Soils and soil cover patterns of volcanic plateaus in Indochina

摘要

The soils of volcanic plateaus of different ages and different elevations have been studied in detail in the course of large- and medium-scale soil-ecological surveys in Cambodia and Laos. These plateaus are composed of basaltic rocks covered by ferrallitic and ferrsiallitic weathering crusts. Dark red soils are developed from thick (> 10 m) ferrallitic weathering crusts of basalts erupted at the early stages of volcanism, as well as from less thick (up to 2-4 in) ferrallitic weathering crusts of weatherable pyroclastic materials and volcanic tuff of the Late Pleistocene and Holocene. Red ferrallitic and, especially, brown ferrsiallitic soils are typical of the Late Pleistocene mantles of dense and porous basalts. The soil cover of basaltic plateaus is generally homogeneous. Against this back-round, the mesostructures of the soil cover related to the topographic and lithological differentiation of the territory are clearly seen. The microstructures of the soil cover are not typical of the basaltic plateaus in Indochina. The soils of the volcanic plateaus are characterized by high natural fertility owing to their favorable water-physical and chemical properties. They represent an important resource for the agricultural development of this territory and the growing of technical crops and orchards.