Description: Clonal plants are prevalent in wetlands and play important roles in maintaining the functions of the ecosystem. In the present study, we determined the effect of clone sizes (R1, R2, and R3 comprising 1, 3, and 5clumping ramets) on the tolerance of Carex brevicuspis growing under 30-cm-deep water to three different periods (one, two, and three months) of submergence and its growth recovery one month after de-submergence. Our results showed that the relative growth rate (RGR) of C. brevicuspis significantly declined with increasing submergence time, and was higher in R3 and R5 than in R1 plants under both submergence and post-submergence conditions. The concentration of water-soluble carbohydrates (WSCs) was highest in R3, intermediate in R5, and the lowest in R1 plants during the first two months of submergence, indicating an optimal trade-off between energy investment and vegetative growth ( i.e. , buds and ramets production) in C. brevicuspis. WSCs were significantly reduced with increasing submergence time, while the starch content was significantly reduced only during the third month of submergence, implying that WSCs were a direct energy source for C. brevicuspis during submergence. The number of buds was higher in R5 than in R3 and R1 plants after two and three months of submergence, which directly resulted in a significantly higher post-submergence ramet production in R5 plants. These results indicated that plants with relatively larger clone sizes display better tolerance to submergence stress and post-submergence growth recovery. Therefore, we speculate that the large clone size in C brevicuspis might be an effective adaptive mechanism to survive under submergence stress in floodplain wetlands.

Description: Both water depth and litter quality are important factors influencing litter decomposition in wetlands, but the interactive role of these factors in regulating mass loss and nutrient dynamics is far from clear. The responses of mass loss and nutrient dynamics to simulated water depths and litter quality are investigated in leaves of Carex brevicuspis and leaves and stems of Miscanthus sacchariflorus from the Dongting Lake, China. Three litter types differing in litter quality were incubated for 210 days at three water depths (0 cm, 5 cm, and 80 cm, relative to the water surface) in a pond near the Dongting Lake. The litter mass remaining, nitrogen (N), phosphorus (P), organic carbon (organic C), cellulose, and lignin contents were analyzed during the controlled decomposition experiment. Moreover, water properties (temperature, dissolved oxygen content, and conductivity) and fungal biomass were also characterized. Initial N and P contents were highest in C. brevicuspis leaves, intermediate in M. sacchariflorus leaves and lowest in M. sacchariflorus stems, whereas the organic C, cellulose, and lignin contents exhibited an opposite trend. After a 210 days incubation, decomposition rate was highest in M. sacchariflorus leaves (0.0034–0.0090 g g -1 DW day -1 , in exponential decay model), intermediate in C. brevicuspis leaves (0.0019–0.0041 g g -1 DW day -1 ), and lowest in M. sacchariflorus stems (0.0005–0.0011 g g -1 DW day -1 ). Decomposition rate of C. brevicuspis leaves was highest at 5 cm water depth , intermediate at 80 cm, and lowest at 0 cm. Decomposition rate of M. sacchariflorus leaves was higher at 5 cm, and 80 cm than at 0 cm water depths. Water depth had no effect on decomposition of M. sacchariflorus stems . At the end of incubation, N and P mineralization was completely in leaf litters with increasing rates along with increasing water depth, while nutrients were accumulated in M. sacchariflorus stem. Organic C, cellulose, and lignin decayed quickly in both leaf litters compared to the stem litter. The fungal biomass was higher in leaf than in stem litters and changed as a response to water depth in both leaf litters rather than stem ones. These data indicate that submergence has no effect on the decomposition of refractory stem litter and shallower submergence stimulates degradation of the labile leaf litter.