关键词: 黄土丘陵区, 林区开垦地, 土壤侵蚀, 土壤退化

Abstract: Based on the soil properties in the forestHlands and reclaimed forest -lands, the changes of the soil particle, organic matter content, >0.25 mm water stable aggregate content, soil weight and shear strength were analyzedwith the increasing of the erosion time. The results showed that the soil properties degenerated gradually withthe increasing of the soil erosion time. In 10 th year eroded after forest land reclaimed, the clay content andphysical clay content decreased 2.74% and 3.01/% respectively, which showed the soil particle have the tenden"cy to skeleton soil, and the soil organic matter content decreased from 45.2 g/ kg to 9. 8 g/kg. the >0.25 mmwater stable aggregate content also decreased from 60.19%to 28. 6%, the soil unit weight increase and the soilshear strength decreased from 0.123 kg/em to 0.074 kg/cm³. The degeneration of soil properties was easier toarise soil erosion. T'hen the correlation among soil particle, >0.25 mm water st able aggregate content, unitweight, sheer strength and the soil erosion intensity was analyzed. The result showed that >0.25 mm waterstable aggregate was the maximum effect factor to soil erosion, the partial correlation coefficient was 0.9728, then were the coarse grain and sheer strength, the partial correlation coefficients were 0.8879 and 0.6020 re-spectively. 'T'he soil degeneration of reclaimed forestry-lands worsened the soil erosion environment and aggrav at-ed soil erosion intensity, so to return slope farmland into forest and grassland, to recover and reconstruct vegetation were the key points to control the soil erosion in Loess Plateau.

Key words: Loess hilly region, reclaimed forest lands, soil degenerationsoil erosion