Effects Of Changing Carbon Input On Soil Respiration Of Picea Schrenkiana Forest In Tianshan Mountains,Xinjiang

Surface plant residues and underground plant roots are the main sources of soil C banks in forest ecosystems,and their subtle fluctuations in quality and quantity may lead to large changes in soil respiration rate.Global warming is significantly altering the productivity of forest organisms,affecting the dynamic balance between carbon pool of the Vegetation-Litter-Soil in forest ecosystems,and then acting on the rate of respiration in forest soils.However,it is still controversial how the soil respiration rate of mountain forests in arid regions responds after cutting off plant roots and controlling litter input.In this study,the Picea schrenkiana in the middle section of the northern slope of the Tianshan Mountains in Xinjiang was studied.By setting the Check Plot?CK?,Double Litter?DL?,No Root?NR?,No Litter?NL?and No Input?NI?five treatment methods,studying the dynamic variation of soil respiration rate after input of different carbon sources,exploring further the relationship between soil respiration rate and its environmental factors.The study has the following conclusions:?1?Monthly dynamic changes in soil respiration rate.The soil respiration rate showed obvious monthly dynamic changes under different carbon source inputs,and there was a similar single kurtosis curve change pattern.The monthly mean value of different treatments is:DL(3.93?mol·m^-2·s^-1)>CK(3.38?mol·m^-2·s^-1)>NL(2.88?mol·m^-2·s^-1)>NR(2.79?mol·m^-2·s^-1)>NI(2.01?mol·m^-2·s^-1);After changing the carbon source input,the soil respiration rate of Picea schrenkiana forest was not consistent.Compared with the control treatment,NI,NR and NL treatments reduced the soil respiration rate by 40.87%,14.50%and 11.06%during the whole observation period.while it increased by an average of 20.05%under DT treatment.?2?Soil temperature and soil moisture are the key factors regulating soil respiration rate.There was an extremely significant exponential correlation between soil 5 cm temperature and soil respiration rate under different carbon source input methods?P<0.01?.The exponential model between soil respiration rate and 5 cm soil temperature can account for 72.31%-83.03%of soil carbon emissions.The soil respiration rate sensitivity coefficient Q₁₀0 value under NI treatment method is greater than the Q₁₀0 value under other treatment methods,the soil respiration rate temperature sensitivity coefficient Q₁₀0 values of NL,DL and NR are less than the Q₁₀0 value under the control treatment.There is a significant linear relationship between soil 5 cm humidity and soil respiration rate under different carbon source input modes.Among them,only DL treatment showed an extremely significant correlation?P<0.01?,and other treatments had significant correlation?P<0.05?.The single factor linear model between soil respiration rate and soil 5 cm humidity can only explain the variation of soil respiration rate from 23.64%to 36.5%.Compared to the single factor model between soil temperature or humidity and soil respiration rate,the two-factor composite factor model of soil temperature and humidity can better describe the dynamic change of soil respiration rate.The two-factor composite model of soil respiration rate and soil temperature and humidity after changing the carbon input method explained the change of soil respiration rate from 75.4%-88.2%,it can be seen that the soil respiration rate of Picea schrenkiana forest is synergistically affected by the temperature and humidity of 5 cm soil layer.?3?Correlation between soil respiration and other soil physical and chemical indicators in Picea schrenkiana forest.Pearson correlation analysis showed that the correlation between soil respiration rate and Total nitrogen?TN?,C/N and soil electricity conductivity?EC?after changing carbon source input was not obvious?P>0.05?,while the correlations between soil organic carbon?SOC?,Total phosphorus?TP?,soil pH and soil bulk density on soil respiration rate were significant?P<0.05?.?4?Contribution rate of soil respiration in each sub-chamber.After the end of the experiment,the relative contribution rate of mineral soil respiration?R_m?,litter soil respiration?R_L?and root soil respiration?R_r?to total soil respiration is:R_m?59.45%?>R_r?17.27%?>R_L?11.41%?.