Soil seed bank of a desert range site infested with Rhazya stricta in Raudhat al-Khafs, Saudi Arabia

摘要

Knowledge of the dynamics of soil seed bank in rangelands is important in planning for range management and improvement. A three-year study of soil seed bank was conducted in an area infested with Rhazya stricta Decne. The object of the study was toevaluate annual and seasonal variations in the soil seed bank over three degrees of infestation by R. stricta (low, moderate, and heavy). Soil samples were placed in germination trays in a growth chamber and irrigated. Emerging seedlings were identifiedand counted by species. Species were grouped into shrubs, legumes, grasses, and forbs. Results revealed the presence of seeds of 44 species, mostly annuals. Low similarity was observed between above-ground vegetation and soil seed components. Significant annual and seasonal variations were observed among groups of species. Generally, seed bank size and species richness were higher under the lower level of R. stricta infestation. It is concluded that most of the desirable species that have the potentialof growing in the area are disappearing.