自然教育園における樹木および森林群落の最近18年間の変化

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The forests in garden of the Institute for Nature Study consist of Piuas thunbergii, P. densiflora-, Cornus controversa-, Quercus serrata-, Aphananthe aspera, Celtis sinensis-, Castanopsis cuspidata forest. These forests which are valuable as an urban forest have been preserved since 1949. Present work is to clarify the changes of forests and trees in this area in the last eighteen years. We report the results of survey following the previous report of 1965 and done in 1983. The results obtained are as follows : 1) From the surveys in 1950,1965 and 1983 it became clear that successional stage of the forests is changing from intermediate stage to climax; namely, number of intolerant species, such as Pinus thuabergii and P. densiflora etc., decreased and numberof seral of climax species, such as Aphananthe aspera, Celtis sinensis var. japonica, Zelkova serrata. Neolitsea sericea. Machilus thunbergii, Castanopsis cuspidata var. sieboldii, Quercus acuta and Ilex integra etc., increased. 2) During the progress of succession, many zoochory species such as Cornus controversa, Prunus grayana, Idesia polycarpa, Aphananthe aspera. Celtis sinensis var. japonica. Machilus thunbergii, Neolitsea sericea, Ilex integra, Eurya japonica, Ligustrum japonicum and Trachycarpus fortunei etc., are spreading rapidly by bird and make up unusual community in species composition. Especially the increase of Trachycarpus fortuaei and Neolitsea sericea are remarkable. Bolochory species, such as C. cuspidata var. sieboldii and Quercus acuta, are spreading rather slowly as compared with bird spreading species mentioned above. Neolitsea sericea forests will be made in the secondary forests which keep apart from mature C.cuspidata forests. 3) The increase in the number of Idesia polycarpa of sun tree is most singular phenomenon, because the forests is progressing to climax. The increase of this species is supposed phenomenon correlative with its fast growth in gaps caused by death of large trees of C. cuspidata var. sieboldii or pine etc.. 4) On the contrary to the general trend of progressive succession, it is remarkable that Cryptomeria japonica, Castanea crenata and Abies firma decreased, which are usually adapted to this area, and Trachycarpus fortunei iacreased, which is usually lacking for natural forests in Kanto district. The decrease of Cryptomeria japonica and disappearance of Abies firma are the possibility of damage by air pollution. The decrease of Castanea crenata is thought to be caused by attack of Dryocosmus kuriphilus YASUMATSU. The increase of Trachycarpus fortunei in this area is closely related to large account of its seeds dispersed by bird from other place, and also related to rising of minimum temperature in winter caused by urban climate resulting in decrease of drought-damage in winter. 5) The C. cuspidata forests are thought to maintain themselves in .a long time owing to appaarance of seedlings and sproutings, although the results show the decrease of large trees of C, cuspidata var. sieboldii accompanied by occational increase of deciduous trees. 6) Aphananthe aspera, Celtis sinensis forests show no obvious changes since 1950 : it is because of (1) these species have long life span and few trees are dead, and (2) they are supposed to be climax species in northern slope of hills in Kanto district as Zelkova serrata (Takahashi et al, 1983) . 7) In a part of Quercus serrata forests and pine forests, evergreen broad-1eaved trees increase resulting in the progress of succession. 8) Cornus controversa forests seem to maintain themselves because they are still younger stage. However, they will change into forests dominated of A. aspera, C. sinensis var japonica of Neolitsea sericea in the remote future.
1985-03-25

自然教育園における樹木および森林群落の最近18年間の変化

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