Instead, the soil is extensively covered by dominant microphytic communities of blue-green algae, cyanobacteria, and fungi that are barely visible to the naked eye (West 1990, Zaady and Shachak 1994).
1987, Jones and Shachak 1990), burrowing desert isopods (Shachak and Jones 1995), and digging porcupines (Yair and Rutin 1981, Gutterman 1982), as well as the microphytic crust communities previously mentioned; the engineering of soil and rock by each of these species has very large effects on desert productivity and species diversity.
The Negev Desert example of autogenic and allogenic engineering by the microphytic crust (West 1990, Zaady and Shachak 1994) discussed earlier illustrates this point particularly clearly.
The amount of runoff is controlled by the microphytic crust, because the polysaccharide secretions of these organisms form a surface that is more or less impermeable to water infiltration, generating runoff into the pits and mounds.
In this example, we have one physical engineer (the microphytic crust community) that is not part of the annual plant-ungulate food web, but that nevertheless prevents annuals from getting established (few cracks in the soil in which to germinate, little moisture infiltrating).