Spatial variability of plant community characteristics and its influencing factors in a small watershed of wind-water erosion crisscross region on the Loess Plateau, China

Abstract

The small watershed is the basic unit of soil erosion control on the Loess Plateau. Consequently, the study of the spatial distribution and influencing factors of vegetation is the basis of vege-tation restoration and reconstruction in this region. A small watershed in the wind-water erosion crisscross region with the most serious soil erosion in the Loess Plateau was selected to investigate the changes of vegetation distribution and soil properties. The spatial variability of plant community characteristics and its main driving factors were studied by geo-statistical method and redundancy analysis (RDA). The results showed that there were 27 plant species in the small watershed, belonging to 12 families and 25 genera. Leguminous, Gramineous and Compositae plants were dominant families, contributing 59.3% of the total species. In general, the community structure was simple and the organization level was low. The aboveground biomass (AGB) and coverage (C) of the community reached 205.7 g·m-2 and 57.7%, which was higher than the mean value of grassland in northern China, but the level of species diversity was lower. There were medium spatial correlation in AGB, but stronger spatial correlation for C, Patrick richness index (R), Shannon diversity index (H), Simpson dominance index (D) and Pielou evenness index (J). The spatial distribution of AGB was mainly patchy and striped, which was highest at the semi-shady slope and near the outlet of watershed. Other community characteristics were relatively fragmented, and R, H and J were higher at the top of the semi-shady slope. AGB and C were mainly affected by soil organic carbon, mineral nitrogen, total nitrogen, soil water content, and altitude, while R, H, D and J were mainly affected by soil saturated hydraulic conductivity, bulk density, sand content, and silt content. The results are helpful for vegetation restoration and evaluation of ecosystem structure and function in the wind-water erosion crisscross region.