| Sichuan province is located in the upper reaches of the Changjiang River. In recent decades, the ecology environment suffered serious destruction owing to unreasonable land utilization and the cutting of forest. A large number of soil erosions occurred seriously, which have endangered the life and property to the people of downstream. In 1999, Sichuan province started the engineering project of converting agriculture land into forest and pasture. Many kinds models of vegetation restoration have being adopted in the project implementation according to local natural conditions and economy development.The study on the water and soil conservation and the soil improvement effect of eighteen kinds of vegetation restoration models, four kinds of forest types and one kind of agricultural land in the area concerned was conducted in this research. The best vegetation restoration models, which could be the example for large-scale project of converting agriculture land into forest and pasture. After the analysis, the conclusion were drawn as following:1 It is evident that soil and water conservation result in new forestland has improved than that which is in sloping cultivated land after converting agriculture land into forest and pasture. The monthly surface runoff and sediment load of crossing bamboo and E.grandis are 0.33m3 and 0.37 m3, which had decreased 37.9% and 30.1%. The slit contents are 2.06kg and 2.45kg(erosion modulus are 246.7t-km-2-a-1 and 292.1t-km-2-a-1),which have decreased 43.4% and 39.0% than contrasting cultivated land. The result of crossing bamboo is better than E.grantdis.2 Through the correlation analysis between obiomass of crossing bamboo and the surface runoff ratio and sediment load ratio on the plantation (same to E.grandis ), we can draw the conclusion that the correlation of the crossing bamboo biomass and its sediment load ratio is significant on the level of 0.05, and rest three correlation coefficients are significant on the level of 0.10. This indicated that biomass and its sediment load ratio of different vegetation types are negative correlation. Along with the growth of forest and overlay degree of grass, the result of soil and water conservation will improve increasingly.3 As far as superstratum soil bulk density, the land of converting agriculture land into forest and pasture is much significant higher than contrasting cultivated land, but the difference of substrate soil bulk density with cultivated land is not significant. As far as the converting land for forestry and pasture modes, the sequence of superstratum soil bulk density is: Arbor and shrub unite< conifer< bamboo< broadleaf forest< forest and bamboo unite< forest and grass unite< grass< cultivated land. The sequence of substratum soil bulk density is: arbor and shrub unite< bamboo< conifer< forest and grass unite< broadleaf forest< forest and bamboo unite< cultivated land< grass.4 The soil anticorrosion of the land of converting agriculture land into forest and pasture is much significant higher than cultivated land. As far as the growth period of timber, the anticorrosion of the adult timber is higher than that of the younger. As far as earth's using styles, fast growth species> grass land> slow growth species> cultivated land. As far as locality types of timber, the anticorrosion of clayey is higher than that of incompact soil.5 Most of sample land's fast result nutrient content in superstratum soil is higher than that in substratum soil. The sequence of fast result nitrogen content in superstratum soil is: Arbor and shrub unite> broadleaf forest > forest and bamboo unite> bamboo> conifer> forest and grass unite> grass. The difference of fast result nitrogen content in substratum soil is not significant. The sequence of soil fast result phosphor is: forest and bamboo unite> conifer> bamboo> Arbor and shrub unite> broadleaf forest> forest and grass unite> grass. The sequence of fast result potassium content in superstratum soil is: Arbor andshrub unite> broadleaf forest> forest and bamboo unito... |
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