内蒙古草原区河流河滨带湿地生态系统退化与恢复演替过程及机理研究

Riparian zone is the interface or ecological ecotone between river system and adjacent terrace terrestrial ecosystems, which is the important part of the riverscape. Now riparian wetland has been included in the national ecological protected region because of its important ecosystem functions and huge value. However, due to human disturbance and utilization, most of the riparian wetlands have been degraded. In Inner Mongolia steppe regions, the riparian wetland (river floodplain wet meadow) is the most productive and highest biodiversity sites compared with adjacent terrace steppe, but due to excessive grazing, the vast majority also becomes degraded meadow. The ecological procession and mechanism for restoration succession of riparian wetland has not been clear because of its particularity and complexity. . Focusing on the reality that the riparian wetlands in Inner Mongolia steppe regions has been severely degraded and need more attention to the ecological rehabilitation and reconstruction, this project takes the typical riparian wetlands of Xilin River in the steppe region of Inner Mongolia where the livestock-husbandry economy is dominated as the study area. Based on the former works on the investigation of wetland biodiversity, spatial pattern of wetland communities, in situ monitoring for the fenced undegraded wetlands and the understanding and the knowledge from the studies on the restoration and succession mechanism of the adjacent typical steppe ecosystems by our research group, this project will take the formation of the spatial heterogeneity during the succession of the degraded riparian wetlands as breakthrough points, by simulated and controlled experiments of grazing, identify the changes, the ways and the leading factors of the different successional stages during the restoration succession. The main research contents focus on: the dynamics characteristics and formation mechanisms of biodiversity and productivity, interspecific relationships, content of water and nutrients in soil, and spatial heteregeneity among plant communities.. Based on the researches above, this project should reveal the mechanisms of degradation and restoration succession of the riparian wetland ecosystem in Inner Mongolia steppe regions. The results from this project will broaden and enrich the research content and field of riverscape and wetland ecology. This project will also provide the theoretical basis for the rational development, protection and management of riparian wetland, and the theoretical reference for rehabilitation, reconstruction and wetland ecosystem health (or ecological integrity) assessment of the degraded riparian wetland ecosystems in the steppe region of Northern China.

河流河滨带是陆地与河流水体系统之间的界面或生态过渡带，是河流景观的组成部分并具有重要的生态功能。然而，由于过度利用，草原区河流河滨带湿地生态系统大多处于较严重的退化状态，亟待恢复或重建。然而，由于湿地生态系统的特殊性与复杂性，其退化与恢复演替过程及其机理尚不明确。因此，本项目基于课题组对内蒙古高原和大兴安岭山地河流河滨带湿地植物多样性调查、湿地植物群落分布格局测定以及河滨带围封未退化湿地定位监测等前期工作，以内蒙古草原区典型的河流河滨带湿地生态系统为例，通过模拟放牧实验和放牧控制实验，系统阐释河流河滨带湿地生态系统退化与恢复演替过程中：1）群落生物多样性与生产力动态及形成机制；2）群落种间关系特征及其形成机制；3）土壤水分与养分资源动态与形成机制；4）群落空间异质性动态与形成机制，进而揭示其演替动力与机理。本项研究将充实恢复演替理论，亦可为草原区受损湿地生态系统的恢复与重建提供理论依据。

在阐释内蒙古自治区湿地空间分布动态及其驱动力的基础上，本项目开展了放牧退化湿地生态系统恢复演替过程和机理研究。依据项目计划任务书，完成既定研究内容，达到预定研究目标，取得预期研究成果。项目执行期内，发表标注论文17篇，合作编写专著1部，合作完成实用新型发明专利3项，计算机软件著作权2项；培养博士研究生3名，硕士研究生15名。.以内蒙古草原区锡林河、莫日格勒河、乌拉盖河、辉河和乌尔逊河等典型河流河滨带湿地生态系统为研究对象，同时，以岱海等湖泊湖滨带湿地生态系统结构与功能研究加以对比。本项目通过设置放牧和围封样地，分析测定了湿地植物群落特征、湿地植物功能性状、土壤理化性质、湿地微地貌、湿地土壤微生物的高通量测序（细菌和真菌的扩增子测序、宏基因组测序）以及稳定性氢氧同位素等指标。定量揭示了退化湿地生态系统恢复演替过程中湿地植物空间分布格局、湿地植物功能性状响应、湿地土壤理化性质变化、湿地土壤微生物多样性及其群落构建、冻融交替作用对河滨带湿地植物群落结构与生态系统功能的影响以及湿地植物水分来源与利用策略。主要研究结论如下：.1）放牧导致湿地植物群落个体“小型化”、生产力衰退，且根系分布浅层化，并出现刺菜等湿地退化指示种，但细菌群落组成结构多样性增加。变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、厚壁菌门（Firmicutes）为河滨带湿地土壤细菌群落组成的优势类群。湿地植物性状间通过互补与替代、在功能上的平衡变化以实现对放牧的适应。.2）放牧导致草原区河流河滨带土壤容重随着土层深度的增加呈增大趋势，含水率呈降低趋势，土壤pH值有所增加，土壤有机碳、全氮和全磷等养分含量降低。土壤水分与养分资源动态因微地形起伏呈现空间异质性。.3）湿地土壤冻融交替作用使得河滨带湿地土壤微地形起伏，进而土壤理化特征呈现空间异质性，为湿地生态系统恢复演替的物理动力。但放牧践踏导致河滨带微地形起伏差异变小，“塔头”和“塔头间”湿地植物出现趋同性。