森林立地学会誌 森林立地47(2),2005,65〜75
Jpn.J.For.Environment 47(2),
65-75 2005
駒止湿原周辺の耕作跡地における植物群落構造と土壌との関係
伊藤祥子＊・星 理恵＊・藤井哲次郎＊＊・谷本丈夫＊
＊宇都宮大学農学部育林・森林生態学研究室・＊＊（株）ジオグリーンテック
福島県駒止湿原周辺の森林を再生させる方策を検討するため，湿原周辺の耕作跡地における群落構造を明らかにし，代表的な群落型の土壌断面を掘って，その土壌の特徴を把握し，さらに群落型と土壌の硬度・透水性との関係を調べた。耕作跡地を除く湿原周辺はブナの二次林で，耕作跡地には林縁および沢や湿原に接する場所にクマイザサやクマイチゴなどの低木型，湿原に隣接し湧水の認められる場所にヨシ型，平坦地に牧草型，斜面にススキ型が分布し，ブナ林を含めて計５型に区分できた。さらにススキ型は斜面上部の生育不良（草丈<2.0m）と斜面下部の生育良好（草丈≧2.0m）の２亜型に区分できた。特にススキ生育不良亜型は農道に接していた。ブナ林の土壌型は適潤性褐色森林土（偏乾亜型）BD（d）であった。一方，耕作跡地の土壌表面はブナ林よりも30〜40cm低くなっており，土壌断面はにぶい黄褐色を呈し，粒状構造の埴土の耕耘層と黄褐色でカベ状構造の埴土のＢ層から成っていた。しかし，ススキ生育良好亜型や牧草型ではススキ不良亜型よりも耕耘層が厚く，根系が多く認められ，腐植の浸透も深かった。土壌硬度は牧草型とススキ生育良好亜型がススキ生育不良亜型よりも柔らかい土壌の割合が多く，ブナ林についで柔らかかった。また土壌透水性も表層から深さ40cmでは，牧草型とススキ生育良好亜型がススキ生育不良亜型よりも優れていた。以上のことから，駒止湿原周辺の耕作跡地で群落型に違いが認められた要因の一つは，表層土壌が失われた程度の違いによると推察した。表層土壌が失われた程度が異なることに付随して，腐植の浸透した深さ，土壌硬度，土壌透水性の違いに表れたと考えられた。このように各群落の立地特性を把握したうえで，耕作跡地に森林を再生させるために，ブナの植林が可能な立地環境を指標する植物群落を明らかにし，再生の過程と方策の一案を示した。
Shoko Ito, Rie Hoshi, Tetujirou Fujii and Takeo Tanimoto : The relationship between the structure of plant community and the soil in an abandoned cropland around Komado Moor.
To consider the way for the
recovery of a beech forest in an abandoned cropland surrounding Komado moor in
Fukushima Prefecture, Japan, we clarified soil profile on each plant community
type. Moreover we examined the relationship between the plant community types
and the characteristics of the soil (soil hardness, and soil permeability). The
area surrounding the moor, excluding the abandoned cropland, was a secondary
beech forest. In the abandoned cropland, five community types were identified.
The shrub type, in which Sasa senanensis or Rubus crataegifolius
was dominant, was distributed at the forest edge and along the stream. The Phragmites
communis type was distributed over the area of water logging. The pasture
type and the Miscanthus sinensis type were distributed on flat land and
on the slope, respectively, and the Miscanthus sinensis type was divided
into the poor-growth subtype ( glass height<2.0m) and the good-growth
subtype (glass height≧2.0m). The
former was distributed on the upper slope near the farm road, and the latter,
on the lower slope. The soil type of the beech forest was moderately moist
brown forest soil drier type. On the other hand, the ground level of the
abandoned cropland was 30-40cm lower than that of the beech forest. The soil
profile of the abandoned cropland was composed of a till layer and B layer. The
till layer was yellowish-brown in color, had a nutty structure, and was composed
of clayey soil. The B layer was yellowish-brown in color, had a massive
structure, and was composed of clayey soil. However, the till layers of the
good-growth subtype and the pasture type were thicker than those of the
poor-growth subtype. Furthermore, the quantity with root and humus of the
good-growth subtype and the pasture type were greater than that of the
poor-growth subtype. The soil hardness of the good-grewth subtype and the
pasture type was softer than that of poor-grewth subtype. Also, the water permeability
of the good-grewth subtype and the pasture type at a depth of 40cm were higher
than that of poor-grewth subtype. These results suggest that the cause of the
difference in the community types seemed to be the difference with the disappearance
quantity of surface soil. The difference of the soil hardness, water
permeability, and humus thickness was estimated to appear the difference with
the disappearance quantity of surface soil. Moreover, we clarified the plat
community type which it is possible for a beech forest to be recovered in
abandoned cropland and showed a way for a beech forest recovery.
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