摘要
运用涡度相关(Eddy covariance)开路系统、树干液流(Sap flow)、土壤水分以及微气象观测系统,于2006年生长季(5～10月)对北京大兴区永定河沿河沙地杨树(Populus euramericana)人工林生态系统的水量和能量平衡进行了连续测定;分析了该系统能量平衡闭合水平及其组分分配特征,不同水分条件下蒸发散及其各组分变化过程和分配特征,以及影响蒸发散的主要环境因子;并对组分求和法、土壤水分平衡法与涡度相关法测得该生态系统生长季蒸发散总量的结果进行了对比。结果表明:生长季内该生态系统的能量闭合水平较高,能量平衡各组分在不同土壤水分环境条件下所占比例变化较大;在水分充足的条件下,潜热通量在可利用能量分配过程中占优势,显热通量在水分胁迫条件下占可提供能量的比例比潜热通量大。雨季到来之前,土壤蒸发与植被蒸腾强度相差较小;进入雨季后,土壤深层水分得到补偿,植被蒸腾显著增强而土壤蒸发强度减弱。涡度相关法所得的总蒸发散量与基于树干液流法等组分求和法得到的蒸发散结果较接近,分别为513和492mm。土壤水分平衡法的观测结果略高于前二者的观测结果,雨季研究界面以下的土体也有水分交换是该方法高估蒸发散的主要原因。与环境因子的响应关系表明,蒸发散以及蒸腾的变化过程对净辐射的响应程度比对饱和水汽压差高;水分条件较好情况下,蒸发散以及蒸腾的变化过程与水汽压差关系不明显,说明水分充足时,水汽压差不是蒸散强弱的限制因子。
Aims Using field data from an eddy-covariance （EC） flux tower and sap-flow sensors installed in a poplar （Populus euramericana） plantation, we investigated the magnitudes and changes of evapotranspiration （ET） under different soil moisture and climatic conditions. Our objectives were to quantify the energy partitioning and energy balance, explore the dynamic process and regulatory mechanisms on ET, and understand primary biophysical regulations, especially soil moisture. Methods An open path EC system, sap-flow sensors, soil water balance monitoring system, and microclimatic station were installed to record various components of energy fluxes and water budget at an 11-year-old poplar plantation in Daxing District, Beijing, China. We used data collected at 30-min intervals in the growing season of 2006 in this study. Important findings The overall energy closure of the study site was high （86%） during the growing season, but with notable dependence on soil water conditions. The ratio between sensible heat and net radiation （Hs：Rn） was much higher during dry conditions than that during moist conditions. With dry soils, net radiation and soil physical properties played important roles in transpiration, which was less than evaporation prior to rain events. In contrast, transpiration exceeded evaporation when the soil water content in the deep layers was more abundant following rain events. The total ET rates quantified by the soil water balance and sap-flow methods were comparable and lower than that determined by the EC method. The ratio between transpiration and ET appeared to be more dependent on net radiation and vapor pressure deficit （VPD） during wet periods than that during dry periods.
出处
《植物生态学报》
CAS
CSCD
北大核心
2009年第4期706-718,共13页
Chinese Journal of Plant Ecology
基金
北京市教育委员会共建项目"北京地区人工林碳平衡与碳汇功能环境响应机理"
教育部重点项目"人工林生态系统碳水通量耦合动态变化研究"(105027)
国家林业局"948"项目(2005-04-01)
高等学校博士专项科研基金"人工林生态系统碳水通量动态变化及其环境影响机理"(20040022013)
国家十五科技攻关课题"森林生态结构与功能"
中美碳联盟USCCC国际合作项目
