ABSTRACT
Reconstruction of disturbed shrub and grassland ecosystems in semiarid regions is a dynamic process involving ecological succession. Reconstruction is influenced by factors related to physical (climate, soil, physiography and disturbance) and biological (plants, animals and microorganisms) conditions of the site. Certain of these factors may be anthropogenically manipulated to influence the rate and direction of the reconstruction process.
Site factors may be altered for various reasons, such as improving the substrate for biological organisms. Topsoiling and fertilization are two approaches to this type of site modification. The introduction of biotic propagules comprises a broad approach to manipulation of biological conditions. Studies on disturbed shrub and grasslands have shown that different site and biotic manipulations can be used to induce corresponding differences in plant community productivity, composition and diversity over the short-term, as well as microbiological function. Longer-term ecosystem dynamics, however, are less well understood because of the limited duration of most research. Nonetheless, various site management practices may prove effective for longer-term manipulation of site and biotic factors. Research suggests grazing management to be one promising 163approach for maintained influence over plant community and soil development.
Successful manipulation of the factors that influence ecosystem reconstruction depends upon ecological propriety of practices implemented. Such propriety requires a theoretical understanding of the reconstruction process and its long-term dynamics. This understanding, however, is limited for disturbed semiarid shrub and grasslands, and must be addressed by long-term ecological research with proper emphasis on functional rather than purely empirical relationships.
