Effects of flooding regimes on the decomposition and nutrient dynamics of Calamagrostis angustifolia litter in the Sanjiang Plain of China

From May 2005 to September 2006, the potential effects of marsh flooding regimes on the decomposition and nutrient (N, P) dynamics of Calamagrostis angustifolia litter were studied in the typical waterlogged depression in the Sanjiang Plain, Northeast China. The decomposition of C. angustifolia litter was related to four sites with different hydrologic regimes [F1 (perennial flooding, average water depth of 480 days was 40.14 +/- A 8.93 cm), F2 (perennial flooding 33.27 +/- A 6.67 cm), F3 (perennial flooding 23.23 +/- A 5.65 cm) and F4 (seasonal flooding 1.02 +/- A 1.09 cm)]. Results showed that flooding regimes had important effects on the litter decomposition, the decomposition rates differed among the four sites, in the order of F3 (0.001820d(-1)) > F1 (0.001210d(-1)) > F2 (0.001040d(-1)) > F4 (0.000917d(-1)), and the values in the perennial flooding regimes were much higher. Flooding regimes also had significant effects on the N and P dynamics of litter in decomposition process. If the perennial flooding regimes were formed in C. angustifolia wetland due to the changes of precipitation in the future, the litter mass loss would increase 23.28-48.88%, the decomposition rate would increase 13.41-98.47%, and the t (0.95) would decrease 1.07 yr-4.50 yr. In the perennial flooding regimes, the net N accumulated in some periods, while the net P released at all times. This study also indicated that the changes of N and P content in the litter of the four flooding regimes were probably related to the C/N or C/P ratios in the litter and the N or P availability in the decomposition environment. If the nutrient status of the decomposition environment did not change greatly, the decomposition rates depended on the substrate quality indices of the litter. Conversely, if the nutrient status changed greatly, the decomposition rates might depend on the supply status of nutrient in the decomposition environment.