滇东喀斯特山原红壤退化过程中剖面颗粒分形特征

山原红壤是在古气候影响下残存于高原面的古红土，近年来退化严重。为认识山原红壤的质地和退化程度，以滇东山原红壤典型发育地带为研究对象，对灌丛、草地、松林、红裸土剖面的土壤颗粒分形特征进行研究分析。结果表明:土壤颗粒分形维数在2.734~2.829，土壤质地整体属于粉质粘壤土。随着深度的增加，灌丛、草地、松林的土壤分形维数逐渐变大，红裸土则呈现出相反的规律。黏粒含量与土壤颗粒分形维数在土壤剖面上表现出相同的变化规律，砂粒和粉粒规律不明显。分形维数与黏粒呈极显著正相关，主要由黏粒决定，与粗砂呈负相关，与细砂和粉粒呈正相关，但均不显著（p < 0.05）。分形维数与有机质呈正相关，与速效钾、速效磷、硝态氮呈负相关，均不显著（p < 0.05）。分形维数可以表征山原红壤退化过程中剖面质地的均一程度，作为判断土壤质地差异的重要指标，在一定程度也可以反映土壤的肥力特征。

Fractal Characteristics of Particles in Soil Profile During the Process of Mountain Red Earth Degradation in the Karst Area of East Yunnan

Mountain red earth is the relic ancient clay remained on the Yunnan Plateau formed under the influence of paleoclimate, however, this soil has experienced degradation recently. To understand the texture and the degree of degradation of mountain red earth, this study examined the mountain red earth based on the analysis of soil profile particle volume fractal dimension (FD) associated with different vegetation types. Particularly, soil samples were taken from areas covered with pineland, shrubland, grassland or unvegetated red soils respectively in the karst area of east Yunnan. The results indicated that FD varied from 2.734 to 2.789, which overall belonged to the silty clay loam. Soil FDs of shrublands, grassland, and pineland became larger with the increase of depth, while red bare soil presented the opposite trend. And the relationship between the content of clay particle and the FD in the soil profile showed the same trend while the distribution charateristics of sand and silt in the soil profile were not obvious. There was a significantly positive correlation between FD and clay which was mainly decided by the clay. FD was negatively correlated with coarse sand, and positively correlated with fine sand and silt. So FD can be expressed in a uniform degree of soil texture in the mountains red earth of degradation process, and an important indicator to determine differences in soil texture. FD was significantly positively correlated with organic matter, and negatively correlated with potassium, available phosphorus, and nitrate nitrogen. Therefore, FD can be used to describe the fertility levels of degradation of mountain red earth fertility characteristics of the soil profile.