Woody-plant encroachment in grasslands: a review of mechanisms and after effects.
Woody-plant encroachment in grasslands has been a much-studied topic in ecology and animal husbandry over the past few decades. This paper clarifies the causes and consequences of this encroachment by reviewing recent progress in the study of invasion stages, invasion mechanisms, the impacts of this encroachment on grassland ecosystems and their aftereffects. The means of woody-plant encroachment include both anthropophyte and natural invasion. In general, this encroachment divides into three stages: dispersal, colonizing and establishing and diffusing. The causes of encroachment have been identified as fire suppression, climate change, changes in nutrient availability and over grazing. These factors effect encroachment through changing plant coverage, soil water use efficiency and allelopathy. We conclude that woody-plant encroachment changes many interfaces in grassland ecosystems and influences the ecological and hydrological processes that lead to grassland degradation and desertification.