A vertical gradient analysis of the flora of Dalaoling Mountain in the Three Gorges region, China
三峡大老岭植物区系的垂直梯度分析

To explore its floristic compositional characteristics, and the ecological significance of the vertical gradient pattern of the Dalaoling Mountain flora in the Three Gorges region, China, this flora was investigated along a vertical vegetation transect. The structural characteristics of the flora and the altitudinal distribution pattern of its floristic components were analyzed, the floristic equilibrium point (FEP) was detected, and the effects of the mountain climate on the vertical variation of floristic composition were studied using clustering method. The results are summarized as follows: 1) The flora of Dalaoling Mountain is of a temperate nature in floristic composition, with a high en- demism in Eastern-Asian and Chinese elements, but exhibits some historical connections with tropi- cal flora. 2) The areal-types of the genera are tropical, temperate, Mediterranean to Central Asian and Eastern Asian. The vertical distribution patterns of the 4 types are different from each other. The floristic equilibrium point between the tropical elements and the temperate ones is roughly locat- ed at the altitude of 650 m. 3) The clustering analysis of the floristic composition and the species number of the genera showed that the vertical distribution pattern of floristic elements and species number of the genera corresponds with that of the mountain climate and vertical vegetation spectrum.