The Spatial Distribution Of Wetland Vegetation And Its Ecological Process And Function On Riparian Zone Of Riverscape In Inner Mongolia Grassland

Riparian zone is the interface or ecological ecotone between river system and adjacent terrace terrestrial ecosystems, which is an important part of the riverscape. Riparian zone possesses an important functions and values of ecosystem. While wetland plants and their communities on riparian zone play essential roles in maintaining these functions and values, and also the spatial distribution pattern of wetland plant communities affects the expression of ecosystem functions. The focus on riparian zone will associate Riverscape Ecology which is one of hot area of current ecological research with Wetland Ecology.Selected the riparian zones of the typical inland rivers-Wulagai River and the Xilin River in the grasslands of Inner Mongolia as the main object of study, this paper determined the field experimental area and the experimental plots firstly, and then by the survey of wetland plant biodiversity and plant communities, the measure of the physical and chemical characterizations of soil and river water column, the analysis of micro-topography of riparian zones, and the mapping of riparian vegetations, the formation and maintenance mechanism for the spatial distribution pattern of riparian vegetations at different scales was illustrated, with combining the spatial habitat heterogeneity with biological adaptation and inter-specific competition of wetland species in riparian zones. In addition, based on a comparative study between the enclosed conservation plots and grazing degradation plots, this paper analyzed the degradation characterization of wetland on riparian zone by the human disturbances. Finally, based on modeling the ecosystem function and process of riparian vegetation on riparian zone, the spatial distribution pattern of vegetation was combined with its ecosystem functions and processes. The main conclusions are as followed:1. On the watershed scale, the wetland vegetation on riparian zone along the longitudinal direction presents wooded swamp, shrub swamp, wet meadow, herbaceous swamp and herbaceous saline meadow, from the river source to the end of river, which is forming the spatial distribution pattern named riparian sourceward banded zonation. The Elevation, Temperature (annual mean temperature, insolation duration) and moisture (annual precipitation) are the main environmental factors affecting the formation and maintenance of this pattern. 2. On the river reaches scale, along the wetland vegetation on riparian zone along the lateral direction presents aquatic plant communities, shoreline pioneer plant clusters, wet meadow communities and saline meadow communities, from river water column to terrace, which is forming the spatial distribution pattern named riparian shoreward banded zonation. The Microtopography, spatial heterogeneity of physical and chemical characteristics of soil, the biological adaptation and inter-specific competition of wetland plants determine this pattern together.3. Grazing affects the riparian shoreward banded zonation of wetland plant communities, which is expressed on the change of dominant species in the wetland communities, the gradually transition of the hygrophyte to the xerophytic, significantly reduction of the aboveground and belowground biomass, the reduction of content of soil organic carbon, total nitrogen and total phosphorus, and the increase of soil compaction.4. Based on system dynamics software (STELLA), the model of ecosystem function and process on riparian zone was built. The model simulation showed that the aboveground and below-ground biomass of plant communities on lower riparian zone was significantly higher than that of the higher floodplain and "Tatou" wetland on riparian zone. The micro-topography of riparian zone is the important factor affecting the accumulation of soil organic carbon. The wetland plant communities on lower riparian zone have the greatest contribution to organic carbon. There are differences of the aboveground biomass, soil respiration, and the decomposition of organic matter of plant community on riparian zone, while the photosynthetic capacity remains constant through the forecast of this model.Based on the principles of wetland ecology and riverscape ecology, from the habitat heterogeneity of riparian zone, the spatial distribution patterns of wetland vegetation at different scales was associated with ecosystem functions and processes in order to broaden and enrich the research content and field of riverscape ecology. The results of this thesis can provide a theoretical basis for the rational development, protection and management of wetland in the grassland region of Northern China. This thesis also provides the theoretical reference for rehabilitation, reconstruction and wetland ecosystem health (or ecological integrity) assessment of the degraded wetland ecosystems. This issue also covers the study of species diversity and species composition in the wetland communities, so it also plays an important role in the guidance on wetland biodiversity conservation and management.