Soil respiration in three types of seasonal pastures in summer on the northern slope of Qilian Mountains

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).