The soil-geomorphic template and biotic change in arid and semi-arid ecosystems

The objective of this paper is to illustrate the concept of the soil-geomorphic template and its relationship to biotic change in arid and semi-arid regions. Such biotic change is typically accompanied by and linked to geomorphic change that involves soil, topography, and soil parent material, which together form the soil-geomorphic template. Soil is a factor in biotic change because it is the substrate that provides water, nutrients, anchorage for plants, and habitat for burrowing animals. Topography is a factor in biotic change because it influences local microclimate by means of elevation, lateral redistribution of water, and slope orientation. Soil parent material is a factor in biotic change because it provides the lithic inheritance from the geologic landscape that gives rise to soils with different particle size distribution (i.e. available water holding capacity) and nutrient status. Numerous linkages and feedback loops occur between the soil-geomorphic template, microclimate, vegetation, and animals. A perturbation in any of these factors can steer an ecosystem from one state to another. The integral relationship between the soil-geomorphic template and biotic change is an example of how biological and geological systems are coupled and co-evolve over long-term (Quaternary landscape evolution) and short-term (human-induced desertification) time-scales.