兴安落叶松林(Larix gmelinii forest) 土壤微生物对火干扰的响应机制研究

Fire is a significant disturbance for the forest ecosystem. However, it was limited for understanding of soil microbial communities and their functions in burned area because of forest fire’s sudden and catastrophic nature, the diversity and complexity of soil microorganisms, especially the limitation of the technology of soil microbiology. In recent years, the improvement of biomarker and other technologies have provided new opportunities for studying the relationship between soil microorganisms and forest fire. A typical ecosystem, Larix gmelinii forest which fire disturbance is frequent and sensitive to climate change, is selected as the research object. The soil microbial habitat indexes, communities composition and functional genes distribution would be studied by phospholipids fatty acid, high-throughput sequencing and real-time quantitative PCR. Adopting the concept of space as a substitute for time, the spatial and temporal distribution pattern of soil microorganisms would be determined, which would change with the temporal and spatial changes of habitats in Larix gmelinii forest burned area. Based on the results of microbial communities changes in chronosequence of soil in burned area, the relationship between microorganisms and fire disturbance and stand factors would be analyzed under the guidance of ecological theories and repeated modelling. The purpose of the study is to reveal the response mechanism of soil microorganisms to fire disturbance in Larix gmelinii forest. This project would fill the gaps in related domestic research and provide a useful exploration for interdisciplinary research such as Forest Fire Ecology and Soil Microbiology in China, and provide technical support for the restoration of forest ecosystem after fire disturbance.

受森林火灾突发性、灾难性和土壤微生物多样性、复杂性的影响，特别是土壤微生物学研究技术手段的限制，对于林火这一显著生态因子干扰下的土壤微生物的认识十分有限。近年来生物标记等技术的进步为研究林火与土壤微生物的关系提供了新的契机。本项目选取火干扰频繁且对气候变化敏感的典型森林生态系统类型—兴安落叶松林为研究对象，利用磷脂脂肪酸(PLFA)、高通量测序(HTS)和实时荧光定量PCR(qPCR)等技术测定其微生物生境指标、群落组成及功能基因分布，采用空间代替时间法确定土壤微生物随生境变化的时空分布格局，基于不同土壤演替序列在生态学理论的指导和模型的反复拟合下，分析火干扰、林分因子及微生物相互关系，以期揭示土壤微生物对火干扰的响应机制，对我国林火生态学与土壤微生物学等交叉学科研究进行有益的探索，填补国内相关研究空白，为森林土壤火干扰后森林生态系统的修复提供技术支撑。

土壤对火干扰的响应是阐明森林生态系统响应火干扰的重要环节，是研究森林火烧迹地生态恢复机制的重要内容之一。受森林火灾突发性、灾难性和土壤微生物多样性、复杂性的影响，特别是土壤微生物学研究技术手段的限制，对于林火这一显著生态因子干扰下的土壤微生物的认识十分有限。针对上述背景，本项目以火干扰频繁且对气候变化敏感的典型森林生态系统类型—兴安落叶松林(Larix gmelinii forest)为研究对象，以火后恢复时间为主线，以火烧迹地立地条件为辅线，选取1990-2018年间12个火烧迹地内80块研究样地，测量地形因子（坡度、坡向、坡位、海拔）、乔木变量（物种、密度、胸径、生物量），采集0-10cm的表层土壤样品，通过量化土壤理化性质和微生物群落的影响因子，明确了火后恢复时间、立地条件、植被状态、土壤生境因子、水溶性有机质（WSOM）、生态酶化学计量特征和土壤微生物群落的关联和作用路径，探索了兴安落叶松林火烧迹地土壤微生物群落的潜在演变特征与形成机制，取得的主要研究结果如下：（1）火干扰可以改变生物和非生物变量对北方落叶松林土壤生境因子的重要性和相对重要性。（2）火干扰、立地条件和植被共同决定土壤WSOM特征。（3）火干扰、立地条件和植被共同决定土壤生态酶化学计量特征。（4）不同火烧迹地的土壤细菌群落在门水平上差异不大，变形杆菌门（Proteobacteria）和酸杆菌门（Acidobacteria）均为优势门类，而氨氧化过程由氨氧化古菌（AOA,Ammonia Oxidizing Archaea）主导。（5）火干扰、立地条件通过植被和土壤理化性质间接影响土壤微生物群落。在此基础上，阐明了火后恢复时间和立地条件影响土壤微生物群落的机制，揭示了恢复时间相同的火烧迹地土壤生态系统存在差异的原因，进而提出了与火后植被演替过程相仿的人工干预或许是促进火烧迹地土壤生态系统恢复进程的有力手段，而与植被演替过程相悖逆的人工干预则很有可能延缓其恢复速率的策略，以上研究成果为优化北方森林管理策略和促进其火烧迹地生态恢复提供了丰实的数据支撑和理论依据。