Remote‐Sensing‐Based Condition Assessment for Nonequilibrium Rangelands Under Large‐Scale Commercial Grazing
1994
Pickup, G. | Bastin, G. N. | Chewings, V. H.
Range condition assessment procedures that rely on field—collected botanical data face major problems in nonequilibrium rangelands, which are spatially variable and extensively grazed. These problems include the difficulty of interpreting changes in plant species composition and the logistics of obtaining representative data for large areas. Consideration of ecosystem behavior through time and in space shows that certain spatial and temporal patterns exist that may be used to isolate the impact of grazing from other processes. The patterns also make it possible to distinguish between temporary changes and those that are more long term. All relevant patterns may be expressed in terms of total plant cover and may be monitored from remote sensing satellites. It is therefore possible to derive a set of range condition indicators that may be measured and monitored from space. These indicators use trends in average vegetation cover with distance from water at the end of very wet periods, trends in cover variance with distance from water, and the magnitude of observed vegetation response at individual points in the landscape compared with that which is expected when vegetation recovers fully from grazing. It is also possible to use spatial variability in the rate of cover depletion after rainfall to infer relative differences in the amount of forage present. When used in combination, the methods offer a realistic alternative to field—based assessment and are capable of detecting many types of rangeland degradation. They are also considerably cheaper to use.
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