Margaret H. Friedel

The stewardship of arid Australia : ecology and landscape management

tag=1 data=The stewardship of arid Australia : ecology and landscape management. by S.R. Morton, D.M. Stafford Smith, M.H. Friedel, G.F. Griffin and G. Pickup tag=2 data=Morton, S.R.%Stafford Smith, D.M.%Friedel, M.H.%Griffin, G.F.%Pickup, G. tag=3 data=Journal of Environmental Management, tag=4 data=43 tag=5 data=3 tag=6 data=March 1995 tag=7 data=195-217. tag=8 data=LAND%ENVIRONMENT tag=9 data=ECOLOGICALLY SUSTAINABLE LAND MANAGEMENT tag=13 data=IND

Ecological impacts of buffel grass (Cenchrus ciliaris L.) invasion in central Australia - does field evidence support a fire-invasion feedback?

Buffel grass (Cenchrus ciliaris L.) has invaded extensive areas of arid and semi-arid Australia following its introduction as a pasture species and for erosion control. It has been suggested that buffel grass has initiated a positive fire-invasion feedback in central Australia, disrupting existing fire regimes, encouraging further buffel grass invasion, and disadvantaging the native woody flora in particular, but this hypothesis has not been tested quantitatively. This study investigated recently burnt woodland areas near Alice Springs for evidence of a fire-invasion feedback, including the impact of changing fire behaviour (intensity) on the native woodland overstorey flora. Despite the limitations inherent in a short study of ecological processes in a highly heterogeneous environment, substantial field evidence was found to support the existence of a buffel grass-initiated fire-invasion feedback. Buffel grass invasion was significantly correlated with increased fuel loads. Increased fuel loads were significantly correlated with increased burn severity, although the direct relationship between the proportion of buffel grass and increased burn severity was marginally non-significant. High field variance resulted in inadequate power to test whether or not the relative abundance of buffel grass had increased in the post-fire community. Burn severity was significantly correlated with the mortality of woodland overstorey species, and with the proportion of fire survivors that were reduced to basal resprouts. Seedling density of canopy species was low. It appears likely that future recruitment of canopy species will be hindered by the dense post-fire reestablishment of buffel grass cover at some sites. The overstorey flora is thus likely to be adversely affected by increased severity of fire associated with buffel grass invasion. As a result, there may be major change in the structure and composition of some woodlands.

A preliminary investigation of woody plant increase in the western Transvaal and implications for veld assessment

Abstract The relationships between tree density and indices of pasture and soil condition were examined in Western Transvaal grasslands where Acacia karroo had increased following disturbance. The correlation between tree density and pasture condition was not linear, indicating a threshold in condition below which dramatic increase in trees is likely. Some evidence is presented for a second threshold where soil compaction inhibits seedling establishment and tree density declines. The necessity for assessing tree and soil status in addition to pasture condition is discussed and a variety of possible indicators of pasture, woody plant and soil status is considered.

The influence of buffel grass (Cenchrus ciliaris) on biodiversity in an arid Australian landscape

Buffel grass [Cenchrus ciliaris L. syn. Pennisetum ciliare (L.) Link] is an exotic species that has been widely planted in Australian arid and semi-arid grazing lands, and has become an important resource for livestock. It establishes readily and has expanded into such a diversity of land types beyond grazing lands that it is also regarded as a serious environmental weed. Although there is an abundance of literature on the production benefits of buffel grass, there is relatively little about its influence on native flora and fauna in arid Australia, particularly when its cover levels are low. This study attempted to clarify the influence of buffel grass and environmental patterns on the occurrence of ground vegetation, birds, reptiles and ants in a gneissic hill habitat in central Australia where buffel grass has encroached. Despite poor conditions for growth, we were able to distinguish the influence of buffel grass from that of other variables like overstorey cover, soil pH, fire and transect orientation. Cover of buffel grass did not exceed ~20% but it still accounted for a small amount of the variation in the composition of ground vegetation and birds, and of the ‘ground-dwelling’ bird guild and the ‘hot climate specialist’ functional group of ants. There were insufficient reptiles for analysis. We conclude that, even when cover is low, buffel grass can have a detectable influence on some aspects of community dynamics. Given the evidence from published literature and from this study, we expect the influence of buffel grass on the diversity of native flora and fauna to increase, particularly if buffel grass expands into land types previously thought unsuited to its environmental needs.

A landscape-scale model of shrub and herbage dynamics in Central Australia, validated by satellite data

Abstract Ecosystem models have an important integrative role in allowing available data to be used to predict the potential impacts of changing climate or disturbance patterns. No such model has previously existed for the rangelands of Central Australia. In this paper we develop an ecosystem model for arid chenopod shrublands south of Alice Springs which takes account of inherent landscape heterogeneity and temporal variability, but which uses simple empirical relationships because of the small amount of available data on which to base any such model. The model is focused on the dynamics of simple herbage and shrub biomass pools; further breakdown of species composition is not attempted. Herbage dynamics are most dependent on grazing effects, as measured by distance from permanent watering points and average paddock stocking rate, and on the erosional status of the soil. Shrub dynamics are most sensitive to erosional status. The model is tested against historical Landsat MSS imagery transformed by a plant cover index. Correspondence is good, except on highly erosional sites which appear more dynamic than predicted. Further work is needed to quantify rates of soil erosion and deposition at different grazing levels, and of shrub growth and dieback in arid climates. Accurate means of assessing plant biomass from satellite imagery also require further development.

Tackling Contentious Invasive Plant Species: A Case Study of Buffel Grass in Australia

Introduced plants that have both production values and negative impacts can be contentious. Generally they are either treated as weeds and their use prohibited; or unfettered exploitation is permitted and land managers must individually contend with any negative effects. Buffel grass (Cenchrus ciliaris) is contentious in Australia and there has been no attempt to broadly and systematically address the issues surrounding it. However, recent research indicates that there is some mutual acceptance by proponents and opponents of each others’ perspectives and we contend that this provides the basis for a national approach. It would require thorough and on-going consultation with stakeholders and development of realistic goals that are applicable across a range of scales and responsive to regional differences in costs, benefits and socio-economic and biophysical circumstances. It would be necessary to clearly allocate responsibilities and ascertain the most appropriate balance between legislative and non-legislative mechanisms. A national approach could involve avoiding the introduction of additional genetic material, countering proliferation in regions where the species is sparse, preventing incursion into conservation reserves where it is absent, containing strategically located populations and managing communities to prevent or reduce dominance by buffel grass. This approach could be applied to other contentious plant species.

The development of veld assessment in the Northern Transvaal savanna II. Mixed bushveld.

Abstract Differences in pasture species composition as a consequence of grazing were used to develop a proposed classification of pasture species response to grazing, for both the Combretum apiculatum and the Acacia tortilis communities of the northern Transvaal mixed bushveld. The limited value of this approach is discussed in view of likely interactions with other driving forces. Woody vegetation changed in response to grazing in Acacia tortilis veld but not in Combretum apicalatum veld. Two thresholds of change were indicated, one of which coincided with soil change. The value of recognizing thresholds in pasture composition rather than attempting to identify benchmarks is discussed. A different approach is required, using multivariate analysis to assess the effect of interacting driving forces and state variables. Advances in ecological knowledge are needed to complement the development of veld assessment techniques. Recommendations are made for veld measurement techniques.

What engages the interest of land managers in rangeland monitoring

For many decades, scientists have been devising and refining ways of monitoring the worlds rangelands. Government land management agencies have often been keen contributors to the process because they are custodians of publicly owned land and need to represent the interests of their constituents in the entire community, not just in rangelands. The approaches which have been developed may tacitly be assumed to be useful to local land users, because they cater for the public interest at scales from local to national, but we are not convinced that they are always as useful as is supposed. We discuss our monitoring experiences on freehold land, protected areas and in communal rangelands in southern Africa, with particular reference to South Africa, Botswana and Namibia, as well as on commercial pastoral enterprises in Australia. From these, we consider who the monitoring is for, how land managers and scientists can work together to devise systems which managers will use, what needs to be monitored as a consequence and what the scale should be. We think that characteristics that define a system useful to land users include less rigour in methods than scientists usually require, greater breadth of information, better feedback on that information and more support to encourage continuing use and integration into decision-making. We argue that the monitoring process is as important as the data that are generated.

Challenging the concept of Aboriginal mosaic fire practices in the Lake Eyre Basin

Mosaic burning is the deliberate creation of a mosaic of patches representing different fire histories. It is often recommended for management of Australia’s natural landscapes, on the assumption that it enhances biodiversity and reduces fire hazard through increased spatial and temporal diversity of fuel loads and species composition. It is also suggested that such fire practices were used throughout Australia by traditionally living Aboriginal people. Although the creation of a patchwork of different fire histories may be an effective management tool in modern land management, the evidence for universal mosaic burning before European settlement deserves scrutiny. The records of explorers, early settlers and anthropologists relating to a large portion of the Lake Eyre Basin, particularly the Channel country and the Simpson Desert region, were examined. It is concluded that extensive gaps in the records of smokes and large fires are important and meaningful, and do not represent a failure to record fires. The case for universal mosaic burning in the region is not supported by the evidence although mosaic burning did occur in specific circumstances. Fire practices were shaped by complex and interacting factors including the vegetation and terrain type, for example the occurrence of spinifex-dominated sandhills or stony deserts; seasonal conditions and the presence or not of adequate fuel loads; how readily Aboriginal people could access country and their reasons for using or not using fire; the stocking of the pastoral country and spread of feral animals; and government policies about fire.

Weeds in Australian Arid Regions

Spread across the vast landscapes that geographically dominate Australia’s arid interior are over 400 alien plant species making up between 0 and 9.7% of the flora, depending on the region being considered. Few of these introductions are genuinely invasive species, and an even smaller proportion is documented as having a negative impact on their local ecosystem. However, those negative impacts that do occur are far ranging and difficult to manage, because of the distances and remoteness of the area, a lack of economic incentives for control, and contention regarding the economic, environmental and social benefits and costs of some species. Management of the weeds of arid regions must involve all aspects of the biosecurity continuum, including quarantine and containment. Depending on the size of invaded areas and the particular species, options can include mechanical control, herbicide applications, fire and grazing in various combinations and biological control. Management will need to respond to changes in climate with research required into adaptive responses.