destruction will result in decreased levels of soil moisture. If soil compaction and surface disruption is not severe, significant changes in soil moisture may not occur due to construction and maintenance activities. Temperature and Heat Flux Few of the recent studies on impacts of walkers and off-road vehicles have examined potential changes in thermal conductivity of compacted soils, and thus the effects of compaction on overall heat flux in the desert ecosystem. Liddle and Moore (1974) found compaction of sand to increase its thermal capacity, as would be expected as density was increased. Conductivity was increased in dry soils, but was decreased in wet. The result was an increase in diurnal soil and air temperature ranges, which Liddle and Moore (1974) attributed more to vegetation removal than to compaction. In any case, significant above-ground destruction of desert habitat would appear to increase heat flux rates in the soil-atmosphere system throughout the day. Significant compaction of soils may alter energy exchange in the desert ecosystem in the following ways: 1. Compaction will increase ground surface reflectivity, resulting in decreased soil heating from incoming radiation. 2. If compaction results in decreased surface emissivity, then more energy will be available for daytime heating of the air by sensible heat, and nighttime radiative cooling of the soil will decrease. 3. Compaction will increase ground conductive capacity resulting in decreased daytime heating and increased nocturnal cooling of the soil. 4. Compaction will increase dry density, resulting in increased ground thermal capacity and thus potential soil heating. The contradictory nature of these processes points to the need for a thorough analysis of what changes may occur in the energy budget of desert ecosystems in which soil compaction occurs. Compaction of soils, together with above-ground destruction of desert habitat, would appear to increase heat flux rates in the soil-atmosphere system throughout the diurnal cycle. It would not be expected, however, to offset the decreased heat flux rates due to the combined influence of shading and wind deflection by an array of heliostats or photovoltaic collectors. Plant and Animal Response Plant and animal response to construction and maintenance disturbance
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