高温天气植被蒸腾与遮荫降温效应的变化特征
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摘要
开展城市中不同树种植被遮荫与蒸腾降温效应的量化研究是科学优化植被温度调控服务的重要基础。以南京市栖霞区某小型绿地单元为研究区,对高温晴朗天气下不同树种典型植株树干液流进行了观测,采用"单位叶面积上的平均液流速率×叶面积指数"的扩展方法实现了由单株到林分尺度上冠层蒸腾量与蒸腾降温效应的估算,并根据林上、林下太阳辐射值计算了不同树种与整个绿地单元的遮荫降温效应,进而阐明了蒸腾与遮荫降温对总降温效应贡献率的变化特征。研究结果表明:1)3个树种树干液流均呈现昼高夜低的变化趋势,树干液流通常在6:00左右启动,正午前后达到峰值,且存在明显的"午休"现象,而在同一树种内树干液流会随着胸径的增大而显著增大;2)林分尺度上的冠层蒸腾量与蒸腾降温效应均为杨树>雪松>香樟,杨树峰或谷出现的时间(11:00—19:00)均明显晚于雪松(10:00—15:00)和香樟(9:00—16:00);3)3个树种遮荫降温效应总体上与太阳辐射的日变化规律基本一致,但树种间日平均降温效应的差异较小;4)3个树种与整个小型绿地单元的总降温效应在夜间均非常微弱,且全部为蒸腾降温,而在白天遮荫对总降温的贡献率(60%—75%)则明显高于蒸腾降温(25%—40%)。
Quantifying the transpiration cooling effect and cooling effect of the shade of different tree species in urban areas is important for improving the vegetation temperature regulating ecosystem services.A small green space patch located in the Qixia District of Nanjing was selected as the study area.The Granier thermal diffusion probe technique was used to monitor the sap flow of three tree species in extremely hot weather.The method "average sap flow of per unit leaf area × leaf area index"was used to estimate the canopy transpiration and transpiration cooling effect.Differences in solar radiation under and above the vegetation canopy were calculated and the cooling effect of the shade of different tree species and the whole green space patch was captured.Finally,we determined the contribution of the transpiration cooling effect and cooling effect of the shade to the total vegetation cooling effect.The results indicated that 1) Diurnal variation of sap flow was regular and was observed to be high in the daytime and low at night.Sap flow typically began at approximately 06:00,peaked at noon,and then showed an obvious midday depression.In the same tree species,sap flow increased with increasing DBH.2) Thevolume of the stand canopy transpiration and transpiration cooling effect were found to have the following order:Populus tomentosa Carr > Cedrus deodara > Cinnamomum camphora,and Populus tomentosa Carr(11:00—19:00) clearly peaked later than C.deodara(10:00—15:00) and C.camphora(09:00—16:00).3) The cooling effect of shade of the three tree species was mostly consistent with the diurnal variation of solar radiation and difference in the average cooling effect between tree species was small.4) The cooling effect of three tree species and small green space patch was very weak at night and nearly equal to the transpiration cooling effect.The contribution of the cooling effect of shade(60% —75%) to the total cooling effect was significantly higher than that of transpiration cooling effect(25% —40%) during the day.
Quantifying the transpiration cooling effect and cooling effect of the shade of different tree species in urban areas is important for improving the vegetation temperature regulating ecosystem services.A small green space patch located in the Qixia District of Nanjing was selected as the study area.The Granier thermal diffusion probe technique was used to monitor the sap flow of three tree species in extremely hot weather.The method "average sap flow of per unit leaf area × leaf area index"was used to estimate the canopy transpiration and transpiration cooling effect.Differences in solar radiation under and above the vegetation canopy were calculated and the cooling effect of the shade of different tree species and the whole green space patch was captured.Finally,we determined the contribution of the transpiration cooling effect and cooling effect of the shade to the total vegetation cooling effect.The results indicated that 1) Diurnal variation of sap flow was regular and was observed to be high in the daytime and low at night.Sap flow typically began at approximately 06:00,peaked at noon,and then showed an obvious midday depression.In the same tree species,sap flow increased with increasing DBH.2) Thevolume of the stand canopy transpiration and transpiration cooling effect were found to have the following order:Populus tomentosa Carr > Cedrus deodara > Cinnamomum camphora,and Populus tomentosa Carr(11:00—19:00) clearly peaked later than C.deodara(10:00—15:00) and C.camphora(09:00—16:00).3) The cooling effect of shade of the three tree species was mostly consistent with the diurnal variation of solar radiation and difference in the average cooling effect between tree species was small.4) The cooling effect of three tree species and small green space patch was very weak at night and nearly equal to the transpiration cooling effect.The contribution of the cooling effect of shade(60% —75%) to the total cooling effect was significantly higher than that of transpiration cooling effect(25% —40%) during the day.
引文
[1]Dimoudi A,Nikolopoulou M.Vegetation in the urban environment:microclimatic analysis and benefits.Energy and Buildings,2003,35(1):69-76.
[2]Sugawara H,Shimizu S,Hagiwara S,Narita K I,Mikami T.How much does urban green cool town?Journal of Heat Island Institute International,2014,9(2):11-18.
[3]Hoelscher M H,Nehls T,Jnicke B,Wessolek G.Quantifying cooling effects of facade greening:shading,transpiration and insulation.Energy and Buildings,2016 114:283-290.
[4]Tsiros I X.Assessment and energy implications of street air temperature cooling by shade tress in Athens(Greece)under extremely hot weather conditions.Renewable Energy,2010,35(8):1866-1869.
[5]Lin B S,Lin Y J.Cooling effect of shade trees with different characteristics in a subtropical urban park.Hort Science,2010,45(1):83-86.
[6]Simpson J R,Mc Pherson E G.Potential of tree shade for reducing residential energy use in California.Journal of Arboriculture,1996,22(1):10-18.
[7]Konarska J,Uddling J,Holmer B,Lutz M,Lindberg F,Pleijel H,Thorsson S.Transpiration of urban trees and its cooling effect in a high latitude city.International Journal of Biometeorology,2016,60(1):159-172.
[8]Chabot R,Bouarfa S,Zimmer D,Chaumont C,Moreau S.Evaluation of the sap flow determined with a heat balance method to measure the transpiration of a sugarcane canopy.Agricultural Water Management,2005,75(1):10-24.
[9]Green S,Clothier B,Jardine B.Theory and practical application of heat pulse to measure sap flow.Agronomy Journal,2003,95(6):1371-1379.
[10]Bosch D D,Marshall L K,Teskey R.Forest transpiration from sap flux density measurements in a southeastern Coastal Plain riparian buffer system.Agricultural and Forest Meteorology,2014,187(8):72-82.
[11]Cˇermák J,Kucˇera J,Nadezhdina N.Sap flow measurements with some thermodynamic methods,flow integration within trees and scaling up from sample trees to entire forest stands.Trees,2004,18(5):529-546.
[12]Juhász,HrotkóK.Comparison of the transpiration part of two sources evapotranspiration model and the measurements of sap flow in the estimation of the transpiration of sweet cherry orchards.Agricultural Water Management,2014,143:142-150.
[13]Granier A.A new method of sap flow measurement in tree stems.Annals of Forest Science,1985,42(2):193-200.
[14]于萌萌,张新建,袁凤辉,何秀,关德新,王安志,吴家兵,金昌杰.长白山阔叶红松林三种树种树干液流特征及其与环境因子的关系.生态学杂志,2014,33(7):1707-1714.
[15]赵平,饶兴权,马玲,蔡锡安,曾小平.基于树干液流测定值进行尺度扩展的马占相思林段蒸腾和冠层气孔导度.植物生态学报,2006,30(4):655-665.
[16]Granier A.Evaluation of transpiration in a Douglas-fir stand by means of sap flow measurements.Tree Physiology,1987,3(4):309-320.
[17]Zhu L W,Zhao P.Temporal variation in sap-flux-scaled transpiration and cooling effect of a subtropical Schima superba plantation in the urban Area of Guangzhou.Journal of Integrative Agriculture,2013,12(8):1350-1356.
[18]Soegaard H,Boegh E.Estimation of evapotranspiration from a millet crop in the Sahel combining sap flow,leaf area index and eddy correlation technique.Journal of Hydrology,1995,166(3/4):265-282.
[19]Nakazato T,Inagaki T.Analysis of plant function as bio-thermal-conditioner using Pothos(Epipremnum aureum).Thermochimica Acta,2012,532:49-55.
[20]白岩,朱高峰,张琨,马婷.基于树干液流及涡动相关技术的葡萄冠层蒸腾及蒸散发特征研究.生态学报,2015,35(23):7821-7831.
[21]Granier A,Huc R,Barigah S T.Transpiration of natural rainforest and its dependence on climatic factors.Agricultural and Forest Meteorology,1996,78(1/2):19-29.
[22]Solberg S.Mapping gap fraction,LAI and defoliation using various ALS penetration variables.International Journal of Remote Sensing,2010,31(5):1227-1244.
[23]骆社周,王成,张贵宾,习晓环,李贵才.机载激光雷达森林叶面积指数反演研究.地球物理学报,2013,56(5):1467-1475.
[24]刘鑫,张金池,谢德晋,庄家尧,邵永昌,张水锋.南京近郊麻栎林冠层蒸腾时间变化及降温效应.浙江农林大学学报,2015,32(4):529-536.
[25]Rahman M A,Moser A,R9tzer T,Pauleit S.Within canopy temperature differences and cooling ability of Tilia cordata trees grown in urban conditions.Building and Environment,2017,114:118-128.
[26]杨士弘.城市绿化树木的降温增湿效应研究.地理研究,1994,13(4):74-80.
[27]吉野正敏.局地气候原理.郭可展,李师融,译.南宁:广西科学技术出版社,1989.
[2]Sugawara H,Shimizu S,Hagiwara S,Narita K I,Mikami T.How much does urban green cool town?Journal of Heat Island Institute International,2014,9(2):11-18.
[3]Hoelscher M H,Nehls T,Jnicke B,Wessolek G.Quantifying cooling effects of facade greening:shading,transpiration and insulation.Energy and Buildings,2016 114:283-290.
[4]Tsiros I X.Assessment and energy implications of street air temperature cooling by shade tress in Athens(Greece)under extremely hot weather conditions.Renewable Energy,2010,35(8):1866-1869.
[5]Lin B S,Lin Y J.Cooling effect of shade trees with different characteristics in a subtropical urban park.Hort Science,2010,45(1):83-86.
[6]Simpson J R,Mc Pherson E G.Potential of tree shade for reducing residential energy use in California.Journal of Arboriculture,1996,22(1):10-18.
[7]Konarska J,Uddling J,Holmer B,Lutz M,Lindberg F,Pleijel H,Thorsson S.Transpiration of urban trees and its cooling effect in a high latitude city.International Journal of Biometeorology,2016,60(1):159-172.
[8]Chabot R,Bouarfa S,Zimmer D,Chaumont C,Moreau S.Evaluation of the sap flow determined with a heat balance method to measure the transpiration of a sugarcane canopy.Agricultural Water Management,2005,75(1):10-24.
[9]Green S,Clothier B,Jardine B.Theory and practical application of heat pulse to measure sap flow.Agronomy Journal,2003,95(6):1371-1379.
[10]Bosch D D,Marshall L K,Teskey R.Forest transpiration from sap flux density measurements in a southeastern Coastal Plain riparian buffer system.Agricultural and Forest Meteorology,2014,187(8):72-82.
[11]Cˇermák J,Kucˇera J,Nadezhdina N.Sap flow measurements with some thermodynamic methods,flow integration within trees and scaling up from sample trees to entire forest stands.Trees,2004,18(5):529-546.
[12]Juhász,HrotkóK.Comparison of the transpiration part of two sources evapotranspiration model and the measurements of sap flow in the estimation of the transpiration of sweet cherry orchards.Agricultural Water Management,2014,143:142-150.
[13]Granier A.A new method of sap flow measurement in tree stems.Annals of Forest Science,1985,42(2):193-200.
[14]于萌萌,张新建,袁凤辉,何秀,关德新,王安志,吴家兵,金昌杰.长白山阔叶红松林三种树种树干液流特征及其与环境因子的关系.生态学杂志,2014,33(7):1707-1714.
[15]赵平,饶兴权,马玲,蔡锡安,曾小平.基于树干液流测定值进行尺度扩展的马占相思林段蒸腾和冠层气孔导度.植物生态学报,2006,30(4):655-665.
[16]Granier A.Evaluation of transpiration in a Douglas-fir stand by means of sap flow measurements.Tree Physiology,1987,3(4):309-320.
[17]Zhu L W,Zhao P.Temporal variation in sap-flux-scaled transpiration and cooling effect of a subtropical Schima superba plantation in the urban Area of Guangzhou.Journal of Integrative Agriculture,2013,12(8):1350-1356.
[18]Soegaard H,Boegh E.Estimation of evapotranspiration from a millet crop in the Sahel combining sap flow,leaf area index and eddy correlation technique.Journal of Hydrology,1995,166(3/4):265-282.
[19]Nakazato T,Inagaki T.Analysis of plant function as bio-thermal-conditioner using Pothos(Epipremnum aureum).Thermochimica Acta,2012,532:49-55.
[20]白岩,朱高峰,张琨,马婷.基于树干液流及涡动相关技术的葡萄冠层蒸腾及蒸散发特征研究.生态学报,2015,35(23):7821-7831.
[21]Granier A,Huc R,Barigah S T.Transpiration of natural rainforest and its dependence on climatic factors.Agricultural and Forest Meteorology,1996,78(1/2):19-29.
[22]Solberg S.Mapping gap fraction,LAI and defoliation using various ALS penetration variables.International Journal of Remote Sensing,2010,31(5):1227-1244.
[23]骆社周,王成,张贵宾,习晓环,李贵才.机载激光雷达森林叶面积指数反演研究.地球物理学报,2013,56(5):1467-1475.
[24]刘鑫,张金池,谢德晋,庄家尧,邵永昌,张水锋.南京近郊麻栎林冠层蒸腾时间变化及降温效应.浙江农林大学学报,2015,32(4):529-536.
[25]Rahman M A,Moser A,R9tzer T,Pauleit S.Within canopy temperature differences and cooling ability of Tilia cordata trees grown in urban conditions.Building and Environment,2017,114:118-128.
[26]杨士弘.城市绿化树木的降温增湿效应研究.地理研究,1994,13(4):74-80.
[27]吉野正敏.局地气候原理.郭可展,李师融,译.南宁:广西科学技术出版社,1989.