observed annual productivity to be greater under shrubs, although increased nutrients under shrubs could be implicated in such a case (Muller 1953). According to Shreve (1931), shading is important for success of herbaceous plants in arid areas due to the more favorable conditions provided during the very critical rainless periods in their early history. Accurate prediction of possible successional changes in plant populations due to decreased solar radiation and increased soil moisture is difficult, especially considering the significant abiotic modifications possible in collector arrays. Many desert plants have precisely evolved germination requirements (e.g., McMillan 1970, 1973) and phenological dynamics (e.g., Davies 1976) dependent upon moisture, photoperiodic, or thermoperiodic signals. Drastic, long term changes in these cues could make the plants which have adapted to the open desert situation not as adaptive, potentially resulting in a relative increase of secondary species with more plastic responses, or invasion of "opportunistic" species such as weeds. Change in animal populations will, to a large degree, depend on vegetation changes as well as man’s activities. An increase in forbs and grasses will result in an increase in rodents, as rodent reproduction is known to be tightly coupled to annual production in the Southwestern deserts (Reynolds 1958, Beatley 1969, 1976, Soholt 1973, Van De Graaff and Baida 1973). High production of annuals could then result in large numbers of rodents near the collector site. Relative proportions of heteromyid rodents and lagomorphs on the sites could depend on the relative success of forbs versus grasses. Amelioration of the radiation balance by collector arrays on a diurnal and seasonal basis may make the areas under collectors a desirable habitat for surface animals. Dawson and Denny (1969) correlated movements of kangaroos in Australia to reduction in radiant temperature by small trees, as previously discussed. Animals of the immediate area around a collector field could seek the shade of collectors during bright, cloudless days in the summer months. This assumes a lack of constant maintenance activity by man. The collectors could also provide a warmer environment on cold winter nights due to a decrease in thermal long-wave radiation from the soil, resulting in
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