都市域における樹木の蒸散特性 : オアシス効果に関する野外実験

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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.
社団法人日本建築学会の論文
2006-10-30

都市域における樹木の蒸散特性 : オアシス効果に関する野外実験

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