Changes And Influencing Factors Of Soil Respiration Components In Quercus Acutissima Plantation In The Hilly Region Of The Lower Yangtze River

China’s subtropical plantations have great potential for carbon sequestration.Soil respiration carbon emission is a key process of carbon cycle in subtropical plantations,and its in-depth understanding and quantitative expression are important scientific propositions related to the realization of"carbon neutrality"goal in China.Under the background of global change,there are great uncertainties in soil respiration and its components in subtropical plantations,and its key driving mechanism is still unclear.Based on this,in this study,the method of static chamber-gas chromatography was used to continuously observe the soil respiration of Quercus acutissima plantations widely distributed in the subtropical regions of China.The dynamic law of the respiration rate of soil respiration and its components with time,the contribution rate of the two components of soil respiration to the total soil respiration,the temperature sensitivity(Q₁₀)changes of the three types of respiration,and the correlation between soil respiration and key meteorological factors and soil active carbon and nitrogen substrate were analyzed and compared.The result is as follows:（1）The seasonal variation of soil respiration and its components presented the dynamic characteristics of single-peak distribution on the whole,their minimum value appeared in December,the maximum value of soil total respiration and root autotrophic respiration appeared in August,and the maximum value of soil heterotrophic respiration appeared in June.（2）The temperature sensitivity Q₁₀ value of soil respiration and its components also had obvious seasonal changes,reaching the lowest value in summer and increasing to the highest value in winter.The variation ranges of the three Q₁₀ value were 1.08-3.97,1.11-5.3 and 0.72-5.81,and the coefficient of variation was large.In addition,the Q₁₀ values of the three components were 1.88,1.81 and 2.28.（3）The contribution rate of different components in soil respiration varies greatly with season.The contribution rate of heterotrophic respiration ranged from 73.82%to 80.77%,with the highest contribution rate in winter;the contribution rate of root autotrophic respiration ranged from 19.23%to 26.17%,with the largest contribution rate in summer.The carbon emissions of total soil respiration,heterotrophic soil respiration and autotrophic root respiration in one year were 2968.56±65.66 g·m^-2,2281.98±47.95 g·m^-2 and 57.21±19.08 g·m^-2.On the whole,the carbon release of root autotrophic respiration was much lower than that of soil heterotrophic respiration.（4）The soil respiration and its component respiration rates in the Quercus acutissima plantation increased with the increase of temperature.Compared with air temperature and soil10cm depth temperature,soil 5cm depth temperature explained the three respiration rates to a higher degree.The respiration rate of soil and its components increased with the increase of soil water content.In addition,the respiration rates of soil respiration and its components were significantly correlated with light and effective radiation,relative humidity,and wind speed,among which relative humidity had the highest explanatory degree to soil total respiration and soil heterotrophic respiration.Combined with the comprehensive effects of various meteorological factors on soil respiration,soil temperature at 5cm depth and wind speed were the main meteorological factors affecting soil respiration rate.（5）The content of soil active carbon and nitrogen in Quercus acutissima plantation had obvious vertical distribution characteristics and seasonal variation.From the perspective of vertical distribution characteristics,the contents of total nitrogen,soluble organic carbon and ammonium nitrogen all decreased with the deepening of soil profile,while nitrate nitrogen had no obvious vertical variation.The results of redundancy analysis showed that the contents of soluble organic carbon,nitrate nitrogen and ammonium nitrogen were the key factors affecting soil respiration and its components,and their contributions to the respiration rate were 50.2%,27%,and 9.3%.