黄土丘陵区红豆草和苜蓿植物篱对土壤颗粒组成的影响

以苜蓿、红豆草两种植物篱为研究对象，对黄土丘陵沟壑区坡耕地布设植物篱后不同坡位土壤颗粒含量的变化、土壤分形维数进行研究，分析了植物篱对土壤颗粒组成的影响。结果表明:（1）同坡面相比，中坡及下坡土壤极细沙粒与粗粉粒含量增加，细粉粒与黏粒含量减少，出现相对于上坡的土壤机械组成粗化现象，且下坡粗化程度大于中坡；（2）相对于对照坡面，植物篱坡面各坡位粗化现象均得到缓解，红豆草对土壤颗粒的影响在上坡表现明显，苜蓿的影响在下坡表现明显；（3）坡面土壤分形维数呈现上部 > 中部 > 下部，苜蓿 > 红豆草 > 对照样地；（4）土壤颗粒与土壤分形维数的相关性分析显示，土壤分形维数与极细沙粒、粗粉粒呈极显著（P < 0.01）负相关，与黏粒呈显著（P < 0.05）正相关。

Effect of Sainfoin and Alfalfa Hedgerow on Soil Particles in Loess Hilly Region

To figure out the effect of hedgerow on soil particles in loess hilly region, the particle contents and fractal dimension of soil were measured, and the their correlation were analyzed at different slope positions in alfalfa and sainfoin hedgerows. The results showed that: (1) very fine sand and coarse silt contents increased from the top slope to the bottom slope, but contents of fine silt and clay decreased from the top slope to the bottom slope. Therefore, the coarsening of soil increased from the top slope to the bottom slope;(2) compared with control slope，hedgerows had significant effect on reducing the coarsening of soil at different slope positions, the effect of sainfoin hedgerow is more effective on soil particle in the top slope, while alfalfa hedgerow is more effective on the bottom slope; (3) the soil fractal dimension at different slope positions showed as following order: the top > the middle > the bottom, and for the order different hedgerow plots was alfalfa > sainfoin > control; (4) the fractal dimension of soil has negative correlation with the contents of very fine sand and coarse silt (P < 0.01), and has positive correlation with content of clay (P < 0.05).