Response Of Soil Organic Carbon Mineralization Rate And Temperature Sensitivity To Long-term Warming In Abies Faxoniana Forests During Growing Season

Forest soil organic carbon?SOC?is an important component of the terrestrial ecosystem carbon pool.Temperature is a critical factor in regulating a large number of biogeochemical processes in terrestrial ecosystems,so temperature plays an important role in many aspects of the soil carbon cycle.Therefore,in the context of global warming,accurately assessing the response of soil carbon pools to warming in different ecosystems can provide an important basis for the dynamics of terrestrial ecosystem carbon in future climate change scenarios.In this study,the in situ open-top chamber?OTC?was used to simulate the warming.In 2017,soil of alpine Abies faxoniana forests in western Sichuan was studied after 10 years of warming,and different layers of soil were collected in the early?mid-May?,mid?mid-July?and final-term?mid-September?of growing seasons.The effects of long-term simulated warming on the SOC mineralization rate and temperature sensitivity(Q₁₀)of different elevations and soil layers in the growth season were studied by indoor incubation method.Combined with the effect of warming on other soil indicators,the intrinsic relationship between soil properties and SOC mineralization rate and Q₁₀ were discussed.Get the following results:?1?Long-term warming slightly increased soil available potassium,available phosphorus,available nitrogen,total nitroge,total potassium,invertase,acid phosphatase,and SOC contents in the early-term of the growing season,and the values after warming were 201.53 mg/kg,17.5 mg/kg,432.56 mg/kg,2.58 g/kg,34.65 g/kg,322.7 mg/g/d,0.46 mg/g/d,and 80.6 g/kg,respectively?p>0.05?.In mid-term,warming slightly increased the contents of soil pH,available phosphorus,available nitrogen,total nitrogen,total phosphorus,total potassium,cation exchange capacity,sucrose,urease,catalase,and SOC?p>0.05?,and significantly increased the contents of acid phosphatase?p<0.05?,and the values after warming were 5.59,19.78 mg/kg,479.56 mg/kg,4.77 g/kg,0.45g/kg,33.34 g/kg,26.51 cmol/kg,342.91 mg/g/d,27.03 mg/g/d,0.13 mL/g,78.73 g/kg,and 0.48 mg/g/d,respectively.In final-term,warming slightly increased the contents of pH,available potassium,available phosphorus,total phosphorus,total potassium,invertase and urease,and the values after warming were 5.52,178.56 mg/kg,10.34mg/kg,0.56 g/kg,40.2 g/kg,483.44 mg/g/d,and 54.58 mg/g/d,respectively?p>0.05?.In addition to soil pH,the SOC was more strongly correlated with other soil indicators in three periods.Elevation and soil layer had a relatively greater impact on the soil indicators than warming.?2?During the growing season,the warming slightly increased the SOC mineralization rate in the early and mid-term,and the values after warming were 82.94and 143.62 mL/kg/d?p>0.05?.A separate elevation or soil layer had a significant effect on the SOC mineralization rate,but temperature reduced their influence.?3?The long-term warming significantly reduced the Q₁₀ at the early-term of the growing season?p<0.05?,and slightly reduced the Q₁₀ at the mid-term?p>0.05?,but significantly increased the Q₁₀?p<0.05?at the final-term.The values after warming were 1.95,1.7,and 2.08,respectively.The effect of the individual elevation effect was significant for Q₁₀0 all the period,and the soil layer only had a significant effect on Q₁₀ in mid and final-term.?4?The SOC contents increased the overall effect of temperature or soil layers on the SOC mineralization rate in the early and mid-term of the growing season,and reduced the effect at the final-term,while the SOC contents increased the overall effect of elevation on the SOC mineralization rate in three periods.In this study,the soil layer was the most influential factor on the SOC mineralization rate among all environmental conditions?temperature,elevation,and soil layer?throughout the growing season.As the growing season progresses,the direct effect of temperature on the SOC mineralization rate gradually increased,even exceeding the elevation at the end-term of the growing season.In the stepwise regression analysis of this study,no significant direct relationship was found between SOC mineralization rate and SOC contents.SOC contents weakened the overall effect of temperature on Q₁₀ in the early and mid-term of the growing season,but enhanced the overall effect at the final-term.SOC contents enhanced the overall effect of soil layer and elevation on Q₁₀ in all periods.In this study,elevation was the environmental factor that has the greatest impact on Q₁₀ throughout the growing season.