森林立地学会誌 森林立地41（2），1999，77〜81
Jpn.J.For.Environment41（2），77-81
1999
酸性水散布による土壌酸性化初期におけるクロマツ苗の生育
丹下 健＊・田村邦子＊＊・古田公人＊
＊東京大学大学院農学生命科学研究科・＊＊大妻女子大学社会情報学部
土壌酸性化が樹木に与える影響を明らかにすることを目的に，硫酸水散布による土壌酸性化の初期段階におけるクロマツ苗の生育を調べた。外生菌根菌に自然感染しているクロマツ苗を，有機物に乏しい土壌をつめた鉢に植栽し，酸性水散布の有無と摘葉（すべての1年生葉を除去）の有無を組み合わせた4処理区を設けた。酸性水を散布した処理区の表層土壌のpHは，6から5に低下したが，下層土壌のpHはほとんど低下しなかった。酸性水を散布した処理区の土壌水には，対照区より高濃度の塩基が含まれていた。いずれの処理区でも土壌水中のマンガンとアルミニウムの濃度は非常に低かった。クロマツ苗の当年葉の養分濃度に処理区間で有意な差はなかった。クロマツ苗の成長量は，対照区と比較して摘葉した処理区で小さく，酸性水を散布した処理区で大きかった。摘葉は，菌根菌への光合成産物の供給量の減少をもたらす要因であるが，土壌酸性化に対するクロマツ苗の反応への影響はみられなかった。菌根の形成率には処理区間で差がなかったが，酸性水の散布によってクロトマヤタケの子実体発生量が有意に減少した。クロマツ苗が影響を受けないような土壌酸性化の初期段階で，菌根菌に影響が表れることが明らかになった。
Takeshi Tange, Kuniko Tamura and Kimito Furuta:
Growth responses of Pinus thunbergii seedlings to weakly acidified soil by
application of acidic solution
Growth responses of Pinus thunbergii seedlings to weakly
acidified soil by application of acidic solution were studied. P. thunbergii seedlings colonized by
ectomycorrhizal fungi naturally were transplanted from the nursery to pots
filled with infertile soil. We made four plots with or without application of
acidic solution and leaf-thinning. The pHs of surface soils were about 5 at the
acidified plots and about 6 at the control plot. The pHs of sub-soils did not
decreased by application of acidic solution. Soil solutions from the acidified
plots contained more base cations than those from the control plots.
Concentrations of manganese and aluminum in soil solutions were very low even
from acidified plots. Nutrient status of P.
thunbergii seedlings was not affected
by the soil acidification. Growth of the seedlings was smaller at the
leaf-thinning plot than at the control plot. Growth of the seedlings was a
little bigger at the acidified plot than at the control plot. Although
leaf-thinning would decrease carbon flow from the host tree to ectomycorrhizal
fungi, it did not affect on the responses of the seedlings to soil
acidification. The formation ratios of ectomycorrhizal roots did not differ
among four plots. Development of Inocybe
lacera basidiome was significantly depressed by soil acidification. It was
implied that ectomycorrhizal fungi were more sensitive to soil acidification
than P. thunbergii seedlings.