スギの水分生理特性と関東平野における近年の気象変動 : 樹木の衰退現象に関連して(<シンポジウム特集>酸性雨と森林衰退,研究の現場から)

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Possible causes of decline on large Cryptomeria japonica D.Don trees in the Kanto plains were discussed from ecophysiological view point. Maximum values of leaf conductance on 51 tree species, and mean values of total resistance to water flow in SPAC (Soil-Plant-Atmosphere Continuum) on 8 tree species, were measured for clarifying the water relations characteristics of C. japonica. Diurnal ecophysiological processes were measured about xylem water potential, transpiration rate, leaf conductance, and apparent photosynthetic rate in a large mature C. japonica tree under natural condition. Apparent specific weight of sun twigs at upper and lower crown on two large C. japonica trees were measured to estmate the long term water stresses. Yearly changes of meteorological data were discussed about air temperature, precipitation, and saturation deficit at the observatories of Tokyo. Yokohama, Chiba, Maebashi, Kumagaya, Chichibu, Cyoshi, Utsunomiya, and Mito in relation to water stress of C. japonica trees growing at these cities. Maximum values of leaf conductanceand mean values of total resistance to water flow in the SPAC of C. japonica were more larger than those of other tree species. This result suggests that large C. japonica trees suffer water deficit under the conditions of large atomospheric vaper demand and soil drying. Stomatal closure under low leaf water potential and daytime depression of apparent photosynthetic rate were observed markedly under natural condition on a fine day. These water stresses will be caused mainly by the water relation characteristics of large C. japonica trees as mentioned above. Morphological characteristics such as large apparent specific weight of sun twigs in the upper crown suggest that these daily water stresse occurrs frequently in large C. japonica trees. Saturation deficit of the atomosphere in the Kanto plains have been gradually increased and yearly precipitation amount have been decreased scince 1950's. On the other hand, the decline of large C. japonica trees have been observed scince 1960's. This correspondance will explain hypothetically the cause of C. japonica decline in the Kanto plain from the ecophysiological characteristics to climatic changes.
森林立地学会の論文
1992-06-30

スギの水分生理特性と関東平野における近年の気象変動 : 樹木の衰退現象に関連して(<シンポジウム特集>酸性雨と森林衰退,研究の現場から)

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