青冈栎次生林土壤活性有机碳对间伐强度的响应

目的 探索不同间伐强度对青冈栎次生林土壤活性有机碳的响应。 方法 以湖南省天心阁林场青冈栎次生林为研究对象，于2018年设置4种间伐强度（对照：0%；弱度间伐：15%；中度间伐：30%；强度间伐：50%），探讨不同间伐强度下4种土壤活性有机碳（土壤微生物量碳、可溶性有机碳、颗粒有机碳和易氧化有机碳）含量变化及其在总有机碳中的分配比例。 结果 （1）与对照样地相比，中度间伐和强度间伐显著提高了土壤总有机碳含量，弱度间伐降低了土壤总有机碳含量；（2）间伐提高了土壤微生物量碳的含量，降低了可溶性有机碳的含量，土壤颗粒有机碳和易氧化有机碳含量在不同间伐处理下的变化趋势与总有机碳一致；（3）不同间伐强度下土壤微生物量碳、可溶性有机碳、颗粒有机碳和易氧化有机碳的分配比例分别为：0.23%～0.54%、0.40%～0.78%、16.54%～47.30%和6.46%～14.29%，强度间伐显著提高了微生物量碳、颗粒有机碳和易氧化有机碳分配比例，降低了可溶性有机碳的分配比例，表明间伐提高了不稳定碳的比例，且颗粒有机碳对间伐处理更敏感；（4）相关性分析表明，土壤总有机碳与各活性有机碳组分间呈极显著正相关，且活性有机碳与土壤含水量和总氮含量呈正相关；土壤活性组分碳间转化依赖于总有机碳量的变化，且在一定的水分和氮素条件下易发生分解转变。 结论 不同间伐处理对土壤有机碳及其活性组分的含量有显著影响，强度间伐显著提高土壤有机碳及其活性组分的含量，加快土壤中的碳素循环。

Response of Soil Labile Organic Carbon to Thinning Intensity in Secondary Forest of Cyclobalanopsis glauca

Objective To study the response of soil labile organic carbon to thinning intensities in the secondary forest of Cyclobalanopsis glauca. Method Experiments were carried out to investigate the changes of SOC and its labile chemical components (MBC, DOC, POC and ROC) as well as their distribution ratio following a short term intensity adjustment of stand woods with 4 treatments: light (15%, LIT), moderate (30%, MIT), high (50%, HIT) and the contrast (unthinning, CK) in secondary forest of Cyclobalanopsis glauca. Result (1) Compared with the CK, the MIT and HIT significantly increased the SOC content, while LIT reduced the SOC content. (2) Thinning increased the soil MBC content and reduced the DOC content. The variation trend of soil POC and ROC contents under different thinning treatments was consistent with that of the SOC. (3) Under different thinning intensity, the distribution proportion for soil MBC and POC, DOC and ROC were 0.23%-0.54%, 0.40%-0.78%, 16.54%-47.30% and 6.46%-14.29%, the HLT significantly Increased the proportion of MBC allocation as well as POC and ROC and reduced the allocation proportion of DOC, showing that thinning treatments increased the proportion of unstable carbon and POC was more sensitive to the thinning processing. (4) Correlation analysis showed that there was a significant positive correlation between soil total organic carbon and labile organic carbon components, and labile organic carbon was positively correlated with soil water content and total nitrogen content, the carbon conversion of soil labile components was dependent on the change of total organic carbon, and it was easy to decompose under certain water and nitrogen conditions. Conclusion Thinning treatment has significant effects on the contents of soil organic carbon and its labile components, and HLT will significantly increase the contents of soil organic carbon and its labile components and accelerate the carbon cycle in the soil.