Effects Of Extreme Drought Stress On Soil Respiration In Typical Steppe Of Different Degradation Degrees In Inner Mongolia

Climate models predict that global warming will lead to a surge in the frequency of extreme weather events.At the same time,under the joint action of extreme climate and human activities,grassland degradation area in China is increasing and the degradation degree is becoming more and more serious.The occurrence of extreme climate events has a potential and profound impact on biological processes from individual to ecosystem level.Soil respiration,as the second largest carbon sink in terrestrial ecosystems,is an important part of the carbon cycle closely related to climate change.It plays a crucial role in regulating atmospheric CO₂ concentration and climate dynamics,and is particularly sensitive to changes in water availability.In this study,the typical steppe in Inner Mongolia was selected as the research object,and three steppe with different degradation levels were used as the platform to study the changes of soil respiration in different degraded steppe under the stress of extreme drought events.The findings:1.Under extreme drought stress,soil respiration and its components had significant seasonal dynamics.The degree of grassland degradation also significantly affected the response of soil respiration to drought,indicating that soil autotrophic respiration in severely degraded grassland was significantly lower than that in moderately degraded grassland and non-degraded grassland during the growing season.Soil water content significantly affected the response of soil respiration to extreme drought,and soil water content in severely degraded grassland was significantly lower than that in moderately degraded grassland and non-degraded grassland.2.Different components of soil respiration were also significantly affected by extreme drought in the middle period,which significantly reduced soil autotrophic respiration and heterotrophic respiration in the growing season.Soil respiration and its components decreased significantly during the period of medium extreme drought.This was consistent with the significant effects of extreme drought on soil water content in the severely degraded grassland.In the middle extreme drought,soil water content in the growing season was significantly lower than that in the early and late periods and without drought treatment.At the same time,extreme drought in middle and late periods will significantly reduce soil water content during the treatment period.3.Soil respiration and its components had a significant positive correlation with soil water content,but a significant negative correlation with underground net primary productivity.These results will provide a basis for future research on soil carbon cycle in typical steppe of Inner Mongolia.In conclusion,extreme drought in growing season significantly reduced the rates of soil respiration components in typical steppe of Inner Mongolia,and its sensitivity to middle extreme drought was significantly higher than that of early extreme drought and late extreme drought.After early and middle extreme drought treatments,soil water content at the end of the growing season could be restored to the control level,but not to the control level after late extreme drought treatments.At the end of the growing season,the rates of all components of soil respiration after different periods of extreme drought treatment could recover to the control level.The effects of extreme drought on soil autotrophic respiration rate were higher than that of total respiration and heterotrophic respiration.