黄土丘陵区林区开垦地土壤退化研究

STUDY ON SOIL DEGENERATION OF RECLAIMED FOREST-LANDS IN LOESS HILLY FOREST REGION

以林地及其开垦地土壤颗粒组成、有机质含量、>0 .2 5mm水稳性团粒含量、土壤容及土壤抗强度等性质为基础 ,分析比较了林地及林地开垦后侵蚀 10年内土壤退化问题。研究结果表明 ,林地一旦开垦后随侵蚀年限的增长 ,土壤性质逐年退化 :侵蚀 10年土壤粘粒和物理性粘粒比林地分别减少 2 .74 %和 3.0 1% ,粗粉粒增加 ,土壤颗粒组成粗化 ;有机质含量从林地的 4 5 .2 g/kg下降到侵蚀 10年开垦地的 9.8g/kg ,>0 .2 5mm水稳性团粒含量从林地的 6 0 .19%下降到侵蚀第 10年开垦地的 2 8.6 0 % ,土壤容重增大 ,土壤的抗剪强度从 0 .12 3kg/cm3 下降到0 .0 74kg/cm3 ;并将林地和开垦地土壤性质与土壤侵蚀强度进行相关分析发现 ,>0 .2 5mm水稳性团粒含量对土壤侵蚀强度影响最大 ,偏相关系数为 0 .972 8,其次为土壤粗粉粒和抗剪强度 ,偏相关系数为 0 .8879和 0 .6 0 2 0 ,说明了林地开垦后侵蚀土壤的退化 ,恶化了土壤侵蚀环境 ,造成土壤侵蚀更易发生 ,加剧着土壤侵蚀强度 。

Based on the soil properties in the forest lands and reclaimed forest lands, the changes of the soil particle, organic matter content, >0.25mm water stable aggregate content, soil weight and shear strength were analyzed with the increasing of the erosion time. The results showed that the soil properties degenerated gradually with the increasing of the soil erosion time. In 10th year eroded after forest land reclaimed, the clay content and physical clay content decreased 2.74% and 3.01% respectively, which showed the soil particle have the tendency to skeleton soil, and the soil organic matter content decreased from 45.2g/kg to 9.8g/kg, the >0.25mm water stable aggregate content also decreased from 60.19% to 28.6%, the soil unit weight increase and the soil shear strength decreased from 0.123 kg/cm 3 to 0.074 kg/cm 3 . The degeneration of soil properties was easier to arise soil erosion. Then the correlation among soil particle, >0.25mm water stable aggregate content, unit weight, sheer strength and the soil erosion intensity was analyzed. The result showed that >0.25mm water stable 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 respectively. The soil degeneration of reclaimed forestry lands worsened the soil erosion environment and aggravated 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.