大兴安岭多年冻土湿地土壤动物群落分布格局及其对环境变化适应机制

The permafrost is a unique type of mountain marsh formed in the conditions of high latitude or high elevation. The Greater Xingan Mountain is only a piece of high latitude permafrost distribution area in China, which is natural defense for Songnen Plain of Northeast China, North China Plain and the Inner Mongolia Hulun Buir Grassland, and it has an important role to prevent permafrost degradation and conservation of soil carbon stocks. By the impact of the climate warming and the influence of human activities, the Greater Xingan Mountain permafrost began to degrade seriously since late Pleistocene, and results in the area of permafrost and marsh shrinking, the loss of soil biodiversity and the ecological functions decline. The degradation of the permafrost and marsh in Greater Xingan Mountain region has become one of the most important issues in ecological studies. The aim of this project is to conduct a study of the composition of soil animal and its diversity of the permafrost and marsh. The distribution pattern of dominant group, food resource and trophic level feature are studied by adopting the molecule technology, ecological stoichiometry and isotope methods in permafrost and marsh of Nenjiang River source at Greater Xingan Mountain permafrost and marsh. We hypothesize that the changes in vegetation characteristic occurring at different development stage of the marsh and at vary degree of disturbance, reduce the food resource of soil animal, which may lead to trophic position and function decrease. To address our hypothesis we will investigate soil animal community and environment factors at undisturbed area and disturbed area with deforestation and wildfire to varying degree. We will use these data to analyze the food resource and trophic level of dominant groups, and change of the key element of permafrost soil under coexist of permafrost and marsh, to elucidate the influence of the food web structure of soil animal and change trend of key element of permafrost soil on wetland ecosystem and trophic cascade effect under environment condition change, which had be resulted by the stage of the development of marsh and disturbance. The result will help to understand the key role of soil animal in biogeochemical cycle at permafrost and marsh, and also benefit to ecosystem conservation and wetland sustainable development of permafrost and marsh of Greater Xingan Mountain.

大兴安岭多年冻土湿地退化导致土壤生物多样性减少、湿地生态功能下降，已成为当前重要的生态学问题之一。项目拟在具有代表性的大兴安岭嫩江源头区域，选择未受干扰的多年冻土湿地与受采伐、火灾干扰的多年冻土湿地两种类型，研究多年冻土区典型的兴安落叶松沼泽湿地土壤动物群落多样性、功能群组成与分布格局。结合稳定同位素、分子生物学与生态化学计量学等技术手段，分析多年冻土与湿地共存条件下，土壤动物优势类群的食物源、营养级变化与多年冻土湿地主要营养元素的迁移规律，阐明沼泽不同发育阶段与外界干扰的不同强度所致湿地环境变化条件下，冻土湿地土壤动物食物网结构与能量流动对湿地生态系统的影响及湿地生态系统营养级联效应，为进一步研究大兴安岭多年冻土湿地土壤动物群落演化规律，揭示土壤动物在多年冻土湿地生物地球化学循环中关键作用及大兴安岭多年冻土湿地生态系统保护与生物多样性保育提供科学依据。

选取广泛分布于大兴安岭的兴安落叶松-狭叶杜香-藓类沼泽、兴安落叶松-兴安杜鹃-藓类沼泽、兴安落叶松+白桦-苔草沼泽以及研究区域内2006年经过重度火烧落叶松-兴安杜鹃和中度火烧后落叶松+白桦两种典型干扰类型，研究植被演替与火干扰对地下与地下土壤动物群落特征与分布格局的影响。研究结果显示，研究时段，土壤表层与地表土壤动物群落分布格局与群落变化趋势不一致，其变化明显与栖息生境环境有关。具体表现为：（1）研究时段，土壤化学计量特征随地上植被演替发生明显的变化，且在兴安落叶松+白桦-苔草沼泽类型土壤C、N、P、S的含量明显高于其他湿地类型。（2）研究区域土壤线虫群落丰度随地上植被演替过程发生明显变化。与土壤化学计量特征相似的是，兴安落叶松+白桦-苔草沼泽类型土壤线虫丰富度指数明显高于其他类型（F=8.20，p=0.003）。研究区域土壤食物网以真菌为基础的分解通道占优势。中度火干扰导致土壤线虫群落种群数量增加。杂食性土壤线虫生态位因演替与重度火干扰变化幅度较大。生态指数特征分析显示，研究区域土壤生态系统较为稳定，是一具有较好自我调整能力的、健康的生态系统，火干扰并未对调查时段整个群落的稳定性造成较大的影响。RDA分析显示，土壤pH对土壤线虫群落发展具有抑制性作用，而土壤全氮、有机质与土壤硫含量均对土壤线虫群落发展具有促进性作用。（3）地表土壤动物主要以蚂蚁、弹尾类-疣跳科等优势类群为主。地表土壤动物群落多样性指数与植被类型存在显著相关性（p =0.05）。地表土壤动物对研究区域资源的利用差异性显著（p＜0.01）。火干扰后，同一沼泽类型地表土壤动物群落相似性较低，因可利用资源减少而导致其生态位普遍重叠值指数下降。（4）对地表优势类群—蚂蚁体内稳定性同位素N、C分析显示，虽然蚂蚁因其食物源和生物的新陈代谢两个方面变化程度较低，受地上植被演替与火干扰影响不显著，但蚂蚁食物网结构因地上植被演替和火干扰而发生了明显的改变，这可能与陆生有机质源的变化有关。（5）地表土壤动物分布与空间尺度相关。不同空间尺度上，土壤动物具有高度的空间异质性，其变异函数理论模型可以通过指数模型、高斯模型以及直线模型进行拟合。土壤动物空间异质性主要与空间自相关因素相关。. 项目执行期内，完成了计划研究内容，发表论文一篇。