[Effects of thinning on accumulation of soil microbial residue carbon of Picea asperata plantations in sub-alpine region of western Sichuan, China].

Microbial residues are an important component of soil organic carbon (SOC). It is unclear how long-term thinning affects the accumulation characteristics of microbial residue carbon (C). We analyzed the differences in soil physicochemical properties, microbial communities, extracellular enzyme activities, and microbial residue C in topsoil (0-10 cm) and subsoil (20-30 cm) in Picea asperata plantation of non-thinned (control, 4950 trees·hm-2) and thinned for 14 years (1160 trees·hm-2) stands, aiming to reveal the regulatory mechanism of thinning on microbial residue C accumulation. The results showed that thinning significantly increased SOC content, total nitrogen content, available phosphorus content, the proportion of particulate organic C, soil water content, C-cycle hydrolase, and acid phosphatase activities, but significantly reduced the proportion of mineral-associated organic C. Thinning significantly affected the content of fungal and microbial residue C, and the contribution of microbial residue C to SOC, and these effects were independent of soil layer. The content of fungal and microbial residue C was 25.0% and 24.5% higher under thinning treatments. However, thinning significantly decreased the contribution of microbial residue C to SOC by 12.3%, indicating an increase in the proportion of plant-derived C in SOC. Stepwise regression analysis showed that total nitrogen and soil water content were key factors influencing fungal and micro-bial residue C accumulation. In summary, thinning promoted microbial residue C sequestration by altering soil pro-perties and changed the composition of SOC sources.微生物残体是土壤有机碳的重要组分,但长期间伐如何影响微生物残体碳积累特征尚不清楚。本研究分析了未疏伐(对照,4950 株·hm-2)和间伐(1160株·hm-2)14年的云杉人工林表层(0~10 cm)和下层(20~30 cm)土壤理化性质、微生物群落、土壤胞外酶活性和微生物残体碳差异,并揭示间伐对微生物残体碳积累的调控机制。结果表明: 与对照相比,间伐显著增加土壤有机碳、全氮、速效磷含量、颗粒有机碳占比、土壤含水量、土壤碳循环水解酶和酸性磷酸酶活性,但显著降低矿物结合态有机碳占比。间伐显著影响真菌残体碳含量、微生物残体碳含量和微生物残体碳对土壤有机碳的贡献,且这些影响与土层无关。间伐处理下真菌残体碳和微生物残体碳含量分别比对照提高25.0%和24.5%。但间伐显著降低了土壤微生物残体碳对土壤有机碳的贡献(降低12.3%),表明土壤有机碳中植物来源碳比例增加。逐步回归分析表明,全氮和含水量是影响真菌残体碳和微生物残体碳积累的关键因子。综上,间伐通过改变土壤性质促进了微生物残体碳的积累,并改变了土壤有机碳来源组成。.