Nitrogen cycling of atmosphere-plant-soil system in the typical Calamagrostis angustifolia wetland in the Sanjiang Plain, Northeast China

The nitrogen (N) distribution and cycling of atmosphere-plant-soil system in the typical meadow Calamagrostis angustifolia wetland (TMCW) and marsh meadow Calamagrostis angustifolia wetland (MMCW) in the Sanjiang plain were studied by a compartment model. The results showed that the N wet deposition amount was 0.757 gN/(m2 x a), and total inorganic N (TIN) was the main body (0.640 gN/(m2 x a). The ammonia volatilization amounts of TMCW and MMCW soils in growing season were 0.635 and 0.687 gN/m2, and the denitrification gaseous lost amounts were 0.617 and 0.405 gN/m2, respectively. In plant subsystem, the N was mainly stored in root and litter. Soil organic N was the main N storage of the two plant-soil systems and the proportions of it were 93.98% and 92.16%, respectively. The calculation results of N turnovers among compartments of TMCW and MMCW showed that the uptake amounts of root were 23.02 and 28.18 gN/(m2 x a) and the values of aboveground were 11.31 and 6.08 gN/(m2 x a), the re-translocation amounts from aboveground to root were 5.96 and 2.70 gN/(m2 x a), the translocation amounts from aboveground living body to litter were 5.35 and 3.38 gN/(m2 x a), the translocation amounts from litter to soil were larger than 1.55 and 3.01 gN/(m2 x a), the translocation amounts from root to soil were 14.90 and 13.17 gN/(m2 x a), and the soil (0-15 cm) N net mineralization amounts were 1.94 and 0.55 gN/(m2 x a), respectively. The study of N balance indicated that the two plant-soil systems might be situated in the status of lacking N, and the status might induce the degradation of C. angustifolia wetland.