One measure of health in an ecosystem is the response of that ecosystem to an environmental perturbation (such as rain) over time. Healthy and unhealthy systems may have different phenological response patterns. Grassland and shrub land sites were selected, and metrics derived from temporal profiles of vegetation index values from Advanced Very High Resolution Radiometer satellite data from 1987 through 1993. The temporal profiles show that the vegetation types may be statistically discriminated, and metric values demonstrate different responses to rainfall.