Vertical gradient analysis of soil environmental factors and vegetation community in mountain areas of frequent debris flow: A case study in the Xiaojiang Watershed, Yunnan

Abstract

Vertical gradient and soil environment are the key factors affecting mountain vegetation community structure. However little is known about the relationship between vegetation community and soil environmental factors. This paper aimed to determine the spatial distribution of vegetation community in typical area with high-frequency debris flow. SPSS principle component analysis, Pearson correlation analysis and CANOCO5.0 Two-dimensional ordination method were applied to determine the vertical gradient differentiation of the soil environmental factors and vegetation community as well as the relationship between them. The vertical zonal soil distribution rules were similar to latitude zonal distribution rules. The order from high to low was Temperate zonal soil, North subtropical zonal soil and Subtropical soil. The shrub-grassland community could be divided into three types, namely Potentilla anserina - Heteropogon contortus community, Oxalis corniculata-Artemisia dubia community and Hyparrhenia bracteata community. In the seriously degraded ecological environment caused by geological disasters and human disturbances, native arbor community was scarcely distributed. The main vegetation types of alpine zone were artificial forests composed of Pinus yunnanensis and Pinus armandii; those of subalpine zone were mixed forests of pine and cypress; and those of lower mountain belt were artificial forests composed of Eucalyptus robusta and Leucaena leucocephala. Canonical correspondence analysis suggested a significant relationship between vegetation and soil environmental factors. The results suggested that the main factors affecting the vegetation distribution in the typical area with high frequency debris flow are elevation gradient, soil organic matter, soil total phosphorus and heavy metals.