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Protecting grazed annual ranges

The Issue

In the early 1980s, managers of grazing on California’s annual rangelands were beset with a host of problems exacerbated by drought. A simple and yet scientifically defensible method for determining grazing capacity and regulating grazing intensity was needed. The available science was primarily based on work by federal agencies outside of the state and on perennial-dominated grasslands.

What Has ANR Done?

Using funding from the Agricultural Experiment Station, the late UC Berkeley Range Professor Harold Heady had been conducting a statewide experiment to test his ideas about the relationships between the local environment, grass growth, grazing and what he called natural mulch. UC Berkeley Professor James Bartolome collaborated with Heady to produce a landmark 1980 publication summarizing their ideas about grazing management. This work has recently been updated in ANR publication 8092, coauthored by Bartolome with UC Extension range scientists Bill Frost, Neil MacDougald and Mike Connor. New methodologies for mapping RDM have been developed and are currently being applied and tested by agencies.

The Payoff

Grazing quickly and accurately assessed

Recommendations based on the work of Heady and Bartolome were quickly disseminated by UC Cooperative Extension, adopted by state and federal agencies, and incorporated into guidelines for managing annual-type ranges. This method of managing grazing, called “management of residual dry matter” or “RDM,” is now the standard for determining the degree of grazing use and was recently issued as a revised and updated ANR publication. The RDM approach has been combined with use of modern remote sensing and geographic information systems, allowing several San Joaquin Valley Counties to save millions of dollars in assessment expenses. Adopted by the US Fish and Wildlife Service, the Bureau of Land Management, the US Forest Service, the National Park Service and many state and local land management agencies, the RDM approach has protected millions of acres of annual rangeland by improving water quality, protecting wildlife habitat, and enhancing forage quality and quantity.


James Bartolome
Professor, Division of Ecosystem Sciences
130 Mulford Hall
University of California, Berkeley
Berkeley, CA 94720-3114