森林立地学会誌 森林立地44(2), 2002, 23〜29
Jpn. J. For. environment44(2), 23-29 2002
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
土壌の養分特性に及ぼす影響
市川貴大＊＊・深澤文貴＊＊＊, ＊＊＊＊・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・＊＊＊＊現勤務先 静岡県庁
ヒノキおよびスギ人工林化による土壌の養分特性の変化を明らかにすることを目的に，落葉広葉樹天然林伐採後に人工造林されたヒノキおよびスギ林と，天然更新した広葉樹林が同一斜面上に成立する調査地において，A0層の乾重および養分含有量，鉱質土壌の化学的性質を調査した。針葉樹林の斜面上部にはヒノキが（ヒノキ林），斜面下部にはスギが（スギ林）それぞれ植栽されている。本研究では，斜面位置ごとに調査結果を広葉樹林と針葉樹林において比較した。ヒノキ人工林化によって土壌深0-30cmにおける交換性塩基量に違いは見られなかった。スギ人工林化によって土壌深0-30cmにおける交換性塩基量は隣接する広葉樹林に比べて多く，特に交換性Ca量は約1.9倍であった。土壌深0-30cmにおける全C，N量，CECは斜面上部のヒノキ林では広葉樹林に比べそれぞれ約0.6, 0.6, 0.8倍であったが，斜面下部のスギ林では広葉樹林とほぼ同じであった。A0層量は斜面位置にかかわらず，広葉樹林で約7.1Mg/ha，ヒノキ林とスギ林では共に約9.5Mg/haであった。本調査地のA0層のC/N比は広葉樹林に比べて針葉樹林で高かった。各調査区のA0層中の元素含有量と土壌深0-30cmの全C，N量および交換性K，Ca，Mg，Na量の関係について検討したところ，Caについてのみ有意な正の相関関係がみられた。スギ人工林化によってA0層中に蓄積されたCaの影響を受けて交換性Ca量が増加していると推察された。
Takahiro
Ichikawa, Fumitaka Fukuzawa, Terumasa
Takahashi and Yoshito Asano: Effects of the
conversion of the forest management type from natural deciduous broad-leaved
forests to artificial Japanese cypress and Japanese cedar forest on soil
fertility
In order to
clarify the effects of the conversion of the forest management type from
natural deciduous broad-leaved forests to artificial Japanese cypress and
Japanese cedar forests on the soil fertility, we investigated the amounts and
nutrient contents of the forest floor and soil chemical characteristics (0-30cm
depth) in the natural deciduous broad-leaved forests and adjacent artificial
Japanese cypress and Japanese cedar (evergreen coniferous) forests. In the artificial
evergreen coniferous forests were planted Japanese cypress (Chamaecyparis obtusa) on the upper slope and Japanese
cedar (Cryptomeria japonica) on the lower slope. In this
study, comparisons of the results were between the natural deciduous broad-leaved
forests and artificial evergreen coniferous forests. The soil exchangeable base
contents in the cypress forest were almost the same to those of the natural
deciduous broad-leaved forest on the upper slope. The soil exchangeable calcium
contents in the cedar forest were about 1.9 times greater than those in the
natural deciduous broad-leaved forest on the lower slope. The soil carbon and
nitrogen contents and CEC in the cypress forest were about 0.6, 0.6, and 0.8
times smaller than those in the natural deciduous broad-leaved forest on the
upper slope, respectively. The soil carbon and nitrogen contents and CEC in the
cedar forest were almost the same to those of the natural deciduous
broad-leaved forest on the lower slope. The amounts on the forest floor were
about 7.1Mg/ha in the natural deciduous broad-leaved forests, and about
9.5Mg/ha in the artificial evergreen coniferous forests regardless of the slope
position. The C/N ratios of the forest floor in the artificial evergreen
coniferous forests were higher than those in the natural deciduous broad-leaved
forests. The amounts of calcium in the forest floor significantly correlated
with the contents of exchangeable calcium in the soil. The accumulation of
calcium in the forest floor was inferred to bring the increase of the
exchangeable calcium in the soil.