Extreme wet precipitation and mowing stimulate soil respiration in the Eurasian meadow steppe

The imbalance of terrestrial carbon (C) inputs versus losses to extreme precipitation can have consequences for ecosystem carbon balances. However, the current understanding of how ecosystem processes will respond to predicted extreme dry and wet years is limited. The current study was conducted for three years field experiment to examine the effects of environmental variables and soil microbes on soil respiration (Rs), autotrophic respiration (Ra) and heterotrophic respiration (Rh) under extreme wet and dry conditions in mowed and unmowed grassland of Inner Mongolia. Across treatments (i.e. control, dry spring, wet spring, dry summer and wet summer), the mean of Rs was increased by 24.9 % and 24.1 % in the wet spring and wet summer precipitation treatments, respectively in mowed grassland. In other hand, the mean of Rs was decreased by -22.1 % and -3.5 % in dry spring and dry summer precipitation treatments, respectively in mowed grassland. The relative contribution of Rh and Ra to Rs showed a significant (p < 0.05) change among simulated precipitation treatments with the highest value (76.18 %) in wet summer and 26.41 % in dry summer, respectively under mowed grassland. Rs was significantly (p < 0.05) affected by the interactive effect of extreme precipitation and mowing treatments in 2020 and 2021. The effects of precipitation change via these biotic and abiotic factors explained by 52 % and 81 % in Ra and Rh, respectively in mowed grassland. The changes in microbial biomass carbon (MBC) and nitrogen (MBN) had significant (p < 0.05) direct effects on Rh in both mowed and unmowed grasslands. The influence of biotic and abiotic factors on Rs was stronger in mowed grass-lands with higher standardized regression weights than in unmowed grassland (0.78 vs. 0.69). These findings high-light the importance of incorporating extreme precipitation events and mowing in regulating the responses of C cycling to global change in the semiarid Eurasian meadow steppe.

Automated summary

The study conducted a three-year field experiment in Inner Mongolia to examine the effects of environmental variables and soil microbes on soil respiration under extreme wet and dry conditions in mowed and unmowed grassland. The results showed that the relative contribution of heterotrophic respiration and autotrophic respiration to soil respiration varied under different precipitation treatments. The study also highlighted the importance of incorporating extreme precipitation events and mowing in regulating the responses of carbon cycling to global change in the semiarid Eurasian meadow steppe.