【作者】 王昭艳；

【导师】 彭镇华； 张旭东；

【作者基本信息】 中国林业科学研究院 ， 森林培育， 2008， 博士

【摘要】 长江流域丰富的土地资源——滩地,因其适宜的气候条件和生态环境,利于钉螺的孳生,导致血吸虫病流行,严重危害当地人民的身体健康,影响经济发展。多年实践证明抑螺防病林可以有效地抑制钉螺生长,防止血吸虫病的流行,越来越得到大家认同,已经成为积极响应的滩地开发模式,但是其抑螺防病林的抑螺机理目前尚未明确。有学者认为滩地环境改变,特别是滩地水分条件改变是其抑螺的根本原因。本论文以湖南岳阳市君山区“兴林抑螺”林业生态重点试验示范的抑螺防病林生态系统为研究对象,从土壤-植被-大气系统的角度出发,在典型调查的基础上,采用运用涡度相关法(Eddy covariance,EC)开路系统、树干液流(Sapflow)法进行定位观测,结合定量与定性分析方法,开展长江滩地抑螺防病林生态系统能量平衡、土壤水分动态变化、蒸腾耗水和水汽通量研究,旨在掌握抑螺防病林土壤水分动态变化特征、蒸腾耗水规律以及水汽通量格局,为全面深入探讨抑螺防病环境机制,揭示其抑螺防病机理奠定基础。主要研究结论如下:(1)长江滩地抑螺防病林生态系统,能量各平衡组分具有相似的日均变化过程规律,但不同时间尺度上,该生态系统能量平衡各组分分配比例不同,不同的季节收入量差异明显,年内的变化过程主要受季节气候的变化影响。2006年,净辐射通量全年共2471.81 MJ/m2,潜热年通量大约消耗77%的净辐射能,显热年通量占净辐射能19.79%,土壤热通量全年为负值,表现为土壤释放热量,植物体储能等部分大约占净辐射能的3.21%。不同时间尺度的能量闭合水平都较高,说明该站点的涡度相关法观测数据通量数据质量可靠,依然存在能量16%不闭合现象。(2)土壤水分具有显著的时空尺度特征,不同层次土壤水分含量变化差异显著。各层土壤水分月动态变化趋势基本一致。土壤含水量主要受3个典型因素(Vi,Ui)(i=1,2,3)的影响。在较强的降水的时候,表层在土壤水分变化中起着较为重要的作用;空气温度和土壤温度所起的作用相反,影响蒸发、蒸腾作用的辐射、降雨量、空气温湿度、风速等环境因子都可以明显改变土壤水分的状况。土壤蓄水量不仅与降水有关,而且跟林分的蒸散密切相关,进入林分生长期以后,随着林分生长活跃,林分蒸散的增强,土壤蓄水量持续减少。(3)不同生长时期、天气条件以及树干不同方向上液流速率的差异。晴天杨树液流速率日变化呈现规律的单峰曲线,表现为白天高,夜间低的昼夜节律变化趋势。雨天杨树液流速率日变化规律性不明显,不同的环境因子对树干液流的响应程度不同,光合有效辐射、空气温度与树干液流速率呈正相关,而空气湿度则与树干液流速度呈负相关。抑螺防病林生长初期(4月上旬)日蒸腾量较低,基本上在1mm以下,到7月上旬日蒸腾均值最高可达到3.0mm以上。蒸腾量季节变化过程与降雨分布时间紧密相关。(4)水汽通量具有规律的日变化进程,不同天气条件下(晴天和多云)水汽通量的日变化有明显区别。晴天水汽通量值要明显大大高于多云天气。各季节水汽通量大都为正值,表现为水汽源,且夏季大于春秋两季,冬季最小。2006年全年蒸散量占全年降水量的48.45%。环境因子在很大程度上制约着水汽通量的变化,以净辐射和土壤热通量地温对水汽通量的影响最大。晴天和多云影响水汽通量的环境因不完全相同,相同因子影响程度也不一样,晴天的相关性高于多云天气,晴天的逐步回归分析建立模型相关系数为0.92,而多云天气的为0.81。更多还原

【Abstract】 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.更多还原