Author
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Whitford, Walter |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 6/1/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: This paper addresses questions about the "health" of desertified (degraded) arid rangeland ecosystems. There is a long history of degradation of southwestern U.S. and northern Mexico arid rangelands. In much of this region, desert grasslands have been replaced by shrublands. Shrubs are more resistant to drought than are grasses because shrubs funnel water down stems and along root surfaces to deep storage sites in the soil profile. Shrubs continue to produce new stems and leaves even when experimentally subjected to long periods of drought. This mechanism confers better drought resistance and greater resilience (the capacity to bounce back) on shrub dominated ecosystems than on grasslands. Shrub dominated ecosystems are less "healthy" than shrublands by the criteria of retention of water and nutrients and production of harvestable commodities. The capacity of shrublands to support a livestock industry is greatly reduced in comparison nto desert grasslands. A measure of ecosystem health proposed for evaluatio of desert rangelands is the range of management options available for a given ecosystem. The example of loss management options is illustrated by revegetation of erosional, desertified watershed by planting the exotic Lehmanns Lovegrass, Eragrostis lehmanniana. This grass restores water retention and reduces water run-off and sediment loss from watersheds but is a low value forage for cattle and results in reductions in biodiversity. |
