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Spatial and seasonal variations of atmospheric N₂O and CO₂ fluxes from a subtropical mangrove swamp and their relationships with soil characteristics

Chen, Guang C., Tam, Nora F.Y., Ye, Yong
Soil biology & biochemistry 2012 v.48 pp. 175-181
ammonium nitrogen, carbon dioxide, denitrification, ecosystems, greenhouse gas emissions, greenhouse gases, mangrove swamps, nitrates, nitrous oxide, phosphorus, seasonal variation, soil organic carbon, swamp soils, China
Marine ecosystems are a known net source of greenhouse gases emissions but the atmospheric gas fluxes, particularly from the mangrove swamps occupying inter-tidal zones, are characterized poorly. Spatial and seasonal fluxes of nitrous oxide (N₂O) and carbon dioxide (CO₂) from soil in Mai Po mangrove swamp in Hong Kong, South China and their relationships with soil characteristics were investigated. The N₂O fluxes averaged from 32.1 to 533.7μgm⁻²h⁻¹ and the CO₂ fluxes were between 10.6 and 1374.1mgm⁻²h⁻¹. Both N₂O and CO₂ fluxes in this swamp showed large spatial and seasonal variations. The fluxes were higher at the landward site than the foreshore bare mudflat, and higher fluxes were recorded in warm, rather than cold, seasons. The landward site had the highest content of soil organic carbon (OC), total Kjeldahl nitrogen (TKN), nitrate (NO₃ ⁻–N) and total phosphorus (TP), while the bare mudflat had the highest ammonium nitrogen (NH₄ ⁺–N) concentration and soil denitrification potential activity. The N₂O flux was related, positively, to CO₂ flux. Soil NO₃ ⁻–N and TP increased N₂O flux, while soil OC and TP concentrations contributed to the CO₂ flux. The results indicated that the Mai Po mangrove swamp emitted significant amounts of greenhouse gases, and the N₂O emission was probably due to soil denitrifcation.