Studies On Ecological Effect Of Converting Cropland To Forest In Datong High-Cold Zone Of Qinghai

Converting cropland to forest has been a basic measure in preventing soil and water losses, increasing water conservation function, improving the ecological environment of west China, and promoting the eco-economy sustainable development, and improving ecological environment effect is the key of converting cropland to forest. In recent years, there are some researches only focused in the impacts of single factor, not systematic study, so the comprehensive ecological efficiency can not be discovered scientifically and objectively. Depending on the national tenth-five year plan of state key task of scientific and technological research, in this paper, the vegetations of converting cropland to forest with different ages and vegetation types were taken as research object, and the ecosystem plotting position was applied in high-cold zone of Datong county, Qinghai province, which was associated with the artificial vegetation recovery and reconstruction for Datong county. The following factors and their interactions were studied in the process of converting cropland to forest, including soil physicochemical property, water utilization efficiency and potential productivity of different vegetations, biomass of major vegetation and biodiversity. The purpose of this paper is to provide evidences vegetation construction of converting cropland to forest, which has great significance in theory and practice.In the soil genetic horizon of 0-20 cm, with the age increasing of converting cropland to forest; the porosity, capillary porosity, and the minimum water-holding capacity took on the uniform trend of"S"curve, and the organic content and carbon content showed"V"curve, the maximum occurred in the arable land and 18a and 32a natural forests of converting cropland to forest; the C/N took on down trend, indicating that the N was in under-supply in the converting cropland to forest; the root density increase from 4,560 roots/ m~3 of arable land (0 year) to 111,940 roots/ m~3 of 18 a, which brought out the3.57 times increasing of anti-scour capacity and 71.98% improvement of anti-scour strengthen value; and the order of stable infiltration velocity was natural forest of 32a > artificial forest of 18a> artificial forest of 5a> artificial forest of 1a>arable land. In addition, in the soil genetic horizon of 0-20 cm, the soil density is negatively related to the N content and C content, and positively related to clay content; however, in the 20-40 cm soil horizon, the soil density is significant positively to the content of N, C and clay particle. When the soil erosion occurred by the different exogenic forces, the soil damage degree increased with the soil horizon deepening. Due to the content of clay particle is positively...