森林立地学会誌 森林立地42（1），2000，23〜28
Jpn.J.For.Environment42(1)，23−28 2000
ヒノキ林林床への落葉広葉樹リターの供給が土壌の養分特性に及ぼす影響
高 橋 輝 昌
千葉大学園芸学部
ヒノキ林林床への広葉樹リターの供給が土壌の養分特性に及ぼす影響について検討するために，隣接する落葉広葉樹林から落葉広葉樹リターが供給されるヒノキ林（広葉混入区），落葉広葉樹リターが供給されないヒノキ林（ヒノキ純林区），落葉広葉樹天然林〈広葉天然林区）において，Ao層，鉱質土壌層の化学的性質と窒素無機化特性を調査した。Ao層量は広葉天然林区と広葉混入区で約17Mg ha-1，ヒノキ純林区で約8Mg ha-1であった。広葉天然林区のAo層中のK，Ca，Mg含有量は広葉混入区よりも2〜7割多く，また，ヒノキ純林区の3〜9倍であった。鉱質土壌層の全C，全N含有率，CEC，土壌深0〜10cmまでの交換性Ca，Mg含有量およびpH（H2O）は概ね広葉天然林区≧広葉混入区＞ヒノキ純林区の傾向にあった。7月から11月にかけての鉱質土壌層（土壌深0〜10cm）のN無機化量は広葉天然林区，ヒノキ純林区，広葉混入区でそれぞれ100，77，67mg kg-1であった。N無機化量に占めるNH4+−Nの割合は広葉天然林区と広葉混入区で約4割，ヒノキ純林区で約1割であった。以上の結果から，広葉樹リターの供給はヒノキ林の土壌養分特性の改善に概ね有効であると考えられる。
Terumasa Takahashi : Effects of supply of deciduous
broad-leaved litter to the forest floor on the soil fertility of a Japanese
cypress (chamaecyparis obtusa )
forest.
In order to study the effects of the
supply of broad-leaved litter to the forest floor of a Japanese cypress (Chamaecyparis obtusa) forest on soil
fertility, we investigated (i) the amounts and nutrition contents of the forest
floor, (ii) the soil chemical characteristics (0-30cm depth) and (iii) the
characteristics of N mineralization (0-10cm depth) in the Japanese cypress
forest and a natural deciduous broad-leaved forest. Investigation was carried out
using pure Japanese cypress forest soil with (JCB) and without (JC) deciduous
broad-leaved litter supplied to its forest floor from an adjacent natural
deciduous broad-leaved forest and from a natural deciduous broad-leaved forest
(NBL) soil at varying depths. Results show that the K, Ca, Mg, contents of the
forest floor in the NBL were approximately 20-70% larger than those of the JCB,
and were 3-9 times larger than those of the JC. The C and N concentrations and
pH (H2O) at a depth of 0-10cm decreased in the order of NBL≧JCB>JC. The amounts of N
mineralization at the depth of 0-10cm in the NBL, JC and JCB were 100, 77 and
67mg kg-1, respectively. The ratio of NH4+−N to N mineralization was approximately
40% in the NBL and JCB and approximately 10% in the JC. From those results, it
was considered that the supply of broad-leaved litter to the forest floor of
the Japanese cypress forest was effective in improving soil fertility.