基于REddyProc的干旱区枣林通量数据插补及能量平衡分析

Flux Data Interpolation and Energy Balance Analysis of Jujube Forests in Arid Areas by Employing REddyProc

【目的】获取完整且有效的枣林通量数据,分析生态系统能量平衡,为评估干旱区枣林生态系统与大气间的能量和物质交换提供理论依据。【方法】选择R语言REddyProc包插补涡度相关法测量的通量数据,采用交叉验证法和能量平衡闭合度评价插补数据质量,并修正热储存项,分析2018、2019年新疆阿克苏地区枣林能量平衡闭合度与能量变化趋势。【结果】1)REddyProc包插补通量数据效果较好,交叉验证的误差统计参数为回归系数b=0.86~0.99、决定系数R^(2)=0.86~0.95、一致性指数d=0.96~0.98、模拟效率EF=0.84~0.92、均方根误差与观测值标准差比率RSR=0.28~0.40;2)经REddyProc包插补后,2018、2019年干旱区枣林能量平衡闭合度分别为73.45%、73.11%,有效能量和可利用能量的决定系数均为0.97;加入热储存项后,能量闭合度分别提高3.72%、2.75%,达77.17%、75.86%,增幅较小;3)各能量分项(净辐射、潜热通量、显热通量、土壤热通量)的日均变化规律在生育期和休眠期相似,日均变化均呈以净辐射变化规律为基础的单峰变化。【结论】干旱区枣林全年能量平衡闭合度符合ChinaFlux范围,热储存项对改善枣林能量平衡闭合度有一定影响,可为研究枣林能量和物质交换提供理论依据。

【Objective】The acquisition of complete and valid flux data as well as the analysis of the energy balance of an ecosystem is the basis for further understanding of the energy and material exchange processes in an ecosystem.【Method】In this paper,the R language REddyProc package was selected to interpolate the flux data measured by the Eddy covariance technique.The interpolated data were evaluated using the cross-validation method and the energy balance closure.At the same time,the terms of the thermal storage in the energy balance were corrected to analyze the energy balance closure of jujube forests in the arid zone and the trend of each energy component.【Result】1)The REddyProc package could interpolate the data better with the error statistic parameters of the regression coefficient b=0.86-0.99,determination coefficient R^(2)=0.86-0.95,index of agreement d=0.96-0.98,efficiency of simulation EF=0.84-0.92,and RMSE-observations standard deviation ratio RSR=0.28-0.40.2)After conducting the R package interpolation,the energy balance closures of the jujube date forests were 73.45%and 73.11%,respectively.R2 of the 2-year effective energy(H+LE)and available energy(Rn-G)both were 0.97.After adding the thermal storage terms,the energy balance closures increased to 77.17%(by 3.72%)and 75.86%(by 2.75%),respectively.The thermal storage terms affected some improvements in the energy balance closure of jujube forests.3)The daily-averaged variation pattern of each energy component(the net radiation Rn,latent heat flux LE,sensible heat flux H,and soil heat flux G)was similar during the fertility and dormancy with a single-peaked daily variation according to the variation pattern of the net radiation.【Conclusion】This paper analyzed the energy exchange patterns of Jujube forest ecosystems in arid areas.The year-round energy balance closure of jujube forests was in line with the range of ChinaFlux and the thermal storage term affected some improvements in the energy balance closure of jujube forests.The achievements can provide a theoretical basis for studying the energy and material cycles in jujube forests.