Native Eucalypt Forest Research Articles

Estimation of plant and leaf area index using three techniques in a mature native eucalypt canopy

Abstract Leaf area index (L) is a critical variable in monitoring and modelling forest condition and growth and is therefore important for foresters and environmental scientists to measure routinely and accurately. We compared three different methods for estimating L: a plant canopy analyser (PCA), a point‐quadrat camera method and digital hemispherical photography at a native eucalypt forest canopy at Tumbarumba in southern New South Wales, Australia. All of these methods produced indirect estimates of L based on the close coupling between radiation penetration and canopy structure. The individual L estimates were compared, and the potential advantages and disadvantages of each method were discussed in relation to use in forest inventory and in field data collection programmes for remote sensing calibration and verification. The comparison indicated that all three methods, PCA, digital hemispherical photography and the modified point‐quadrat camera method, produced similar estimates with a standard error between techniques of less than 0.2 L units. All methods, however, provided biased estimates of L and calibration is required to derive true stand L. A key benefit, however, of all of these estimation methods is that observations can be collected in a short period of time (1–2 h of field‐work per plot).

Additive biomass equations for native eucalypt forest trees of temperate Australia

Biomass additivity is a desirable characteristic of a system of equations for predicting component as well as total tree biomass since it eliminates the inconsistency between the sum of predicted values for components such as stem, bark, branch and leaf and the prediction for the total tree. Besides logical consistency, a system of additive biomass equations when estimated by taking into account the inherent correlation among the biomass components has greater statistical efficiency than separately estimated equations for individual components. Using mostly small sample data from both published and unpublished sources, a system of non-linear additive biomass equations was developed for 15 native eucalypt forest tree species of temperate Australia. Diameter at breast height was used as the independent variable for all 15 species, while the combined variable of diameter and tree height was used for 14 species with height data. The system of additive equations provided more accurate biomass estimates than the common approach of separately fitting total tree and component biomass equations using log transformed data through least squares regression. Residual error variances were collectively estimated for each species by pooling small sample data across species and using indicator variables to represent the scale factor for each species in a residual variance function. This method overcame a common problem in estimating heteroscedastic error variance in non-linear biomass equations with additive error terms for small samples. From the estimated residual variance functions, approximate confidence bands containing about 95% of the observed data about the mean curve of predicted biomass were derived for all biomass components of each species. This system of additive biomass equations will prove to be useful for biomass estimation of native eucalypt forests of temperate Australia.

Flora diversity of farm forestry plantations in southeast Queensland

Summary Plant species composition in plantation monoculture of the native Gympie Messmate (Eucalyptus cloeziana F. Muell.) was assessed and compared with native eucalypt forest and cleared grazing land in southeast Queensland, Australia. A total of 18 sites (11 in the plantations, four in native eucalypt forests and three on cleared grazing land) were surveyed. The four plantation age classes during the 18‐month survey period were 0.3–1.8 (very young), 2.1–3.8 (young), 15–16.5 (mid‐aged) and 38–40.5 (old) years of age. Significantly more native plant species were recorded in the plantations, regardless of their age, than on cleared grazing land. The number of native plant species in the old plantations was not significantly different from the native eucalypt forests. Native tree and shrub species richness increased significantly with plantation age. Two species (Ricinocarpos speciosus Muell. Arg. and Xanthostemon oppositifolius F. M. Bailey) listed as Vulnerable and one species (Alyxia magnifolia F. M. Bailey) listed as Rare were recorded in the old plantations. Two Rare species (A. magnifolia and Acianthus amplexicaulis (F. M. Bailey) Rolfe) were recorded in the native eucalypt forests. Exotic plant species, consisting mainly of herbs, grasses and shrubs in the plantations, were significantly more abundant in the very young and young plantations. However, the number of exotic species decreased significantly with increasing age of the plantations. The results suggest that even small‐scale plantation can increase landscape heterogeneity and help protect biodiversity.

Evidence that creation of a Pinus radiata plantation in south-eastern Australia has reduced habitat for frogs

Loss and fragmentation of habitat resulting from the clearing of forests for agriculture and urban development threaten the persistence of thousands of species worldwide. The clearing of native forest to plant a monoculture of exotic trees may also reduce and fragment the habitat available for indigenous plants and animals. Metacommunity theory suggests that the species richness of a community in a patch of habitat will increase with patch size but decrease with patch isolation. We investigated whether replacement of native Eucalyptus forest with a plantation of Pinus radiata has reduced and fragmented habitat for frogs, leading to a lower species richness of frog communities in the pine plantation and in small and/or isolated remnant patches of native forest. We surveyed frogs at 60 sites at streams and wetlands in the pine plantation, remnant patches of native forest surrounded by pines, and adjacent areas of contiguous native forest near Tumut in New South Wales, Australia. Only two of eight species of frogs were recorded in the pine plantation, and regression modelling indicated that streams and wetlands in the pines supported fewer frog species than those in remnant patches or the intact native forest. In addition, species richness tended to be higher at wide, shallow swamps and marshes near the headwaters of streams, with herbs, grasses, shrubs, reeds, sedges and rushes in the emergent and fringing vegetation. There was little evidence to suggest that larger eucalypt remnants supported more species of frogs, or that remnants isolated by greater expanses of pines supported fewer species, but we had low power to detect these effects with our data set. Our results support the preservation of all remnants of native forest along drainage lines and around swamps, soaks and bogs, regardless of size. Where new pine plantations are established, for example, on cleared agricultural land, care should be taken to maintain the structural and vegetative characteristics of water bodies to ensure that they continue to provide suitable breeding habitat for frogs.

Assessing forest canopy density in a highly variable landscape using Landsat data and FCD Mapper software

Summary Forest canopy density (FCD), estimated with the FCD Mapper, was correlated with basal area and predominant height (PDH) for 48 field plots, measured in highly variable native eucalypt forest at Toolara, south-eastern Queensland, Australia. The Mapper was produced for the International Tropical Timber Organisation and is available on a CD-ROM. It estimates FCD as an undefined index of canopy density using reflectance characteristics of Landsat Enhanced Thematic Mapper images. The Mapper is a ‘semi expert’ computer program which uses interactive screens to allow the operator to make decisions concerning the classification of land into bare soil, grass or forest. The results of a FCD classification are therefore dependent on the operator's decisions and were found to be highly sensitive to small changes in settings. A positive, weak (r 2 = 0.36) nonlinear relationship of FCD with basal area was observed, while a strong (r 2 = 0.68) similar relationship was observed between FCD and PDH. The strong relationship of FCD with PDH suggests that this remote sensing technique has promise for forest inventory, but that a quick and robust method of measuring FCD in the field is still required for ground truthing.

Is soil carbon a useful indicator of sustainable forest soil management?—a case study from native eucalypt forests of south-eastern Australia

The area and percent of forest land with significantly diminished soil organic matter (SOM) and/or changes in other soil chemical properties has been proposed as a regional sustainability indicator for Australia’s forests. This study examined for native eucalypt forest in south-eastern Australia how representative soil organic carbon (SOC) is of important ecosystem properties and processes. In addition, it was investigated how sensitive the proposed indicator is to management-induced disturbance of these forests. Three sites in Victoria with a known disturbance history and a mapped distribution of soil disturbance (different intensities of fire, snig tracks, and soil perturbation) were included. These sites (2× Eucalyptus regnans, 1× Eucalyptus sieberi) had been clearfelled 9–10 years prior to sampling. The fine-soil fraction (<2 mm) was analysed for SOC, microbial C and N, mineralisable C and N, and available P. In addition, SOC was determined in rocks, plant residues, and charcoal in the fraction greater than 2 mm. Non-labile SOC in the fine-soil fraction contributed to 47–66% of the total in soil profiles (litter layer and 0–30 cm mineral soil). Charcoal in the >2 mm fraction contributed to 13–27% of total SOC. The relationships between SOC and measures of organic matter quality and N and P availability were inconsistent across sites and management practices. The effects of disturbance were most pronounced in the surface soil (0–7.5 cm). Including deeper soil layers in the statistical analysis diluted disturbance effects. Significant differences in the SOC content between soil disturbance intensities in the fine-soil fraction disappeared when size fractions>2 mm were considered. In addition, soil compaction masked changes in SOC concentration in some cases, when SOC was expressed on a volume basis. When all size fractions were considered, SOC stocks increased with fire intensity as a result of charcoal inputs. Physical soil disturbance appeared to be more critical for regrowth productivity than the effects of slash fires. Our results showed that the proposed indicator, changes in SOC, does not meet several of the attributes of what is commonly regarded as a good ecological indicator. Of particular concern are the changes in SOC resulting from charcoal inputs, which are difficult to interpret with regard to soil fertility. Without further qualifications, the changes in SOC cannot be recommended for implementation as an indicator of sustainable soil management in native eucalypt forests. Alternative approaches for the monitoring of changes in soil properties are discussed.

EFFECTS OF FOREST FRAGMENTATION ON BIRD ASSEMBLAGES IN A NOVEL LANDSCAPE CONTEXT

We report findings of a large-scale study in a 100 000-ha subsection of the Tumut region in southern New South Wales, southeastern Australia. The study was designed to measure the effects of landscape context and habitat fragmentation on forest birds. The study region consisted of a forest mosaic characterized by different landscape contexts: large, continuous areas of native Eucalyptus forest, extensive stands of exotic softwood (radiata pine, Pinus radiata) plantation, and remnant patches of native Eucalyptus forest scattered throughout the extensive areas of radiata pine plantation. A set of 85 eucalypt remnants was randomly selected across several stratifying variables: four patch size classes (1-3 ha, 4-10 ha, 11-20 ha, and .20 ha), two isolation age classes (,20 years and .20 years since fragmentation), and five dominant eucalypt forest type classes. In addition to the 85 eucalypt remnants, a further 80 3-ha sites were selected for study: 40 in large, continuous areas of eucalypt forest and 40 in radiata pine stands. Point-interval counts of forest birds at the 165 sites were conducted in 1996 and 1997. Of 90 species recorded, 23.1 species (95% confidence interval, 22.0, 24.2 species), on average, were present in continuous eucalypt forest, 20.6 (19.5, 21.7) species in patch- shaped eucalypt remnants, 20.6 (19.5, 21.7) species in strip-shaped eucalypt remnants, and 16.7 (15.6, 17.8) species in radiata pine. Strong gradients in bird assemblages were found. These gradients were governed by a combination of landscape context, remnant size, and remnant shape effects, and, in the case of radiata pine sites, the extent of native forest surrounding the pine. These gradients could, in part, be explained by bird life history attributes such as foraging guild and nesting height. For example, birds more often detected in patch-shaped remnants were smaller, produced smaller clutches, were more likely to be migratory, and typically had cup nests or burrows. The results of our study showed that eucalypt fragments of all sizes and shapes have significant conservation value. This is because they contain many native species of birds, some of which are more abundant in fragments than they are in continuous eucalypt forests, and also because they increase native bird populations in nearby non-native pine plantations.

Effects of Forest Fragmentation on Bird Assemblages in a Novel Landscape Context

We report findings of a large-scale study in a 100 000-ha subsection of the Tumut region in southern New South Wales, southeastern Australia. The study was designed to measure the effects of landscape context and habitat fragmentation on forest birds. The study region consisted of a forest mosaic characterized by different landscape contexts: large, continuous areas of native Eucalyptus forest, extensive stands of exotic softwood (radiata pine, Pinus radiata) plantation, and remnant patches of native Eucalyptus forest scattered throughout the extensive areas of radiata pine plantation. A set of 85 eucalypt remnants was randomly selected across several stratifying variables: four patch size classes (1–3 ha, 4–10 ha, 11–20 ha, and >20 ha), two isolation age classes (<20 years and >20 years since fragmentation), and five dominant eucalypt forest type classes. In addition to the 85 eucalypt remnants, a further 80 3-ha sites were selected for study: 40 in large, continuous areas of eucalypt forest and 40 in radiata pine stands. Point-interval counts of forest birds at the 165 sites were conducted in 1996 and 1997. Of 90 species recorded, 23.1 species (95% confidence interval, 22.0, 24.2 species), on average, were present in continuous eucalypt forest, 20.6 (19.5, 21.7) species in patch-shaped eucalypt remnants, 20.6 (19.5, 21.7) species in strip-shaped eucalypt remnants, and 16.7 (15.6, 17.8) species in radiata pine. Strong gradients in bird assemblages were found. These gradients were governed by a combination of landscape context, remnant size, and remnant shape effects, and, in the case of radiata pine sites, the extent of native forest surrounding the pine. These gradients could, in part, be explained by bird life history attributes such as foraging guild and nesting height. For example, birds more often detected in patch-shaped remnants were smaller, produced smaller clutches, were more likely to be migratory, and typically had cup nests or burrows. The results of our study showed that eucalypt fragments of all sizes and shapes have significant conservation value. This is because they contain many native species of birds, some of which are more abundant in fragments than they are in continuous eucalypt forests, and also because they increase native bird populations in nearby non-native pine plantations.

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.

Small mammals, habitat patches and PVA models: a field test of model predictive ability

The results are described of comparisons between actual values for patch occupancy for two species of Australian small mammals (Bush Rat Rattus fuscipes and Agile Antechinus Antechinus agilis) determined from field sampling and predictions of patch occupancy made using VORTEX, a generic simulation model for Population Viability Analysis (PVA). The work focussed on a fragmented forest in south-eastern Australia comprised of a network of 39 patches of native eucalypt forest surrounded by extensive stands of exotic softwood Radiata Pine ( Pinus radiata) plantation. A range of modelling scenarios were completed in which four broad factors were varied: (1) inter-patch variation in habitat quality; (2) the pattern of inter-patch dispersal; (3) the rate of inter-patch dispersal; and (4) the population sink effects of the Radiata Pine matrix that surrounded the eucalypt patches. Model predictions were made for the total number of animals, the distribution of animal density among patches, the total number of occupied patches, and the probability of patch occupancy. Predictions were then compared with observed values for these same measures based on extensive field surveys of small mammals in the patch system. For most models for the Bush Rat, the predicted relative density of animals per patch correlated well with the values estimated from field surveys. Predictions of patch occupancy were not significantly different from the actual value for the number of occupied patches in half the models tested. The better models explained 10–16% of the log-likelihood of the probability of patch occupancy. While some of the models gave reasonable forecasts of the number of occupied patches, even in these cases, they had only moderate ability to predict which patches were occupied. Field surveys revealed there was no relationship between patch area and population density for the Agile Antechinus—an outcome correctly predicted by only a few models. Five of the 18 scenarios completed for the Agile Antechinus gave predicted numbers of occupied patches not significantly different from the observed number. In each of these five cases, large standard deviations around the mean predicted value meant uncertainty generated by the simulation model limited the predictive power of the PVA. Some of the models gave reasonable predictions for the number of occupied patches, but those models were unable to predict which ones were actually occupied. The results of our study suggest that key processes influencing which specific patches would be occupied were not modelled appropriately. High levels of variability and fecundity drive the population dynamics of the Bush Rat and Agile Antechinus, making the patch system unpredictable and difficult to model accurately. Despite the fact that both the Bush Rat and the Agile Antechinus are two of the most studied mammals in Australia, there are attributes of their biology that are presently poorly understood (which were not included in the VORTEX model), but which could strongly influence patch occupancy. For example, local landscape features may be important determinants of inter-patch movement and habitat utilisation in the patch system. Further empirical studies are needed to explore this aspect of small mammal biology.

Insect pests of Tasmanian blue gum, Eucalyptus globulus globulus, in south‐western Australia: History, current perspectives and future prospects

AbstractTrends in, and potential causes of, insect pest problems of the Tasmanian blue gum, Eucalyptus globulus globulus, in south‐western Australia are reviewed. Historical evidence suggests that insect pest problems of E. g. globulus in south‐western Australia have greatly increased in the last 10 years, which corresponds to a time of rapid expansion of the blue gum industry in the region. Current major establishment pests include the African black beetle, Heteronychus arator, spring beetles, Liparetrus spp. and Heteronyx spp., and the wingless grasshopper, Phaulacridium vittatum. Current major pests of established trees are the Eucalyptus weevil, Gonipterus scutellatus, and chrysomelid beetles, Chrysophtharta spp. and Cadmus excrementarius. The occurrence of these insects on an introduced eucalypt is not unexpected because insect‐rich native eucalypt forests dominate the landscape where E. g. globulus plantations are grown. Insect damage may also be exacerbated because E. g. globulus is grown as a monoculture.

The spatial distribution of non-native plant invaders in a pine–eucalypt landscape mosaic in south-eastern Australia

Factors influencing the spatial distribution of two major species of non-native plants, blackberry ( Rubus fruticosus) and radiata pine ( Pinus radiata) wildlings in a fragmented forest landscape in south-eastern Australia were quantified. A total of 1067 plots within three broad groups of sites was surveyed for these two non-native plant species. The sites were in large continuous areas of native eucalypt forest, an extensive plantation of P. radiata, and sites in patches of remnant eucalypt forest embedded within the pine plantation. In the case of the 507 plots located within patches of remnant eucalypt forest, an array of variables (e.g. distance to surrounding pine plantation, and floristic and structural attributes) was measured and used in statistical analyses of non-native plant occurrence. P. radiata wildlings were totally absent from plots in large continuous areas of native eucalypt forest, but present at 5% of plots within patches of eucalypt remnants embedded within the pine plantation. Logistic regression showed that the occurrence of P. radiata wildlings in the eucalypt remnants was significantly higher in plots where the neighbouring pine plantation had been established for a long time, plots that were dominated by dry eucalypt forest types, and plots with a limited cover of ground vegetation. The occurrence of R. fruticosus differed significantly ( P<0.001) between the groups of sites; 59% of plots in the pine plantation, 41% in the eucalypt remnants, and 7% in continuous areas of native forest were invaded. For the eucalypt remnants, the occurrence of this species was significantly greater in plots close to the surrounding pine plantation, with fewer species of native shrubs, in wet eucalypt forest types, and with low values for both eucalypt basal area and rock cover. The results of this study indicate that even though non-native plant invasion is already relatively extensive in the study area, it is likely to further increase. The array of factors influencing the spread and establishment of P. radiata wildlings and R. fruticosus indicate that the control of these non-native plants will be extremely difficult in the existing plantation estate. However, the adoption of some simple protocols could make it feasible to limit their spread to newly established areas of the pine plantation estate.

EFFECTS OF WITHIN- AND BETWEEN-PATCH PROCESSES ON COMMUNITY DYNAMICS IN A FRAGMENTATION EXPERIMENT

The effects of the experimental fragmentation of native eucalypt forest on the beetle community were tested, in a controlled, replicated, long-term experiment. Included in our design were three fragment sizes, fragment edge and interior sites, and sites in the surrounding exotic pine plantation matrix. We followed 325 species through 28 sampling periods over seven years, including two years pre-fragmentation. We examined effects of fragmentation on four attributes of community structure: (1) species richness, (2) species composition, (3) relative abundance, and (4) the changes in occurrence of all species individually by the traits of rarity, degree of isolation (dispersal ability), and trophic group. We also considered how changes in these attributes altered community dynamics (turnover). We used both community-level and species-level responses to determine the relative importance of processes acting at the within-patch and between-patch scales. At the within-patch scale there were two findings. (1) There was no evidence of an increase in the extinction rate on fragments, as was hypothesized. Neither species richness nor the occurrence of rare species declined on fragments compared to continuous forest. (2) Edge effects altered species occurrences and abundances on fragments compared to continuous forest. There was evidence of two edge effects, with different penetration distances. Species richness increased at fragment edges in response to a shallowly penetrating edge effect. Species relative abundance and composition changed on fragments in response to a deeply penetrating edge effect, which also caused increases in the occurrences of detritivores and fungivores. At the between-patch scale there were three findings. (1) There was no evidence of a reduction in the colonization rate of fragments. There was no reduction in species richness or in the occurrence of individual species with poor dispersal abilities on fragments compared to continuous forest. (2) The matrix between fragments altered between-patch processes by providing alternative habitat for some species. These species increased in occurrence on fragments compared to continuous forest, supporting the predictions of recent metacommunity theory. However, the matrix did not act as a source of invading species. (3) Turnover was reduced in fragments compared to continuous forest. Thus, the effect of fragmentation was to stabilize community dynamics.

Does nitrogen limit the growth of native eucalypt forests:some observations for mountain ash (Eucalyptus regnans)

It is often stated that the availability of N limits the rate of growth of native forests. We discuss this hypothesis with particular reference to the mountain ash (Eucalyptus regnans) forests of south-eastern Australia. The abundance of 15 N in leaves and soil of mountain ash forest is in accord with data for Northern Hemisphere temperate forests and for tropical forests,and indicates that N availability is relatively high.None of the nutrient elements has limited the rate of growth of mountain ash forest regenerating after major disturbance (clear-felling and intense wild-fire). There is some evidence that P may be limiting to some ecological processes (e.g. the rate of litter decomposition). We conclude that phosphorus is more likely to be limiting than nitrogen in mountain ash forest because nitrogen cycling is conservative and continual inputs of N through biological fixation supplement this conservative N supply, and the stands never become N-deficient. The development of methodologies to determine the rate of N2-fixation in forests should be of high priority in ecological research.

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.

Colonisation of experimentally immersed wood in south eastern Australia: responses of feeding groups to changes in riparian vegetation

We investigated macroinvertebrate abundance and functional feeding groups colonising experimentally-positioned woody substrates of different species in streams with three different riparian vegetation types. Native Eucalyptus forest formed a dense closed canopy over our streams; introduced (exotic, alien) pine plantation forest did not fully shade the streams, and grassland streams were completely open, although with woody riparian vegetation well upstream of our sites. Macroinvertebrate assemblages varied taxonomically and functionally with both wood species and riparian vegetation composition. Two specialist feeding groups responded clearly to riparian vegetation: wood gougers were most common in forested streams, and algal grazers in more open streams. Gougers colonised native Eucalyptus wood in preference to alien species. Other feeding groups responses showed complex interactions between vegetation and wood type. Our results indicate the importance of sampling appropriate substrates when assessing questions of this type – if seeking shifts in functional organisation, the substrates on which the feeding groups of interest occur must be sampled. The composition of the riparian strip may influence xylophilous communities as much as the structure (i.e. whether closed or open).

HABITAT FRAGMENTATION, LANDSCAPE CONTEXT, AND MAMMALIAN ASSEMBLAGES IN SOUTHEASTERN AUSTRALIA

We examined relationships between mammalian assemblages and landscape context and habitat fragmentation in southeastern Australia. Data were gathered from spotlighting and hair sample surveys at 166 sites in 3 different spatial (landscape) contexts: remnant patches of native eucalypt forest surrounded by an extensive plantation of exotic radiata pine ( Pinus radiata—86 sites), the radiata pine plantation (40 sites), and large areas of continuous native eucalypt forest that occurred at the margins of the plantation (40 sites). Continuous eucalypt forest supported more species than eucalypt patches, although some species were more common in the patch areas. All assemblages in the radiata pine sites were substantially impoverished. There was a significant patch size effect for the total mammalian assemblage and for terrestrial native mammals but not for arboreal marsupials. Bigger remnants supported an assemblage different from (and more species rich) that found in smaller remnants, particularly those ,3 ha where many mammal species occurred less frequently. The landscape context and patch area effects recorded in this study have important implications for plantation design in southern Australia. Eucalypt remnants should be exempt from clearing during plantation development; larger remnants are the most important areas.

Mining disturbance alters phosphorus fractions in northern Australian soils

The brown kandosol soils at Weipa, North Queensland, contain little soil phosphorus (P). Plant-available fractions (considered in this study to include resin, hydroxide, and dilute acid extractable P) approximate 85 ˜g P/g, or 70% of total soil P, the majority of which is in labile organic forms, highlighting the importance of P cycling within the native eucalypt forest. A field experiment was undertaken to evaluate the effect of soil handling during bauxite mining on the distribution of P between the various soil fractions. This study showed that soil stripping and replacement disrupts the P cycle and affects the proportional distribution of P between soil fractions. Horizon mixing during soil handling severely reduces the size of plant-available soil P fractions in surface soils ( 0–5 cm depth) and this can only be partially compensated by the addition of fertiliser. A survey of rehabilitated sites of differing ages showed that restoration of soil organic P fractions is extremely slow, with the overall distribution of P within replaced soils remaining different from that within undisturbed soils 15 years after rehabilitation to native forest or exotic pasture species.

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 &lt;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.