微生物残体是土壤有机碳的主要组分，其对人工混交林的响应目前尚不清楚。以我国亚热带杉木(Cunninghamia lanceolata)纯林和杉木-火力楠(Michelia macclurei)混交林0～20 cm 土壤为研究对象，以氨基糖为微生物残体标识物，采用基于革兰氏阳性菌与革兰氏阴性菌比值确定的细菌残体转换系数，研究了长期杉木-火力楠混交对土壤微生物残体积累的影响。结果表明，与杉木纯林相比，杉木-火力楠混交林0～10cm土壤细菌残体含量降低了 25。3％，进而导致土壤有机碳含量降低了 11％。混交林中细菌残体的降低主要归因于大团聚体内细菌残体含量的降低。林木混交并未影响0～20 cm 土壤微生物残体含量以及微生物残体对土壤有机碳的贡献。以上结果表明，火力楠引入杉木林35年后降低0～10 cm 土壤细菌残体和土壤有机碳的固持，可能不利于维持长期土壤肥力。
Microbial residues are major contributors to soil organic carbon(SOC).However,their responses to mixed plantation forests remain unclear.In this study,we examined the accumulation of microbial residues in soil at depths of 0-20 cm in Cunninghamia lanceolata-Michelia macclurei mixed plantation and C.lanceolata pure planta-tion by analyzing amino sugars and using the ratio of Gram-positive to Gram-negative bacteria to determine the con-version coefficient of bacterial residues.The results showed that bacterial residues at depths of 0-10 cm were 25.3％lower in the mixed plantation than that in the monoculture,leading to SOC being 11％lower in the mixed planta-tion.The lower accumulation of bacterial residues in the mixed plantation was mainly due to the lower accumulation in macroaggregates.However,the accumulation of total microbial residues and their contribution to SOC did not dif-fer between the mixed plantation and monoculture.These results indicate that the M.macclurei and C.lanceolata mixed plantations after 35 years would reduce bacterial residues as well as soil carbon sequestration,which would be detrimental to the long-term maintenance of soil fertility.
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