Key Direction Project of Knowledge Innovation Program, Chinese Academy of Sciences
Taking the water-land interaction (interface of water, soil and organism) process of wetlands as research core, taking human activity effect on mass flux of wetlands and the effects of resources and experiments as the main line, this project intended to explore the evolution model of wetlands and the relation of human activities and wetland evolution, to reveal the balance relation of the water-land interaction of wetlands and the variety of mass flux and experimental effects, to reveal the time and space rule of CH4 emission of natural wetlands in China, and to suggest management strategies of wetlands which are fit for the situation of sustainable development in China. Wetlands are the key zone of sphere layers interaction of the ground. They are important experiment for human living, sensitive area and information base. Currently, it is very serious for wetland degradation in China. This research has theoretical significance for the establishment of theory system of wetland science. It also has instructive significance for wetland protection in China.
I. The water-land interaction process of palustrine wetland was mainly the changing process of the interactions of water, soil, and organisms caused by durative flooding time and flooding frequency. On one hand, it was resulted by the fluctuation of water level caused by alternation of wetting and drying. On another hand, it was caused by the change of contrast relation of wetland area and land area in drainage area. Water-land interaction process of lacustrine wetlands was mainly the redistribution of water and waterborne matter in wetlands.
II. Palustrine wetland was not only the source, but also the sink. On one hand, the unstable water level and the alternation of wetting and drying result the alternation of anaerobic environment and aerobic environment. At the same time, the change of wetland area in the drainage were resulted the change of the functions of “source” and “sink”.
III. The depth of static water level of palustrine wetland was the main reason of the difference of CH4 emission of different plants. The difference of plant density caused the difference of CH4 emission at different sampling sites growing the same species. The diurnal fluctuation of oxidization rate of CH4 was caused by the temperature and oxygen produced by photosynthesis transporting to the plant rhizome and rhizosphere. Palustrine wetland was converted from the sink of CH4 to the source when wetland was dredged. The emission of CH4 of palustrine wetlands in China is 1.76 Tg/a.
IV. Human activities were the main reasons why wetlands had changed seriously.
Innovation: This project revealed the characteristics and environmental effects of the modern processes of water-soil-organism surface in wetlands and gave the conclusion that human activities are the main reasons which cause the change of the modern process of water-land interaction in wetlands.