Louise Gilfedder

Maintaining integrity compared with maintaining rare and threatened taxa in remnant bushland in subhumid Tasmania

The native vegetation remnants in the agricultural country of subhumid Tasmania are important strongholds for regionally and globally rare and threatened species. A detailed survey of the best 100 of these remnants indicated that there was no relationship between the size, age and juxtaposition of the remnants and an index of rare and threatened species, either in the data set as a whole or in phytosociologically defined subsets. Rare and threatened species were found in remnants of widely varying integrity, as indicated by native and exotic species richness and cover. Some species were only found in remnants that were of poor integrity. Efforts to preserve vegetation remnants need to be directed towards both those that are representative and of high integrity, and those that contain rare and threatened species. No great coincidence can be expected, because the causes of maintenance of good condition are not necessarily the causes of survival of many rare and threatened taxa.

Germinable soil seed and competitive relationships between a rare native species and exotics in a semi-natural pasture in the Midlands, Tasmania

Helipterum albicans, a disturbance-dependent, rare, native daisy, survives in a few semi-natural paddocks grazed by stock in the Tasmanian Midlands. The germinable soil seed bank in a basalt paddock with a large population of this daisy largely consisted of exotic and annual species. The peak germination for native species was in winter and early spring, while exotics dominated from late spring to autumn. The peak germination of H. albicans occurred soon after a similar peak of an exotic rosette herb, Hypochoeris radicata. An experiment with different mixtures of these two species demonstrated that H. radicata had a depressive effect on the growth of H. albicans while the reverse was not apparent. As both species colonize bare ground, a managed reduction in Hypochoeris density is likely to favour the rare native.

Factors influencing the integrity of remnant bushland in subhumid Tasmania

The relationships between remnant integrity and size, age, shape, environment and disturbance are not well-established. One hundred of the remnants in relatively good condition ranging in size from 5 to 200 ha in the drier parts of Tasmania were sampled and the relationships between independent variables and the dependent variables of remnant native species richness, remnant exotic species richness, the ratio between the two, native species cover, exotic species cover, and the ratio of exotic/native cover were investigated. Age, shape and proximity of remnants had few or no effects on the dependent variables. Size appeared to affect the condition variables only through habitat heterogeneity. The nature of the surrounding vegetation and fire and grazing management were the critical independent variables. However, the different aspects of integrity had different relationships with these variables.

Climate, Grazing and Disturbance, and the Population Dynamics of Leucochrysum albicans at Ross, Tasmania

A population of an endangered daisy, Leucochrysum albicans (syn. Helipterum albicans), was monitored monthly in grazed and ungrazed plots for several years in a paddock near Ross, Tasmania. The population declined dramatically during the extremely dry summer of 1987, and also experienced high mortality in the dry summer of 1988. Adult plants and germinates were more abundant in grazed than in ungrazed plots for most of the period after this decline. The development of axillary branches on adult plants was much more prominent outside than inside the exclosures. Seedling establishment preferentially occurred on ground dominated by herbs, with establishment being low and extremely brief on grass-covered ground. The frequently disturbed margins of the exclosures were the most favourable sites for establishment of new individuals. The future of this unpalatable rare species seems to be dependent upon management that maintains open and, preferably, disturbed ground.

Genecological Variation in the Germination, Growth and Morphology of Four Populations of a Tasmanian Endangered Perennial Daisy, Leucochrysum albicans

Seed was obtained from four populations of an endangered perennial daisy, Leucochrysum albicans (syn. Helipterum albicans), in Tasmania. These populations were from montane basaltic soils, montane limestone soils, lowland basaltic soils and lowland soils derived from mudstone. All populations had their highest percentage germination at 20°c, but the montane populations had lower germination rates than the lowland populations, especially at lower temperatures. The low altitude populations exhibited more rapid germination than the high altitude populations. In a glasshouse experiment droughting decreased the growth of the provenances from limestone and mudstone, while having little effect on the basalt provenances, mulching increased the growth of the lowland provenances relative to the highland provenances, and the application of fertiliser depressed the growth of the montane basalt provenance. Variations in leaf characteristics and flowering rates were evident between either provenance or treatment. The marked geographic variation in germination, morphology and ecological responses indicates that it is important to maintain the species over its full environmental range.

Culturally Induced Rarity? The Past and Present Distributions of Leucochrysum albicans in Tasmania

Herbarium records indicate that the endangered straw daisy, Leucochrysum albicans (syn. Helipterum albicans), is less widespread and rarer in Tasmania today than in the past. Currently it has a sparse distribution within a relatively wide ecological range, which spans most of the climatic variation in Tasmania, hut which does not include poorly drained or infertile soils. There is evidence of recent local extinctions and invasions. These and the nature of the local environments in which the species occurs indicate that the species requires freedom from competition for the maintenance of its populations. Cultural activities, such as heavy stock grazing or bulldozing, promote its establishment and survival, whereas the establishment of healthy improved pasture or the exclusion of grazing from native pasture tend to lead to its exclusion or demise. The future of the species may thus largely depend on cultural activities that are usually regarded as antipathetic to nature conservation.

Noah's Ark Conservation Will Not Preserve Threatened Ecological Communities under Climate Change

Background Effective conservation of threatened ecological communities requires knowledge of where climatically suitable habitat is likely to persist into the future. We use the critically endangered Lowland Grassland community of Tasmania, Australia as a case study to identify options for management in cases where future climatic conditions become unsuitable for the current threatened community. Methods We model current and future climatic suitability for the Lowland Themeda and the Lowland Poa Grassland communities, which make up the listed ecological community. We also model climatic suitability for the structurally dominant grass species of these communities, and for closely related grassland and woodland communities. We use a dynamically downscaled regional climate model derived from six CMIP3 global climate models, under the A2 SRES emissions scenario. Results All model projections showed a large reduction in climatically suitable area by mid-century. Outcomes are slightly better if closely related grassy communities are considered, but the extent of suitable area is still substantially reduced. Only small areas within the current distribution are projected to remain climatically suitable by the end of the century, and very little of that area is currently in good condition. Conclusions As the climate becomes less suitable, a gradual change in the species composition, structure and habitat quality of the grassland communities is likely. Conservation management will need to focus on maintaining diversity, structure and function, rather than attempting to preserve current species composition. Options for achieving this include managing related grassland types to maintain grassland species at the landscape-scale, and maximising the resilience of grasslands by reducing further fragmentation, weed invasion and stress from other land uses, while accepting that change is inevitable. Attempting to maintain the status quo by conserving the current structure and composition of Lowland Grassland communities is unlikely to be a viable management option in the long term.

Distribution, Disturbance Tolerance and Conservation of Stackhousia gunnii in Tasmania

Although being possibly widespread on the mainland of Australia, where it is recognised as part of the Stackhousia monogyna Labill. complex, S. gunnii Hook.f. is an endangered species in Tasmania, with only 10 known extant populations, all in the drier parts of the southern Midlands. These populations occur largely on roadsides or lightly grazed paddocks in vegetation that was originally either Themeda triandra grassland or Eucalyptus pauciflora woodland. An ordination of floristic data from sites with and without S. gunnii showed that the species occupies a floristically distinct environment. The floristic differences between stands of S. gunnii relate partly to the presence or absence of tree cover and substantially to precipitation. The groups of species that preferentially occur with S. gunnii are geophytes, non-geophytic herbs and exotic plants, while those that are concentrated elsewhere include shrubs, grasses and non-geophytic graminoids. Permanent transects were monitored over a 4-year period at seven sites with varying grazing, firing and disturbance. The number of shoots varied markedly between years in all sites, but not synchronously, even when transects were in close proximity. Although shoot numbers increased after fires occurred on several ungrazed transect lines, they decreased on one grazed line. Deep mechanical disturbance of one site resulted in a dramatic decrease in shoot numbers in the following year. However, they increased steadily over the following 2 years. Shoot emergence occurred at twice the expected rate on bare ground in all years and at all sites, and a substantial proportion of shoots was confined to this type of surface. However, shoots were also recorded in fewer numbers in grass cover, herb cover and non-vascular plant crusts. Like some other threatened plants of grassy ecosystems, S. gunnii seems to be rare because it cannot survive with heavy grazing disturbance, ploughing and fertilisation, and, at the other extreme, because it is susceptible to elimination in the absence of environmental conditions and disturbances that create bare ground.

The Tasmanian endemic shrub, Acacia axillaris: conservation ecology applied to the question of rarity or vulnerability

Acacia axillaris Benth. had been recommended for downgrading from a conservation status of vulnerable to one of rare in response to changed knowledge of its distribution. Ecological investigations of its phytosociology, stand structure, germination requirements, soil seed store and response to fire and disturbance indicate, however, that it is susceptible to elimination by fire regimes that allow the survival of most of its co-occurring species and most other Australian species of Acacia. The species is also vulnerable to land clearance and weed competition in the lowland part of its range, which is largely on private land.A. axillaris may be a refugial species, better suited to glacial Tasmania than to interglacial Tasmania. On ecological evidence, the species should retain its conservation status of vulnerable to extinction.

Private land manager capacity to conserve threatened communities under climate change

Major global changes in vegetation community distributions and ecosystem processes are expected as a result of climate change. In agricultural regions with a predominance of private land, biodiversity outcomes will depend on the adaptive capacity of individual land managers, as well as their willingness to engage with conservation programs and actions. Understanding adaptive capacity of landholders is critical for assessing future prospects for biodiversity conservation in privately owned agricultural landscapes globally, given projected climate change. This paper is the first to develop and apply a set of statistical methods (correlation and bionomial regression analyses) for combining social data on land manager adaptive capacity and factors associated with conservation program participation with biophysical data describing the current and projected-future distribution of climate suitable for vegetation communities. We apply these methods to the Tasmanian Midlands region of Tasmania, Australia and discuss the implications of the modelled results on conservation program strategy design in other contexts. We find that the integrated results can be used by environmental management organisations to design community engagement programs, and to tailor their messages to land managers with different capacity types and information behaviours. We encourage environmental agencies to target high capacity land managers by diffusing climate change and grassland management information through well respected conservation NGOs and farm system groups, and engage low capacity land managers via formalized mentoring programs.