Effect of Water Level and Submergence Time on Leaf Growth, Stoichiometry and Homeostasis of Carex brevicuspis

Water level and submergence time are important factors influencing plant growth and plant C:N:P characteristics in freshwater wetlands. However, the effect of their interaction on plant stoichiometry and homeostasis is far from clear. Here, we performed a controlled experiment using four water levels (0, 10, 20, and 40 cm, relative to the soil surface) and under three submergence times (30, 60, and 90 days) with the aim of investigating the changes in plant growth and stoichiometric characteristics, as well as the strength of N, P, and N:P homeostasis in C. brevicuspis in the Dongting Lake, China. Results showed that biomass, density, height, and total carbon (TC) decreased significantly with increasing water level; however, the latter total nitrogen (TN) and total phosphorus (TP) increased significantly. The highest TN and TP were at 40 cm water level, while the highest C:N, C:P, and N:P ratios were at 0 cm water level. Furthermore, significant stoichiometric homeostasis of C. brevicuspis was found for N (HN) and P (HP) except for N:P (HN:P). HN and HP decreased with increasing submergence time, and HN was consistently greater than HP, indicating that C. brevicuspis had a weak ability to maintain its internal P balance under long-term submergence. Therefore, the impact of water level and submergence time on plant growth and stoichiometric characteristics in this study, are applicable to the conservation and management of the wetlands dominated with C. brevicuspis.