QUANTITATIVE CLASSIFICATION AND ENVIRONMENTAL INTERPRETATION OF FOREST TREE SPECIES IN HUNGOU, ZHONGTIAO MOUNTAIN

Abstract

The forest vegetation was investigated through 40 carefully designed sampling plots in Hungou, Zhongtiao Mountain. Within each plot, the main environmental factors, such as altitude, slope, aspect and soil depth, were measured using portable GPS instruments and field tools. Soil samples also were collected and analyzed in the laboratory for total N, organic matter content, and pH. Topographic relative moisture index (TRMI) and annual total solar radiation were calculated using a Digital Elevation Model (DEM) (scale 1:50 000). Community types were classified using TWINSPAN and the relationship between the distribution and abundance of species to environmental gradients was analyzed using CCA ordination. The 40 plots were divided into 7 plant formations: Pteroceltis tatarinowii, Koelreuteria paniculata, Quercus aliena, Quercus variabilis, Carpinus turczaninowii + Acer grosseri, Acer truncatum + Carpinus cordata, and Quercus liaotungensis. The floristic composition of the arboreal species in each community represented the characteristics of the different deciduous broad_leaved forests in the warm temperate zone of North China. The distribution pattern of the community types classified by TWINSPAN was coincident with the environmental gradients shown in the diagram of the first two CCA axes. The first CCA axis mainly expressed altitude and soil fertility, and the second axis had distinct relationships with soil pH, TRMI, and slope gradient. These results, in general, indicate that the spatial distribution of tree species in Hungou is mainly controlled by altitude, soil fertility, and biotope humidity, whereas soil depth, annual global radiation and slope aspect are secondary controls. Environmental and spatial variation accounted for 46.14% of the spatial distribution of tree species, of which environmental variation alone explained 30.79%, spatial variation was 8.48%, and the interaction of spatial and environmental variation was 6.87% of the variation. These results indicate that we measured the important environmental factors regulating species distribution patterns in this forest.