森林立地学会誌 森林立地46(1), 2004, 1〜8
Jpn.J.For.Environment
46(1), 1-8 2004
中国黄河河口域における塩類土壌の理化学性に及ぼす脱塩・植栽の影響
伊與田朱美*,**・尹 建道***・戸田浩人*・生原喜久雄*・峰松浩彦*
*東京農工大学農学部・**現在，山形県庁農林水産部・***中国・天津理工大学環境科学院
中国の黄河河口域において，塩類土壌の灌水による脱塩と緑化木植栽が土壌に及ぼす影響を明かにするため，植栽区（灌水による脱塩後に樹木を植栽し２〜６年後）３ヶ所と対照区（無処理で植生は草木と低木がわずかにある程度）２ヶ所の土壌の理化学的性質を調査した。植栽区は対照区に比べて，土壌表層（0 〜30cm）で粗孔隙率，全炭素，全窒素および交換性Ca濃度が高かったが，土壌下層（30〜60cm）では土壌硬度およびpHが高く，植裁区のpHは8.5を超えていた。また，植栽区では対照区よりも全層（0 〜60cm）で水飽和抽出液の電気伝導度（ECe）および陽イオン交換容量に対する交換性Naの割合（ESP）が著しく低かった。対照区のECeは30〜70mS/cmであり，ESPは約20%でソーダ質の塩類土壌に分類されるのに対して，植裁区のECeは約4mS/cmであり，ESPは4 〜8%であった。以上より，植栽区では脱塩・植栽によって改善された土壌理化学性が，少なくとも2 〜6年間は維持されていることが示唆された。また，樹木の植栽はリター等による低C/N比の有機物の供給を促し，土壌肥沃度の向上が期待できると考えられた。植栽区の表層は耕耘と灌水によって，透水性が改善されるとともに塩類（特にNa）が溶脱されていたが，下層では土壌のアルカリ化と土壌硬度の上昇が起きている可能性が示唆された。
Akemi Iyota, Jian
Dao Yin, Hiroto Toda, Kikuo Haibara and Hirohiko Minematsu : Effects of
desalinization and plantation on physicochemical characteristics of salinity
soil in the mouth region of the Huang He River, China
Physicochemical characteristics of soil were investigated to
clarify the effects of desalinization and plantation on salinity soil. Three
plantation sites, which were desalinized by irrigation and planted trees 2 to 6
years ago, and two control sites were set in the mouth region of the Huang He
River, China. The percentages of the large pores (under pF1.8),total carbon,
nitrogen and exchangeable calcium concentration in upper soil (0-30cm)were
higher in the plantation sites than in the control sites. In lower soil
(30-60cm), soil hardness and pH in the plantation sites were higher than the
control sites, and the pH values were over 8.5. The soil in the control sites
was categorized into saline-sodic soil because the electric conductivity of
saturated water (ECe) was 30-70 mS/cm and the exchangeable sodium percentage
(ESP) was 20%. In the plantation sites, ECe and ESP were 4 mS/cm and 4-8%,
respectively. Therefore, sodium was leached by cultivation and irrigation in
the upper soil of the plantation sites that had a high rate of percolation.
However, the soil pH and hardness increased in the lower soil of the plantation
sites. In the plantation sites, the desalinization effect by irrigation was
kept for at least 2 to 6 years and soil chemical properties were ameliorated by
the low C/N ratio litterfall supply.