Suchergebnisse

In January 1989, a wildfire burnt 120 ha (45%) of the 267 ha of native
vegetation in Kings Park, Perth, Western Australia. The area burnt included a
transect along which birds had been censused during 1986 for comparison with
censuses on the same transect during 1928–37 and 1952–55. Counts
of birds along the transect from 1989 to 1995 indicate a slow recovery in
numbers for 11 (38%) of 29 species present in 1986. Two species
disappeared from the transect, but one of these was found elsewhere in the
park. There are many reasons for the changes in the avifauna of Kings Park,
including changes to the structure of the vegetation, the increasing isolation
of the park from other native vegetation, and changes in the distribution and
abundance of species outside the Perth region. The long-term trends in the
avifauna and the impact of the 1989 fire indicate that a new approach to the
management of the Park's vegetation may be required. For example, to
avert continuing declines in the Park's avifauna, it may be helpful to
re-establish a canopy of eucalypts and to create a more open understorey with
some bare ground. However, the impact of the 1989 fire and the slow recovery
of the avifauna illustrate the sensitivity of small reserves to major
disturbances and the difficulty of conserving the original biota without
intensive intervention.

This paper reports a study of ground-dwelling, small mammals in coastal eucalypt forest in south-eastern Australia from 1970 through 2005. During this time, the study area burnt in an intense fire in December 1972 and was partially burnt in November 1980. Both fires were associated with prolonged drought. The mammals studied comprised two dasyurid marsupials, Antechinus agilis and A. swainsonii, two native murid rodents, Rattus fuscipes and R. lutreolus, and the introduced house mouse Mus musculus. After intensive sampling throughout the year from 1970 through 1972 to establish basic ecological and population parameters of the small mammal community, populations were sampled annually during late autumn and early winter before the onset of breeding. There were marked differences in the annual (autumn/winter) abundances of all species; numbers of A. agilis ranged from 4 to 142 individuals; A. swainsonii 0 to 43; R. fuscipes 4 to 54; R. lutreolus 0 to 11; M. musculus 0 to 23. Following the 1972 fire, numbers fell to the lowest level recorded during the study and each population subsequently disappeared from the plot between the 1973 and 1974 winter censuses. The less intense 1980 fire did not lead to extirpation, but numbers of A. agilis, A. swainsonii and R. fuscipes declined as drought conditions persisted through 1983. R. lutreolus occurred consistently only following the fires, when a grassy ground vegetation favoured by this species developed. Similarly, M. musculus colonised within two years of the fires and persisted on the plot for 3–4 years before disappearing. Following the fires, populations of the omnivorous R. fuscipes recovered first followed by the scansorial, insectivorous A. agilis and last by the fossorial, insectivorous A. swainsonii. Two primary conclusions emerged from this study. First, the intense fire of 1972 did not kill all the animals immediately, but led to the disappearance of each species from the plot over 18 months. Thus, intense fire had a delayed but catastrophic impact on small ground-dwelling mammals. The fluctuations in population levels, covering more than an order of magnitude, demonstrate that factors other than fire, such as rainfall and drought, drive the population dynamics of these small mammals. As stability and recovery are not features of local populations, long-term studies of benchmark populations are necessary to manage forest biodiversity.

Mulga is a distinctive woodland or shrub community with a wide distribution across the semi-arid zone of southern and central Australia. Mulga (Acacia aneura) is the dominant shrub and small tree, but other species of Acacia are common. Typical of Australian habitats in the arid zone, mulga has a core of resident bird species that is augmented by nomadic (opportunistic) species when conditions are favourable. This paper describes the foraging behaviour and habitat use of a mulga avifauna in the vicinity of Alice Springs during late winter, when many opportunistic species were present. Data were obtained for 24 species, of which 16 were confirmed as nesting. Many birds, regardless of their normal foraging habits, converged on a common food resource: a geometrid moth (Geometridae) that was abundant on mulga plants. Despite their use of a common food resource, species differed in their foraging behaviour, proportions of different substrates used, and foraging heights. Ground-foraging species dominated the avifauna, but in most respects the guild structure of the community was a scaled-down version of Eucalyptus forest avifaunas. Differences in guild structure between mulga and eucalypt forest are best explained by differences between the two habitats in the kinds of resources (e.g. foraging substrates, types of food) that are available.

There are extensive revegetation programs in the wheatbelt of Western Australia. Revegetation has many objectives including lowering water tables to combat water logging and soil salinisation, improving agricultural productivity, and producing a commercial crop of trees for harvesting.Trees are planted by farmers, conservation groups and Government authorities to rehabilitate, beautify and manage degraded agricultural land, parks and road verges.In addition to improving plant diversity and restoring ecosystem functions, revegetation is an opportunity to provide food and habitat for wildlife and to conserve regional biodiversity. The objective of the study reported here was to investigate whether the tree species planted in the wheatbelt are colonized by invertebrates (e.g.insects and spiders) and whether the abundance and variety of invertebrates on planted trees differs between tree species and between revegetation and remnant native vegetation. The study also investigated the use of revegetation by birds and compared this to bird communities in remnant vegetation. Invertebrates were sampled on trees planted along the Great Eastern Highway as part of the Main Roads Department 'Ribbons of Green' program, as well as trees planted by community groups and Greening Western Australia. We asked whether the best species of trees were being planted to restore and enhance regional biodiversity. The canopy invertebrate fauna of 10 trees of each of eight species of Eucalyptus and jam wattle (Acacia acuminata) was sampled by chemical knockdown. Jam wattle and three of the eucalypts, including wandoo (E. wandoo), are indigenous to the Northam District. Three of the eucalypts are indigenous to the south coast of Western Australia, one to northwestern Western Australia, and the eighth is indigenous to coastal South Australia. Wandoo was sampled in both revegetation and remnant natural vegetation. In addition to sampling invertebrates, leaf toughness and levels of foliar nutrients (NPK) were sampled for all tree species. Leaf toughness and foliar nutrients were measured as other studies had found relationships between toughness and nutrients, with the abundance and variety of canopy invertebrates. Moderate to high invertebrate densities were found on all tree species. Indigenous trees tended to support the most diverse and abundant invertebrate faunas: species originating from southern coastal regions and northwestern Western Australia supported the least. Wandoo trees in revegetation tended to have higher populations of some insects than wandoo growing in remnant vegetation. Leaf toughness appeared to affect the size of invertebrate populations on some eucalypt species, but the effects of foliar nutrients were inconsistent, possibly because nutrient levels were elevated as a result of fertiliser applications. During winter (June),three patches of remnant vegetation and seven replanted areas were surveyed for birds. Twenty-five species of birds were recorded of which three were found only in remnant vegetation and six were found only on the replanted areas. However, all species recorded are widely distributed throughout the Western Australian wheatbelt and, with the possible exception of the White-browed Babbler (Pomatostomus supercilosus), no significance can be attributed to the differences in bird species composition between remnant and replanted areas: at least in winter, birds are as likely to use revegetated areas as remnant vegetation. The absence of the babbler from revegetated areas is possibly due to the lack of logs and woody debris on the planted sites. Sixteen of the 25 bird species are predominantly insectivorous, four are nectarivores, four are seed-eaters, and one is a frugivore. This suggests that a similar range of foraging resources are available in both remnant vegetation and revegetation. To restore and enhance regional biodiversity, we recommend that revegetation programs, including commercial plantings, should use a variety of tree species and emphasise regional species. Where this is not possible, species from nearby regions should be used. Planted areas should also be diversified by using a variety of indigenous shrubs and herbs, as well as trees, and by adding logs and coarse woody debris to the area planted. Provision of nest boxes would accelerate the colonization of revegetated areas by hole-nesting birds.