Energy Balance And Water Vapor Flux Of Snail Control And Schistosomiasis Prevention Forests Ecosystem In Yangtze Rive Beach Land

As the rich land resources of the Yangtze River Basin, feasible climate conditions and ecological environment of the beach land are being advantage to multiply of the snail and infection of the schistosomiasis, and harmful to the health of the local people, and also become an obstruct for economic development. Snail control and schistosomiasis prevention forests are ecological forests, have multiple benefits such as snail control and schistosomiasis prevention, economic, ecological etc, and restrain growth of the snail effectively, prevent infection of the schistosomiasis and those effects are well recognized by people gradually. Hence, snail control and schistosomiasis prevention forests were become exploitation method of the beach land. But its snail control mechanism, such as how snail control and schistosomiasis prevention forests control the snail, is still unclear. Some researchers thought the change of beach land environment especially the changes of water cycle is the main reason of its snail control effect. From the aspect of soil-vegetation-atmospheric system, and by using open eddy covariance system and tree sap flow methods, studies were carried out in schistosomiasis prevention forests ecosystem which was the key experiment and demonstration spot of forests ecology to control snail project in Junshan district of Yueyang city, Hunan province, the ecological system energy balance and water vapor flux of the snail control and schistosomiasis prevention forests were analyzed in this paper, and also characteristics of energy distribution of energy balance components and its energy closure level, dynamics of soil moisture condition were well discussed. The purposes of this research are to understand the energy flow; characteristics of water consumption by transpiration and water vapor flux of the snail control and schistosomiasis prevention forests, and lay the foundation for further researches on environmental mechanism of snail control and schistosomiasis prevention. Main results and conclusions are the following:Energy partitioning components had similar diurnal variation in snail control and schistosomiasis prevention forests ecosystem. The ratio of energy partitioning in different components were not the same in different time scale. Those ratio was mainly controlled by the seasonal change. The annual net radiation was 2471.81 MJ/m2 in 2006; the latent heat flux was 77% of the net radiation, the sensible heat flux was 9.79% of the net radiation, the soil heat flux and others only took about 3.2% of net radiation. The energy closure level was high in different time scale, which showed datum observed by Eddy Covariance open path system was credible. But there still had 16% energy missed.Soil moisture had the feature of spatial and temporal scale, and the difference of soil water content in different soil layers is significant. The monthly dynamic changes of soil moisture in different soil layers are uniform. Three typical factors (Vi,Ui)(i=1,2,3) influenced the soil water content. Under stronger precipitation, the surface soil play more important function in water change; temperature and soil temperature took contrary action. Environmental factors affected evaporation and transpiration such as radiation, rainfall precipitation, air temperature and humidity, wind speed, etc, can change soil water status significantly. Soil water storage capacity is affected by precipitation and evapotranspiration of stand. When entering into the growth period, with the active growth of stand and enhanced evapotranspiration, soil water storage capacity gradually decreased.Difference of sap flow velocity during different growth stages, different weather conditions and tranks in different directions. In sunny days, Poplar sap flow density variations showed regular single-peak curve. The tendency of circadian rhythm was high in daytime, while was low at night. In wet days, Poplar sap flow velocity daily variations were irregular and different environmental factors had different influences on sap flow. It was positive correlation between photosynthetically active radiation, air temperature and sap flow velocity, while it was negative correlation between air humidity. Snail control and schistosomiasis prevention forest's transpiration rate was low during early growth period and less than 1mm, while its mean value reached more than 3.0mm at the beginning of July. It was close correlation between transpiration rate quarterly variation and precipitation timely distribution.Water vapor flux had regulated diurnal process; dynamic process was different in sunny days and cloudy days. The water vapor flux in sunny was higher than that in cloudy days. Water vapor flux of the ecosystem was positive in each season, which showed the ecosystem was water sink. Water vapor flux in summer was higher than in spring and autumn, while the water vapor flux in winter is lowest whole year. The evapotranspiration was 48.45% of precipitation in 2006. Environment factor effected the water vapor flux variation. Net radiation and ground heat were key factors to affect water vapor flux. The response of environment factors was different in different weather condition, while the same factor is also has different influence in different weather condition. Correlative coefficient of stepwise regression analysis model was 0.92 in sunny days, and that was 0.81 in cloudy days.