Effects of enclosure on plant diversity and community characteristics in pasture of Middle Tianshan Mountain

Three types of artificial grasslands fenced for 25 years in Middle Tianshan Moutain were used to examine the effects of enclosure on vegetation characteristics and plant diversity. The results showed that after longterm enclosure, the coverage, height and above ground biomass were improved remarkably inside of fence than those of the outside in three types of grasslands. The above ground biomass and plant average height in the fenced meadow in three types of grasslands decreased in the following order: subalpine prairie meadowsubalpine meadow prairiesubalpine prairie. The differences of above ground biomass and plant coverage between the fenced meadow and the grazed meadow were significant (P0.01). In subalpine prairie meadow and subalpine meadow prairie, the plant average height showed significant difference between inside and outside of the fence (P0.01). After fencing for 25 years, the richness index and diversity index were higher outside of the fence than that of the inside in three types of grasslands; however, the evenness index had the opposite result.