The change of species-abundance distribution patterns of Carex cinerascens community along a hydrological gradient in the Poyanghu wetland

The variation of water level in Poyanghu plays a significant effect on the dominant vegetation of Carex spp. community. However, the community assemblage mechanism under the change of hydrology is unclear now. Five species-abundance distribution pattern (SDP) models, including broken stick model (BSM), niche preemption model (NPM), dominance preemption model (DPM), random assortment model (RAM) and overlapping niche model (ONM) were employed to detect the community assemblage mechanism of C. cinerascens along a hydrological gradient in Poyanghu wetland. The results showed that the number of species firstly increased and then decreased along the hydrological gradient from high to low. Meanwhile, the curve of species-abundance distribution became steep. The optimal fitting SDP models were BSM, NPM and NPM for high humidity community, medium humidity community and low humidity community, respectively. These indicated that the hydrology condition resulted in the change of SDP. With the decrease of humidity, the community assemblage mechanisms of C. cinerascens were replaced from stochastic niche to niche preemption.