Canopy transpiration from a boreal forest in Sweden during a dry year
Canopy transpiration from a boreal forest in Sweden during a dry year
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DOI：
10.1016/s0168-1923(97)00026-9
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发表时间：
1997-09-01
影响因子：
6.2
通讯作者：
Halldin, S
中科院分区：
文献类型：
--
作者：
Cienciala, E;Kucera, J;Halldin, S
区域蒸散量的估算对于气候模式中土壤-植被-大气界面的参数化和评估土地利用变化对水资源的影响至关重要。目前关于森林蒸散量如何取决于森林物种组成和年龄的知识是不够的。本研究以樟子松和欧洲云杉为研究对象，测定了24株（每种林分12株）针叶树的树干液流，估算了50年生和100年生针叶林的蒸腾量。日冠层蒸腾（E-Q）的缩放从单个树流量使用的干周长的样本树的林分的那些的系数。E-Q被用在一个重新排列的Penman方程推导出一个潜在的冠层电导，有效的非限制性土壤水分条件下，从一个时期时，土壤水分储存不限制蒸腾。这使得量化的季节性蒸腾赤字，在这两个立场达到至少五分之一的总潜在蒸腾在生长季节。E-Q通量的估计值较低，最大日值约为2.8毫米，在50岁的立场。对于干燥的天气天，E-Q是很好的相关性，以每日总额的立场蒸散量估计涡相关测量。对干旱的反应是物种特异性的。从50岁的立场，松树蒸腾受干旱的影响较小，云杉或老松树，这也反映了在本赛季的干增量。(C)1997年Elsevier Science B.V.
Estimation of areal evapotranspiration is crucial for the parameterization of the soil-vegetation-atmosphere interface in climate models and for the assessment of land-use changes on water resources. Present knowledge on how areal forest evapotranspiration depends on forest species composition and age is insufficient. In this study, transpiration of 50- and 100-year-old coniferous stands was estimated on the basis of sap-flow measurements on 24 trees, 12 in each stand. The measured samples represented the size distribution of Pinus sylvestris and Picea abies trees. Daily canopy transpiration (E-Q) was scaled from individual tree flow rates using the quotients of stem circumferences of the sample trees to those of the stands. E-Q was used in a rearranged Penman equation to deduce a potential canopy conductance, valid for non-limiting soil-water conditions, from a period when soil-water storage was not limiting transpiration. This enabled quantification of the seasonal transpiration deficit, which in both stands reached at least one fifth of the total potential transpiration over the growth season. The estimated fluxes of E-Q were low with a maximum daily value of about 2.8 mm in the 50-year-old stand. For dry-weather days, E-Q was well correlated to daily sums of stand evapotranspiration estimated from eddy-correlation measurements. Responses to drought were species specific. Transpiration in pines from the 50-year-old stand was less affected by drought relative to spruce or older pine trees, which was also reflected by stem increment during the season. (C) 1997 Elsevier Science B.V.