海南儋州地区橡胶林生态系统水汽通量变化特征及其对环境因子的响应

运用涡度相关观测技术对海南儋州地区的橡胶人工林（简称橡胶林）进行长期观测，研究了2017-2018年水汽通量变化特征，并结合该地区的梯度系统数据以及气象观测数据，分析了水汽通量对环境因子的响应；同时根据降雨量和蒸散量对该生态系统的水分收支情况进行探讨，以揭示橡胶林生态系统的水分利用能力。结果表明:1）2017-2018年橡胶林生态系统水汽通量为正值，即水汽通过生态系统向大气散发，表现为水汽源；水汽通量日变化曲线为单峰形，在11:00-13:00达到最大值，雨季日间的水汽通量约为旱季的3倍，全年夜间水汽通量保持平稳且接近于0，水汽通量表现出明显的季节变化，雨季（5-10月）最高，旱季（1-4月）次之，11-12月最低；2）2017、2018年度总降雨量分别为1 687.6、2 264.7 mm，蒸散总量为962.24、1 209.29 mm，分别占降雨的57.02%、53.40%；旱季蒸散量约为降雨的2倍，雨季6-10月常出现当月降雨量远大于蒸散的情况，且年蒸散量和降雨量均集中在6-9月；3）影响水汽通量的主要环境因子有净辐射、气温、饱和水汽压差、风速、土壤热通量、土壤含水量等，其中净辐射和大气温度是影响水汽通量的最主要因素，尤其在水分充沛的雨季相关性最高。4）海南儋州橡胶林的蒸散量略高于热带雨林，但其蒸散率属于正常水平，不是导致植胶区缺水的主要因素。

Water Vapor Flux Exchange of Rubber Forest Stand in Hainan Danzhou and Its Response to Environmental Factors

Using field data from the eddy-covariance(EC)fluxtower for long-term observation,we investigated the magnitudes and changes of water vapor flux(WVF)in rubber plantations in Danzhou,Hainan during 2017-2018.The objectives were to analyze the responses of WVF to environmental factors,and to explore the dynamic process of evapotranspiration(ET).According to precipitation and ET,we explored the water budget and water utilization capacity of the ecosystem of rubber plantations.The results showed that 1)the WVF of rubber plantation ecosystem was basically positive in 2017-2018,and the water was transmitted to the atmosphere through the rubber plantations,manifested as water vapor sources.The characteristics of daily WVF variation curve was a single-peak,reaching the maximum value between 11:00 and 14:00.The WVF in the daytime in rainy season was about three times that in the dry season,and at night remained stable and close to 0 in the whole year.It also presented a seasonal variation:(May to October>(January to April>November to December.2)The annual precipitations in 2017 and 2018 were 1687.6 and 2264.7 mm,while the annual evapotranspirations were 962.24 and 1209.29 mm,which accounted for 57.02%and 53.40%of the rainfall,respectively.In dry season,evapotranspiration was about twice as much as the rainfall,and in the rainy season,the monthly rainfall was usually much more than evapotranspiration.The maximum precipitation and evapotranspiration both occurred in the rainy season.3)The environmental factors influencing WVF were net radiation,temperature,saturation vapor pressure,wind speed,soil heat flux and soil volumetric moisture content.The most significant factors were the net radiation and the air temperature.The WVF showed a significant positive correlation with the net radiation(Rn),and the WVF also showed a significant positive correlation with the atmospheric temperature(Ta).4)The evapotranspiration of rubber plantations in Danzhou was slightly higher than that of tropical rain forest,but the evapotranspiration rate was normal and was not the main factor leading to water shortage in the rubber planting area.