声生演習林における森林情報のデータベース化とその利用

Abstract

芦生演習林で1964 - 1965年に調査された, ほとんどが天然生の林分から成る計63プロットの全3, 073本の毎木調査結果がデータベース化され, そのデータを使って芦生演習林の森林の特徴と変量相互間の関係が調べられた。その結果, 1) 全木ではスギの出現本数頻度が最も高かったが, 上層木だけで見ればその比率は低下する。上層を構成する広葉樹で卓越するのはブナ, ミズナラである。2) 単木材積を大きい順に並べると, 順位の高い樹種は出現頻度の低いカツラで, 以下ブナ, ミズナラなどの広葉樹が続き, スギは出現頻度に比して材積の大きい個体は少ない。3) 森林蓄積量の多いプロットは, 標高が700m以上で斜面部位が谷部や末端部を除く箇所であるが, 蓄積量の少ないプロットは流域内に散在している。その原因として人為的な影響が考えられる。4) プロットの全木に占める上層木の材積割合は82. 5％である。5) 上層木について針葉樹冠の占める割合を変数として全樹冠面積率とプロット蓄積量の関係を調べた結果, 特に針葉樹冠面積率が20％以上のプロットでは, 全樹冠面積率が上がればプロット蓄積量が増加する傾向が認められる。6) 上層を占める樹木を針葉樹, ブナ, ミズナラ, その他広葉樹に区分して胸高直径と樹高, 樹高と樹冠幅, 胸高直径・樹高と樹冠幅, 材積と樹冠幅の関係式が求められた。

The forest information investigated at sixty-three plots in the Ashiu Experiment Forest of Kyoto University, in 1964-1965, was included in the data base. Most of plots were composed of natural forest. The relationships of the valiables each other, such as tree species, tree diameter at breast height, tree height, crown width, were analyzed. The results are as follows : 1.The number of Cryptomeria japonica is the highest in the Ashiu experiment forest, but the ratio of it for total tree numbers decreases in the trees occupied the upper layer. The ratios of tree numbers of both Fagus crenata and Quercus mongolica increase in the upper layer. 2. The stem volume of each tree is sorted in descending, and is arranged from top to the fiftieth. It shows that Cercidiphyllum japonicum occupies the No.1 and No.2 position despite a low frequency in the total tree numbers. A lots of Fagus cremnata and Quercus mongolica are included in the list, but Cryptomeria japonica is sparsely included in the list in spite of the majority in the frequency of tree numbers. 3. The plots possessed the more wood volume are located in the higher points than 700 meter a.s.l. and in the middle to upward of hillslope, but those possessed the less wood volume are dispersed in the whole area. 4. The wood volume of the trees in the upper layer is 82.5 percent of the whole trees, in average. 5. The wood volume for the whole crown ratio by the ratio of the needle-tree crown shows that it increases in proportion to the crown ratio more than 20 percent, the ratio of the needle-tree crown. 6. Tree species in the upper layer are classified in four groups such as the needle tree, Fagus crenata, Quercus mongolica and the residual broad-leaved tree. And the relationships between the diameter at breast height, tree height, crown width and wood volume each other were analyzed, and those parameters were determined.