Bioindicators, as taxa or functional groups, are widely used as indicators of environmental change, specific ecological factors or taxonomic diversity. The use of ecological, environmental and biodiversity indicators, is reviewed here. Although indicator taxa are considered to be generally unreliable as broad indicators of biodiversity, they may serve a useful function in identifying ecological characteristics or monitoring the effects of habitat management. Use of only a narrow range of taxa may be unreliable, and is particularly vulnerable to distortion by a small number of invasive species. Taxa also need to be selected to reflect the specific ecosystem being studied. It is recommended that isopods be used for soil systems (if there is sufficient local diversity), in some areas earthworms or mites may be useable but are generally too difficult to identify to be practically useful. In the ground layer indicator sets could include ants, millipedes, molluscs (snails in particular), ground beetles, harvestmen and gnaphosid spiders. Foliage-inhabiting indicators could comprise ants, chrysomelid leaf beetles, theridiid spiders and arctiid moths. Ants, orthopterans and butterflies may be appropriate for use in open habitats. These basic sets should be supplemented by other taxa where appropriate resources and taxonomic expertise are available.

Terrestrial invertebrates as bioindicators: an overview of available taxonomic groups

One of the most complex and contentious issues in Australian ecology concerns the environmental impact of Aboriginal landscape burning. This issue is not only important for the development of a comprehensive understanding of the dynamics and evolution of the Australian biota, but is central to the formulation of appropriate strategies for the conservation of the nation's biodiversity. Ethnographic evidence leaves little doubt that Aboriginal burning played a central role in the maintenance of the landscapes subsequently colonized by Europeans. Both 19th century European colonists and anthropologists in the 20th century documented the indispensability of fire as a tool in traditional Aboriginal economies, which have aptly been described as ‘fire-stick farming’. Aborigines used fire to achieve short-term outcomes such as providing favourable habitats for herbivores or increasing the local abundance of food plants, but it is not clear whether or not Aborigines had a predictive ecological knowledge of the long-term consequences of their use of fire. A large body of ecological evidence suggests that Aboriginal burning resulted in substantial changes in the geographic range and demographic structure of many vegetation types. Aboriginal burning was important in creating habitat mosaics that favoured the abundance of some mammal species and in the maintenance of infrequently burnt habitats upon which the survival of specialized fauna depends. Aboriginal fire regimes were probably critical for the maintenance of at least one species of tree (Callitris intratropica) in the monsoon tropics.

The question of the original impact of humans on the Australian environment is fundamentally speculative because of vague, disputed time frames proposed for the waves of colonization and shifting settlement patterns of Aborigines in the late Quaternary period. There is an inherent circular argument concerning the cause and effect of climate change, vegetation change, and burning through the late Quaternary. Charcoal and pollen evidence from long sedimentary cores is ambiguous and cannot be used to demonstrate unequivocally the initial impact of Aboriginal people on the landscapes of Pleistocene Australia. The sparse available evidence does not support the hypotheses that Aboriginal burning was primarily responsible for the extinction of Pleistocene megafauna; was critical for the maintenance of habitats of small mammals that have become extinct following European colonization; initiated widespread accelerated soil erosion rates in either the Pleistocene or Holocene; or forced the evolutionary diversification of the Australian biota. Burning may have caused the extinction of some fire-sensitive species of plants and animals dependent upon infrequently burnt habitats, and it must have maintained structurally open vegetation such as grasslands and also extended the range of fire-adapted species, such as Eucalyptus, into environments climatically suitable for rain forest. Palaeoecological research concerning prior impacts of Aborigines must give way to focused studies of the role of different anthropogenic fire regimes in contemporary ecosystems that have not been destroyed by European colonization. Such research is crucial for comprehending the role of Aboriginal burning in the maintenance of Australia's unique, rich biodiversity.

The impact of Aboriginal landscape burning on the Australian biota

This volume contains the texts of invited papers presented at the Fourth International Conference on Mediterranean Ecosystems (MEDECOS) held in Perth, Western Australia during August 1984. It thus follows three previous meetings, Chile (1971), California (1977) and South Africa (1980). There has been no formal international body to organize these meetings, merely a continuity of purpose provided by the common interests of the scientists concerned in the English-speaking world. Following previous themes on structure, fire and role of nutrients in mediterranean ecosystems, MEDECOS was structured around the theme 'Resilience in Mediterranean Ecosystems'. The invited speakers were requested to deal with particu lar aspects of this subject, and offered papers were encouraged to do so as well. This provided a broad framework for discussions which at the same time highlighted many of the major conservation issues arising from extreme natural events and human-induced disturbances in the mediterranean regions. The proceed ings were issued on the last day of the conference and provided two-page accounts of each of the contributed papers and posters (Dell, B. (ed. ) 1984 Proceedings of the 4th International Conference on Mediterranean Ecosystems. Botany Dept., University of Western Australia). This volume was reserved for the review papers whose aim was to explore general principles and unifying concepts at all levels in the study of resilience. Perth, December 1985. VII List of contributors B. Dell 1. E."

Resilience in Mediterranean-type ecosystems

Summary


1. The distribution, ecology, and behaviour of ants (Hymenoptera: Formicidae) is profoundly influenced by environmental stress and competition. As in plants, trade-offs in adaptations to these factors are the basis for functional classifications of ant taxa and communities at a global scale.



2. Theory predicts a trade-off between stress tolerance and competitive dominance in both plants and ants. In ants, low temperature is thought to be stressful, so I hypothesized that there would be a positive relationship between temperature and behavioural dominance. I evaluated this relationship in a South American, Chaco ant community.



3 The activity and behaviour of ground-foraging, omnivorous ants were examined at baits in open and closed, forested habitats during different seasons and times of day to characterize the responses of ant taxa to variation in microclimate and competitors.



4. Behaviourally dominant ants were most active at moderately high temperatures, whereas subordinate species were active at extreme temperatures, when they had virtually exclusive access to resources.



5. The patterns presented here and those observed in other studies suggest that there is a general trade-off between behavioural dominance and thermal tolerance in ants. This trade-off creates a linear relationship between temperature use and dominance for ants up to ≈ 35 °C, but extremely high temperatures may also be stressful such that the full relationship is actually unimodal.

https://www.jstor.org/stable/info/2647160

The trade‐off between thermal tolerance and behavioural dominance in a subtropical South American ant community

Pattern analysis in agricultural science

Sixteen 1-ha study plots covering five regeneration stages were simultaneously trapped five times over a 20-month period to provide data on small mammal response to vegetation changes following fire. Areas regenerating after fires from 9 years to 1 month before the investigation were sampled in a uniform open forest on a coastal sand plain. Two types of understorey were recognized: one dominated by true forest shrubs with which Rattus fuscipes, Antechinus stuartii and Sminthopsis murina were associated, and another dominated by heath elements where the addition of Pseudomys novaehollandiae and Mus musculus produced a significantly more diverse small mammal community. The two communities exhibited different responses to post-fire vegetation changes.



Rattus fuscipes was the most abundant species and showed a logistic growth in biomass. No resident populations were established in the first 3 years, but a rapid increase in biomass occurred from 3 to 5 years to plateau after 8 years. Regeneration age had the greatest effect on R. fuscipes biomass mediated through the amount of accumulated leaf litter with additional variation being attributed to several vegetation structure variables and plant species diversity.



A replacement sequence in time was observed for species reaching their maximum abundance (P. novaehollandiae and/or M. musculus S. murina A. stuartii R. fuscipes) and was interpreted as species occupying stages in the succession when their optimal habitat requirements were fulfilled. These results have important implications for the design of management policies using fire or fire regimes as tools for habitat maintenance or alteration. A mosaic of forest patches of adequate size covering the entire range of seral stages is necessary to meet the optimum requirements of all the above species.

Small mammal responses to pyric successional changes in eucalypt forest

Ant species diversity was monitored along a mining path rehabilitated four to eleven years previously. The mining path at Hawks Nest (32°30′S, 152°30′E) passes through closed heath and scrub with some open forest patches. Ant species richness, ant species diversity and the number of individuals seemed to be more dependent on the structure of the ant community present than on site variables. The equitability component however showed a linear increase with time, from which it could be predicted that mined plots would not reach the values on control plots in less than 17 years (95% C.I. 13–21 yrs).

Evidence for interspecific competition influencing ant species diversity in a regenerating heathland

The regeneration of coastal heath after disturbance by mineral sand mining was studied on mid-seral stages from 4 to 11 years old at Hawks Nest, N.S.W. The main purpose was to gain some understanding of factors influencing recolonization by pioneer species of small mammals such as Pseudomys novaehollandiae. Changes in floristics and vegetation structure with time were studied as possible contributing factors together with environmental variables. An apparently linear relationship was found between plant species diversity (X1) and P. novaehollandiae biomass which was also correlated with an index representing the proportion of heath species present (X2). Both plant species diversity and P. novaehollandiae biomass showed a linear increase with regeneration age.



A multiple regression analysis revealed a predictive equation explaining 96% of the variation in P. novaehollandiae biomass (Y): Y=-7.92 + 1.21X1+3.92X2 - 3.09X3



The third variable (X3) is a measure of soil hardness. A path diagram using contribution coefficients based on a partial correlation analysis included the effects of vegetation structure below 50 cm and regeneration age.



On mid-seral stages after sand mining P. novaehollandiae is associated with areas having a variety of heath plants, with vegetation cover below 50 cm and softer substrates; its abundance increases with increasing regeneration age and with the total amount of vegetation present.



A minimum of 20 years is seen to be necessary for both total amount of vegetation and P. novaehollandiae biomass to reach values encountered on control plots of undisturbed heath.

Recolonization of coastal heath by Pseudomys novaehollandiae (Muridae) following sand mining

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Small mammal responses to pyric successional changes in eucalypt forest

Evidence for interspecific competition influencing ant species diversity in a regenerating heathland

Recolonization of coastal heath by Pseudomys novaehollandiae (Muridae) following sand mining