凋落物对土壤有机碳与微生物功能多样性的影响

森林凋落物是影响土壤微生物群落和有机碳含量的重要因素，但其作用的程度和机制尚不清楚，研究该问题对于分析森林生态系统碳循环和资源管理具有重要意义。研究凋落物去除与添加处理下土壤有机碳含量与土壤微生物对碳源利用的差异，明确凋落物去除与添加对土壤微生物群落代谢功能及其多样性的影响，探究不同处理下SOC含量变化的土壤微生物群落代谢机理。选取承德市雾灵山1405-1435 m海拔范围内核桃楸-蒙古栎混交林的表层土壤，采用室内培养结合Biolog-ECO方法，测定了培养第21天的土壤有机碳（soil organic carbon，SOC）含量及微生物群落的AWCD值、Shannon-Wiener多样性指数、Simpson优势度指数、McIntosh均匀度指数、Pielou丰富度指数，分析培养期内凋落物的不同处理下SOC含量与微生物功能多样性的变化特征。结果表明：1）不同凋落物处理对SOC含量与土壤微生物群落多样性具有显著影响（P<0.05），DL > HL > NL > CK；2）不同凋落物处理下土壤微生物群落代谢活性和土壤微生物对碳源的利用程度具有显著差异（P<0.05），碳水化合物类和氨基酸类是土壤微生物的主要碳源；3）不同处理的SOC含量与土壤微生物多样性具有正相关关系。双倍凋落物添加在短期内对土壤微生物多样性影响难以达到显著水平且在一定程度上对土壤微生物的代谢活性具有抑制作用，土壤微生物群落功能多样性对SOC含量具有重要影响。

Effects of litter on soil organic carbon and microbial functional diversity

Forest litter is an important factor affecting soil microbial community and organic carbon content, and plays an important role in soil organic carbon formation and microbial growth and reproduction. The changes of soil organic carbon content and microbial community during litter decomposition have become the focus of current forest ecology research,but the extent and mechanism of its role are still unclear. It is of great significance to analyze the carbon cycle and resource management of the forest ecosystem. This study aimed to study the differences of soil organic carbon content and carbon source utilization by soil microorganisms under litter removal and addition treatments, to clarify the effects of litter removal and addition on the metabolic function and diversity of soil microbial community, and to preliminarily explore the metabolic mechanism of soil microbial community under different treatments. We hypothesized that soil organic carbon content was affected by the functional diversity of soil microbial community when litter input changed. The surface soil of the mixed forest of Catalpa chinensis and Quercus mongolica in the altitude range of 1405-1435 m in Wuling Mountain, Chengde City was selected. Using incubation combined with the Biolog-ECO method, the content of soil organic carbon (SOC) and the average well color development (AWCD) value of the microbial community, Shannon-Wiener index, Simpson index, Mclntosh index and Pielou index of the microbial community were measuredon the 21st day of cultivation. The changes of the soil organic carbon content and microbial functional diversity under different treatments of litter during the cultivation period were analyzed. The results showed that 1) different litter treatments had significant effects on the soil organic carbon content and soil microbial community diversity (P<0.05), DL > HL > NL > CK; 2) There were significant differences in the metabolic activity of soil microbial community and the utilization of carbon sources by soil microorganisms under different litter treatments (P<0.05). The carbohydrate and amino acids were the main carbon sources of soil microorganisms; 3) There was a positive correlation between soil organic carbon content and soil microbial diversity. The effects of double litter addition on soil microbial diversity were difficult to reach a significant level in the short term, and it inhibited the metabolic activity of soil microbes to a certain extent. The functional diversity of soil microbial communities had an important impact on soil organic carbon content. The results of this study can provide scientific basis and practical reference for the sustainable management of the mixed forest of Catalpa chinensis and Quercus mongolica.