Effects Of Fresh Carbon Addition On Soil Organic Carbon Fractions And Soil Priming Effect Along An Elevation Gradient In Wuyi Mountain,China

Forest soil organic carbon is the main body of soil carbon stocks in terrestrial ecosystems,and its small changes will cause changes in atmospheric carbon dioxide concentration.Fresh carbon is the main source of soil organic carbon,so studying the input of fresh carbon in the context of global warming is of great significance to the dynamic changes of soil organic carbon.In this paper,the elevation gradient(1400 m,1000 m,600 m)of Wuyi Mountain in Fujian Province is used as a research platform to study the different altitudes of Wuyi Mountain imported by different quality fresh carbon(,3C-labeled Castanopsis carlesii leaves and '3C-labeled Cunninghamia lanceolata leaves)using the stable isotope 13C tracer technique.The effect of soil organic carbon and quantification of the fate and priming effects of fresh carbon in different components of soil organic carbon.The main results are as follows:(1)Light fraction organic carbon from fresh carbon(Castanopsis carlesii and Cunninghamia lanceolata leaves)was 0.13-0.17 g kg-1 in 0-10 cm soil layer,and heavy fraction organic carbon from fresh carbon was 0.20-3.14 g kg-1 in all altitudes.After the decomposition of fresh carbon,it mainly enters into the heavy fraction organic carbon,which was related to the large proportion of heavy organic matter and fixation of microorganisms.The content of fresh carbon in total organic carbon is shown at an altitude of 1400 m>1000 m>600 m.Among them:Light and heavy fractions organic carbon from fresh carbon in 0-5 cm soil layers was significantly greater than 5-10 cm.There was no significant difference in light fraction organic carbon from Castanopsis carlesii leaves and Cunninghamia lanceolata leaves in 0-5 cm and 5-10 cm soil layers at all altitudes.However,heavy fractions organic carbon from Castanopsis carlesii leaves is greater than that of Cunninghamia lanceolata leaves,which is mainly due to the different quality of fresh carbon and microbial substrate use efficiency.At the same time,light fraction organic carbon from fresh carbon(Castanopsis carlesii and Cunninghamia lanceolata leaves)did not change significantly with the altitude in the 0-5 cm and 5-10 cm soil layers,whereas heavy fraction organic carbon from fresh carbon(Castanopsis carlesii and Cunninghamia lanceolata leaves)generally decrease with altitude of the decline,which indicates that the decomposition and desorption of fresh carbon at different altitudes were affected by temperature and moisture.(2)Cumulative organic carbon mineralization treated with Castanopsis carlesii leaves and Cunninghamia lanceolata leaves was h]gher than that of the control in all altitudes,indicating that the addition of fresh carbon will increase the rate of organic carbon mineralization.The cumulative mineralization of soil organic carbon in the three treatments showed the highest elevation at 1000 m and the lowest elevation at 1400 m.This is mainly due to differences in quantity and quality of soil substrate,microbial carbon use efficiency,soil physical and chemical properties,temperature,^and so on.(3)The CO2-C accumulation of 1400 m Cunninghamia lanceolata leaves was significantly higher than that of Castanopsis carlesii leaves,but the cumulative mineralization of Castanopsis carlesii leaves was significantly higher at 1000 m and 600 m than that of Cunninghamia lanceolata leaves.There was no significant trend in the cumulative mineralization of Castanopsis carlesii leaves and Cunninghamia lanceolata leaves at all altitude.It shows that the decomposition rate of litterfall at different altitudes is not only related to litter quality,temperature and moisture,but also affected by microorganisms.(4)Positive priming effect was observed after the addition of fresh carbon at different altitudes,indicating that the input of fresh organic carbon provided the energy for microbial activity and accelerated the decomposition of the native organic carbon.At the same altitude,the intensity of soil organic carbon stimulated by the addition of Castanopsis carlesii leaves was significantly higher than that of Cunninghamia lanceolata leaves at the altitudes of 1400 m and 600 m,but opposite at 1000 m.In the same treatment,the priming effects of Castanopsis carlesii leaves and Cunninghamia lanceolata leaves were the largest at the altitude of 600 m,but there was no significant trend with the elevation,indicating that the size of the priming effect was not only closely related to the quality of fresh carbon and the organic carbon content of the native soil,but also influenced by environmental and microbial factors.