森林立地学会誌 森林立地39（1）．1997．36〜45
論 文
森林土壌の破壊・非破壊培養における炭素無機化特性
戸 田 浩 人・島 田 博 匡・生 原 喜久雄
同一斜面で斜面位置の異なる5ケ所の森林土壌（斜面下部よりスギ林，スギ・ヒノキ混交林，斜面中部ヒノキ林，上部ヒノキ林，落葉広葉樹林）を用い，斜面位置と土壌の破壊培養が炭素無機化特性に与える影響を調べた。炭素無機化特性は反応速度論によって解析し，3つの特性値（可分解性炭素量（Co），反応速度定数（k（25℃）），見かけの活性化エネルギー（Ea））として求めた。Coは表層（0〜10cm）で，斜面下部のスギ林を除き，非破壊が破壊培養より15〜35%大きかった。深さ10〜20cmでCoは，斜面下部のスギ・ヒノキ林を除き，非破壊が破壊培養より15〜65％大きかった。Coが破壊培養により小さくなる土壌は，細根の多い土壌とほぼ一致していた。破壊培養は細根等の粗大有機物の除去により，炭素供給量の低下と根圏微生物の減少をもたらし，Coが小さくなると考えられる。しかし，Coの斜面位置や探さによる傾向は，非破壊と破壊培養で著しい違いを生じなかった。k（25℃）は，例外はあるものの破壊が非破壊培養より若干大きかった。これは，破壊によって土壌微生物を一時活性化させること，およびCO2の拡散の容易な環境を作るためと考えられる。破壊培養による細根の除去〈炭素源の減少）は，Eaを増大させると推察される。しかしEaは，スギ林を除き，破壊が非破壊培養よりも小さいかほぼ同程度であった。これは，細根等の粗大有機物が，分解に大きなエネルギーを必要とするリグニン等や，有機物の分解を阻害する物質（テルペン類，フェノールなど）を多く含むためと考えた。
Hiroto
TODA, Hiromasa SHIMADA, Kikuo HAIBARA, :
Characteristics of carbon mineralization in disturbed and undisturbed
incubations of forest soil. Jan. J. Fon. Environment 39, 36-45, 1997.
The effect of disturbed incubation on
the mineralization of soil carbon (C) in a forest soil was investigated. Soil
samples from different plot (a lower slope cedar (Cryptomeria japonica D.Don)
plot, a lower slope mixed cedar and cypress (Chamaecyparis obtuse ENDL) Plot, a mid-slope cypress plot, an upper
slope cypress plot and an upper slope deciduous broad-leaved plot) and soil
depths were investigated to clarify the characteristics of C mineralization.
The C mineralization process in the soils was modelled mathematically using a
simple kinetic model, and three parameters(C mineralization potential(Co) ,
Rate constant of mineralization (k(25℃)) and Apparent activation energy (Ea)) were
examined in relation to temperatures and soil properties. Disturbed incubation
of soil from the middle and upper slope positions decreased the Co by 15-34% at
0-10cm depth and by l5-65% at 10-20cm depth. There were many fine roots in the
plots where Co was decreased by disturbed incubation. This suggests that the
amount of C and the microbial activity in the rhizosphere were reduced by
removing the fine roots. However, disturbed incubation had no great effect on
the relationships between Co and slope positions or depth. k(25℃) was higher in disturbed incubation in
most soil samples because microbial activity and CO2 diffusion were
greater in disturbed soils. It was assumed that the rermoval of fine roots (C
source) would increase Ea. However, except for the cedar plot, Ea was lower or
similar level in disturbed than in undisturbed incubations. It was concluded
that this was because the fine roots and other large organic matter had a lot
of material that difficult to mineralize(e.g. Lignin) or which inhibits
mineralization (e.g. Terpenoids and Polyphenols).