Effects Of Litter Addition And Different Precipitation Gradient On Soil Respiration In Horqin Sandy Grassland

Grassland ecosystems in arid and semi-arid regions are an important part of terrestrial ecosystems and one of the most vulnerable ecosystem types.The main loss pathway for soil carbon in this region is soil respiration.Studying the effects of various environmental factors on soil respiration helps to grasp the laws of soil respiration under different factors.Nowadays,under the accumulation of human behavior and industrial activities,the ecosystems in arid and semi-arid regions have been severely damaged,facing global challenges such as carbon loss,changing precipitation patterns and climate warming.Therefore,the effects of litter addition and soil respiration of different artificial precipitation gradient arid-semi-arid grassland ecosystems have a positive effect on the exploration of soil ecosystem material circulation,carbon cycle prediction and degraded grassland protection.Based on the Naiman Desertification Research Station of the Chinese Academy of Sciences,this study selected a sandy grassland without a fertilization and nitrogen treatment in the test site of the station.The field-based soil respiration observation experiment was carried out based on the combination of two litter additions and five precipitation gradients.According to the precipitation law in the region,the single precipitation is set to 3mm,6mm,12 mm,24mm,45 mm,and the precipitation frequency is 2 days,4 days,8 days,16 days,30 days.At the same time,two kinds of litter were added,which were the leguminous plant Caragana microphylla and the Gramineae plant.Through five different frequency precipitation controls at the end of spring(May)and the summer(July),the study was carried out on different respiratory substrates.The results are as follows:(1)The total soil respiration,microbial respiration and root respiration of Horqin sandy grassland peaked after artificial precipitation.The peak phenomenon in May appeared in the middle of the experiment,and the peak phenomenon in July appeared in the early stage of the experiment.(2)Different artificial precipitation gradients significantly affect the dynamic changes of soil respiration,microbial respiration and root respiration rate.The precipitation gradient of 3mm/2d makes the soil under constant humidity conditions,and the average value of soil respiration rate is the largest;the precipitation gradient of 45mm/30 d makes the soil relatively dry and the average value of soil respiration rate is the smallest.Different artificial precipitation gradients also had significant effects on microbial respiration and root respiration rate: in the dynamic monitoring in May and July,the microbial respiration increased by 93.45% and 25.95% in the3mm/2d precipitation gradient compared to the 45mm/30 d precipitation gradient.The rate increased by 10.82% and 29.17%.(3)The addition of respiratory substrate significantly affected soil respiration(p< 0.001),microbial respiration(p < 0.001),and root respiration rate(p < 0.001).After the addition of litter,the fluctuation of soil respiration rate was more severe due to the intervention of artificial precipitation.The organic matter released by the genus Caragana under the action of precipitation was larger than that of the Gramineae plant,so the litter of Caragana microphylla was added.The treated respiration rate value is much larger than the clinch grass litter addition treatment.Microbial respiration and root respiration rate values also follow this rule and are greater than the blank value.(4)Litter addition and proper moisture input are beneficial to increase soil respiration rate.In this study,artificial precipitation of 6mm/4d and 12mm/8d was carried out on the basis of the addition of litter of Caragana microphylla,which was the most favorable for soil respiration.However,the growth of soil respiration needs to be dialectically treated,although its increase means an increase in soil biological activity and metabolism,but it may also result in loss of soil carbon.Therefore,the relationship between the amount of litter added to soil carbon and the increase in carbon emissions caused by soil respiration under this addition needs further investigation.In summary,the addition of Caragana microphylla and Gramineae in this study can effectively increase the supply of soil respiration substrate,increase soil microbial biomass,and significantly increase soil respiration rate.A small number of artificial precipitation patterns,such as 3mm/2d,6mm/4d,are more conducive to soil respiration rate.The leguminous plant Caragana microphylla has a faster decomposition rate,which is beneficial to the increase of soil organic matter.Theaverage soil respiration rate under the litter addition treatment is greater than that of the clinch grass litter.Litter addition did not change the floating trend of soil respiration,indicating that although litter addition can significantly promote soil respiration,it does not change the law of soil respiration.The mean soil respiration rate in July was greater than the mean soil respiration rate in May,most likely due to temperature differences.The research results can provide a theoretical basis for soil respiration carbon cycle research and arid-semi-arid grassland ecosystem protection in Horqin Sandy Land.