森林立地学会誌 森林立地38(2),1996,92〜97

  

Dynamics of water-soluble base cations in a forest

soil measured by an in situ combined IER method

 

Guonan WuKikuo HAIBARATakayoshi KOIKEYoshinori AIBA 

 

  呉 国南・生原喜久雄・小池孝良・相場芳憲:イオン交換樹脂による森林土壌の水溶性塩基の動態 森林土壌における水溶性塩基のバランスはインプットとしての林内雨からの付加,Ao層および鉱質土壌層からの放出(コロイドとの交換による溶出と有機物の分解)と,アウトプットとしての林木による吸収と下層土への溶脱によって保たれる。その動態を量的に把握するために,イオン交換樹脂バッグおよびイオン交換樹脂コアを複合させ,18年生のスギ林の表層土壌中の水溶性塩基の移動量を測定した。試験地の林内雨とイオン交換樹脂近くの土壌水も採取した。KCaMgともに,林内雨からの付加,Ao層および土壌からの放出量は大きく異なった。インプットに占めるそれらの割合はそれぞれK54%,12%,34%,Ca15%,36%,49%,Mg22%,36%,42%であった。一方,アウトプットに占める林木による利用と下層土への溶脱の割合は,それぞれK66%,34%,Ca42%,58%,Mg45%,55%であった。森林の表層土壌におけるKの植物による利用効率はCaMgより高かった。土壌中の水溶性塩基の動態を明らかにするのに複合されたイオン交換樹脂法の有効性が指摘された。

キーワード:土壌生態系,水溶性塩基,イオン交換樹脂,インプット,アウトプット

 

Guonan Wu, Kikuo HAIBARA, Takayoshi KOIKE, Yoshinori AIBA: Dynamics of water-soluble base cations in a forest soil measured by an in situ combined IER method. Jpn. J. For. Environment 38, 92-97, 1996

 The budget of water-soluble base cations in a forest soil system is presumably balanced between inputs via canopy throughfall, Ao-layer and soil release (mainly by organic decomposition and ion exchange with soil colloid), and outputs via biological uptake and leaching. An in situ method combining ion exchange resin (IER) bag and core ion exchange resin (core-IER) was adopted in this study to investigate water-soluble base cation dynamics in an 18-yr-old Japanese cedar (Cryptomeria japonica D. Don) stand over a 7-month period. Chemical characteristics of the canopy throughfall and the soil solution beside the IER bags were also measured. Inputs of K, Ca, Mg to the soil system via canopy throughfall, Ao-layer & soil release differed greatly from each other. Canopy throughfall provided 54% of the total input of K to the soil, and Ao-layer and soil release provided 12% and 34%, respectively. Ao-layer and soil release supplied more Ca and Mg (85% and 78%) to the soil than canopy throughfal1 (l5% and 22%). Among the outputs, biological uptake accounted for 66% of K, 42% of Ca and 45% of Mg. The higher biological uptake of K in comparison with Ca and Mg indicated that potassium was rapidly recycled in this forest ecosystem. Evaluation of the applicability of the in situ combined IER method suggested that this method may be useful for comparative analysis of water-soluble cation dynamics in a forest soil.

Key words: soil ecosystem, water-soluble base cations, ion exchange resin, inputs, outputs


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