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

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 533.7 mu g m(-2) h(-1) and the CO2 fluxes were between 10.6 and 1374.1 mg m(-2) h(-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 (DC), 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. (C) 2012 Elsevier Ltd. All rights reserved.

海洋生态系统是已知的温室气体排放净源，但大气气体通量，特别是来自潮间带红树林沼泽的气体通量，特征尚不明确。对中国香港米埔红树林沼泽土壤中氧化亚氮（N₂O）和二氧化碳（CO₂）的空间和季节通量及其与土壤特性的关系进行了研究。N₂O通量平均为32.1至533.7微克每平方米每小时，CO₂通量在10.6至1374.1毫克每平方米每小时之间。该沼泽中的N₂O和CO₂通量均显示出较大的空间和季节变化。向陆一侧的通量高于前滨裸滩，且在温暖季节的通量高于寒冷季节。向陆一侧的土壤有机碳（DC）、凯氏氮总量（TKN）、硝酸盐（NO₃⁻ -N）和总磷（TP）含量最高，而裸滩的铵态氮（NH₄⁺ -N）浓度和土壤反硝化潜在活性最高。N₂O通量与CO₂通量呈正相关。土壤NO₃⁻ -N和TP增加了N₂O通量，而土壤有机碳和TP浓度对CO₂通量有贡献。结果表明，米埔红树林沼泽排放了大量温室气体，N₂O排放可能是由于土壤反硝化作用。（C）2012爱思唯尔有限公司。保留所有权利。