和歌山演習林におけるモミ, ツガ林の生産力調査 : 第7報 9林班学術参考林

Abstract

本報告は, 和歌山演習林のモミ, ツガ天然林の生産力調査の一環として行われているもので, 9林班に学術参考林 (19. 11ha) として保存されている天然林の概況について記述されたものである。調査は, 1979年から1984年に行われ, 50m×50mの標準地12ヵ所および標高650mの斜面下部から930mの中腹へ585mと標高810mから1050mの斜面上部へ659m, 延1244m で幅10mの帯状区の標準地の毎木調査により, 樹種, 幹材積を求めた。針葉樹は, カヤ, イヌガヤ, モミ, ツガ, アカマツ, スギで, カヤおよびイヌガヤは胸高直径10cm未満の小径木だけで, 上層林冠には他の樹種が生育し, モミ, ツガが多く, アカマツおよびスギはすくなかった。胸高直径100cmを越えるツガの大径木が14個体標高900m以上の区域に散在しているのを確認した。上層林冠に生育していた広葉樹は, 常緑ではアカガシだけで, 他の21種は落葉性のものであった。隣接木と根が連結しているために生きているモミおよびツガの伐根の年輪から1920年 (大正9年) から1922年 (大正11年) に, 前生樹が伐採されたことが確認された。林分の蓄積は, 方形区標準地の調査で, 533. 8m_3/ha - モミ187. 4m_3, ツガ131. 5cm_3, その他の針葉樹5. 7m_3, 常緑広葉樹34. 4m_3, 落葉広葉樹174. 8m_3 - , 帯状区標準地調査で558. 4m_3/haと推定され, 胸高直径5cm以上のものは, それぞれ2, 116本/ha, 1, 638本/haであった。

In a series of studies on the productivity of the natural forest mixed Japanese fir (Abies firma Sieb. et Zucc.) and hemlock (Tsuga sieboldii Carr.) in Kyoto University Forest in Wakayama (Lat. 30°04′, Long. 135°30′E, Alt. 500-1, 200 m), this report dealt with the profile of natural reservation forest in compartment-9 (Alt. 650-1, 050 m). The investigations were carried out from 1979 to 1984. The tree species and the stem volume were measured in twelve quadrates (50 × 50 m) and in two belt transects (10 × 659 m and 10 × 585 m) (Fig. 2). Six coniferous species of Abies firma, Tsuga sieboldii, Pinus densiflora, Cryptomeria japonica, Torreya nucifera and Cephalotaxus durpacea were observed in research area. However, Torreya and Cephalotaxus composed lower stratum had been small D.B.H. less than 10 cm, on the other, in upper stratum, there were fourteen large size trees of Tsuga sieboldii over 100 cm in D.B.H.. The broad leaved trees occupied at the canopy of upper stratum were classified in twnety-one species of deciduous tree except Quercus acuta, and these main species were Betura grossa, Castanea crenata, Fagus crenata, Quercus crispula, Prunus donarium v. spontanea Stewartia monadelpha, Carpinus spp. and Acer spp.. It was considered that the trees were not cut down after 1922 by the measurement of annual rings in living stump of Abies and Tsuga in this natural forest (Fig. 1). The number of trees above 5 cm in D.B.H. was 2, 116 individuals per hectare, namely 344 of Abies, 270 of Tsuga, 7 of other conifer, 929 of evergreen broad leaved species and 616 of deciduous broad leaved species by quadrate measurement, and was 1, 638 individuals, namely 203, 313, 41, 591 and 490 respectively by belt transect measurement (Fig. 9). The trees less than 5 cm were 2, 461 individuals per hectare, respectively 164, 186, 11, 1, 667 and 433 by quadrate measurement (Fig. 4). The biomass of stem volume of tree above 5 cm in D.B.H. was from 423.9 m3 to 659.8 m3 (533.8±74.8 m3 in mean) per hectare in twelve quadrates, namely 187.4 m3 of Abies, 131.5 m3 of Tsuga, 5.7 m3 of other conifer, 34.4 m3 of evergreen and 174.8 m3 of deciduous broad leaved species in mean, and also the stem volume was estimated 558.4 m3 per hectare by belt transect measurement.