浮萍对福州平原稻田CH4和N2O排放的影响分析

浮萍是稻田中常见的漂浮在水面的水生植物,具有固氮作用,但是,浮萍对稻田温室气体排放的影响尚不明确.以位于湿润亚热带的福州平原稻田为研究对象,探讨浮萍对该区域稻田CH4和N2O排放的影响,为科学评价、准确编制我国水稻田温室气体排放清单提供基础数据.研究结果表明,观测期内,有萍小区和无萍小区CH4排放范围分别为0.19～26.50 mg·m-2·h-1和1.02～28.02 mg·m-2·h-1,平均值分别为9.28 mg·m-2·h-1和11.66 mg·m-2·h-1,有萍小区CH4排放低于无萍小区(P＜0.01),有萍小区CH4排放高峰比无萍小区约提前1周,高峰期后排放迅速降低；有萍小区和无萍小区N2O排放范围分别为-50.11～201.82 μg·m-2·h-1和-28.93～54.42μg·m-2·h-1,平均值分别为40.29 μg·m-2·h-1和11.93 μg·m-2·h-1,有萍小区N2O排放高于无萍小区(P＜0.05).稻田排干后,N2O排放迅速上升,2个小区N2O排放呈现出相似的规律.有萍小区和无萍小区的CH4与N2O排放的影响因子有所不同.综合考虑CH4和N2O两种温室气体,CH4仍是稻田温室效应产生的主要贡献者,浮萍可降低位于沿海区域的福州平原稻田综合温室效应的17.3％.

Effect of azolla on CH4 and N2O emissions in Fuzhou Plain paddy fields

Azolla is a common aquatic fern that floats in paddy fields.It grows rapidly and has the ability to fix N2 into the soil.However,the effects of azolla growth on emissions of greenhouse gases are yet uncertain.This study measured CH4 and N2O emis-sions in two paddy fields in Fuzhou Plain,one with floating azolla and the other with non-floating azolla.The purpose of the study was to draw on the benefits of scientific evaluation of emissions of greenhouse gases in China’s paddy fields.The results showed that CH4 emissions were in the range of 0.19~26.50 mg·m-2·h-1 and 1.02~28.02 mg·m-2·h-1 and with average values of 9.28 mg·m-2·h-1 and 11.66 mg·m-2·h-1 in the azolla treatment and non-azolla treatment,respectively.CH4 emission in azolla plots was significantly lower than that in non-azolla plots at P < 0.01.Peak CH4 emission in azolla plots was early by about one week compared with non-azolla plots,after which period it decreased rapidly.N2O emissions were in the range of 50.11~201.82 μg·m-2·h-1 and 28.93~54.42 μg·m-2·h-1 with average values of 40.29 μg·m-2·h-1 and 11.93 μg·m-2·h-1 in azolla plots and non-azolla plots,respec-tively.N2O emission in azolla plots was significantly higher than that in non-azolla plots at P < 0.05.N2O emission increased rapidly after paddy fields drainage and both plots followed similar trends.Different driving factors of CH4 and N2O emissions were noted in azolla and non-azolla plots.A comprehensive consideration of CH4 and N2O greenhouse gases showed that CH4 was the key con-tributor to greenhouse effects in paddy fields.Azolla reduced integrated greenhouse effects by 17.3% in the humid sub-tropical Fuzhou Plain region.