Recent debris-flow deposits were colonized by shrub assemblages of different species composition than those on the surrounding, older debris-flow deposits and other geomorphically stable surfaces. Colonization of human-disturbed sites was highly variable, but species compositions were different from the predisturbance species composition. In Grayia-Lycium andersonii assemblages, Grayia spinosa reasserted its dominance over colonizers relatively quickly. In Coleogyne assemblages, typically found on older geomorphic surfaces, species composition differences persisted considerably longer, depending on the severity of the initial disturbance. Extremely stable assemblages, dominated by Coleogyne ramosissima, occurred on the oldest, least disturbed surfaces. The variability of species composition, among disturbed sites was greater than the variability among undisturbed and geomorphically stable sites, in accord with 'convergent succession'. Models of desert succession should consider: 1) colonization is dependent largely on the severity of disturbances and residual biotic components; 2) the time span for recovery may be longer than past periods of climatic and geomorphic stability; and 3) colonizing species may have considerable range in their life-history strategies.-from Authors
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Dynamics of Mojave Desert shrub assemblages in the Panamint Mountains, California.