Abstract: This research studied the distribution of plant communities in response to soil environmental factors in desert steppe. We selected a soil habitat transition gradient from sierozem to sandy soil in Yanchi, Ningxia, China. Within, at the edge of, and outside of the sierozem habitat, vegetation characteristics and soil sampling were conducted using a line transect method. Based on the soil environmental factors and community species composition data, we quantitatively classified the plant communities using multivariate regression trees and redundancy analysis. Then we analyzed the differences between the different plant communities using principal component analysis. It was found that dominant species of the plant communities changed from Stipa breviflora+Cleistogenes squarrosa+Thermopsis lanceolate to Sophora alopecuroides+Pennisetum centrasiaticum and to Artemisia scoparia+Salsola collina across the soil gradient. Key soil factors associated with the shift of plant community species dominance included soil coarse sand, soil organic carbon and soil total phosphorus contents. Across the habitat gradient from sierozem to sandy soil, height, cover and biomass of the plant communities showed a statistically significant increase, community species abundance showed a significant decrease, and plant community diversity showed an increase and then a decrease. As soil texture became coarser and soil nutrient content decreased along the gradient, perennial plant communities were replaced by annual plant communities. Compared with the plant communities in the sierozem habitat, the proportion of perennial plant species, plant species diversity and biomass were low in sandy habitats.

Key words: desert steppe, multivariate regression trees, quantitative classification, restoration in grassland