Edge effect of the ecotone of wetland and arid grassland in a semi-arid region of China

Abstract

The edge effect of plant communities was investigated in a wetland-dry grassland ecosystem at the Siertan Wetland in Yanchi County, Ningxia Hui Autonomous Region, China. Four transects lines, with each about 1 km long, were established for a vegetation survey in July 2005, along biotope gradients in four directions: east, northeast, west and northwest. The data was analyzed using TWINSPAN classification method. The vegetation in this wetland was classified into three vegetation types: halophytic marsh vegetation, meadow vegetation and grassland vegetation. Based on the calculation of the community structure indices, the edge effect was studied which revealed distinct differences among those three vegetation zones along each transect line. The ecotone had high richness indices (R), a high diversity index (SW) and ecological dominance (SP). Evenness, as measured by the index (E), was less apparent. From the four transect lines, it appears that the ecotone in the northeasterly direction scored higher in each community structure indicator than any of the other directions and those towards the northwest were least. The variation in the edge effect between the different transect lines is caused by human disturbances and topographic uplift.