Heat waves (HWs), characterized by periods of unusually high temperature, would inevitably affect the soil microenvironment and then soil respiration (Rs), which is considered to be the most active part of the global carbon cycle. An in situ spring and summer HWs simulation experiment combined with a locally common human disturbance (mowing) was conducted to separate Rs into autotrophic respiration (Ra) and heterotrophic respiration (Rh) on a natural Eurasian meadow steppe in 2018 and 2019. HWs significantly affected grassland Rs, Rh and Ra (p < 0.01) and also interacted with mowing, but the effect of spring HW and summer HW were different. During the summer HWs, daily Rs of the non-mowed plots increased by 1.07 μmol m−2 s−1 (11.71%) and increased in the mowed plots by 2.15 μmol m−2 s−1 (23.81%). During the spring HWs, daily Rs of the non-mowed plots decreased by 0.13 μmol m−2 s−1 (2.36%) and decreased by 0.52 μmol m−2 s−1 (9.02%) in the mowed plots. Rs, Rh and Ra were inhibited by spring HWs, but promoted by summer HWs. Our results indicated that the occurring time change in HWs would cause widely divergent influences on the ecosystem, and mowing would decrease the anti-interference ability of the ecosystem, which acted as an enhancement on both the positive and negative effects of HWs. These findings have important implications for accurate model prediction and carbon budget assessment.
Shao et al. (Tue,) studied this question.