三江平原寒地稻田CH_4、N_2O排放特征及排放量估算

利用静态暗箱-气相色谱法,于2003-2006年对三江平原寒地稻田CH4、N2O通量进行了为期4年的田间原位观测研究.结果表明:三江平原寒地稻田CH4和N2O排放具有明显的季节变化,水稻生长季淹水期是CH4排放的强源,稻田排水后CH4排放显著下降,休闲期CH4排放微弱或呈弱吸收汇,整个生长季CH4排放呈现单峰型态,并随水稻植株生长和叶面积指数而变化;水稻生长季和休闲期N2O排放通量都很小,冬季休闲期有时还出现微弱的吸收现象.生长季一般在施肥和表土落干时都会出现不同强度的排放峰,除了几次比较显著的排放峰值外,其它淹水状态下N2O排放很弱;温度和土壤水分状况是影响稻田CH4和N2O排放的重要因子,稻田积水深度和气体排放无明显的相关性;水稻植株对稻田土壤CH4排放起促进作用而对稻田土壤N2O排放起抑制作用;稻田氮肥用量增加可以降低土壤CH4排放,但却增加了N2O的排放.根据试验数据对三江平原地区寒地稻田CH4和N2O排放总量估算值分别为0.1035 Tg/a和0.0021 Tg/a.

Characteristics and estimation of CH_4,N_2O emissions fromcold paddy field in the Sanjiang Plain

CH4and N2O emissions from the cold paddy field were measured with static-closed-chamber and GC(Aglient 4890) by the continuous experiments in the Sanjiang Plain in Heilongjiang Province in Northeast China from 2003 to2006,the characteristics of CH4and N2O emissions from the paddy field were defined,and the main influence factorsthat the paddy field CH4and N2O discharges were analyzed at the same time.The results show that it has obviouscharacteristicsof seasonalvariationsthatthe paddyfield CH4 andN2O are discharged,itisstrong CH4source duringthewaterlogging period of rice paddy,CH4 flux drops notably until paddy field drains off water,and CH4 flux is faint orweak to absorb in whole fallow period.Unimodal type of CH4 emission changed with the changes of rice plant growthsand leaf area index.N2O emission is very small because the rice pours water continuouslywhile growing,and the weakabsorption phenomenon appears sometimes at temperature drops and in cover of ice and snow while lying fallow at thesame time.It generally appears N2O discharge peak after using the base manure and topdressing,and it always presentsdischarging weak peaks when the water level declines during the growing period.Temperature and moisture are two ofthe important factors to influence paddy field CH4 and N2O emissions,but the water depth and gas fluxes do not haveobvious relevance.The rice plant influences the gas fluxes greatly.The CH4 emission is promoted and N2O emission isreduced because of the absorption of nitrogen and impact on soil structure of roots of the rice plant;During in growingseason,it influences and differs greatly the paddy field CH4 emission to use the nitrogen,but promotes the emission ofN2O greatly.According to the emission rates of CH4,N2O and the area of the paddy field in Sanjiang Plain,the total amounts of emissions of CH4,N2O were estimated and they were 0.1035 Tg/a and 0.0021 Tg/a,respectively.