凋落物分解是陆地生态系统养分循环的关键过程,明确凋落物多样性如何影响土壤微生物群落构成和多度,继而潜在地改变凋落物分解的微生物学机制有助于认识生物多样性和森林生态系统功能的关系.通过小盆模拟试验,应用磷脂脂肪酸谱图的方法研究了我国南方红壤丘陵区典型物种马尾松和湿地松的凋落物分别与白栎和青冈的凋落物混合,与单一针叶凋落物分解时相比,针阔混合凋落物分解过程中土壤微生物群落结构的变化,结果显示:(1)针阔混合凋落物分解时土壤微生物群落磷脂脂肪酸(Phospholipidfatty acids,PLFA)总量低于单一针叶处理,细菌和放线菌的相对多度高于单一针叶处理,真菌则相反,群落真菌/细菌低于单一针叶处理,土壤微生物生物量的差异主要来自于真菌;(2)主成分分析表明:针阔混合凋落物分解与单一针叶凋落物分解的土壤微生物群落结构差异显著,两个时期(分解9个月和18个月)主成分一分别可以解释65.74%和89.63%的变异,第一主成分主要包括18:2ω6,9、18:1ω9c、17:0和l0Mel8:0等磷脂脂肪酸;(3)土壤微生物群落结构受凋落物初始C/N和木质素/N调控,土壤微生物群落细菌的相对多度与凋落物初始C/N和木质素/N显著负相关,真菌则与凋落物初始C/N和木质素/N显著正相关,群落真菌/细菌与凋落物初始C/N和木质素/N显著正相关.针阔凋落物混合分解通过改变凋落物C/N和木质素/N,提供了对分解者更为有利的微环境.%Litter decomposition is the key process in nutrient recycling in the terrestrial ecosystem.A clear knowledge about how litter diversity affects composition and abundance of the soil microbial community and then potentially changes the microbiological mechanism of litter decomposition will help understand the relationship between biological diversity and functions of a forest ecosystem.A pot experiment was carried out to compare mixed litters from massion pine, slash pine, white oak and blue Japanese oak, which are all typical species of the hilly red soil regions in South China, with litter of conifer leaves only in effect of their decomposition on soil microbial community structure with the PLFA method.Results show that ( 1 ) the mixed litter treatment was lower in total PLFA,in relative abundance of fungi and in fungi/bacteria of the soil microbial community, but higher in relative abundance of bacteria and actinomyces than the single litter treatment.And the difference in soil microbial biomass between the treatments was contributed mainly by fungi; (2) The principal component analysis (PCA) of the PLFA data demonstrated that mixed litter treatment differed significantly from the single litter treatment in soil microbial community structure.Principal component one ( PC1 ) explained 65.74％ and 89.63％ of the variation respectively in the two decomposition periods (9 and 18 months).PC1 consisted mainly of fatty acids of 18∶2ω6,9、18∶1ω9c,17∶0 and 10Me18∶ 0; (3) Soil microbial community structure was affected by initial carbon-nitrogen ratio (C/N)and lignin-nitrogen ratio (lignin/N) of the litter, which were negatively related to relative the abundance of bacteria, but positively to the relative abundance of fungi and fungi/bacteria in the soil microbial community.Decompositions of mixed conifer-broadleaved leaf litters provided a more favorable microenvironment for decomposers by changing the chemical composition of the litters such as carbon-nitrogen ratio and lignin-nitrogen ratio.
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