森林立地学会誌 森林立地49(2), 2007, 93〜101
Jpn.J.For.Environment 49(2), 93−101 2007
スギ・落葉広葉樹混交林の表層土壌の化学性に及ぼす樹幹流，林内雨
およびリターの影響
澤田智志＊*・加藤秀正＊＊*
**秋田県農林水産技術センター森林技術センター・***宇都宮大学農学部
秋田地方のスギと広葉樹の混交林において，スギとブナの養分動態の違いが表層土壌の化学性におよぼす影響を比較検討した。調査地内のスギの樹冠下ではスギの本数割合が高くなるにつれて土壌に供給されるスギのリター量が多くなった。そのためO層にカルシウムを主とする多量の塩基が蓄積し，土壌表層部の塩基飽和度が高くなり，土壌pHは上昇した。一方，ブナ樹冠下ではスギ樹冠下と同様に全炭素量は高くCECが大きいものの，単位面積あたりのリターからのカルシウム供給量が少ないため，土壌表層部の塩基飽和度は低く，
pHは強酸性を示した。スギの樹幹流のpHは4.3の強酸性であったが，樹幹流として土壌に供給される量は32 kg m-2と少なく，降雨よりもpHが5.6と高い林内雨の方が1,134
kg m-2とはるかに多く土壌に流入していた。林内雨と樹幹流から供給されるカルシウムやマグネシウムは，スギおよびブナ樹冠下のO層および土壌の蓄積量に比べて著しく少なかった。ただし，カリウムはブナ樹冠下では樹幹流と林内雨から供給されるO層の量より多かった。このように混交林の上層を構成するスギとブナの養分動態の違いが土壌表層部の化学性に影響を与えており，林内雨や樹冠流よりも混交林を構成する樹種や密度が表層土壌の化学性に重要な影響を及ぼしているものと判断された。
Satoshi Sawata，Hidemasa Kato :Chemical
Properties of Surface Soil in Relation to the Quantity of Stemflow, Throughfall
and Litter in a Mixed Forest of Japanese Cedar (Cryptomeria
japonica) and Beech (Fagus crenata) Trees
The chemical characteristics of the surface soil in a mixed forest of Japanese cedar (Cryptomeria japonica) and beech (Fagus crenata) trees were investigated with special reference to nutrient dynamics. The amount of litterfall from the Japanese cedars was found to increase in proportion to increasing density of Japanese cedars in forest sites, resulting in large accumulations of cations (especially Ca+) and increases in base saturation and soil pH. The amount of litterfall from the Japanese cedars was found to increase in proportion to numbers of Japanese cedars, resulting in large accumulations of Ca+, and increases in base saturation and soil pH, under the Japanese cedars. In contrast, the surface soil under the beech trees was found to be strongly acidic and with low base saturation, due to the small amounts of Ca+ supplied from the litterfall of the beech trees. In the Japanese cedar areas, the measured total amount of the stemflow (with a measured pH of 4.3) was found to be only 32kg m-2, whereas that of the throughfall (with a measured pH of 5.6) was found to be 1,134kg m-2. Thus the throughfall was far in excess of the stemflow. Total Ca and Mg were found to be far lower in the throughfall and stemflow than in the organic layer and surface soil. Total K was much higher in the stemflow and the throughfall than in the organic layer. We conclude that the organic layer originating from litterfall determines the chemical properties of the surface soil, and the stemflow and throughfall have little influence on the chemical properties of the surface soil. This suggests that the specific characteristics of the forest crown, including tree species, tree spacing and tree density will affect the chemical properties of the surface soil.