长期粗放经营毛竹林土壤微生物群落演变特征

目的]通过分析土壤微生物生物量及群落结构的演变趋势,筛选影响土壤微生物群落的关键环境因子,揭示土壤微生物群落对毛竹林长期粗放经营的响应机理。方法]选取不同粗放经营年限(5 a、9 a、15 a、18 a)毛竹林,以天然马尾松林(Masson pine,MP)作为对照,采用磷脂脂肪酸(Phospholipid fatty acids,PLFA)分析方法表征土壤微生物量及群落结构。结果]结果表明,毛竹林土壤微生物总PLFA含量以及细菌、真菌、放线菌等PLFA含量均显著低于马尾松林(P0.05),但不同经营年限毛竹林之间没有显著差异。土壤碱解氮及有效磷含量对土壤微生物总PLFA含量以及细菌、真菌、原生动物等PLFA含量影响显著(P0.05),而土壤碱解氮、p H值以及有机质含量对放线菌PLFA含量影响显著(P0.05)。长期粗放经营过程中毛竹林土壤微生物丰富度及多样性均呈逐渐下降趋势。非度量多维尺度转换排序(Non-metric multidimensional scaling,NMDS)分析结果表明,毛竹林土壤微生物群落结构与马尾松林有明显区分(R=0.388 1,P=0.009)。土壤含水量、碱解氮、有效磷以及p H值合计解释了90.28%的微生物群落结构变异量,其中土壤含水量、碱解氮、有效磷贡献显著(P0.05)。结论]长期粗放经营降低了毛竹林土壤微生物量,改变了群落结构,其生态风险还有待于进一步评估。

Variation Patterns of Soil Microbial Community of Phyllostachys edulis Stands under Long-term Extensive Management

Objective]To investigate the effect of long-term extensive management on soil microbial communities and the related mechanisms.Method]Moso bamboo (Phyllostachys edulis) stands with different extensive management time (5, 9, 15, and 18 years) were selected and compared with natural masson pine forest (Pinus massoniana Lamb.) as control. The phospholipid fatty acids (PLFA) were analyzed to indicate the soil microbial biomass and community composition.Result]Results showed that the total soil microbial PLFA contents as well as bacterial, fungal, actinomycic and protozoal PLFA contents under moso bamboo stands were all significant lower than that of masson pine forest (P<0.05), while no significant difference was found among bamboo stands. The total PLFA contents of soil microbial community as well as bacterial, fungal and protozoal PLFA contents were all significantly correlated with soil alkalytic nitrogen (AN) and available phosphorus (AP) contents (P<0.05), while the actinomycic PLFA content correlated with AN, organic matter contents and pH significantly (P<0.05). Soil microbial diversity, i.e. richness, Shannon diversity and Simpson diversity indexes, decreased progressively with the extensive management time of moso bamboo. According to the results of non-metric multidimensional scaling (NMDS), the soil microbial communities under moso bamboo and masson pine forest were significantly different (R=0.388 1, P=0.009). Furthermore, the soil microbial communities were different between the moso bamboo stands with short-term (5a, 9a) and long-term (15a, 18a) extensive management. The soil moisture, AN, AP and pH explained 90.28% of the total microbial community variation, among which the soil moisture, AN and AP contributed significantly to the microbial community variation (P<0.05). Conclusion]The results indicate that long-term extensive management has a negative effect on soil microbial biomass and result in shifting of microbial community structure. However, the ecological risks of the forest substitution and long-term extensive management still need to be further assessed.