Association of Vegetation Patterns and Environmental Factors on the Arid Western Slopes of the Helan Mountains, China

We studied the distribution and composition of plant communities along an altitudinal gradient on the arid western slopes of the Helan Mountains in northwestern China by means of multivariate analyses. Two data sets that originated from fieldwork in 2005-2006 were subjected to principal component analysis (PCA), resulting in 3 major vegetation categories: desert shrubland, desert grassland, and prairie shrubland. Ordination based on canonical correspondence analysis (CCA) divided the desert shrubland category into a Caragana tibetica community, a Salsola passerina-Oxytropis aciphylla community, and a Reaumuria soongarica-S. passerina community; the desert grassland category into a Stipa grandis community and a Stipa breviflora community; and the prairie shrubland category into an Ulmus glaucescens-Prunus mongolica community, a P. mongolica-Potentilla fruticosa community, and a P. mongolica community. In the desert shrubland category, the C. tibetica, S. passerina-O. aciphylla, and R. soongarica-S. passerina communities appear consecutively along the soil alkalization gradient, and the C. tibetica, R. soongarica-S. passerina, and S. passerina-O. aciphylla communities appear consecutively along the soil texture gradient. In the desert grassland category, the S. breviflora and S. grandis communities appear consecutively along the soil water gradient. In the prairie shrubland category, the U. glaucescens-P. mongolica, P. mongolica-P. fruticosa, and P. mongolica communities appear consecutively along the soil organic matter and total nitrogen gradient, while the P. mongolica, P. mongolica-P. fruticosa, and U. glaucescens-P. mongolica communities appear consecutively along the soil pH gradient. Better understanding of these and similar relationships can enable better management of arid and semiarid ecosystems, which may be more vulnerable to such environmental factors than their counterparts in more humid regions.