|Title||Soil and vegetation indicators for assessment of rangeland ecological condition|
|Publication Type||Conference Proceedings|
|Year of Publication||1996|
|Authors||Herrick JE, Whitford WG, de Soyza A.G., Van Zee JW|
|Conference Name||North American Workshop on Monitoring for Ecological Assessment of Terrestrial and Aquatic Ecosystems|
|Publisher||USDA, Forest and Range Experiment Station, General Technical Report RM-GTR-284|
|Conference Location||Mexico City, Mexico|
Indicators of rangeland ecological condition should be (1) quantitative, (2) rapid, (3) repeatable, (4) easily communicated, and (5) susceptible to sensitivity analysis. Most importantly, the indicators should be related to ecosystem function and to the capacity of the system to resist and recover from disturbance. Based on these criteria, we have developed a suite of indicators for North American desert rangelands. Most of these rangelands are located on fragile, nutrient- and organic matter-poor soils and suffer from periodic moisture deficits. Consequently, we have focused on indicators which reflect the capacity of the system to trap and retain soil and water resources. These indicators include size of bare soil patches, cryptogamic crust cover and soil surface stability, and the ratio of long-lived to short-lived perennials. Another suite of indicators reflect rangeland productivity. These include proportion of total perennial plant cover of species palatable to livestock as well as total biomass production. We have developed and tested these and a number of other indicators in a wide variety of plant communities with known disturbance histories at the Jornada Experimental Range in the Chihuahuan Desert in New Mexico, and validated them on cooler, more mesic rangelands in Idaho and Oregon, as well as an arid site in Utah. We will present results from the Chihuahuan Desert evaluation, together with a preliminary version of a variable-weighting system to combine these indicators into flexible indices of ecological condition which can be adapted to address the objectives of individual agencies and land managers.