Sensitivity Testing of Indicators of Ecosystem Health

Abstract

ABSTRACT

The sensitivities of three indicators of ecosystem health were evaluated at several sites in the Jornada Basin of the Chihuahuan Desert in southern New Mexico. The size of bare patches, proportion of total grass cover contributed by long-lived perennial grasses, and soil stability are interdependent indicators of ecosystem functions related to the retention and use of water and nutrients. Sensitivity tests were chosen using data collected along disturbance gradients and then tested using independent, ungrazed exclosures and adjacent grazed pastures. The mean size of bare soil patches was sensitive to anthropogenic disturbance. When bare soil patch data were transformed using natural logarithms, the skewness of the frequency distribution weighted by mean bare patch size could be used to indicate early disturbance to the ecosystem. The proportion of total vegetation that was long lived also was sensitive to anthropogenic disturbance and appears to be a good indicator of ecosystem degradation. The slake test for soil surface stability was extremely sensitive to disturbance and may serve as an early-warning indicator of soil degradation for the coarse-textured soils that were evaluated.