祁连山北坡3个季节性牧场夏季的土壤呼吸

摘要

To facilitate the management of carbon sink,soil respiration and factors affecting it were measured and analysed in summer pasture,winter pasture,and spring-autumn pasture on the northern slope of Qilian Mountains in summer.Daily soil respiration(Rs)was 0.24,0.19,and 0.26 μmol·(m2·s)-1 in the winter pasture,spring-autumn pasture,and summer pasture,respectively.With increase in stocking rate,Rs decreased in winter pasture,whereas that in the spring-autumn pasture and summer pasture revealed the opposite trend.In winter pasture,Rs was significantly positively correlated with soil moisture(SM)and significantly negatively correlated with stocking rate(SR)and soil temperature(Ts)(P<0.05).However,in spring-autumn pasture,Rs was significantly positively correlated with SR,photosynthetically available radiation(PAR),and SM(P<0.05),but significantly negatively correlated with soil temperature(Ts)and community coverage(C)(P<0.05).A structural model revealed that the indirect negative effect of SR by Ts on Rs was higher than the direct positive effect of SM in winter pasture.The direct negative effect of C on Rs was higher than the direct positive effect of SR in spring-autumn pasture.In winter pasture,Rs can be estimated better by Ts and SM,Rs=0.436-0.012ST+0.018SM(R2=0.775,P=0.037).In spring-autumn pasture,Rs can be estimated better by PAR and C,Rs=-0.239+0.003PAR-0.001C(R2=0.979,P=0.004).%以祁连山北坡高寒灌丛化草甸和高寒草原为对象,测定比较夏季、冬季和春秋季牧场的夏季土壤呼吸特征及与其影响因素之间的关系,为牧场碳汇管理提供依据.以高山灌丛化草甸为主的夏季牧场日均土壤呼吸速率(Rs)为0.26 μmol·(m2·s)-1,以高寒草原为主的冬季和春秋季牧场日均Rs分别为0.24和0.19 μmol·(m2·s)-1.随放牧增强,冬季牧场Rs减小,春秋季和夏季牧场Rs增加.冬季牧场Rs与土壤含水量(soil mosture,SM)显著正相关(P<0.05),Rs与放牧率(stocking rate,SR)和土壤温度(soil temperature,Ts)显著负相关(P<0.05);春秋季牧场Rs与SR、光合有效辐射(photosynthetically awailable radiation,PAR)、Ts显著正相关(P<0.05);春秋季牧场Rs与SM和群落盖度(community coverage,C)显著负相关(P<0.05).结构模型方程表明,冬季牧场放牧率通过Ts对Rs的负向间接作用最强,SM对Rs正向的直接作用次之;春秋季牧场群落盖度对Rs负向直接作用最大,放牧率对Rs正向的直接作用次之.冬季牧场Rs可分别由Rs=0.436-0.012Ts+0.018SM(R2=0.911,P=0.038)和Rs=0.707+0.002SR-0.02Ts(R2=0.775,P=0.037) 估测;春秋季牧场可由Rs=-0.239+0.003PAR-0.001C(R2=0.979,P=0.004)估测.