人为干扰对闽江河口短叶茳芏湿地N_2O排放的影响

Effects of human-caused disturbance on nitrous oxide flux from Cyperus malaccensis marsh in the Minjiang River estuary

采用静态箱-气相色谱法和浮箱-气相色谱法,分别对闽江河口潮间带短叶茳芏(Cyperus malaccensis var.brevifolius)湿地、互花米草(Spartina alterniflora Loisel)入侵斑块湿地、输入养分的短叶茳芏湿地和踩踏形成的裸露湿地N2O通量进行测定,以研究不同的人为干扰方式对短叶茳芏湿地N2O通量的影响.结果表明:互花米草入侵斑块N2O通量[15.37μg/(m2.h)]低于短叶茳芏湿地[18.77μg/(m2.h)],互花米草入侵降低了短叶茳芏湿地的N2O排放,互花米草入侵的减排作用与潮汐关系密切,而与植物生长季节关系不明显;养分输入显著增加了短叶茳芏湿地N2O排放.秋季,养分输入后,短叶茳芏湿地N2O排放平均值为163.72μg/(m2.h),春季,养分输入后,高潮淹水时和高潮无淹水时,短叶茳芏湿地N2O排放平均值分别为227.62μg/(m2.h)和1178.64μg/(m2.h),极显著高于对照,高潮淹水时N2O排放峰值出现较高潮无淹水时早,N2O通量远低于高潮无淹水时;踩踏形成的裸露湿地N2O平均通量为-0.76μg/(m2.h),表明踩踏降低了短叶茳芏湿地N2O通量,但降低程度因植物的生长季节和潮汐环境的差异而不同.

N2O fluxes from the Cyperus malaccensis var.brevifolius marsh were measured using enclosed dark static chamber and float chamber technique during three periods（before flood,in course of flooding and ebbing,and after ebb）,and N2O fluxes from the invasive Spartina alterniflora Loisel marsh,C.malaccensis marsh added nutrient and bare marsh treaded by peoples were also determined before flood and after ebb in the intertidal zones Minjiang River estuary.The results showed that N2O fluxes from invasive S.alterniflora marsh and C.malaccensis marsh were 15.37μg/（m2？h） and 18.77μg/（m2？h）,respectively,S.alterniflora invasion decreased N2O fluxes from C.malaccensis marsh,and the reduction effect on N2O fluxes from C.malaccensis marsh related closely to tide,and not to seasonal variation.N2O fluxes from C.malaccensis marsh increased after adding nutrient.The average N2O flux was 163.72μg/（m2？h） after adding the nutrient in autumn,and were 227.62μg/（m2？h） and 1178.64μg/（m2？h） in submerged and exposed periods in C.malaccensis marsh at high tide dates in spring,respectively.The peak of N2O emission occurred earlier during tidal inundation period.Average N2O flux was-0.76μg/（m2？h） from bare marsh,which suggested that N2O fluxes from C.malaccensis marsh was decreased by tread,and the reducing range was relevant to seasons and changes of environment factors resulting from flood and ebb.