不同坡长扰动土壤微团聚体及颗粒组成的分形特征
Fractal features of soilmicro-aggregate and particle-size distribution under different slope length and disturbance surface

为研究径流小区紫色土在不同坡长下人为扰动地表后土壤微团聚体及颗粒组成的分形特征，通过野外采样与室内分析相结合的方法，研究了在20、40和60 m坡长下扰动地表与自然坡长下土壤微团聚体及颗粒组成的分形特征及其与土壤理化性质的关系。结果表明：土壤颗粒组成中的优势粒级是0.250~0.050 mm，含量在33.21%~22.55%。土壤微团聚体中的优势粒级是0.250~0.050 mm，次级优势粒级是0.050~0.010 mm。扰动地表下的土壤分形维数小于自然坡长下的分形维数，坡长越长分形维数越高。坡长越长土壤养分含量越高，即：60 > 40 > 20 m，3种坡长扰动地表处理下的土壤养分均小于自然坡长下的土壤养分。土壤分形维数同土壤容重呈极显著正相关（P<0.01），同土壤全量养分呈极显著相关（P<0.01），扰动地表下的土壤分形维数同土壤孔隙度呈显著或极显著相关（P<0.01或P<0.05）。土壤微团聚体机及颗粒组成的分形维数能较好地反映紫色土区土壤的理化性状，更加直观的体现人为扰动地表后土壤理化性质及土壤性状的变化，为紫色土区土壤质量评价和农业评价提供科学依据。
To provide a scientific basis for the rational development and utilization of land resources micro-aggregate and particle-size distribution under different slope lengths and disturbance surface were studied.Through field sampling and laboratory analysis,fractal features of rhizosphere soil micro-aggregate and particle-size and its relationship with soil physicochemical properties in the natural slope and disturbance surface in 20,40 and 60 m were investigated.The results showed that:Soil particle-size distribution in the dominant aggregates was 0.250-0.050 mm,and the content was 33.21%-22.55%;Soil micro-aggregates in the dominant aggregateswere 0.250-0.050 mm and secondary advantage was 0.050-0.010 mm;The fractal dimension under disturbance surface was less than the fractal dimension under natural slope length. The length of slope was longer and the fractal dimension was higher;Soil nutrient content of the longer slope length was higher in the order of 60>40>20 m;Soil nutrients under disturbance surface were less than those under natural slope length in three slope lengths;Positive correlation between soil fractal dimension with the soil bulk density was significant (P<0.01) while soil total nutrient was significantly associated (P<0.01) and the dimension of soil fractal under disturbance surface with soil porosity were significant or very significantly correlated (P<0.01 or P<0.05).In conclusion,the fractal dimension of soil micro-aggregate and particle-size distribution better reflected physical and chemical structure of soil in the purple soil area and more intuitively reflected the changing of soil structure and physical and chemical properties after the disturbance,which providing a scientific basis for soil quality evaluation and agricultural assessment in purple soil area.