a less negative, and possibly even a positive nighttime radiant temperature (Lowe and Hinds 1971). Shading, due to its effects on radiation input, thermal flux, and soil moisture, could have profound effects on the biota of the southwestern desert ecosystems in which large-scale solar collector arrays are placed. If soil moisture is indeed significantly increased (or at least droughts decreased) the desert literature indicates the possibility of significantly greater plant production, potentially of an economically beneficial nature. However, prediction of change in altered systems with a history of disturbance will be difficult, as short term changes are not necessarily indicative of site potential. Although not directly related to shading, an increase in man’s activities at a solar collector site could cause dispersal of many of the existing animal populations; however, historically it has been shown populations of some mammal species such as rats and coyotes increase as a result of man's activities. Reptile species with small territorial ranges may increase in population because of the ameliorated environment created by the solar collectors. Wind Deflection Velocity and Turbulence It is generally assumed that arrays of solar collectors will decrease local wind speeds in both heliostat fields (Black and Veatch 1977, ERDA 1977b) and in photovoltaic or distributive photothermal arrays (ERDA 1977a, Sears et at. 1977). Wind flowing across a field of collectors will probably be forced upwards if striking the reflective surface of the collectors or downwards if striking the backside so that, although wind velocities may be greater than normal above the field, if the wind is from the South, they will be reduced below the array of collectors, although wind from the backside may also cause turbulence below the collectors. This area below the collectors is the area of importance when discussing ecological impacts of solar arrays in the desert. Wind velocity in the southwestern deserts is more intense than most other areas of the continent. High wind velocity makes a region more arid
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