Tw Norton

Modelling environmental heterogeneity in forested landscapes

Abstract Models for estimating the spatial distribution of radiation, thermal and hydrologic regimes in topographically complex forested catchments are presented. These models use topographic attributes derived from a grid-based digital elevation model (DEM) as the primary input data. The models are based on simplified representations of the underlying physics of the processes, but include the key factors that modulate system behaviour. They represent an attempt to relate pattern to process. Model SRAD is an approximate method for estimating the spatial distribution of global short-wave radiation, net long-wave radiation, net radiation and maximum, minimum and average temperature, and accounts for the effects of topographic shading. Model WET estimates spatially distributed soil water content and evapotranspiration and catchment runoff. SRAD and WET applied to a 21.65 km2 forested area within the Brindabella Range in south-eastern Australia to illustrate the potential applications of the approach. A 20 m × 20 m grid DEM was developed for the area. The computed radiation fluxes are consistent with measurements made at Canberra. The computed average annual runoff conversion efficiency was 18.6%, which compares reasonably well with the annual runoff conversion efficiency of 17.6% measured over an 11 year period on a 97.5 ha catchment located near the study area. The study area contains five main sub-alpine forest types, as well as a small area of exotics. The computed fluxes were used to characterize the fine-scale environmental heterogeneity and environmental domains of these forest types. Average minimum temperature in the coldest month (July) and annual net radiation were two environmental variables differentiating the occurrence of the three eucalypt species (Eucalyptus pauciflora, E. fastigata and E. delegatensis) investigated.

Influence of fragmentation and disturbance on the potential impact of feral predators on native fauna in Australian forest ecosystems

The current knowledge is reviewed of the diet and predator–prey relationships of the feral cat (Felis catus), fox (Vulpes vulpes) and dingo (Canis familiaris dingo) (including wild dogs). The effect of forest fragmentation by roads on the use of native forest ecosystems by these species and the significance of this for native fauna is considered. The cat, fox and dingo are significant predators in Australia that interact with native fauna in various ways, including predation, competition for resources, and transmission of disease. On the basis of current knowledge, it is clear that the nature and impact of predation by the cat, fox and dingo on native fauna are primarily determined by prey availability, although there are exceptions to this rule. Generally, dingoes prey upon large to medium-sized prey species (e.g. wallabies, common wombats, and possums), foxes prey upon medium-sized to small prey (e.g. possums and rats) and consume a significant component of scavenged material and vegetation, while cats also prey upon medium-sized to small prey, but may have a greater proportion of reptiles and birds in their diet. The cat is generally considered to be an opportunistic predator and to have contributed to the demise of a number of mammals. The fox is considered more of a threat to small native mammals and it has been asserted that all species of mammals that fall within the critical weight range (CWR) of 120–5000 g are at risk of local extinction when the fox is present. The severity of the impact of the dingo upon the native fauna is considered to be minimal, at least in comparison with the impact that the cat and fox can have on populations. The dingo is not considered a threat to CWR mammals in undisturbed environments. The fox, feral cat and dingo are all considered to have the ability to selectivity prey upon species and, to some extent, individual sexes and age-classes of a number of larger prey species. Although many of Australias forested areas are relatively heavily fragmented by roads, there are no published studies specifically investigating the use of roads by feral predators. Information on the distribution and abundance of foxes, cats and dingoes in these ecosystems, their ecology and their impact on native fauna is particularly limited. Further, the extent to which roads influence the distribution and abundance of these species and the consequences of these for native fauna are poorly known. One of the most important research needs is to establish the relative impact that exotic predators may have on native fauna under varying degrees of road construction within native forests. For example, are areas with and without roads in forests used differently by exotic predators and what is the significance of this in terms of the potential impact on fauna? The extent to which feral predators forage away from roads needs further investigation, as does the rates of predation within edges, because this may have several consequences for the design, location and size of retained strips and wildlife corridors as well as restoration programmes. Further observations on regional differences influencing predator–prey interactions are required, as is research on the potential impacts on native fauna resulting from prey selection in forests subjected to various degrees of fragmentation and modification.

Metapopulation viability analysis of the greater glider Petauroides volans in a wood production area

Successful forest wildlife management is dependent on information that estimates long-term viability of popu- lations in response to different management practices. In this paper we couple information captured in a GIS database, relationships between habitat attributes and habitat quality, and the dynamics of those habitat at- tributes, to assess the long-term metapopulation viability of a forest-dependent arboreal marsupial, greater glider Petauroides volans Kerr, in the Ada Forest Block in south-eastern Australia. Estimates of the size and spatial distribution of populations in remnant patches of old- growth forest, and the dynamics of key elements of that habitat, are input to ALEX, a computer package for population viability analysis. The model is used to predict the probability of persistence of P. volans within the Ada Forest Block concentrating on scenarios that assess the value of different old-growth patches and the impact of wildfire. We conclude that small patches of old-growth forest (< 20 ha) make almost no contribution to the per- sistence of the species. In addition, control of wildfire will significantly increase the viability of the species in the remaining habitat.

Uncertainty, ecology, sustainability and policy

Using an Australian focus to explore theoretical and policy issues of wider concern, this article examines linkages between public policy and the science of ecology. This is done within the broader framework of sustainability, emphasizing the problem of decision making in the face of ‘uncertainty’. Insights from the ecological, risk, sustainability and policy literatures are used. The sustainability-uncertainty problem is characterized, and the adequacy of existing policy support techniques and approaches noted, particularly the precautionary principle. The problem is further defined using the notion of ignorance. The treatment of ignorance and uncertainty in ecology is discussed. We suggest that the science of ecology has had a limited influence on policy formulation and discuss the basis of this using biodiversity conservation and ecosystem management as examples. We conclude by considering challenges for handling risk, uncertainty and ignorance in ecological science for policy formulation. We emphasize the need for improved communication between the science and policy communities, greater recognition of the limits of quantitative techniques in addressing uncertainty, and contingency planning.

Conservation of biological diversity in temperate and boreal forest ecosystems

Abstract The regions of the world most uniformly and extensively modified by human activities are the temperate zones. Settlement and development of these productive and hospitable regions have a long history and have often resulted in dramatic impacts on biological diversity. Temperate and boreal forest ecosystems have not avoided these impacts. Impacts on biodiversity have occurred at the ecosystem, species, population and genetic levels. The geographic range of many species has been reduced, and in a number of cases species have become extinct. The extent of remaining old growth forest varies from less than 1% in western Europe to about 25% in New Zealand. In Australia, only about 2–3% of the old growth, temperate eucalypt forests on the most productive soils remain since European occupation of the continent in 1788, and these ecosystems are considered to be endangered. Given a broad definition of temperate forest ecosystems that includes various types of boreal forest in the Northern Hemisphere, approximately 2 billion ha of these ecosystems remain globally. By area, the majority of these forests occur in Russia (41%) and in North America (32%). The nature of these ecosystems, their biological productivity, complement of biological diversity, and use by humans varies considerably within and between major geographic regions. In general, most temperate and boreal forest ecosystems are poorly protected in conservation reserves and many are increasingly used for wood production to supply regional, national and international demand. Many conflicts have arisen over the conservation and management of these forests in the past few decades. This paper introduces the concept of sustainable development and briefly considers some of the policy processes concerned with the conservation of biological diversity and sustainable management in temperate and boreal forests. The International Forest Conference, from which the papers presented in this journal issue arise, is then described and the main findings of the papers summarised. Issues that need more attention include: how to adequately assess biodiversity from the local to the regional scale and integrate this information in a manner useful for landscape planning and management; how to develop policy processes that are genuinely open to community evaluation and scientific peer review; what is a sufficient precautionary approach to forest use given the uncertainties and risks arising from imperfect knowledge, predicted climate change and unforeseen events; and, how the needs of indigenous forest peoples can be best accommodated in the sustainable development of temperate and boreal forests. In addition, much more time needs to be dedicated to external strategies that will help relax many of the increasing demands that humans place on temperate and boreal forest ecosystems. Without the latter scope to enhance forest conservation and management and adapt over time may be limited.

Biological inventory for conservation evaluation III. Relationships between birds, vegetation and environmental attributes in southern Australia

Relationships between diurnal, terrestrial birds, vegetation and environmental attributes were investigated in the open Eucalyptus forests of south east Australia. Of the 83 bird species recorded, the probability of occurrence of the Yellow-faced Honeyeater, Superb Fairy-wren, Golden Whistler, Fan-tailed Cuckoo and Shining Bronze-Cuckoo was modelled. The Yellow-faced Honeyeater was the only taxon modelled whose distribution could be best explained using climatic variables. The other four species were related to habitat features at the site level. The models developed for these species were specific to each data set used and are unlikely to be appropriate for other data collected at other times of the year. Statistical modelling was used to investigate the response of bird assemblages to environmental and biological regimes. The models reflect differences in the bird species composition of sites in relation to elevation and soil moisture/nutrient gradients across the region. Birds favouring higher elevations were separated from birds favouring mid and lower elevations. Birds favouring wetter environments were separated from those using drier habitats although these species were also present in the wetter environments. Differences in the distribution of birds related to elevation were explained by the environmental attributes minimum temperature of the coldest month and mean precipitation of the driest quarter which also affect vegetation formations and associations across the study region. Vegetation floristics and topographic position, which can reflect the moisture and nutrient status of sites, were important in characterising the specific habitat requirements of a number of birds. Physical and biological regimes were significantly related to bird species richness. Species richness was found to be greatest in moist forests found at mid and low elevations throughout the year. A stratified field survey was successful in recording the majority of forest birds that can occur in the eucalypt forests of south east Australia but sufficient data for reliably modelling the distribution and habitat quality of birds were obtained for only about 10% of the birds recorded. Even when data from two census periods were aggregated, data were sufficient for only 27% of the total number of birds recorded to develop a habitat model. Suggested modifications to the survey design based on the data and analyses used in this study, are discussed in terms of the intended purpose of the field survey.

Designing surveys for microchiropteran bats in complex forest landscapes—a pilot study from south-east Australia

Abstract Most of Australias forest-dwelling microchiropteran bats are reliant on hollows in trees for shelter and breeding. These bats typically comprise a significant proportion (at times over 40%) of the mammalian fauna of a forest region. Because of past and current impacts of timber harvesting and other human activities on native forest ecosystems, insectivorous bats may be threatened by the loss of habitat, hollow-bearing trees and food sources that provide essential life requirements. Unfortunately, reliable assessment of the conservation status of most species remains problematic because of a lack of basic data on distribution, abundance and autecology. Here, we outline an approach for designing regional surveys of microchiropteran bats based on the use of sophisticated, geographic information system techniques. The forests of south-east New South Wales are used as a case study. We also assess the duration of trapping on the detection of bats and compare the efficacy of harp traps and ultrasonic detectors in censusing forest bats. A gradsect or gradient-oriented transect approach was employed in the design of the regional survey. We characterised regional variation in climate, forest vegetation, and terrain as a basis for sampling. The assessment of bat sampling methods was restricted to three areas (South Brooman/Shallow Creek, Quart Pot/Buckenbowra, and Badja State Forest) with specific climate attributes within unlogged portions of one of the common forest types (Dry Forest dominant over Moist Forest) in the region. A total of 13 species of insectivorous, forest-dwelling bats was detected with the use of harp traps. Three of these species, the Golden-tipped Bat (Kerivoula papuensis), Eastern False Pipistrelle (Falsistrellus tasmaniensis) and the Eastern Little Freetail-bat (Mormopterus norfolkensis) are listed as vulnerable and rare on Schedule 12 of the N.S.W. National Parks and Wildlife Act 1974. One further species, the White-striped Mastiff bat (Tadarida australis) was detected only by the use of ultrasonic equipment. Our data indicate that two to three nights trapping per area may be adequate to estimate species presence but this must be qualified with regard to weather. Variation in the trapping of bats between sites within an area indicated that improved sampling may be achieved by using more traps per night rather than extending the duration of trapping.

Biological inventory for conservation evaluation. IV. Composition, distribution and spatial prediction of vegetation assemblages in southern Australia

Data on the floristics of the vegetation collected as part of a systematic, stratified regional survey of birds in the open Eucalyptus forests of south east Australia, were used to investigate the composition and distribution of vegetation assemblages across the region, and the extent to which associations between plant species could be used to predict the potential species complement of unsampled areas of the region. One hundred and ninety-three plant species were recorded in the open Eucalyptus forests in this study. These comprised 22 tree overstorey species, 46 tree understorey species, 114 shrub and herbaceous species, and 11 ground cover species from approximately 106 genera. Broad trends in the distribution of vegetation assemblages were associated with perceived elevation and soil moisture/nutrient gradients across the study region. BIOCLIM provided a means of characterising these broad trends in the distribution of vegetation assemblages by defining climatic envelopes for clusters of sites. Of the variables used to define these climatic envelopes, temperature variables were the most useful in discriminating between groups of sites. However, only a limited number of discrete assemblages of plants associated with groups of sites could be used for predicting the occurrence of vegetation assemblages in unsampled areas in the landscape.

Biological inventory for conservation evaluation II. Composition, functional relationships and spatial prediction of bird assemblages in southern Australia

Data collected from a systematic, stratified regional survey of the open Eucalyptus forests of south east Australia were used to determine if predictable patterns exist in the bird assemblages identified in the region and the extent to which these associations could be used to predict the potential complement of bird species in unsampled areas of the region. Eighty three bird species were recorded in the open Eucalyptus forests considered in this study. Approximately 30 to 40% of the bird species were recorded in a range of environments and appeared to be widely distributed across the region. Less than 20% of the species recorded occurred in more than half of the sites censused. The birds recorded did not appear to form consistent, discrete and predictable assemblages. Few birds were consistently associated with each other throughout the year. However, two assemblages of species consistently occurred together: a group of 11 of the most frequently recorded and widespread species and two relatively sedentary species restricted to wetter environments. The use of the ubiquitous bird species as indicators of the likely species complement at a particular site or area is limited. The Yellow-tufted Honeyeater and Bell Miner were consistently associated with each other throughout the year and were found in wet forests in gullies and along creeks and rivers. These environments also had the highest species richness of birds. These birds may be useful as indicators of particular types of environments and areas of relatively high species richness. Broad trends in the distribution of birds were associated with perceived elevation and soil moisture/nutrient gradients across the study region. BIOCLIM provided a means of characterising these broad trends in the distribution of birds by defining climatic envelopes for clusters of sites. Of the variables used to define these climatic envelopes, temperature variables were the most useful in discriminating between groups of sites. However, only a limited number of discrete assemblages of birds associated with groups of sites could be used for predicting the occurrence of birds in unsampled areas in the landscape.

Biological inventory for conservation evaluation I. Design of a field survey for diurnal, terrestrial birds in southern Australia

Abstract A systematic, stratified, regional biological survey was designed and implemented to sample the variation in bird and vegetation assemblages in an area of some 758 129 hectares of open Eucalyptus forest in south east Australia. The survey design was based on spatial estimates of abiotic attributes (terrain, climate and nutrient-supply potential of the substrate) and vegetation cover for a 9 second grid of longitude and latitude (250 × 250 metres) for the study region. A climate stratification consisting of a matrix of five classes of minimum temperature of the coldest month and four classes of mean precipitation of the driest quarter was constructed representing an environmental gradsect which inherently incorporated the steepest altitudinal gradients in the study region. Using digitally-stored LANDSAT vegetation cover data, the climate stratification was constrained to climate domains associated with the extant forest cover. Fourteen climate domains identified across the forested region were then stratified on two broad categories of the nutrient-supply potential of the substrate. This resulted in the definition of 24 climate/nutrient domains across the study region, of which 23 were sampled by the survey.