Comparative Studies On Potential Carbon Sequestration Of Lakeshore Plants In Plateau Wetland, Northwestern Yunnan

Wetlands in northwestern Yunnan plateau, situated in the upstream of the Yangtze river and Mekong River, It is a typical wetland with enclosed and semi-enclosed character, which play key roles of adjusting the water and biodiversity conservation for middle-lower reaches of the rivers Meanwhile, for its lying the transition region of farming and grazing and noted as beauty spots, where yarded up many minority such as Tibetan, wetlands were regarded as the ecological barrier and environment foundation for local economic development and society stabilization. Wetland possess an important carbon sink function. Wetland lakeshore plants are the foundation of the wetland carbon sink function and the core. Photosynthesis of lakeshore plants and litter decomposition of wetland plants are two important phases for carbon cycle of wetland ecosystems and its trade-off is essential for the carbon sink function and carbon sequestration research on wetland ecosystems. Napahai wetland, one of the12Ramsar plateau wetlands, is located in the northwest Yunnan plateau. Its high biodiversity and uniqueness has received considerable concern worldwide. However, there is few studies on its function of regional carbon cycle and carbon sink and balance of greenhouse gases under a chilly and humid plateau climate. In this paper, three dominant lakeshore plants, Zizania caducifolia, Scirpus tabernaemontani and Heleocharis liouana were selected as target species. For each species their photosynthesis efficiency, population characteristics and biomass were measured by field survey and monitor and laboratory analysis, and their litter decomposition rate was determined by mesh bag method. The emphasis of this study were1)their photosynthetic efficiency, population characteristics and biomass, and their litter decomposition process and the characteristics of the decomposition,2)to analyze different lakeshore plants photosynthetic carbon sequestration, litter decomposition characteristics and ecological process,3) to discuss the carbon cycle process of wetland ecosystems and their roles of different lakeshore plants. The results showed that Photosynthetic rate, Transpiration rate, Stomatal conductance, Intercellular CO2concentration of three lakeshore advantage plants were different. Net photosynthetic rate of Zizania caducifolia (9.9±0.3mmol m-2s-1) and Scirpus tabernaemontani (8.5±1mmol m-2s-1) was significantly higher than those of Heleocharis liouana (7.6±1mmol m-2s-1)。 Zizania caducifolia, Scirpus tabernaemontani, and Heleocharis liouana all formed typical lakeshore monoculture communities with high biomass that varied among species. Aboveground biomass of Zizania caducifolia (853.6±58.2g/m2a) was significantly higher than those of Scirpus tabernaemontani (730.7±7.8g/m2a), and Heleocharis liouana (338.9±32.6g/m2a). In addition of a general trend of increase with rising mean monthly temperatures, their litter decomposition rates differed. The decomposition rate value k of Heleocharis liouana (0.067±0.0026) was the largest, followed by Zizania caducifolia (0.062±0.0072) and Scirpus tabernaemontani (0.039±0.0062). Cellulose content present significantly negative correlation with the decomposition rate, which is the main influence factors of plants litter decomposition of plateau wetland.Meanwhile, after one-year decomposition, the litter residual was62.0%±8.8%,47.5%±9.0%and44.5%±7.9%for Scirpus tabernaemontani, Zizania caducifolia and Heleocharis liouana respectively. Further analysis showed that the annual retention of aboveground biomass of Scirpus tabernaemontani (453.1±4.9g/m2a) was significantly higher than those of Zizania caducifolia (405.4±27.7g/m2a) and Heleocharis liouana (150.9±14.5g/m2a). These results indicated that litter decomposition rate of the lakeshore plants were low under the chilly and humid condition of Napahai wetland. Consequently a large amount of biomass of lakeshore plants could be accumulated into the soil in the form of organic matter, which served as a carbon sink function in such ecosystem. This study obtained a primary picture on carbon sink function and carbon sink process in Napahai wetland in the northwestern Yunnan Plateau and further study on plant-specific processes and their roles is needed to reveal the carbon sequestration processes and functions in this region.