岷江上游河谷土壤发生的空间分异及环境意义

Spatial Heterogeneity and Environmental Significance of Pedogenesis in Soils from Valley of the Upper Minjiang River

分析了岷江上游河谷沿岸及九顶山西北坡表层土壤粒度、氧化铁、有机质、碳酸盐、p H、有机碳同位素、阳离子交换性、粘土矿物等理化性质。结果表明,三江至映秀段土壤具有较高的粘粉比、铁游离度及粘粒和有机质含量,而碳酸盐含量、p H和有机质δ13C值相对偏低,说明土壤发育较好、淋溶作用较强,反映了气候湿润和植被以乔木为主的环境特征;草坡至凤仪段土壤颗粒较粗、碳酸盐含量和p H较高,而铁游度和有机质含量较低,有机质δ13C值偏重,反映出干旱的气候和以C4植被为主的环境特征。九顶山西北坡土壤随海拔的增加粘粉比、有机质含量增大,出现纤铁矿而方解石缺失,反映干旱河谷区高海拔气候湿润;而海拔低于2 000 m的土壤粘粉比和粘粒、有机质含量较低,方解石含量和p H值较高,指示了干旱的气候特征。

Investigation on the pedogenesis of soils from the upper reaches of the Minjiang River is necessary for ecological reconstruction and vegetation restoration in this region. The soils development from the valley of the upper Minjiang River and the Jiuding Mountain were investigated based on the physical and chemical properties such as grain size distribution, oxide of iron, organic matter, carbonate, pH, organic stable isotope, cation exchange capacity, and clay mineralogy. The well development and eluviation prevailed in the soils from the Sanjiang to the Yingxiou, demonstrated by the higher values of clay/silt, iron free degree, clay and or- ganic mater contents and lower values of carbonate content, pH and organic δ13C, indicating an environmental property of warm-wet climatic conditions and prevailed trees. However, the soils from the Caopo to the Fengyi were characterized by the higher sand and carbonate contents, pH and organic δ13C, and lower values of iron free degree and organic mater content, showing an arid climate in where Ca vegetation prevail. The clay/silt and organic mater content increase, iepidocrocite arising and calcite lack occurred in the high altitude region of the Jiuding Mountain, indicating a wet climatic condition. While the soils under 2000 metre above sea level presented an arid climatic feature, as demonstrated by the lower values of clay/silt and contents of clay and or- ganic mater, as well as the higher calcite content and pH.