Effects Of Typical Plant Litter On Soil Respiration In Desert Steppe Under Nitrogen Addition And Precipitation Change

Nitrogen deposition and changes in precipitation patterns are important phenomenon in global climate change,and desert grasslands in arid and semi-arid regions are fragile ecosystem types that are highly susceptible to water and nitrogen limitation,with dead litter on their soil surface acting as a major source of input to the soil carbon pool.In addition,soil respiration,as a key process for terrestrial ecosystems to release CO2 into the atmosphere,is an important link in the ecosystem carbon cycle.Therefore,it is important to study the contribution of litter to soil respiration to understand the role of litter in the process of material cycling and energy flow between plants and soil.In this paper,four species of desert grassland plants(Stipa breviflora,Agropyron mongolicum,Sophora alopecuroides and Artemisia scoparia)were selected to study their litter through nitrogen addition(nitrogen addition,no nitrogen addition)and precipitation change(increasing rainfall by 30%,normal and decreasing rainfall by 30%).The soil respiration(soil respiration with litter,soil respiration with litter removed,litter respiration)was measured under different treatments,and the characteristics of soil respiration,litter respiration and carbon emission were analyzed to reveal the response of desert grassland soil respiration to nitrogen addition and precipitation changes and the main factors affecting respiration changes,and to further contribute to the carbon balance of desert grassland ecosystems under global change.This study provides scientific basis and data support for modelling the carbon balance of desert grassland ecosystems under global change.The results of the study show that.(1)The daily dynamics of soil respiration showed an obvious single-peak curve variation pattern,reaching a maximum value at 12:00-16:00;and a minimum value at 2:00-6:00.The maximum value of soil respiration rate was 0.99 μmol·m2·s-1,and the minimum value was-0.22 μmol·m-2·s-1.The soil respiration rate of different deadfall surfaces showed that short-flowered Stipa breviflora>Agropyron mongolicum>Artemisia scoparia>Sophora alopecuroides>Blank control.(2)The seasonal dynamics of soil temperature and humidity and soil respiration varied significantly,with similar trends,and the changes in soil respiration between treatments were summer>spring>autumn>winter.The difference in soil respiration between treatments was significant(P<0.05),and the contribution of litter to soil respiration was up to 49.10%.Soil respiration was promoted by rainfall addition and nitrogen addition(RS+L,RS,RL),while rainfall addition reduced the contribution of nitrogen addition to soil respiration(RS+L,RS,RL),and rainfall reduction enhanced the contribution of nitrogen addition to litter respiration(RL).The accumulation of soil carbon emissions showed the highest in summer and the lowest in winter,with mean values of soil carbon emissions reaching 126.37 g·m-2.(3)The differences in soil microbial load,microbial entropy and microbial community between the different deadfall surfaces under nitrogen addition and rainfall changes were significant(P<0.05).The rainfall treatment weakened the promoting effect of nitrogen on soil microbial load nitrogen and soil microbial nitrogen entropy;the rainfall addition treatment reduced the content of soil bacteria,actinomycetes and protozoa and increased the content of soil fungi;the rainfall reduction treatment increased the content of soil microorganisms The rainfall augmentation treatment significantly enhanced the contribution of nitrogen addition to the microbial community.(4)Soil respiration showed a highly significant exponential function with 0-10cm(P<0.001),which could explain 49.1%of the variation in respiration rate,while the temperature sensitivity index was up to 1.65.soil microbial mass carbon and soil microbial carbon entropy showed a significant correlation with soil respiration(P<0.05).Soil carbon(SOC,MBC)was the main factor influencing the change in soil respiration with litter(RS+L),soil hydrothermal factor and soil carbon were the main factors influencing the change in soil respiration with litter removal(Rs),soil carbon and soil microorganisms were the main factors influencing the change of litter respiration(RL).The results show that the response of soil respiration to N addition and precipitation changes differed among different litter surfaces,and to a certain extent rainfall addition and N addition promoted soil respiration and rainfall reduction suppressed litter respiration;soil temperature and soil carbon were the key factors affecting respiration changes.However,the interaction between litter decomposition,N addition and precipitation changes is a long process that needs to be explored in more depth through subsequent long-term observations.