野猪翻拱对土壤氮同化网络影响研究

Wild boar grubbing has been reported to affect soil physical, hydrological and chemical properties seriously, and its influence on the composition and function of the soil biome is still little known. The composition of forest soil biological community is extremely complicated, and it is very sensitive to disturbance. It is difficult to clarify its response mechanism to wild boar disturbance. This project will select the temperate broad-leaved Korean pine forest that is a typical vegetation as the research object and measure soil biological community composition periodically in the boar disturbed and undisturbed plots. Combining with the determinant of soil physical and chemical properties, biological community activity and nitrogen assimilation process using network analysis theory and technology, we will plan to know the relationship between soil biological interactions between each taxon clearly. After determining the trophic relationship between all kinds of group, we will build the soil N assimilation network and give a model that represents soil nitrogen assimilation network of the forest ecosystem by wild boar grubbing. We will explore the mechanism of grubbing disturbance on soil nitrogen assimilation network topology structure and function, and document the relations of the network structure and the function of nitrogen assimilation. Our results would provide scientific evidence for evaluating the nitrogen cycle and large-scale animal management of forest ecosystem in China.

野猪对森林地被层翻拱干扰逐年加重，土壤结构、理化性质和水文条件均受到严重影响，而对土壤生物群落组成和功能的影响却鲜见报道。森林土壤生物群落组成复杂，对诸如野猪翻拱的干扰极为敏感，研究单一类群难以澄清其对该干扰的响应机制。本项目以温带典型植被阔叶红松林为研究对象，采用网络分析理念和技术，将土壤生物群落作为有机整体考量，通过对翻拱迹地和未翻拱样地比较，研究野猪翻拱对土壤微生物和主要动物群落组成和活性的影响，探明土壤生物各分类单元间的共存关系；结合15N稳定同位素示踪、探针技术和巢式标签DNA宏条形码技术，剥离出营养型互作关系，构建土壤N同化网络。提出野猪翻拱干扰情景下的森林生态系统土壤氮同化网络模式，阐述翻拱对土壤氮同化网络拓扑结构和功能的作用机制，探讨土壤氮同化网络结构与氮同化功能的关系，为评估大型动物对森林生态系统氮循环影响提供科学依据。

本研究以我国温带地带性顶级群落阔叶红松林为研究对象，定期检测野猪翻拱迹地和围栏对照样地土壤微生物群落组成，结合土壤理化性质、土壤酶活性和氮转化过程测定，探究了野猪翻拱对土壤生物群落组成和功能的影响，初步阐明温带森林生态系统土壤微生物组成和功能对野猪翻拱干扰的响应机制，以及影响生物群落氮同化的主要因素。主要结论如下：(1)翻拱后，土壤细菌群落更容易受到外界环境的干扰，稳定性较弱；优势门均为变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和酸杆菌门(Acidobacteriota)；优势属均包括Candidatus Udaeobacter，Subgroup_6，Subgroup_2，热酸菌属 (Acidothermus)。翻拱后，土壤真菌群落稳定性较弱，更容易受到外界环境的影响；优势门均为担子菌门(Basidiomycota)和子囊菌门(Ascomycota)；优势属均包括中国丝盖伞属(Inocybe)，被孢霉属 (Mortierella)，Urnula和短梗蠕孢属(Trichocladium)。翻拱后，土壤原生动物物种丰富度增加，群落更加稳定；优势门为后鞭毛生物(Opisthokonta)；优势属均包括Chrysophyceae_C和秃毛虫科(Oxytrichidae)。(2)翻拱有利于提高土壤铵态氮、硝态氮的浓度，在我们的研究中，翻拱对土壤铵态氮和硝态氮的影响幅度存在时间效应，这可能是因为年份间降水和气温因素引起的土壤温湿度差异造成的。但翻拱确实会影响土壤氮库且促进了土壤氮转化速率。翻拱有利于提高纤二糖苷酶(BCE)和β-N-乙酰氨基葡糖胺苷酶(NAG)的活性，在我们的研究中，翻拱对土壤酶活性的影响幅度存在时间效应。(3)值得注意的是，在生长季初，野猪翻拱提高了疣微菌门(Verrucomicrobia)和芽单胞菌门(Gemmatimonadetes)相对丰度，二者均是参与土壤氮循环过程的主要微生物类群，与土壤氮含量呈负相关；降低了热酸菌属 (Acidothermus)和假丝酵母菌属(Candidatus Solibacter)的相对丰度，这可能是影响森林氮同化的原因。同时，我们分离鉴定线虫属68个，翻拱显著影响不同营养类群的相对丰度。综上，野猪翻拱改变了一些重要微生物和动物功能群的相对丰度，进而对土壤氮同化网络产生影响。