The Nutrient Dynamics And Spring Litter Decomposition Of Carex Cinerascens In Poyang Lake

Poyang Lake is the largest freshwater lake in china. Its water level fluctuation is frequent and amplitude is large. Carex cinerascens is the dominant species of Poyang Lake wetland vegetation. The special hydrological rhythm in Poyang Lake makes the C. cinerascens forming two unique growing season, which are called "spring grass" and "autumn grass".In this study, we selected three C. cinerascens communities in Jiang Xi Nanji mountain wetland national nature reserve to study the C. cinerascens growth and nutrient dynamic, the community and nutrient difference of “spring grass” and “autumn grass”, and litter decomposition process in different elevation gradient. The main results are as follows:(1) The annual average underground dry weight of C. cinerascens was 2506.63 ± 1375.69 g/m2, which is 3 times higher than the 587.48 ± 198.96 g/m2 for aboveground dry weight. The growth dynamic of C. cinerascens in Poyang Lake could be divided in two four stages. They are autumn growing season(after the flooding to December), natural withering period(January to February), spring growing season(March to the flooding) and flooding period(usually from May to August). The aboveground of C. cinerascens may die if the plant totally submerged more than 3 months.(2) The height, aboveground dry weight of spring grass were higher than autumn grass. The TN content and coverage of spring grass were lower than autumn grass in overall, but this patterns were not consistent in different elevation gradient. There were no difference of TOC content and P content between spring grass autumn grass.(3) The decomposition rate of C. cinerascens litter was high in the early two weeks. As a result, the 37% of the material was lost in end of this period. However, decomposition rate decreased to a very low level after that. In the end of the experiment, the content of K, Mg, Mn in the litter of C. cinerascens were reduced by 88.3%, 58.4% and 88.3% respectively. There was no significant effect of elevation gradient on the decomposition process of C. cinerascens.