Pangquangou National Nature Reserve, established in 1986, is located in Shanxi Province at 37°45′～37°55′N, 111°22′～111°33′E. Its peak, Xiaowen mountain, is 2831m above sea level. The main protected objects are Crossoptlon mantchuricum and cold temperate coniferous forest in this reserve.Quantitative analysis of ecological relationships between vegetation and environment has become an essential means in research field of modern vegetation ecology. In this paper, based on data from 84 quadrates, forest communities in this reserve were investigated using TWINSPAN, DCA and DCCA. These results will be helpful to the construction and development of Pangquangou National Nature Reserve.
By TWINSPAN, the forest communities were classified into 7 types. The distribution pattern of vegetation reflects the comprehensive influence of environments. The results of DCA and DCCA clearly reflect the relationship between the pattern of forest communities and environmental gradients. The ordination result of DCCA indicates that altitude is more important than other environmental factors, because the change of altitude gradient will lead to the varieties of temperature gradients and humidity gradients. The first of the DCA ordination axes indicates the humidity gradients, and the second of that indicates the temperature gradients. All these results show that the main factors restricting distribution of the communities are temperature and humidity in this reserve.
The ecological meaning of ordination axis in DCCA is much clearer than that in DCA, and the species-environment correlation of DCCA is more obvious than DCA. The first axis of DCCA indicates the altitude gradient among the communities, and the second axis is the gradient in aspect and slope among the communities. DCCA ordination can simultaneously express similarities of species and environment. Therefore the quadrat location in DCCA ordination figure is much closer than in DCA.
The research results suggest that Larix principis-rupprechtii is widely distributed in this nature reserve at altitude from 1600 to 2500m. Picea spp. (P. meyeri and P. wilsonii) are mainly distributed in middle mountainous areas at altitude from 2000 to 2350m where Crossoptlon mantchuricum inhabits, so that this area should be primarily preserved.