干旱区生态环境知识资源中心

The gradual decline in the ecological condition of natural pastures as a result of over-utilization and the application of insufficient management decisions, coupled with the detrimental effects of long-term drought, has left extensive areas of high potential grazing land in southern Africa in urgent need of restoration. However, due to the limited number of grasses currently available for rehabilitating and restoring the vast number of different habitats encountered, an extensive research programme was initiated aimed at selecting indigenous grasses suitable for restoration of denuded areas in the arid and semi-arid grasslands of southern Africa. Forty-five specimens of Digitaria eriantha were collected and included in an investigation using 23 morphological characters in a principal component analysis to assist in the delimitation of ecotypes. Results presented here are representatives of this sample of the species. Digitaria eriantha can be delimited into five ecotypes, each associated with a particular rainfall region and/or habitat condition. The second part of the paper deals with the mode of reproduction employed by each D. eriantha ecotype identified, where the degree of sexuality and reproductive potency of each ecotype was determined. Ecotypes DEBTUF, DEBSENW and DEKTUF displayed the best seed germination and the worst vegetative reproductive potencies. Ecotypes DEBSTOL and DEKSTOL proved to be better adapted for vegetative reproduction by stolen scions. The presence of ecotype variation, different reproductive modes and a wide geographic distribution imply that an extensive and diverse genetic adaptability for survival under fierce environmental conditions exists within D. eriantha. Acquisition of hardier, more viable ecotypes may prove invaluable for the restoration and reinforcement of degraded land, especially areas subjected to extreme environmental stresses. (C) 1997 Academic Press Limited.