Soil Water Balance

Abstract

In the more than 80 references related to banded vegetation patterns, five continents and 12 countries are represented. The early research concerned only the vegetation pattern itself (Clos-Arceduc 1956). Hypotheses regarding ecological functioning were then proposed between 1956 and 1970 and clearly synthesized by (1971) for seven countries. He defined the minimum common characteristics necessary for the existence of banded vegetation spatial structure. These characteristics are now well known and include a semiarid climate, high-intensity rainfall, and a gentle slope. These characteristics are cited in almost all the publications on banded vegetation. We will not further review them here but focus instead on what they imply: the importance the spatial redistribution of water in the dynamics and the functioning of tiger bush bands. The areas of sealed, substantially bare soils yield a high proportion of runoff. On encountering the thicket bands immediately downslope, the flow rate diminishes and infiltration occurs, thus providing an additional water supply to the thicket. This process is more active in the upslope part of the thicket and progressively decreases to nil on the downslope edge, where many dead trees are observed. The zone located immediately upslope of the thicket is often called the “pioneer front” (Table 5.1) and is a zone of active plant colonization.