application of ecological theory to management of arid drylands: an example from china

rangeland ecosystems shift across dynamic thresholds between differentecological states in response to natural or human-induced factors. these differentecological states are the result of interactions among climate, soils, grazing history,and management practices. the notion of a single ‘‘pristine’’ final state is onlyconceptual in nature, and because of this, dynamic thresholds and the effects ofvarious processes on ecosystem structure and function must be incorporated intodecision-making. rangeland managers should have a working knowledge of thekey ecological processes in each state, and the processes that drive a system acrossa dynamic threshold from one state to another. to do this they need indicators forcritical decision-making points. it is essential to identify the thresholds of anecological transition state and ecological indicators of these states. the criteria ofthese ecological indicators might be measurable, sensitive to stress on the system,have a known response to disturbance and easy to measure. the state and transitionapproach may offer an appropriate framework as an aid for decision making andcan be used to highlight ‘‘management windows’’ where opportunities can beseized and hazards avoided. china’s vast drylands are used as a case study and thepotential to apply these principles is discussed.