摘要
【目的】量化北京城郊密云水库周边油松人工林蒸腾降温[ΔT(E_(f))]和土壤蒸发降温[ΔT(E_(s))],确定2种降温在昼夜和季节尺度上的调节因子,为减缓北京城市热岛效应的策略制定提供科学支撑。【方法】于2021年5—11月生长期,分别采用热扩散探针和涡度相关法对油松人工林树干液流(SFD)和蒸散发(ET)进行连续监测,并计算林分蒸腾(E_(f))和土壤蒸发(E_(s)),同步监测主要气象因子和土壤含水量(SWC),运用Mantel检验和随机森林算法等方法,分析密云水库周边油松人工林E_(f)、E_(s)、ΔT(E_(f))和ΔT(E_(s))时间变化特征及其影响因子。【结果】1)在昼夜尺度上,ΔT(E_(f))和ΔT(E_(s))分别在白天和夜间占主导地位。白天空气温度(Ta)对ΔT(E_(s))的影响最显著,土壤含水量(SWC)和短波辐射(RSD)对ΔT(E_(f))的影响最显著(Mantel’s P<0.01,0.2≤r<0.4)。2)在季节尺度上,ΔT(E_(f))的降温贡献比重高于ΔT(E_(s)),且夏季ΔT(E_(f))和ΔT(E_(s))高于其他季节。7—9月ΔT(E_(f))和ΔT(E_(s))日均值分别为3.49和1.66℃,E_(f)和E_(s)日均值分别为1.64和0.77 mm。空气温度和土壤含水量分别是影响ΔT(E_(s))和ΔT(E_(f))季节变化的主要环境因子。3)参数优化后,随机森林模型对ΔT(E_(s))和ΔT(E_(f))均有较好的模拟效果(R^(2)>0.93)。【结论】蒸发降温和蒸腾降温的比重在昼夜和季节尺度上存在显著差异。热量条件(土壤温度和空气温度)和土壤含水量分别是影响蒸发降温和蒸腾降温的最重要因子。相较于土壤蒸发降温,植物气孔的调节作用可使蒸腾降温快速地对饱和水汽压差和气温作出响应。
【Objective】In the context of exacerbated urban heat island(UHI)effect,the evapotranspiration cooling effect of suburban forests plays a crucial role in alleviating UHI and regulating urban heat island circulation.However,the cooling regulation process remains poorly understood.This study aims to quantitatively analyze the transpiration cooling[ΔT(E_(f))]and soil evaporation cooling[ΔT(E_(s))]of Pinus tabuliformis plantation around Miyun Reservoir in Beijing,and determine the regulating factors of these two cooling processes at diurnal and seasonal scales,so as to provide scientific support for the formulation of strategies to mitigate the UHI effect in Beijing.【Method】During the growing season from May to November 2021,thermal diffusion probes and eddy covariance methods were used to continuously monitor sap flow density(SFD)and evapotranspiration(ET)of the plantation.The forest evapotranspiration(E_(f))and soil evaporation(E_(s))were calculated,and the major meteorological factors and soil water content(SWC)were simultaneously monitored.Mantel-Test and random forest algorithms were used to analyze the temporal variation characteristics of E_(f),E_(s),ΔT(E_(f)),andΔT(E_(s))in P.tabuliformis plantation and their influencing factors.【Result】1)At diurnal scale,ΔT(E_(f))andΔT(E_(s))dominated during the day and night,respectively.During the day,air temperature(Ta)had the most significant influence onΔT(E_(s)),while soil water content(SWC)and shortwave radiation(RSD)significantly influencedΔT(E_(f))(Mantel’s P<0.01,0.2≤r<0.4).2)At seasonal scale,ΔT(E_(f))contributed more thanΔT(E_(s)),and bothΔT(E_(f))andΔT(E_(s))were higher in summer than in other seasons.From July to September,the daily averages ofΔT(E_(f))andΔT(E_(s))were 3.49 and 1.66℃,respectively,while E_(f) and E_(s) had daily averages of 1.64 and 0.77 mm.Ta and SWC were the main environmental factors affecting the seasonal variations ofΔT(E_(s))andΔT(E_(f)),respectively.3)After parameter optimization,the random forest model showed good simulation results forΔT(E_(s))andΔT(E_(f))(R^(2)>0.93).【Conclusion】The proportions of transpiration cooling and soil evaporation cooling differ significantly at diurnal and seasonal scales.Thermal conditions(soil temperature and air temperature)and soil water content are the most important factors influencing soil evaporation and transpiration cooling,respectively.Compared to soil evaporation cooling,plant stomatal regulation allows transpiration cooling to quickly respond to the vapor pressure deficit and air temperature.
作者
孙丽丽
孙艳丽
王菁黎
周泽圆
于海群
陈文婧
刘鹏
田赟
查天山
Sun Lili;Sun Yanli;Wang Jingli;Zhou Zeyuan;Yu Haiqun;Chen Wenjing;Liu Peng;Tian Yun;Zha Tianshan(National Key Laboratory of Efficient Production of Forest Resources,Beijing Forestry University,Beijing 100083;Beijing Landscape Planning and Resources Monitoring Center,Beijing 101118;College of Art and Design,Nanjing University of Technology,Nanjing 210023)
出处
《林业科学》
北大核心
2026年第3期36-47,共12页
Scientia Silvae Sinicae
基金
国家重点研发计划项目(2020YFA0608103)
生态监测网络运维与森林体验指数预报项目“北京园林绿化生态系统监测网络新建站数据管理”(GJH-2024-015)。
关键词
林分蒸腾
蒸腾冷却
热岛效应
树干液流
土壤蒸发
evapotranspiration
evapotranspiration cooling
urban heat island effect
sap flow density
soil evaporation
