我国不同森林生态系统中木腐真菌物种多样性与群落构建机制研究

Community assembly has long been the central interest of ecologists. Habitat filtering and dispersal limiting are the key ecological processes involved in community assembly. At present, the studying about community assembly is mainly focus on the botanical community while fewer on the microbial community. As the important microbial group, wood-decaying fungi are the key components of forest ecosystem due to their ability of wood degrading and promoting the nutrient cycling of the forest ecosystem. In China, there are various forest types. For the difference of trees, soils and climate in different forest ecosystems, we guess there must be the variation with species diversity and community assembly of wood-decaying fungi. To verify this assumption, a series of studying will be carried out, including the wood-decaying fungal species and the relevant environmental factors (including the characters of fallen wood, geographical conditions and climate factors) investigation with ten durable monitoring big plots across 10 different forest types of temperate zone, subtropical zone and tropical zone in China. The fungi identification will carried out by their morphology and ITS sequence. The high-throughput sequencing will be used to detect the fungal biodiversity in the fallen wood. The relevant analysis between fungal diversity and the environmental factors, including wood character and climate.The discrepancy of species composition and community assembly of wood-decaying fungi will be found in different forest ecosystems. After analyzing the causes of discrepancy, the mechanism of wood-decaying fungal community assembly in China will be revealed. These studies will help to find the ecological function of microbe in forest ecosystems.

群落构建机制是生态学研究的核心论题，而环境选择和扩散限制是群落构建的两个重要过程，目前关于群落构建机制的探讨主要集中在植物群落，而对微生物群落的关注较少。木腐真菌作为降解木材的微生物类群在森林生态系统中具有重要生态功能。我国森林类型多样，不同森林生态系统的植物、土壤、气候不同，其木腐真菌的物种多样性和群落构建机制是否也存在很大差异？为此，本研究拟依托在我国不同森林生态系统（温带、亚热带、热带）中建立的永久性监测大样地进行木腐真菌调查，以宏观形态和ITS序列进行物种鉴定；对倒木木屑进行DNA提取，运用高通量测序技术研究倒木中木腐真菌多样性；对木腐真菌物种多样性与倒木特征、气候等因子进行相关性分析，阐明不同森林生态系统中木腐真菌物种组成和群落构建的差异；通过对比分析差异的形成原因，揭示不同森林生态系统中木腐真菌群落构建机制。本研究将为深入研究微生物在森林生态系统中的生态功能提供理论依据。

在对我国温带、亚热带和热带森林生态系统的代表林分和大样地进行充分采样的基础上，共采集真菌标本近5000份，倒木样品近1000份，土壤样品500余份，详细记录了各样地中的环境因子和倒木信息。对所采集的真菌标本进行形态和分子鉴定，明确了不同类型林分中木腐真菌的种类组成、优势种及其功能。对倒木样品和土壤样品开展了高通量测序和理化因子的测定，查明了不同基质中的真菌群落组成及其理化性质，包括含水量、pH值、CNP含量、纤维素、木质素和半纤维素含量，测定了木屑中纤维素降解酶和木质素降解酶活，在获得上述数据的基础上，采用PCA分析和NMDS分析查明不同林分、不同倒木中真菌群落的组成差异及其主要影响因子。基于木腐真菌子实体，中国目前已报道木腐真菌种类1823种，有77种在7大区域均有分布，为全国广布种，在森林生态系统木腐真菌群落中占有优势地位，对生态系统中的物质循环具有重要作用。热带地区独有种最多，为370种。林分类型、倒木直径和数量、腐烂程度是影响木腐真菌种类和数量的重要因素。基于高通量测序结果，不同地点、不同树种、不同特征倒木基质中的木腐真菌组成均有很大差异，倒木中全C、全N、全P和水分含量是造成这种差异的最主要原因，不同真菌对营养偏好存在差异，有些担子菌和子囊菌倾向于高氮基质，有些担子菌倾向于选择高C和高C/N比的倒木基质，而多数子囊菌倾向于选择高P基质。另外，土壤真菌是倒木中真菌的主要来源，倒木中木生真菌的群落组成与土壤真菌群落的相似度随着与土壤空间距离的减少而增加。倒木不同理化性质对真菌群落组成的影响造成多种木质素降解酶活的差异，不同树种倒木中的降解酶活表现出不一样的规律。本研究结果阐明了不同森林生态系统中木腐真菌物种组成和群落构建的差异；揭示了不同森林生态系统中木腐真菌群落构建机制，为今后深入研究微生物在森林生态系统中的生态功能提供了理论依据。