Assembly of plant communities in coastal wetlands-the role of saltcedar Tamarix chinensis during early succession

Abstract

Aims The mechanisms of plant community assembly are hypothesized to vary at different stages of succession. Here, we explore the local assemblage structure of a herbaceous plant community at its early stage of succession in a supratidal wetland. Specifically, we assess the role of Chinese saltcedar (Tamarix chinensis), the lone dominant shrub species, in shaping the spatial structure and species composition in the local plant community, after landscape alteration. Methods We used the multivariate trend-surface analysis for analyzing the spatial structure of the community composition. A null model was also used to detect potential biotic interactions between species. Statistical significance was derived from a permutation test by randomizing the presence-absence matrix and functional traits independently. Sensitivity analysis by randomly selecting 50 subplots and repeating the null model tests was also done. Finally, rank correlation analysis was used to study the relationship between effect sizes and distance to nearest T. chinensis individuals. Important Findings The herbaceous plant community was highly structured and shaped by the presence of T. chinensis. At local scale, two functional traits, plant height and leaf area, were found to be significantly convergent. Dispersal, environmental stress and interspecific competition played a trivial effect on the local community assembly. The facilitating effect of T. chinensis on the pioneering herbaceous plants, through acting as a wind shelter, was put forward as the dominant community assembly process.