Short-term effects of nitrogen deposition on nitrogen spatial and temporal distributions in a Calamagrostis angustifolia wetland of the Sanjiang Plain

Nitrogen (N) availability is an important factor regulating the feedback mechanisms of global change. This research uses a small Calamagrostis angustifolia wetland i = on the Sanjiang Plain of Northeast China as the research object and (15)N tracer technology to study the effects of different nitrogen deposition levels (0 gN/m(2), 4 gN/m(2), and 8 gN/m(2)) through in situ controlled field experiments. Temporal and spatial distribution patterns of nitrogen in plants and soils and their short-term effects on nitrous oxide emissions fluxes were studied. The results showed that 1) the nitrogen content in the stems, leaves and roots of C. angustifolia decreased slowly with the growing season. Nitrogen application significantly increased the absorption of tracer nitrogen in the aboveground and underground plant parts (P<0.01), and the more nitrogen applied, the larger the absorption amount was (P<0.01). The absorbed amount accounted for 52%-86% of the total tracer nitrogen. 2) The tracer nitrogen in the soil did not show a significant change; the more nitrogen that was applied, the more nitrogen that was retained in the soil, and the tracer nitrogen adsorbed by the soil was mainly ammonium nitrogen. 3) The variation in the (15)N-labeled nitric oxide emissions flux under different nitrogen treatments was consistent; nitrogen application increased the (15)N-labeled nitric oxide emissions flux, but the difference between the low-nitrogen and high-nitrogen treatments was not significant (P>0.05).