Asymmetrical warming of growing/non-growing season increases soil respiration during growing season in an alpine meadow

Abstract

Soil respiration (R_s) is an important carbon flux in the global carbon cycle, and understanding the influence of global warming on R_s is critical for precise prediction future climate change. Actually, global warming is expected to be seasonally asymmetric, however, it is still unclear on the response of R_s to asymmetrical warming of growing/non-growing season in alpine regions. In this study, an experiment with asymmetrical warming of growing/non-growing season (including three treatments, CK: control; GLNG: warming magnitude of growing season lower than non-growing season; GHNG: warming magnitude of growing season higher than non-growing season) was performed in an alpine meadow of the Northern Tibet since June 2015. The 'GLNG' and 'GHNG' treatments increased mean R_s by 71.22% (1.89 μmol CO₂ m^-2 s^-1) and 34.32% (0.91 μmol CO₂ m^-2 s^-1) during growing season in 2019, respectively. However, the 'GLNG' and 'GHNG' treatments did not significantly affect mean R_s during growing season in 2015, 2016, 2017 and 2018, respectively. The variation coefficient of growing season mean R_s was 32.95% under the CK treatment in 2015-2019. Therefore, warming may have a lagging effect on R_s. The warming scene with a greater warming during non-growing season may have a stronger effect on R_s than the warming scene with a greater warming during growing season. Inter-annual variation of R_s may be greater than the warming effect on R_s in alpine meadows.

Keywords: Aboveground biomass; Alpine grasslands; Asymmetric warming; Increased temperature; Phenological changes; Soil respiration.