Decomposing Spatial β-Diversity in the temperate forests of Northeastern China

β-Diversity, which describes the extent of change in species composition in a given region, has become a core issue in ecology in recent years. However, it is hard to understand the underlying mechanisms of β-diversity by using indices that yield identical values under species replacement and nestedness pattern. Partitioning β-diversity into turnover (caused by species replacement among plots) and nestedness components (caused by species loss or gain among plots) may provide improved understanding of the variation in species composition. Here, we collected presence-absence data of 456 one-tenth ha circular plots in the temperate forests of Northeastern China spanning a latitudinal range of 12° (41-53°N). We decomposed β-diversity to assess the relative contribution of the turnover and nestedness components across latitudinal gradients. We used regression analysis to assess the relationship between spatial distance and β-diversity. We applied variation partitioning to evaluate the importance of the measured environmental and spatial variables in explaining β-diversity. We used the Tukey honest significant difference test to test the differences of β-diversity along latitudinal gradients. Pearson correlations (r) and significance (p-value) were computed using the Mantel tests to verify the relationship between distance and β-diversity. The ANOVA test was used to verify whether the variation of β-diversity explained by the environment and distance was significant. Our results showed that (1) β-diversity and the turnover component were higher at low latitudes (zones A and B) than at high latitudes (zones C and D), while there was no relationship between the nestedness component and latitude. (2) The turnover component was dominant. (3) The spatial distance explained more variation of β-diversity than the measured environmental factors. Therefore, we conclude that β-diversity is mainly a product of species turnover in our temperate forests, suggesting that different localities harbor different species. We find that decomposing β-diversity into the turnover and nestedness components is a useful approach to explore the variation of community composition and their causes.