The effects of flooding regimes and soil nutrients on lakeshore plant diversity in a pristine lake and a human managed lake in subtropical China

Abstract

Abstract The hydrological regimes of many freshwater lakes have been dramatically changed by human activity. Nevertheless, few studies have reported the effects of human water management on the formation mechanisms of lakeshore plant communities. In this study, we investigated the effects of flooding and soil nutrients on the plant diversity of lakeshore Carex communities fringing a pristine lake (Poyang Lake) and a human managed lake (Shengjin Lake), two adjacent floodplain lakes in the middle and lower reaches of the Yangtze River. Over time, the Carex meadow at Shengjin Lake experienced a lower flooding frequency and a smaller amplitude of water level fluctuations in comparison with those obtained at Poyang Lake, but similar flooding durations were found for both sites. Soil total nitrogen (TN), total phosphorus (TP) and the ratio of TN to TP in study plots at Shengjin Lake tended to be higher than those in the plots at Poyang Lake at the 0–100\u2009cm soil depth except for soil TP at the 0–10\u2009cm soil depth. A total of 23 plant species were recorded in the Carex communities at the two lakes. Artificial water management increased plant diversity but had no effect on plant biomass in the Carex community. The primary factor in determining plant diversity changed from the flooding regime to the concentrations of soil nutrients as the water regime underwent management. Flooding regimes had strong direct impacts on the plant communities, while imposing few indirect effects on plants by changing soil nutrients in the pristine lake. Our results represent essential information for enhancing the robustness of management efforts for these large and important freshwater lakes.