Species abundance distribution models of Toona ciliata communities in Hubei Province, China

Abstract

The study of plant species abundance distribution (SAD) in natural communities is of considerable importance to understand the processes and ecological rules of community assembly. With the distribution of tree, shrub and herb layers of eight natural communities of Toona ciliata as research targets, three different ecological niche models were used: broken stick model, overlapping niche model and niche preemption model, as well as three statistical models: log-series distribution model, log-normal distribution model and Weibull distribution model, to fit SAD of the different vegetation layers based on data collected. Goodness-of-fit was compared with Chi square test, Kolmogorov–Smirnov (K–S) test and Akaike Information Criterion (AIC). The results show: (1) based on the criteria of the lowest AIC value, Chi square value and K–S value with no significant difference (p > 0.05) between theoretic and observed SADs. The suitability and goodness-of-fit of the broken stick model was the best of three ecological niche models. The log-series distribution model did not accept the fitted results of most vegetation layers and had the lowest goodness-of-fit. The Weibull distribution model had the best goodness-of-fit for SADs. Overall, the statistical SADs performed better than the ecological ones. (2) T. ciliata was the dominant species in all the communities; species richness and diversity of herbs were the highest of the vegetation layers, while the diversities of the tree layers were slightly higher than the shrub layers; there were fewer common species and more rare species in the eight communities. The herb layers had the highest community evenness, followed by the shrub and the tree layers. Due to the complexity and habitat diversity of the different T. ciliata communities, comprehensive analyses of a variety of SADs and tests for optimal models together with management, are practical steps to enhance understanding of ecological processes and mechanisms of T. ciliata communities, to detect disturbances, and to facilitate biodiversity and species conservation.