TRANSPIRATION RATA OF TREES IN AN URBAN AREA : Field experiments on oasis effect
TRANSPIRATION RATA OF TREES IN AN URBAN AREA : Field experiments on oasis effect
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城市地区树木的蒸腾速率：绿洲效应的现场实验
DOI：
10.3130/aije.71.59_6
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发表时间：
2006
影响因子：
2.2
通讯作者：
Takano Takemasa
中科院分区：
文献类型：
--
作者：
N. Ken;健一 成田;理 萩島;H. Aya;Tanimoto Jun;潤 谷本;武将 高野;Takano Takemasa
城市地区的绿色空间有望缓解城市热岛效应。根据最近的研究，城市地区的潜热通量比预期的要大。换句话说，我们必须考虑到城市地区的树木比大片森林地区的树木更有效地蒸腾。在地表干燥的地区，植被需水量增加的现象在气候学上一般称为“绿洲效应”。上述结果表明，居住区的行道树和绿篱也存在绿洲效应。本研究通过田间试验，对绿洲效应进行了定量研究。大约两百棵两米高的盆栽植物被用于这个实验。试验分为三种密度：隔离型（3行3行，间隔6m）、稀疏型（5行5行，间隔1m）和密集型（13行13行，间隔0.5m）。对其中的55个样地，每天在日落后测定一次重量，得到日蒸腾速率。为避免土壤水分亏缺的影响，每盆灌水至97%的饱和度后再摆位进行试验。由于每棵树样本的条件，如总叶面积，光合作用的活化，变化很大，每个样本的个体蒸腾速率进行了检查，作为一个初步的测试下，足够稀疏的均匀排列。除采用该个体速率进行补偿外，每次均采用随机数表改变样本位置。最后，从9月初到11月中旬获得了28个数据集。隔离模式的蒸腾速率与密集模式核心区的蒸腾速率之比为1.59。利用各个例数据集的平均率，而不是平均率，分析了风向和日照对密集型的影响。在这样的分析中，由于这些物理因素而产生的明显差异不会出现。
Green space in an urban area has been expected to mitigate urban heat island. According to the recent study, the latent heat flux in urban area is larger than expected. In other words, we have to consider that trees in an urban area transpire more effective than that of vast forest area. The phenomenon that water demand of vegetations increases in the area surrounded by dry surface is generally called “oasis effect” in climatology. Above results imply that the oasis effect also exists for the roadside trees and the hedge in residential area. In this study, field experiments were performed in order to get quantitative data of the oasis effect. About two hundreds of potted plants, which is two meter in height, were used for this experiment. They were arranged in three types of density; isolate pattern (3 rows, 3 lines, 6m interval), sparse pattern (5 rows, 5 lines, 1m interval), and dense pattern (13 rows, 13 lines, 0.5m interval). As for 55 samples selected among them, their weights were measured once a day after sunset to get a daily transpiration rate. To avoid the influence of soil water deficit, each pot was irrigated until 97% of saturated condition before setting the position for experiment. Because the conditions of each tree sample like total leaf area, activation of photosynthesis, were varied widely, the individual transpiration rate of each sample was examined as a preliminary test under the sufficiently sparse uniform arrangement. In addition to the compensation using this individual rate, positions of sample were changed with random number table every time. Finally, 28 data sets were obtained from the beginning of September to mid November. The ration of transpiration rate of isolated pattern to this core zone of dense pattern becomes 1.59. Using not averaged rate but that of each case data set, the influence of wind direction and sunshine were analyzed about dense pattern. In such an analyses, clear difference owing to these physical factors dose not appears.