Latitudinal gradients and ecological drivers of β-diversity vary across spatial scales in a temperate forest region

Aim Our understanding of the mechanisms driving beta-diversity is still rather rudimentary. This study evaluates the influences of environmental filtering versus spatial scale of regional communities on beta-diversity across latitudes. Location North-eastern China. Methods The beta-diversity was calculated in each regional community. The spatial extent of these "regional communities", which included five or 10 plots, was <= 140 km. A random assembly null model was used to assess the effects of species abundance distribution on the beta-diversity. Moreover, the deviation of observed beta-diversity from a null model (called beta-deviation) was also assessed. The variations of the beta values were partitioned into environmental, latitudinal and their joint effects. Results The observed beta-diversity declined with increasing latitude, although the beta-deviations showed a non-monotonic pattern as the latitude increased at two studied scales. All the regional communities consisting of five or 10 local plots exhibited significantly positive beta-deviations. The total amount of variation in beta-deviations explained by environmental and latitudinal variables increased dramatically with increasing scale. A significant pure environmental effect was observed at both scales, explaining 30% of the variation in beta-deviation for regional communities consisting of five local plots and 58.7% for regional communities consisting of 10 local plots. The spatial variation in precipitation primarily accounted for the beta-gradient. Main conclusions This is one of the few multiscale analyses to investigate latitudinal patterns and driving mechanisms of tree beta-diversity in temperate forests. The beta-deviation showed a similar trend of change with latitude, but the variation of beta-deviation explained by the environments and latitude was highly dependent on the scale of regional communities studied. Environmental filtering and the spatial scale of regional communities jointly accounted for the beta-gradient, with environmental filtering appearing to determine the high variation of species turnover along the latitudinal gradient.