氮沉降促进西北干旱区高寒湿地生态系统N_(2)O排放

Nitrogen deposition increases N_(2)O emission in an alpine wetland in the arid region of Northwest China

在气候变化背景下,大气氮沉降的增加会对干旱区高寒湿地N_(2)O排放产生影响。以天山中部的巴音布鲁克天鹅湖高寒湿地,不同水分条件的常年淹水区、季节性淹水区和常年干燥区为研究区,设置3个氮添加量处理(0、10 kg·hm^(−2)·a^(−1)和20 kg·hm^(−2)·a^(−1)),采用静态箱-气相色谱法监测了植物生长季生态系统N_(2)O的排放量,并探究了N_(2)O排放与主要环境因子之间的关系。研究结果表明:(1)在不同水分条件下,氮素增加显著促进了生态系统N_(2)O的排放(P<0.05);在植物生长季不增氮的处理下,生态系统N_(2)O累积排放量表现为吸收,10 kg·hm^(−2)·a^(−1)和20 kg·hm^(−2)·a^(−1)处理N_(2)O累积排放量均表现为排放;氮沉降量增加显著增加了不同水分条件下N_(2)O累积排放量,氮沉降增加会促进湿地生态系统由N_(2)O的“汇”向“源”转变。(2)氮施加量极显著影响生态系统N_(2)O排放速率(P<0.01),季节性淹水条件生态系统N_(2)O平均排放速率(F)与施氮量(N)、土壤5 cm地温(T)呈多元一次方程关系(F=-2.763+0.209N+0.151T,R^(2)=0.483,P<0.01)。综上所述,氮沉降的增加促进了干旱区高寒湿地生态系统N_(2)O排放。

With the basis of climate change,nitrogen deposition will have an impact on N_(2)O emissions between the soil and atmosphere in the alpine wetland in the arid region of Northwest China.Taking the alpine wetland at Swan Lake of Bayinbuluke in the middle of Tianshan Mountain as a study area,three nitrogen addition treatments(0,10,and 20 kg·hm^(−2)·a^(−1))were set in different water conditions(perennial seeper area,seasonal water area,and perennial dry area).The measurement of N_(2)O was made via static chamber-gas chromatography during the growing season.The relationship between N_(2)O emissions and main environmental factors was explored.The results showed that the following:(1)increased N significantly contributed to N_(2)O emissions under different water conditions in the alpine wetland ecosystem(P<0.05).Under 0 kg·hm^(−2)·a^(−1)treatment,the N_(2)O accumulation showed an uptake from the ecosystem with the growing season.Under 10 and 20 kg·hm^(−2)·a^(−1)treatments,the N_(2)O accumulation were emitted.The cumulative N_(2)O emissions increased significantly when nitrogen deposition increased in different water conditions.Increased nitrogen deposition influenced the wetland ecosystem from N_(2)O to sink to the N_(2)O source.(2)nitrogen application significantly affected the rate of N_(2)O emissions from the ecosystem(P<0.01).In seasonal water area,the relationship between the average N_(2)O emission rate(F),nitrogen addition(N),and soil temperature(T)at a depth of 5 cm was in accordance with the multiple first-order equation(F=−2.763+0.209N+0.151T,R^(2)=0.483,P<0.01).Therefore,N deposition increases N_(2)O emissions in the alpine wetland in the arid region of Northwest China.