Refine
Document Type
- Article (2)
Language
- English (2)
Has Fulltext
- yes (2)
Is part of the Bibliography
- no (2)
Terrestrial, freshwater and estuarine native vegetation of the Eden region was classified into 79 floristic assemblages and mapped at 1:100,000 scale. Assemblages were derived from multivariate analysis of 1604 quantitative vegetation samples. Mapping was carried out using a hybrid decision tree-expert system approach based on quantitative relationships between floristic assemblages and spatial variables (land cover pattern, substrate, climatic variables and terrain variables) and qualitative expert knowledge derived from field experience. The use of vegetation environment relationships and sampling of remnants allowed prediction of vegetation patterns prior to European clearing. The map was validated using three procedures: qualitative checking by experts; reliability mapping using sampling intensity; and accuracy quantification using independent sample data. The map units were described using comprehensive profiles of diagnostic species, structural features, habitat characteristics and sample distributions.
The 79 floristic assemblages include rainforests, mesic eucalypt forests, dry grassy eucalypt forests of the coastal rain shadow valleys, hinterland and tableland, dry shrubby eucalypt forests, grasslands, heathlands, scrubs and wetlands. Variation in climate and geological substrate influence vegetation patterns at regional scales, while variation in topography, local soil moisture and nutrient status and disturbance regimes influence vegetation patterns at local scales. Sixty-eight per cent of the region retained a cover of native vegetation in 1994. Processes threatening various portions of the remainder include further habitat loss from clearing, high-frequency disturbances and certain other disturbance regimes, overgrazing, habitat degradation due to nutrification, dumping and vandalism, and feral animal activity. Past depletion of habitat has been highly biased. Some grassy assemblages on fertile flat terrain are depleted by more than 90%, while some forests with shrubby understories in steep infertile terrain retain close to their original extent. The former assemblages are distributed principally as remnants on privately owned land, while the latter occur in remote areas of public land. Representation in conservation reserves is also biased against grassy assemblages in fertile flat terrain, as well as some other assemblages with restricted distributions. Opportunities for conservation of these assemblages are now very limited and rely on integrated planning, reservation and cooperative management with emphasis on private land.
Clearing of native woody vegetation in the New South Wales northern wheatbelt was mapped for the period 1985–2000. The study area comprises the Moree 1:250,000 scale map sheet and portions of adjacent map sheets. Unpublished draft mapping of native woody vegetation types, based on 1985 aerial photography and a large set of floristic data from field surveys, was used as a baseline for this study. Mapping of clearing was carried out by intensive visual interpretation of Landsat TM satellite imagery. Systematic validation, which compared the satellite interpretation to low-level aerial photography at randomly allocated point locations, showed that the method was highly accurate in detecting vegetation clearing including in the open woodlands and shrublands that characterise much of the study area. Comparisons with previously published mapping of statewide clearing patterns, based on an automated classification of Landsat TM imagery, showed that our intensive visual interpretation detected substantially more clearing. Average annual clearing rates were 8 times higher that those derived from the previous mapping.
Results of the study show that substantial clearing of native woody vegetation is continuing in the northern wheatbelt. Over 110,000 ha of native woody vegetation were cleared between 1985 and 2000. Clearing rates were highest in the four year monitoring period that preceded the introduction of the Native Vegetation Conservation Act. The subsequent two year monitoring period saw substantially lower clearing rates, though further monitoring is needed to determine if this trend will continue. An analysis of spatial patterns highlighted continued high rates of loss in the most depleted parts of the study area. Results for individual vegetation types indicate that regrowth open shrublands and woodlands and Coolabah (Eucalyptus coolabah) dominated woodlands were the most heavily cleared.