中国カルチン沙地における土地利用状況と土壌理化学性

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本研究は,中国カルチン沙地の土地利用状況と土壌の理化学性との関与を明らかにするため,農牧交錯区である奈曼旗において砂地,従来の草原地と灌木地,砂地をポプラで緑化した林地,および草原地を農地に開墾した畑地と水田の植物種分布と土壌理化学性を調査した.各調査地で,植生改善の回復現状は人工植被から複雑な灌木群落へ変遷する過程がみられた.理化学性では,含水比と有機物含有量の3層および陽イオン交換容量の表層では,水田>畑地>林地>草原地>灌木地>砂地の順に低くなっている.pHは採取土壌の全てが8.04～10.29とアルカリ土壌であった.ECはとくに畑地表層部において0.59mS/cm と高かった.土壌の比重は2.55g/cm_3から2.68g/cm_3と大差は認められなかった.それぞれの地点で採取した土壌の構成粒子径の比較では,水田と畑地で粘土が7%,粘土からシルトが約50%で残りは粗砂であった.また,修復された林地では約70%が微細な砂土で残りは粗砂であり,灌木地,草原地,砂地では約40%が細砂で残りは粗砂であった.保水性については,有効水分量をpFl.8～pF4.2として深度0～30cmの砂地,灌木地,林地の体積含水比の比較によると,それぞれ3%,8%,17%と植生回復の効果が認められた.土地利用の際に利用状況と理化学性の関与に注意すべき点を把握するのは,カルチン沙地の生態環境の保全および農牧業の可持続的発展に不可欠であることが示唆された.Transitional changes of soil physical and chemical properties after implementing the plant recovering trials against desertification were studied at Naimanchi province in the Horqin desert, northeast district in China. The soil were sampled at typical points of each land use within the area about 20 km times 30 km square. Land uses conditions were classified into sand dune desert, grassland, bush, forest, upland crop filed and rice filed. In the grassland and bush area, native plants and imported plants seeded by air were growing. Especially, two kinds of Artemisa Halodendron and Setaria viridis which is common to this sandy area. Air dried water content, organic contents, cation exchange capacity (CEC), pH, electric conductivity (EC), soil composition particle diameter, specific gravity and moisture characteristic curve (pF) were observed. When arranging the air dried water content, organic content and cation exchange capacity in high order, it became paddy field>upland field>forest>grassland> shrub>sand dune desert. The pH of all soil samples were between 8.04～10.29 and presented alkaline soil. Maximum electric conductivity (EC) with 0.59 mS/cm was observed at upland crop field. This phenomenon indicates that irrigation management and chemical fertilizer should be done appropriately to avoid the salt accumulation. As for the specific weight of the soils ranged from 2.55～2.68 g/cm_3 and a great difference weren't found in each other. In upland and rice field, the percentages of the composition of clay and silt were about 7% and 50%, respectively. The remainders were coarse and fine sands. In the forest, silt and fine sand consist of 70 %, and in the sand dune, grassland and bush area, about 60% was occupied by coarse sand and the remainder was fine sand. The moisture characteristic curve of soils shows that effective soil moisture within the surface 30 cm layer in sand dune, bush and forest were 3%, 8% and 17%, respectively. Soil characteristics for retaining water have been improved as the plant density increase.
九州大学の論文

中国カルチン沙地における土地利用状況と土壌理化学性

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