| The Loess Plateau features unique geographical conditions. The soil erosion and fertility degradation of the region has been recognized worldwide, which have predominately arisen as a result of a long history of traditional grain crop farming systems. Perennial pasture has the proven ability to form extensive root systems, with the benefits of soil organic matter storage and sequestration. In order to evaluate the carbon sequestration effect of perennial pasture in the region, an experiment was conducted from June 2007 to June 2008. Soil total carbon (TC), soil organic carbon (SOC),＞0.25 mm particular organic carbon (POC), dissolved organic carbon (DOC), easily oxidized organic carbon (EOC), CPMI and soil organic carbon mineralization speed constant in pure and mixed perennial pastures were measured and compared to that of winter wheat:1. Soil TC in the 0-5 cm layer from pure cultivated lucerne, sainfoin, clover, crowtoe, sweet pea and brome grass pastures after five years was found to be 19.28 g/kg～25.42 g/kg, SOC was 9.84 g/kg～16.10 g/kg, DOC was 33.82 g/kg～40.58 g/kg, EOC was 9.65 g/kg-13.4 g/kg, values which were 21%～52%,34%～120%,17%～40%,61%～123% higher than winter wheat respectively; In the 5-10 cm soil layer, each index were 16.42 g/kg～18.55 g/kg,7.84 g/kg～10.04 g/kg,28.59 g/kg～38.06 g/kg,5.88 g/kg～8.58 g/kg respectively, which were 2%～11%,18%～51%,11%～45%,4%～51% higher than winter wheat respectively.2. In the mixed-pasture containing lucerne, sainfoin and brome grass, soil TC, SOC, POC and EOC in the 0-5 cm layer were 17.91 g/kg～21.97 g/kg,9.93 g/kg～11.33 g/kg,5.00 g/kg-4.06 g/kg,8.71 g/kg-10.15 g/kg respectively,7%～31%,35%～54%,45%～115 %,59%～69%higher than winter wheat; In 5-10 cm layer, the indexes above are 1%～38 %,36%-78%,169%-336%,33～69%higher than that of winter wheat, with POC having the largest range. POC, DOC and EOC are more sensitive than SOC. The TC content under cultivated pasture in 0-10 cm layer decreased with depths, but under winter wheat increased with depths. Cultivated pasture led the space distribution poise.3. In the 0-10 cm soil layer, soil organic carbon density content under clover pasture was 1.41 kg/m2 which was the highest in the seven single-spices sowing forages where as for crowtoe it was found to be 1.05 kg/m2 which was the lowest. Winter wheat was 0.95 kg/m; Brome grass+Lucerne+sainfoin was 1.36 kg/m2, which was 23% higher than winter wheat and is the highest of mixed-spices sowing forages, leading to the conclusion that perennial pasture is superior for soil organic carbon storage.4. In the 0-5 cm soil layer, the CPMI in single-spices sowing of forages was 81%～179% higher than winter wheat soil. The highest was clover, the lowest was crowtoe. In the 5-10 cm layer, the CPMI in single-spices sowing of forages was 51%～114% higher than soil under winter wheat; the CPMI in the soil of single-species sowing of forages was 42 %～105% higher than winter wheat. Perennial pasture significantly increased the CPMI, which is preferable for soil organic carbon storage.5. In the 0-10 cm soil layer total nitrogen was significant correlated with soil total carbon, soil organic carbon and easily oxidized organic carbon.6. After 170 days of incubation in the lab, for the 0-10 cm soil layer, the organic carbon mineralization release capacity under winter wheat was the lowest; the 0-5 cm layer was 13%～30% higher than 5-10 cm layer. There was significant space difference, but winter wheat was 0.77 mg C/g～0.87 mg C/g; Soil organic carbon potential mineralization capacity was 1.670～2.989 mg C/g under single-spices sowing of forages, whereas under mixed-spices sowing of forages it was 1.354 mg C/g～1.510 mg C/g; in winter wheat, soil organic carbon mineralization potential was 0.86 mg C/g. The soil organic carbon mineralization capacity is higher in perennial pasture than winter wheat, soil organic carbon mineralization speed constant is lower than winter wheat, leading to the conclusion that the capacity of soil storage of carbon is lower in winter wheat than perennial pasture.
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