Submergence in the Dry Season Alters Microbial Nitrogen Transformations in the Root Zone of Carex cinerascens: A Mesocosm Study in One Floodplain Lake

Abstract

The increasing demand for water resources has triggered a series of water level regulation (WLR) projects, which exerts considerable effects on local hydrologic conditions. In particular, artificial impoundments, which may occur during the dry season in wetlands, increase the periods of waterlogging. However, little is known about their potential effects on biogeochemical cycling. To evaluate how impoundments affect nitrogen (N) cycling in the floodplain ecosystem, we conducted a mesocosm experiment to investigate N dynamics and the potential N-gene changes in the root-zone soil of the dominant plant in one large floodplain lake (Poyang Lake, China). The results indicated that, compared with the control, the 12 cm submergence treatment (SP 12 ) caused NH 4 + -N accumulation in the root-zone soil on day 14 and day 41. On the contrary, NO 3 − -N levels in SP 12 were statistically lower than those in the control from day 7 to day 28. The curve of organic N had a tendency of declining as a whole. Changes in N-gene abundances revealed that SP 12 significantly inhibited nitrification and enhanced denitrification in root-zone soil. Moreover, SP 12 enhanced the links and complexity of the N-gene network, reflecting the increased correlations among the N transformations under flooding stress. Considering the increasing demand for WLR worldwide, the study about the effects of anti-seasonal submergence on biogeochemical cycling in floodplains provides insight into the ecological impacts of anthropogenic activities. Supplementary Information The online version contains supplementary material available at 10.1007/s13157-022-01656-1.