Effect of a grazing ban on restoring the degraded alpine meadows of Northern Tibet, China

Banning of grazing is a widely used means of restoring degraded rangeland in China. However, little is known about the time required to restore degraded alpine meadows through the use of a grazing ban. Height and cover of individual plant species and total cover, herbage mass and root mass of each plot of a grazing ban and communal free-grazing alpine meadows in Northern Tibet were examined. Soil samples were also collected and total organic carbon, microbial biomass carbon, total phosphorus and ammonium nitrogen contents were measured. The results showed that both the level of plant species diversity and herbage mass were higher in areas of a grazing ban than in communal free-grazing land without a grazing ban. No significant differences in root mass and soil nutrient contents were observed. There was a higher plant species diversity and herbage mass in the early years of a grazing ban but there was a subsequent decline. It is suggested that some grazing after a grazing ban may be necessary according to the dynamics of ecosystem responses with time.