中国亚热带典型天然次生林土壤微生物碳源代谢功能影响因素

天然次生林地比人工林地不仅土壤肥力较高，且土壤碳代谢功能更强。然而维持天然次生林高碳代谢功能的原因尚不十分清楚。分析天然次生林中土壤微生物碳源代谢功能的影响因素对于调控土壤微生物的功能乃至天然次生林的保护具有重要意义。本文选择中国亚热带地区典型天然次生林，研究了土壤微生物碳源代谢功能与土壤化学和物理因素及植物因素的关系。结果表明，3类因素能显著解释土壤微生物碳源代谢功能54.4% 的变异。乔木层植物多样性、土壤碳氮比、pH值和含水量是导致天然次生林碳代谢功能差异的主要因素，分别显著解释了土壤微生物碳源代谢16.7%、12.4%、10.5%和10.5%的变异。天然次生林较低的土壤碳氮比、较高的土壤含水量和土壤pH值（酸性范围内），有利于土壤微生物碳源代谢功能的提高，同时天然次生林较高的阔叶树种的比例也能增加土壤微生物碳源代谢功能。

Relationships between carbon source utilization of soil microbial communities and environmental factors in natural secondary forest in subtropical area, China

Compared with artificial plantation,natural secondary forest has higher function of nutrient cycling,especially carbon source metabolism function.However the reasons for higher nutrient cycling function in natural secondary forest are still not clear.To understand the nutrient cycling function of natural secondary forest,we analyzed the relationship between carbon source metabolism properties of soil microbial communities and the environmental factors in subtropical area,China.From 40 sample plots 40 soil samples at 0—10 cm depth were sampled.The carbon source metabolism capacity of soil microbial communities was analyzed using Biolog method.The soil properties and plant composition of the plots were also surveyed. Variance partitioning showed that three groups of factors significantly explained 54.4% variation of carbon source utilization by soil microbial communities.Among them,soil chemical characteristics and vegetation factors explained 13.0%(P = 0.001) and 13.4%(P = 0.001) variation,respectively.There existed interaction among three groups of factors.The interaction between soil chemical and physical characteristics explained 13.8% variation,the interaction between vegetation and soil physical characteristics explained 12.9% variation and the interaction of soil chemical factors and vegetation factors explained 1.5% variation of carbon source utilization. Redundancy analysis(RDA) was used to analyze relationship between carbon source utilization ability and vegetation factors,soil physical characteristics and chemical characteristics respectively.Monte Carlo permutation test(n=999) was used to preselect factors that significantly influenced carbon source utilization of soil microorganisms.RDA showed that among the 7 vegetation factors,tree layer species richness,root biomass and tree biomass significantly influenced carbon source utilization ability of soil microbial communities,which explained 16.7%(P = 0.001),6.3%(P = 0.017) and 4.6%(P = 0.046) variation of carbon source utilization,respectively.The soil physical characteristics,including soil moisture content,sand content and soil bulk density,also significantly influenced carbon source utilization of soil microbial communities,which explained 10.5%(P = 0.003),8.8%(P =0.01) and 7.2% variation(P = 0.005) of carbon source utilization.As for the 6 soil chemical characteristics,only soil pH,C∶N ratio and available nitrogen content significantly explained the variation of carbon source utilization by soil microbial communities,which explained 10.5%(P = 0.006),12.4%(P = 0.002) and 5.2%(P = 0.047) variation of carbon source utilization. According to the explained variation of carbon source utilization by soil microbial communities,the lower C∶N ratio in soil,higher soil moisture content and soil pH(within the scope of acid soil) were the main factors improving soil carbon source metabolism capacity in natural secondary forest.The higher broad-leafed species ratio also benefit soil carbon source metabolism capacity in natural secondary forest.