Species presence frequency and diversity in different patch types along an altitudinal gradient:Larix chinensisBeissn in Qinling Mountains (China)

Abstract

Forest communities are mosaic systems composed of patches classified into four different developmental patch types: gap patch (G), building patch (B), mature patch (M) and degenerate patch (D). To study the mechanisms maintaining diversity in subalpine coniferous forests, species presence frequency and diversity in the four distinct patch types (G, B, M and D) ofLarix chinensisconifer forests at three altitudinal gradients in the Qinling Mountains were analyzed. Our results were as follows: (1) Different species (or functional groups) had distinct presence frequencie s in the four different patch types along the altitudinal gradient; (2) Some species or functional groups (species groups sharing similar traits and response to environment) only occurred in some specific patches. For seed dispersal, species using wind mainly occurred in G and D, while species using small animals mainly occurred in B and M; (3) Species composition of adjacent patch types was more similar than non-adjacent patch types, based on the lowerβdiversity index of the former; (4) The maximum numbers of species and two diversity indices (D′ andH′) were found in the middle altitudes. Various gap-forming processes and dispersal limitation may be the two major mechanisms determining species diversity inLarix chinensisconiferous forests at the patch scale.