will be two-fold, namely the response of biota to soil compaction and the abiotic changes it causes, and to actual destruction of individual organisms or populations of organisms. In the case of mobile animals, populations may not be destroyed, but destruction of habitat could result in removal of organisms via migration from within collector fields. Return of these organisms would thus be dependent on the degree of restoration of the habitat. Compaction has been observed to inhibit growth of herbaceous plants by decreasing germination or inhibiting root growth (Kubota and Williams 1967, Davidson and Fox 1974). In very sandy soils, compaction has been found to be beneficial to plants (Liddle and Greig-Smith 1975). Unless serious compaction occurs on clayey or loamy sites, it should not be a major limiting factor on ephemeral populations. Soil texture and pore volume are recognized as very important variables in determining distribution of shrubs in arid regions (Noy-Meir 1973). Although comparative water relations undoubtedly plays a major role, several studies have indicated aeration of roots as a reason for many shrubs with fibrous, near-surface root systems occurring exclusively on sandy soils (Cannon 1915). Several common types of plants requiring high levels of soil aeration are creosote bush (Lunt et at. 1973), and some of the cacti (Cannon and Free 1917). Several studies have noted decreases in oxygen content of soils due to compaction (Lutz 1945, Liddle and Greig-Smith 1975) but as yet, apparently no similar results are available for disturbed desert systems. Even so, succession of perennial vegetation in the desert due to compaction effects appears unlikely. Complete above-ground destruction of desert sites is eventually followed by new populations of plants. The important question is what type of plants succeed on the site relative to what existed there before. Some studies indicate plant succession to be essentially lacking in desert vegetation (Muller 1940, Shreve 1951), i.e., if a creosote bush community is destroyed, then creosote bush will return. Indeed, desert studies have shown this (Wright 1970, Beatley 1974a, Mirpagel and Zembel 1976). Conversely, other desert studies have indicated distinct invader species to
RkJQdWJsaXNoZXIy MTU5NjU0Mg==