陕西省退耕还林对土壤粒径分布体积分形特征的影响

Effects of Grain-for-green on Volume Fractal Characteristics of Soil Particle Size Distributions in Shaanxi Province,China

退耕还林可引起土壤粒径分布的变化,通过测定陕西省吴起县和礼泉县两个样区不同土地利用类型下表层土壤各粒级百分含量,分析退耕还林对土壤粒径分布体积分形特征的影响。应用马尔文2000激光粒度分析仪测量各粒级体积百分含量,用双对数模型计算体积分形维数(D)。结果表明,吴起县和礼泉县两个样区土壤PSD的D值分别在2.490~2.526和2.638~2.699之间,顺序均为荒地】人工林地】农地。D值与黏粒和粉粒含量极显著正相关,相关系数分别为0.991和0.968,与极细砂和细砂含量极显著负相关,相关系数分别为-0.986和-0.851,与有机质含量显著正相关,相关系数为0.608。多元统计分析表明对土壤黏粒、粉粒和砂粒及D值影响较大的环境因子为区域,海拔,土地利用类型和退耕年限,其中土地利用类型和区域各自独立、互不相关地影响土壤粒径分布。

Grain-for-Green can cause the change of soil particle distribution. Effects of Grain-for-Green on the volume fractal characteristics of soil particle distribution( PSD) were analyzed by measuring topsoil percentage of different grades under different land use types of Wuqi and Liquan county in Shaanxi Province. Volume percentage of different grades was measured by Marvin2000 laser particle size analyzer and volume fractal dimension( D) was calculated by double logarithm model. Results showed D of soil PSD ranged from 2. 490 to 2. 526 and from 2. 638 to2. 699 in two sample areas of Wuqi and Liquan county respectively and the order was waste land > planted forest >cropland. There were very significant positive relationships between D and clay and silt content and correlation coefficients were 0. 991 and 0. 968 respectively,very significant negative relationships between D and very fine sand and fine sand content and correlation coefficients were- 0. 986 and- 0. 851 respectively,significant positive relationship between D and soil organic matter content and correlation coefficient was 0. 608. Multivariate Statistical Analysis showed environmental factors of region,elevation,land-use types and vegetation restoration years had more effects on soil clay,silt,sand and D. Land-use types and region affected soil particle size distribution independently.