Gary Bastin, Robyn Cowley, Margaret Friedel, Chris Materne
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引用次数: 0
Abstract
Objective monitoring methods that reliably identify grazing impact are required for long-term sustainable management in the arid rangelands. In Australia such methods must contend with highly unpredictable rainfall and large paddocks incorporating spatially complex land types with differing grazing preferences. Retrospective analysis of data collected following very dry and very wet periods removes vegetation dynamics generated by lesser rainfall events and should increase our ability to separate grazing effects from seasonal variability. Two remote-sensing methods were tested for their capacity to quantify trends over 30 years in vegetation-cover dynamics on a pastoral lease in central Australia with a history of heavy grazing. Following destocking by 2002, one section became a conservation reserve and another transitioned to a research station. During drought, the Dynamic Reference Cover Method (DRCM) showed that ground-cover deficit was less negative on both areas towards the end of the study. This improvement was attributable to increased ground cover after removal of grazing, followed by a reduced, but variable, grazing intensity on the research station and the spread of an introduced palatable perennial grass. Ground-cover response following rainfall was highest in 2011. Likewise, increased ground cover meant that the percentage Cover Production Loss (%CPL) index, calculated using grazing gradient methods (GGMs), was considerably less than a decade earlier following similar rainfall. Results from an associated recovery index (R) were inconclusive. Landscape heterogeneity potentially affected calculation of cover deficit using DRCM but, because heterogeneity was stable over time, reported change between dry years reliably indicated a trend owing to grazing. Interpreting trend from successive %CPL values in wet periods was complicated on the research station by altered waterpoint locations being superimposed on pre-existing degradation; however, the method should be effective in large paddocks with stable waterpoint locations. Despite their limitations, both methods can assist in objectively judging the long-term sustainability of grazing practices in contrasting seasonal conditions.
期刊介绍:
The Rangeland Journal publishes original work that makes a significant contribution to understanding the biophysical, social, cultural, economic, and policy influences affecting rangeland use and management throughout the world. Rangelands are defined broadly and include all those environments where natural ecological processes predominate, and where values and benefits are based primarily on natural resources.
Articles may present the results of original research, contributions to theory or new conclusions reached from the review of a topic. Their structure need not conform to that of standard scientific articles but writing style must be clear and concise. All material presented must be well documented, critically analysed and objectively presented. All papers are peer-reviewed.
The Rangeland Journal is published on behalf of the Australian Rangeland Society.