森林立地学会誌 森林立地45(1),2003,35〜42
Jpn.J.For.Environment
45(1),35-42 2003
落葉広葉樹天然林のヒノキおよびスギによる人工林化が
生態系内の養分動態に及ぼす影響
市川貴大＊＊・高橋輝昌＊＊＊・浅野義人＊＊
＊＊千葉大学大学院自然科学研究科・＊＊＊千葉大学園芸学部
ヒノキおよびスギ人工林化による養分動態特性の変化が土壌養分特性を変化させる機構を明らかにすることを目的に，落葉広葉樹天然林（広葉樹林）と同一斜面に隣接した広葉樹林を伐採して造成されたヒノキおよびスギによる人工林（針葉樹林）において，リターフォールの乾重および元素含有量，林害雨，林内雨による養分供給量，および生態系外へ流亡した養分量を調査し，斜面位置ごとに広葉樹林と針葉樹林間で比較した。斜面上部のヒノキ林では広葉樹林に比べて土壌深0−30cmにおける全C量は約0.6倍で，リターフォールによるC供給量は約0.9倍であることから，ヒノキ林の土壌では有機物が無機化されやすく，蓄積しにくい可能性が示唆された。斜面下部のスギ林では広葉樹林に比べて土壌深0−30cmにおける全C量はほぼ同じであったが、リターフォールによるC供給量は約0.8倍であることから，スギ林の土壌では有機物が無機化されにくく，蓄積しやすい可能性が示唆された。斜面上部のヒノキ林ではAo層を通過して鉱質土壌に供給されるK+量は広葉樹林の約0.4倍であった。斜面下部のスギ林ではAo層を通過して鉱質土壌に供給されるCa2+量は広葉樹林の約2.1倍であった。土壌深0−10cmの交換性K量と土壌深0−30cmの交換性Ca量は鉱質土壌に供給されるK+，Ca2+量と有意な正の相関関係にあった。このことから，鉱質土壌に供給されるK+，Ca2+量が土壌の交換性塩基量に影響を及ぼしていた。
Takahiro
Ichikawa, Terumasa Takahashi and Yoshito Asano: Effects of the conversion of
forest management type from natural deciduous broad-leaved forests to
artificial Japanese cypress (Chamaecyparis obtusa) and Japanese cedar (Cryptomeria
japonica) forests on nutrient dynamics.
In order to
clarify the effects of the conversion of the forest management type from a
natural deciduous broad-leaved forests (broad-leaved forests) to an artificial
Japanese cypress (Chamaecyparis obtusa) and Japanese cedar (Cryptomeria
japonica) forests (coniferous forests) on soil fertility, we investigated
the amounts and nutrient contents of the litterfall, and the amounts of
dissolved elements in the precipitation, throughfall and percolated water
through 0, 5, 25, and 50cm depths of the soil in each forest. In this study,
comparisons of the results were made between the broad-leaved forests and
coniferous forests. The soil carbon content and the amount of annual litterfall
in the cypress forest were about 0.6 and 0.9 times lower than those in the
broad-leaved forest on the upper slope, respectively. Therefore, it is
considered that organic matter in the cypress forest soil had been easily
mineralized and had been difficult to accumulate relative to that in the
broad-leaved forest on the upper slope. On the other hand, the soil carbon
content and the amount of annual litterfall in the cedar forest were about 1.0
and 0.8 times lower than those in the broad-leaved forest on the lower slope,
respectively. Therefore, it is considered that organic matter in the cedar
forest soil had been mineralized with difficulty which provided a rapid
accumulation relative to that in the broad-leaved forest on the lower slope.
The amount of K+ in the percolated water through the forest floor in
the cypress forest was about 0.4 times lower than that in the broad-leaved
forest on the upper slope. The amount of Ca2+ in the percolated
water through the forest floor in the cedar forest was about 2.1times higher
than that in the broad-leaved forest on the lower slope. The soil exchangeable
potassium at a 0-10cm depth and the soil exchangeable calcium at a 0-30cm depth
were significantly correlated with the amounts of potassium and calcium ions dissolved
in the water that reached the soil. The amounts of potassium and calcium ions
dissolved in the water-reached soil influenced the soil exchangeable base
contents.