Persistence of desertified ecosystems: explanations and implications

TitlePersistence of desertified ecosystems: explanations and implications
Publication TypeConference Paper
Year of Publication1994
AuthorsWhitford WG, Martinez-Turanzas G., Martinez-Meza E.
Conference NameInternational Symposium and Workshop on Desertification in Developed Countries: Why Can't We Control It?
Date PublishedOctober 24-29, 1
Conference LocationTucson, AZ
Keywordsdesert scrublands, desertification, desertified landscapes, maintaining grasslands, management

Desertification in much of the southwestern U.S. and northern Mexico has resulted in the replacement of perennial grasslands with desert scrublands. Scrublands dominated by C3 shrubs exhibit long-term persistence, resist control efforts, and are resilient in areas where control and revegetation with grasses have been attempted. Experiments using 5 consecutive years of summer drought using "rain-out" shelters and 5 consecutive years of approximately doubling the summer rainfall resulted in no significant changes in annual net above-ground primary production of creasotebush, barren tridentata, in either of the treatments. There were significant changes in species composition and above-grind net primary production of spring annual plants and some reduction of perennial grasses and fortis in droughted plots. There were small changes in decomposition rates and nitrogen mineralization potential but no quantitative differences in the Studies of shrub water budgets demonstrated that between 6 percent and 25 percent of the intercepted rainfall was translocated to deep soil storage by stemflow and root channelization. Nutrient minerals in stemflow water on creosotebush were 5 to 10 times more concentrated in stemflow than in thrnttghfsli and bulk precipitation. These data demonstrate that once shrubs are established, islands of resource enrichment of water and nutrients develop under the shrubs. The result is self-reinforcing systems that are resistant to disturbance. The characteristics of the shrub-dominated ecosystems documented in the experiments demonstrate that they are likely to persist with climate change. The data from these studies suggest that management of desertified landscapes in North America should focus on maintaining the residual grasslands and on the economic uses of the shrub-dominated ecosystems.