Responses of wetland vegetation in Poyang Lake, China to water-level fluctuations

The effect of water-level fluctuations (WLF) on vegetation distribution and the makeup of the wetland environment is of growing interest as hydrological regimes become even more profoundly modified by human actions and climate change. It is necessary to develop a scientifically defensible and empirically testable relationship between changes in WLF and the corresponding ecological responses on a regional scale. We utilized correlation analyses, curve-fitting methods, and the classification and regression tree model to quantify both the linear continuum responses and the discontinuous threshold responses of the distribution of spring sedges in the Poyang Lake wetland in relation to different indicators of WLF. Our results suggest that: (1) the sedges exposed to a rapidly fluctuating water regime adjust their distribution pattern approximately every 30 days in an attempt to adapt to the new and ever changing environment; (2) the continual presence of high water levels lasting up to 20 days during the spring or extremely low water levels during the previous retreating season could trigger substantial changes in the distribution of spring sedges. Results of this study will help water resource managers to make informed decisions about how to regulate water conservation projects and protect the degrading wetland ecosystems.