乌兰布和沙漠东北缘稀疏灌丛能量平衡及蒸散特征

Characteristics of Energy Balance and Evapotranspiration of Sparse Shrubs in the Northeastern Edge of Ulan Buh Desert

以乌兰布和沙漠东北边缘稀疏灌丛为研究对象,基于2019年涡度相关系统观测得到的水热通量及气象观测数据,研究生态系统能量平衡及蒸散的变化特征,分析其能量闭合和分配情况。结果表明,观测期间稀疏灌丛净辐射总量为2758 MJ·m^(-2),净辐射日变化呈单峰型二次曲线,季节变化特征明显,各能量分量与净辐射呈类似变化,各能量分量绝对值由大到小为净辐射通量>感热通量>土壤热通量>潜热通量。稀疏灌丛土壤热通量总和为正值,表明土壤为热汇。湍流通量由感热通量主导,感热通量约占净辐射的62%,潜热通量约占4%,土壤热通量约占1%。研究区能量不闭合,采用最小二乘法得到的30 min和日平均通量的能量闭合度分别为64%和67%,能量平衡比率范围为0.54~0.73,白天能量闭合度为65%,夜间能量闭合度为20%。稀疏灌丛群落蒸散总量为85.6 mm,大于降水总量(79.6 mm),日均蒸散强度为0.36 mm·d^(-1),蒸散量随植被生长在各个时期有明显变化,月蒸散总量在7月达到峰值。

Based on the 2019 eddy covariance observations and meteorological observation data,the characteristics of the variation in energy balance and evapotranspiration of the sparse shrub ecosystem in the northeastern edge of Ulan Buh Des⁃ert were studied,and its energy closure and distribution were analyzed.The total net radiation during the observation peri⁃od was 2758 MJ·m^(-2),and the diurnal variation of the net radiation showed a single⁃peak type quadratic curve with obvi⁃ous seasonal variation characteristics.Each energy component showed changes similar to the net radiation,and the absolute value of each item showed the following order:net radiation>sensible heat flux>soil heat flux>latent heat flux.The sum of soil heat flux was positive,indicating that the soil is a heat sink.The turbulent flux was dominated by sensible heat,which accounted for 62%of net radiation,4%of latent heat,and 1%of soil heat flux during the observation period.The energy balance closure in the study area was not achieved.The energy closures of the half⁃hour period and daily aver⁃age flux calculated by the least square method were 64%and 67%,respectively.The energy balance ratio ranged from 0.54 to 0.73,and the energy closure was 65%during the day and 20%at night.The total evapotranspiration during the observation period was 85.6 mm,which was larger than the total amount of precipitation(79.6 mm).The daily average e⁃vapotranspiration intensity was 0.36 mm·d^(-1).The evapotranspiration changed significantly with the plant growth in differ⁃ent periods,and the monthly cumulative evapotranspiration reached the peak in July.