湿地生态系统对气候变化的响应

气候变化常伴随着区域气温及降雨条件等发生变化,对湿地水文、生物地球化学过程、水质与水循环、湿地能量平衡与湿地生态功能等产生较大的影响。湿地水文条件是决定湿地生态过程的关键因子,气候变化引起的地表积水水位变化直接影响湿地植物优势种群结构的演替及氧化-还原环境条件的变化,导致湿地生态过程的变化及温室气体排放强度和时空分布特征等的变化。气候对湿地结构和功能的影响还包括营养物质和矿物质的循环及食物链的动态变化等。

Influence of Global Climate Change on Wetlands

Climate change is generally accompanied by the change of regional atmospheric temperature and precipitation pattern. These will bring great impacts on the hydrology and biogeochemistry processes, water quality, water cycle, energy balance and ecological function of wetlands. Wetland hydrology is a key factor that determines wetland ecology. Water-table fluctuation due to climate change will directly influence the succession of dominant plant communities and the shift of the oxidation/reduction condition within wetland, which will result in the change of ecological processes, the discharge rate and spatial-temporal distribution of greenhouse gas. Wetlands play a key role in controlling the terrestrial carbon cycle as they have the ability to mitigate atmospheric carbon into peat. Though wetlands have mainly acted as C sinks, but they also release C back into the atmosphere over time. The main sources of loss are; as C02 from plant respiration and aerobic peat decomposition; CH4 from the anaerobic decomposition of peat; and as dissolved organic carbon from the i-nundating of soil organic matter in water. Wetlands also are an important source of dissolved organic carbon for ponds and streams, The outflow of dissolved organic carbon is related to total annual precipitation and will be affected by temperature and precipitation, Some climate change scenarios suggest a decrease in wetland discharge and dissolved organic carbon outflow. As to the response of wetlands to climate change, there are many aspects remain unclear. C losses in wetlands are very important, especially in response to a changing climate, the main control on a wetland's ability to retain carbon and to generate CH4 and dissolved organic carbon is determined by its ability to remain wet in large part, Shifts in seasonal hydrology caused by a changing climate should have measurable impacts on the accumulation or loss of organic carbon from wetland soils. Climate changes that results in lower water table could significantly alter the quantity and quality of wetland habitats for waterfowl. A warmer, drier climate could be lower waterfowl production directly by increasing the drought frequency in the basins and indirectly by producing less favourable cover ratios and encouraging dense growth of entagering vegetation, which generally provides lower quality waterfowl habitat. Wetland response to the conditions depends on the type of wetland and its geomorphology and water depth. The response of the plant community depends on factors such as past plant distribution, vegetative spread, germination conditions , survival rates under flooding and drought and dispersal mechanisms. The simulation study on the change of wetland biotope relative to climate change, the relationship between wetland hydro-geochemical processes and succession of wetland plant communities, and the quantification study on the impact of climate change on the structure and function of wetland should pay more further attentions in the future research.