Estimating Landscape Resilience From Satellite Data and Its Application to Pastoral Land Management.

Abstract

Episodic rainfall provides infrequent opportunities for vegetation recovery from grazing in the arid rangelands. The magnitude of resultant vegetation growth, or resilience, varies widely in space and is not simply controlled by rainfall amount or past grazing practices. The non predictable nature of vegetation response fits within the model of nonequilibrium rangeland behaviour and we propose use of the Resilience Method as a means of spatially assessing vegetation resilience, or the ability of herbage to respond to infrequent rainfall. Information required to calculate an index of resilience is obtained from remotely-sensed satellite data, is plant cover-based and is processed to produce landscape-scale maps of vegetation resilience. In this paper, we demonstrate and evaluate products developed to transfer the Resilience Method to a pastoralist family to assist in their future property management. These products include maps of scaled herbage response to rainfall, herbage response in conjunction with dry period vegetation cover and herbage biomass derived from vegetation cover. The cover-based products effectively showed herbage response following a large rainfall. Much of the variation in response was natural and was related to timber density and soil factors. Some areas with below average herbage response were attributable to damage caused by high rabbit populations. Herbage response on much of the productive grazing country was average to above average indicating good resilience and potential for continued beef production. The resilience approach to landscape assessment provided a useful pictorial representation of herbage response across the whole station following one rainfall. The participating pastoralists consider that the Resilience Method will have greater validity when repeated following further significant rainfalls. Some insights were gained into future property development. However, the technology was difficult to understand and requires a close liaison between the technician and client. Confusion arose where below average herbage response could occur in areas of both high and low initial cover when the two areas appear vastly different and require separate management for beef production and rehabilitation. Both the nonequilibrium approach to understanding vegetation dynamics and the Resilience Method need further explanation and demonstration before they are accepted as being useful for pastoral land management.