PROBE TENTATIVELT INTO SOUS AND ECOLOGIC CONSTRUCTION ON DADU RIYER VALLEY WITHIN THE BOUNDARIES OF LUDING, SHIMIAN COUNTY, SICHUAN PROVINCE
四川泸定,石棉境内大渡河河谷土壤及其生态建设

This paper mainly deals with the genesis features of soils on Dadu River Valley within the boundaries of Luding, Shimian country, sichuan province, and probe tentatively into the problem about ecologic construction on it.1. The mountain drab soil is distributed mainly over Dabu River Valley in north of Luding Town.Its organic matter is in a small amount, C/N is limited (<10) , it has a certain clay action, but the clay action of the drab soil in the North of China is more intensive, SiO3/Al2O3 of clay(<0. 001 mm) is between 2.9 and 3.2, the total profile has calcareous reaction, and CaCO3 is illuviated at C horizon.2. The mountain plateau red earth is distributed mainly over Dadu River Valley in South of Luding Town.It is reddish-darkbrown reddishin color and dry in soil, it has iron-manganese concretion in soil and iron manganese capsule on the face of soil structure; PH3.5-6.5, CEC I8-20m.e /100gsoil, its percentage base saturation is 70-30%; SiO2/Al2O3 of clay(<0.001mm) 2.0-2.3 in B horizoa.3. The ecological balance is disturbed seriously in Dadu River Valley. The limiting factors in agriculture, forestry and animal husbandry are r e-latively arid and precipitous in this River valley, but the destruction of vegetation leads to the serious soil erosion; they aggravate conversely the arid degree. For this reason, the key is to make the waste slope green,con-servet he water, and to improve the habitat.It is necessary for me to take project measure, The problems concerning Dada River Valley should be tackled in a comprehensive way.