[Effects of thinning on soil active organic carbon contents and enzyme activities in Larix principis-rupprechtii plantation].

The effects of thinning on soil active organic carbon and related soil enzyme activities were investigated in a Larix principis-rupprechtii plantation in Taiyue Mountain. With the increases of soil depth, the content of soil labile organic carbon, soil nitrogen content and enzyme activities all reduced. For each soil layer, moderate thinning increased soil carbon and nitrogen contents dramati-cally. The activities of sucrase (SC) and peroxidase (PEO) and the activities of polyphenol oxidase (PHO) and urease (UE) in the layer of 0-10 cm could be significantly improved by low thinning and moderate thinning, respectively. For the 10-50 cm layer, the activities of SC and UE were reduced by low thinning, while moderate thinning markedly reduced the activities of cellulase. Results from redundancy analysis showed that dissolved organic carbon (DOC) was the main factor affecting soil enzyme activity in both 0-10 cm and 20-30 cm soil layers and that soil organic carbon (SOC) contents affected the activities of PHO and SC in 10-20 cm soil layer. The microbial biomass nitrogen (MBN) mainly affected the activities of PHO, PEO and UE in 30-40 cm soil layer. The contents of total P (TP) and readily oxidized carbon (ROC) played an important role in affecting soil enzyme activities in 40-50 cm soil layer. The results indicated that thinning could dramati-cally affect soil active organic carbon content and soil enzyme activity in L. principis-rupprechtii plantation. Moderate thinning treatment could obtain the highest soil nutrients and achieve better soil chemical properties such as soil pH, water content and organic matter content than other treatments, which could improve vegetation structure, litter and nutrient cycling process. Therefore, we recommended moderate density adjustment (1404-1422 trees·hm-2) to L. principis-rupprechtii plantation to promote soil carbon and nitrogen retention.本研究以太岳山华北落叶松人工林为对象,研究间伐对土壤活性有机碳及相关土壤酶活性的影响.结果表明: 随着土壤深度的增加,土壤活性有机碳含量、土壤氮含量和酶活性降低;同一土层中,中度间伐下土壤碳、氮养分含量显著增加.在0～10 cm土层,轻度间伐处理下蔗糖酶和过氧化物酶活性显著增加,中度间伐处理下多酚氧化酶和脲酶活性显著增加;在10～50 cm土层,轻度间伐处理下蔗糖酶和脲酶活性降低,中度间伐处理下纤维素酶活性显著降低;冗余分析显示,溶解性有机碳在0～10和20～30 cm土层是影响土壤酶活性的主要因素;在10～20 cm土层中,土壤有机碳是影响多酚氧化酶和蔗糖酶的主要因素;在30～40 cm土层,微生物生物量氮主要影响多酚氧化酶、过氧化物酶和脲酶活性,土壤全磷和易氧化有机碳对40～50 cm土层土壤酶活性起着重要的作用.间伐对华北落叶松人工林土壤活性有机碳含量和土壤酶活性有显著影响,中度间伐处理下土壤养分含量总体最高,土壤pH、含水率、有机质含量等化学性质优于其他几种处理,能较好地改善林下植被、枯落物及养分循环过程.因此,建议对落叶松人工林进行适度密度调整(1404～1422 trees·hm-2),以促进碳、氮养分在土壤中的固存.