Response Of Soil Respiration Of Typical Vegetations To Changing Carbon Input In Loess Hilly Region

Litter and roots regulate the input of organic carbon in the soil and participate in the process of soil respiration.Therefore,it’s of great significance to explore the effect of different carbon input methods on the soil respiration of the ecosystem.This study took Robinia pseudoacacia,Caragana intermedia plantations and typical Grassland as research objects in the Loess Hilly area.By setting up the No Litter（NL）,Double Litter（DL）,No Root（NR）,No Litter and Root（NI）and Check Plot（CK）treatments to study the effect of carbon input on the time dynamics of soil respiration.Analyze the relationship between soil respiration and environmental factors at different time scales in combination with factors such as soil physical and chemical properties,vegetation and meteorology.The results of the study are as follows:（1）The diurnal differences of soil respiration in the three vegetation types under different treatments fluctuated greatly,and the differences of soil respiration between C.korshinskii and Grassland were more obvious than that of R.pseudoacacia.Compared with the CK treatment,the soil respiration intensity of the DL treatment increased,while it decreased under other carbon input methods and the NI treatment had the largest decrease.The daily dynamics of soil respiration in C.korshinskii and Grassland showed an obvious single-peak curve.The soil respiration peaks of the three plants in the early growing season were mainly concentrated at 9:00-11:00 and the peak appeared later with time.（2）The monthly dynamics of soil respiration intensity in different treatments showed a single-peak curve,with the peak appeared in July or August and the lowest in the late growing season（October）.The monthly mean values of soil respiration in DL treatment were higher than in other treatments.Under the same treatment,R.pseudoacacia had the highest soil respiration intensity under NL,DL and NR treatments,while C.korshinskii and Grassland had the highest soil respiration intensity under CK and NI treatments,respectively.C.korshinskii plantation was not conducive to soil carbon emission reduction compared with other vegetations.（3）Vegetation types,carbon input methods,and months will all cause a high degree of variation in soil respiration intensity.The carbon input methods and months were the main causes of the difference in soil respiration,which interpret the variation of 27.47%and31.72%,respectively.Relatively,the soil respiration of C.korshinskii was more sensitive to NL than DL treatment,while the situation in Grassland was the opposite.The R.pseudoacacia was more sensitive to DL and NI treatments,and its soil respiration values were reduced by 25.17%and 32.38%,respectively.（4）Soil temperature（ST）had a strong positive effect on soil respiration with different carbon input methods（P<0.01）,while the impact of ST on soil respiration and Q₁₀ values on a monthly scale were lower than those on a daily scale.The Q₁₀ values of CK treatment were presented as:C.korshinskii（1.92 and 2.08）>R.pseudoacacia（1.69 and 1.63）>Grassland（1.63 and 1.34）,and the Q₁₀ values of DL treatment were R.pseudoacacia（1.85and 1.60）>C.korshinskii（1.73 and 1.48）>Grassland（1.57 and 1.23）.（5）On the daily scale,the soil respiration（Rs）of three vegetation types showed extremely significant positive correlations with air temperature（AT）and relative humidity（RH）（P<0.01）.The Rs of C.korshinskii were correlated with photosynthetically active radiation（PAR）（P<0.01）.On a monthly scale,the Rs of R.pseudoacacia and C.korshinskii were significantly correlated with soil moisture（SV）,and the leaf area index（LAI）was extremely significantly positively correlated with Rs of R.pseudoacacia（P<0.01）.The pH,0-10 cm fine root biomass（RB₁）,AT,PAR,and RH were extremely significantly correlated with the Rs of R.pseudoacacia and C.korshinskii（P<0.01）.（6）The contribution rates of mineral soil respiration（R_m）in R.pseudoacacia and Grassland were higher than that of root respiration（R_r）and litter respiration（R_L）,and the contribution rates of R_m exceeded 60%,while the performance of C.korshinskii was:R_r（40.85%）>R_m（31.00%）>R_L（28.16%）,the highest contribution rate of R_r for the three vegetation types occurred in July.