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林火对重庆缙云山典型林分土壤细菌群落及酶活性的短期影响

Short-term effects of forest fire on the soil bacterial community-enzyme activity in typical forest stands in Jinyun Mountain, Chongqing

  • 摘要: 森林火灾是森林土壤及生物多样性产生的一个驱动因素。特别是在容易发生火灾的生态系统中,火灾对土壤微生物群落以及酶活性的影响复杂,在很大程度上仍然是未知的。因此,分析火灾后短期土壤细菌以及酶活性的变化动态对理解森林群落的重建过程具有重要的生物学意义。以重庆缙云山火灾后针阔混交林和竹林的土壤为研究对象,在火灾发生的1个月内,对不同火烧强度下针阔混交林和竹林0~10 cm和10~20 cm土层进行采样,测定土壤中蔗糖酶、纤维素酶和脲酶的活性以及土壤养分及pH的变化情况,采用高通量测序测定技术分析土壤中细菌群落结构变化。结果表明:1)在林火发生后短期内土壤细菌多样性、丰富度、土壤有机质以及土壤酶活性都有所下降,土壤pH、速效钾、有效氮、有效磷都不同程度的上升,尤其在0~10 cm土层受林火的影响更强。2)土壤中变形菌门、放线菌门和绿弯菌门的相对丰度在遭受中度和重度林火后最高;酸杆菌门的相对丰度在未遭受林火时最高;厚壁菌门的相对丰度在轻度火烧后最高。3)在土壤细菌结构与土壤化学因子的冗余分析中发现,火灾后土壤化学性质的改变也会影响土壤细菌群落和土壤酶活性。森林火灾会导致土壤细菌群落多样性下降,土壤酶活性显著下降。中度和重度火灾对土壤细菌多样性和酶活性的影响最大,通过冗余分析得知变形菌门与土壤养分呈正相关,酸杆菌门与土壤养分和pH值呈负相关。

     

    Abstract:
    Background Forest fires are a driver of forest soil and biodiversity, especially in fire-prone ecosystems. The effects of fire on soil microbial communities as well as enzyme activity are complex and largely unknown. Therefore, analyzing the dynamics of soil bacteria and enzyme activities in the short term after fire is of great biological significance for understanding the reconstruction process of forest communities.
    Methods The soil of conifer and broad-leaved mixed forest and bamboo forest after the fire in Jinyun Mountain, Chongqing was used as the research object. The activities of sucrase, cellulase and urease as well as the changes of soil nutrients and pH were measured in the soil layers of 0-10 cm and 10-20 cm of conifer and broad-leaved mixed forest and bamboo forests under different fire intensities within one month of the fire, and the changes of soil bacterial community structure were analyzed by high-throughput sequencing technology.
    Results 1) The soil bacterial diversity, richness, soil organic matter and soil enzyme activities decreased in the short term after the occurrence of forest fires, and soil pH, available potassium, available nitrogen and available phosphorus increased to varying degrees. Especially in the 0-10 cm soil layer, it was more affected by forest fire. 2) The relative abundance of Proteomycetes, Actinomycetes and phylum Aerugula in the soil was the highest after moderate and severe forest fires. The relative abundance of Acidobacterium phylum was the highest when not exposed to forest fires. The relative abundance of Firmicutes was the highest after mild fire. 3) In the redundant analysis of soil bacterial structure and soil chemical factors, the changes of soil chemical properties after fire also affected soil bacterial communities and soil enzyme activities.
    Conclusions Forest fires can lead to a decrease in soil bacterial community diversity and a significant decrease in soil enzyme activity. The results indicate that moderate and severe forest fires have the greatest impact on soil bacterial diversity and enzyme activity, with a positive correlation between Proteobacteria and soil nutrients. Acidobacteriota demonstrates negative correlation with soil nutrients and pH value.

     

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