Asymmetric effect of increased and decreased precipitation in different periods on soil and heterotrophic respiration in a semiarid grassland

Climate models predict significant changes in precipitation magnitude and timing in semi-arid grasslands, where soil carbon release is particularly sensitive to changing precipitation. Using data from a 4-year (2015-2018) field manipulation experiment, we explored effects of changed precipitation in different periods on soil respiration (SR) and heterotrophic respiration (HR) in a semi-arid grassland in northern China. The results showed that: (1) Decreased precipitation both in the early (DEP), late (DLP), and entire growing season (DP) reduced SR, whereas DP and DLP rather than DEP reduced HR. The declines of SR in DLP and DP are larger than in DEP; (2) Increased precipitation in the early (IEP), late (ILP), and entire (IP) growing season promoted SR, but had little effect on HR. Enhancement of SR in IEP is larger than in ILP; (3) The change of SR and HR can be attributed to varied plant community cover which is related to soil water content; and (4) SR and HR are more sensitive to decreased than to increased precipitation, to DLP than DEP, and IEP than ILP. The findings suggest an asymmetric response of soil carbon process to precipitation in different periods, highlighting that future study should not neglect the role of precipitation timing in regulating ecosystem carbon fluxes.