Effects of area, temperature and geometric constraints on elevational patterns of species richness: a case study in the Mountain Taibai, Qinling Mountains, China

Abstract

Aims Recent studies have illustrated that area, climate and geometric constraints were the main determinants of elevational patterns of species richness; however, the relative importance of these factors is unknown because these factors co-vary with elevation. Based on these factors, the power law species-area relationship (SAR), the metabolic theory of ecology (MTE) and the mid-domain effect hypothesis (MDE) have been proposed to explain elevational patterns of species richness. Our objective is to compare the relative performance of SAR, MTE and MDE in shaping elevational patterns of species richness, using vegetation and climatic data from Mt. Qinling Mountains as a case study. Methods We used a database, Distribution of Plants in Mt. Taibai, composed of 2 132 plant species, to derive species richness values for different plant groups. A digital elevation model was used to calculate the area of each elevational band. Eighteen data loggers were set along south and north slopes and at different elevations to record air temperature. RangeModel software was applied to predict species richness of each elevational band, based on the MDE hypothesis. We then compared the explanatory strengths of SAR, MTE and MDE models and used variation partition and stepwise regression to assess their relative importance in shaping elevational patterns of species richness. Important findings Plant species richness followed a unimodal pattern; however, species richness of each plant group peaked at a different elevational band. As single predictors, SAR, MTE, and MDE explained 66.4%, 19.8% and 37.9% of the variation in species richness, respectively. Together they explained 84.6% of the variation. When