Plant species diversity of wetland ecosystem in an arid and semi-arid region in northwest China

Abstract

In order to study the changes of plant species diversity along the biotope gradient and its influencing factors in a wetland-arid grassland ecosystem in the arid and semi-arid regions of northwest China, four transect lines were set along the biotope gradient in four directions: east, northeast, west and northwest, and altogether 123 sample plots were investigated on species composition, density, foliage cover, height and biomass (calculated in fresh weight). The whole study area was divided into the wetland zone, the ecotone and the arid grassland zone in terms of habitat characteristics and vegetation types. In this paper, we analyzed and compared the species diversity in the ecotone of a wetland-dry grassland ecosystem in Yanchi County, Ningxia Hui Autonomous Region, with the help of biodiversity software BioDiversity Pro and statistical software Microcal Origin, as well as the combined measurement of species diversity indices. The results revealed distinct differences between those three vegetation zones along each transect line. The ecotone had the highest richness indices (R) and comprehensive diversity indices (Y), reflecting the edge effect. The greatest evenness indices (E) were found in the arid grassland zones. This result agreed with the phenomenon of desertification reversion, vegetation restoration and dominant communities  formation. As for the four transect lines, the east and the northeast scored higher in each diversity index than the others due to less human disturbance, gentler topography uplift and more intercepted materials and energies. The highest Simpson index value was found in the northeast transect line, which was 39.9% higher than the lowest in the Northwest.