exhibit a different trend to that seen for arboreal marsupials. Relative abundance of small ground-dwelling mammals is negatively correlated with site nutrient status as indicated by nutrient concentrations in tree foliage. Small mammals are present at all measured nutrient levels, but their abundance falls substantially as habitat complexity decreases. The influence of nutrients is masked in habitats of high complexity, there being no relationship with nutrient status. Many ground-living mammals occur across the gradients of lithology, terrain and climate, although there is wide variation in relative abundance for some species. The importance of structural variables for explaining distributions of both arboreal and ground-living fauna in eucalypt forests indicates that adequate modelling of habitat requirements for these fauna can only be achieved if surveys obtain adequate data on forest structure to encompass gradients in seral stage and disturbance history. The present-day mammalian fauna of the southeastern Australian forests has been influenced strongly by the effects of urbanisation, clearing for farming, forestry activities and fire on forest structural complexity and nutrient dynamics as well as by predation by introduced camivores. While modelling with respect to broadly defined climatic and terrain variables might be useful for broad-scale spatial prediction of faunal distributions, such models are unlikely to provide descriptions of habitat requirements or predictions of impacts of forest management at a scale necessary for sustainable management of faunal biodiversity.

On large-scale dynamics and community structure in forest birds: lessons from some eucalypt forests of southeastern Australia

Models of ecological communities, including coevolved patterns of resource use among sympatric species (for example, ‘resource partitioning’), are poor or inadequate representations of natural systems despite intense theoretical effort for many years. Some of these difficulties are due to a failure to recognize the necessary conditions for community patterns to develop, which are largely controlled by the dynamic characteristics of individual species. In continental bird communities — examples of which are considered here - these necessary conditions often will not be met owing to the mobility of most species. Here I document the degrees to which the large-scale dynamics (over hundreds of km) of individual bird species are expressed in community terms in five forest-habitat types throughout the year. These data demonstrate that continental bird communities are so dynamic that the conditions for the development of definite structure are unlikely to be met in either proximate or evolutionary time. The failure of community theories to account for and predict structure probably reflects too much concentration on mechanisms at inappropriate spatial scales.

Metapopulation Viability of Arboreal Marsupials in Fragmented Old‐Growth Forests: Comparison Among Species

Computer simulation analyses using a generic package for population viability analysis (PVA) were used to examine the dynamics of a limited number of metapopulation structures of the mountain brushtail possum, Trichosurus caninus, and the greater glider, Petauroides volans. These arboreal marsupials inhabit tall eucalypt forests in southeastern Australia. As in a parallel study of Leadbeater's possum, Gymnobelideus leadbeateri, the results indicated that there are some metapopulation structures in which increased movement between habitat patches may have a detrimental effect on demographic stability and, in turn, reduce population persistence. These negative impacts were most pronounced in model metapopulations composed of an ensemble of very small subpopulations of 4, 10, or 20 animals. The patterns were accentuated with increased inter‐patch movement as well as the addition of further small subpopulations. These counter‐intuitive findings appear to result when animals from already unstable and declining sub‐populations disperse into unoccupied patches of habitat that act as a type of population sink. These trends in population demography were reversed in scenarios in which larger subpopulations of 40 animals were modeled. In such cases the impacts of movement and additional habitat patches on subpopulation and metapopulation dynamics were positive. In contrast to the results for various demographic parameters, increased movement and added subpopulations had a beneficial effect on genetic variability among all the types of metapopulation structures that were examined. Results for the two species were compared to each other and also with investigations of Leadbeater's possum, Gymnobelideus leadbeateri. These comparisons confirmed general trends but also revealed potential quantitative differences in the behavior of metapopulations of T. caninus, P. volans, and G. leadbeateri. Many of these differences were attributed to variations in key life history parameters such as birth and death rates, but trends in metapopulation viability did not correlate simply with intrinsic rates of population growth. The three species differed in the size of metapopulations required for demographic and genetic stability, and the rank order of their susceptibility to demographic and genetic stochasticity may not be consistent. Different species, even those within the same guild, may vary in vulnerability to disturbance and environmental perturbation. Our analyses also emphasized the need to understand the structure and composition of metapopulations in the development of strategies for conservation of wildlife at the landscape and regional scales.

The need for a more sophisticated approach toward wildlife corridor design in the multiple-use forests of southeastern Australia: the case for mammals

The native eucalypt forests of southeastern Australia are managed for wood production, water protection, human recreation and the conservation of plants and wildlife. One strategy to conserve forest wildlife within wood production areas involves the use of unlogged strips or corridors of habitat. Most corridors are situated in gullies within forest catchments. However, a review of recent studies undertaken in southeastern Australia shows that many species of forest mammals either require habitat outside of gullies to find food and shelter, or make regular movements between forest on different parts of the topographic sequence. These findings illustrate that strategies for the design and implementation of wildlife corridors need to become more sophisticated and ensure: (i) the conservation of forest on ridges and midslopes, and (ii) the linkage of uncut stands on ridges and midslopes with forest in gullies.

Silvicultural research for sustained wood production and biosphere conservation in the pine plantations and native eucalypt forests of south-eastern Australia: R. O. Squire, D. W. Flinn & R. G. Campbell, FRI Bulletin — New Zealand Ministry of Forestry, Forest Research Institute, 161, 1991, pp 3–28

Silvicultural research for sustained wood production and biosphere conservation in the pine plantations and native eucalypt forests of south-eastern Australia: R. O. Squire, D. W. Flinn & R. G. Campbell, FRI Bulletin — New Zealand Ministry of Forestry, Forest Research Institute, 161, 1991, pp 3–28

Silvicultural research for sustained wood production and biosphere conservation in the pine plantations and native eucalypt forests of south-eastern Australia

Summary In the last decade, greatly increased public and political awareness of the need for biosphere conservation has placed strict controls on the productive use of Australia's already limited forest resource. The challenge is considerable. Ultimately, it could mean that much of Australia's native forests will no longer be available for wood production either directly or indirectly through conversion to plantations of pine of eucalyptus. This paper describes how the Department of Conservation and Environment in the State of Victoria is meeting this challenge for forested public land. Specifically, it addresses silvicultural research: to sustain wood production in second and subsequent rotations of pine plantations; and to balance sustained wood production and ecosystem conservation in native forests. From a review of field trials and fundamental studies motivated by reports of a “2R-decline” in wood production on sandy soils in South Australia, it is concluded that a serious irreversible decline is unlikely to be caused by pines in themselves. It is more likely to be caused by silvicultural practices that compact the soil and, especially in the case of sandy soils, deplete soil organic matter. A reversible decline is most likely to be due to a water X nutrient interaction related to water consumption by weeds and nutrient losses from practices such as slash burning. In native forests, Victoria has embarked upon a silvicultural investigation of a magnitude and complexity never before attempted in Australia. The main issues are the use of the clearfelling silvicultural system, and harvesting of residual wood mainly for wood chipping and conversion to pulp and paper products. Organisational arrangements for planning, managing and monitoring the research, with strong community involvement, are described together with the research studies which are based on three main systems; namely: the forest ecosystem; the forest management system; and the socio-economic system. It is concluded that success will require the achievement of high scientific objectivity and strong community involvement.

Soil respiration in eucalypt forests of southeastern Australia

Soil respiration was measured in five eucalypt forests of southeastern Australia. Regardless of the type of forest, the rate of respiration in soils responded to the addition of an available C source (glucose) and did not to the addition of N or P. Addition of glucose, at up to 100% of the glucose equivalent in soil, increased the rate of respiration sigmoidally. The concentration of glucose needed to achieve the maximum rate of respiration in the topsoil (0–2 cm) of an Eucalyptus regnans forest was at least an order of magnitude greater than its equivalent in the soil. The results indicate that microbial respiration in soils from eucalypt forests is limited by an available source of C.

In situ studies of nitrogen mineralization and uptake in forest soils; some comments on methodology

Aspects of the methodology of and interpretation of results from, in situ studies of N-mineralization are discussed with reference to data collected from 17 eucalypt forests in south-eastern Australia during a 5-year period. Results suggest that: (i) it is possible to maintain moisture of soils contained within corers at levels not significantly different from those of the surrounding soil; (ii) inorganic-N is not produced linearly over time under field conditions, nor should we expect it to be; (iii) mineralization rates are affected by all in situ methods. In each of the forests examined, the average rate of net N-mineralization decreased as the period of containment increased; (iv) shorter periods of containment (e.g. 1–2 weeks) reduce artifacts due to containment and are therefore preferable to longer periods (e.g. 4–8 weeks); and (v) longer periods of containment cannot substitute for increased replication of sampling. Further, when annual or seasonal rates of N-mineralization and uptake are to be calculated, it is desirable to increase replication of the bulk soil sampling for the first and last sampling dates.

Nutrient cycling and nitrogen mineralization in eucalypt forests of south-eastern Australia

Nutrient pools in litter and soil and the major nutrient transfers and additions in rainfall, throughfall and litterfall were measured in eight mature, undisturbed eucalypt forests covering a range of species, climate, productivity and soil type. Litterfall is the major pathway for the return of N, P, Ca and usually Mg, to the soil. The forests covered almost the range of litterfall reported for eucalypt forests and, in conjunction with published data, litterfall was strongly related to climatic variables. Extractable P in the soil and P concentrations in litter and litterfall were significantly higher in two sub-alpine forests (Eucalyptus pauciflora andE. delegatensis) than in all other forests. In general, nutrient turnover, particularly N turnover, was related to the rate of organic matter turnover. Rates of organic matter turnover in these forests and in other studies of eucalypts were correlated with climatic conditions using the simple climatic scalar developed by Vitousek. Nitrogen turnover, especially that proportion cycling via leaf litterfall is primarily a function of organic matter turnover, but litter quality appears also to have an influence.

Nutrient cycling and nitrogen mineralization in eucalypt forests of south-eastern Australia

Summary Nutrient pools in litter and soil and the major nutrient transfers and additions in rainfall, throughfall and litterfali were measured in eight mature, undisturbed eucalypt forests covering a range of species, climate, productivity and soil type. Litterfall is the major pathway for the return of N, P, Ca and usually Mg, to the soil. The forests covered almost the range of litterfall reported for eucalypt forests and, in conjunction with published data, litterfall was strongly related to climatic variables. Extractable P in the soil and P concentrations in litter and litterfall were significantly higher in two sub-alpine forests (Eucalyptus pauciflora and E. delegatensis) than in all other forests. In general, nutrient turnover, particularly N turnover, was related to the rate of organic matter turnover. Rates of organic matter turnover in these forests and in other studies of eucalypts were correlated with climatic conditions using the simple climatic scalar developed by Vitousek. Nitrogen turnover, especially that proportion cycling via leaf lJtterfaU is primarily a function of organic matter turnover, but litter quality appears also to have an influence.

Acetylene reduction in soil and litter from pine and eucalypt forests in south-eastern Australia

Rates of C 2H 2-reduction in surface soil and litter from pine and eucalypt forests were measured for 1 yr. Rates of reduction increased significantly with moisture content, and mean rates (nmol kg −1 h −1) decreased in the order pine litter (339), eucalypt litter (220), eucalypt soil (54), pine soil (7). Asymbiotic N 2-fixation in litter and surface soil was estimated to be 108 mg m −2 yr −1 in eucalypt forest and 64 mg m −2 yr −1 in pine forest. About 80% of total fixation in eucalypt was in the soil, while 80% of the total in pine was in the litter. N 2ase was active in rotting wood but not in fresh foliage.