Responses Of Soil Respiration To Extreme Precipitation Under Simulation Experiment

More than one third of the surface of the land is composed of arid and semi-arid ecosystems,and precipitation is a key factor in regulating moisture and carbon balance in the region.Soil respiration is an important part of the terrestrial ecosystem carbon cycle and is the largest component of terrestrial ecosystems and atmospheric carbon exchange.Understanding the extent and characteristics of soil respiration to extreme precipitation in arid and semi-arid areas will help us deeply understand the impact of climate change on the global carbon cycle in this region.In this study,several simulated experiment was conducted on bare loess soil from the semi-arid Chinese Loess Plateau.The main research was as follows:1)Three precipitation regimes with total precipitation amounts of 150 mm,300 mm and 600 mm were carried out to simulate the extremely dry,business as usual,and extremely wet summer.The three regimes were individually materialized by wetting soils in a series of sub-events?10 mm or 150 mm?over equal time intervals.Soil temperature,soil moisture and CO₂ emissions from surface soil were continuously measured in-situ for one month.2)Two precipitation regimes with total precipitation amounts of 300 mm and 600 mm were carried out to simulate business as usual,and the extremely wet summer.The responses of soil microbial respiration to precipitation and their differences were investigated by adding nitrogen,straw and both of them on soil microbial respiration.Main results were as follows:?1?Extreme precipitation events significantly affected the dynamics of soil microbial respiration rate and soil cumulative respiration.Fluctuation range of soil microbial respiration rate under P150 was higher than that under P10.The cumulative respiration rate under different precipitation regimes showed a trend of 600 mm> 300 mm> 150 mm.Soil cumulative respiration showed P10> P150 trend under 600 mm total precipitation amount,and it showed an opposite trend under 150 mm total precipitation amount.The duration of soil microbial respiration stress is an important factor in affecting soil microbial respiration.?2?Substrate addition significantly affected the dynamic response of soil microbial respiration and soil cumulative respiration to precipitation n.The fluctuation range of soil microbial respiration rate increased significantly after adding maize straw,especially under single precipitation event of 100 mm.The cumulative respiration raised with the increase of total precipitation?P10: 176 g·m-2 vs 299 g·m-2;P100: 305 g·m-2 vs 368 g·m-2?.However,under the same total precipitation amount,the cumulative respiration increased by 73% under the total precipitation of 300 mm?176 g·m-2 vs 305 g·m-2?,compared with that of 23% under 600 mm total precipitation amount?299 g·m-2 vs 368 g·m-2?.?3?There was no significant effect of nitrogen on the response of soil microbial respiration to precipitation.In this study,nitrogen had a slight inhibitory effect on soil microbial respiration,and which was canceled by the excitation effect of precipitation.The inhibitory effect of nitrogen on soil microbial respiration was slightly increased after adding straw,and the decrease of soil cumulative respiration under 300 mm total precipitation amount was higher than that under 600 mm total precipitation amount.Extreme precipitation events significantly affect soil CO₂ flux,soil nitrogen and substrate are important factors influencing the process.Under the background of climate change,the assessment of soil CO₂ flux in arid and semi-arid area should take change of precipitation patterns and the influence of soil properties into account.