水库消落带土壤颗粒组成分形及其空间分异特征

颗粒组成作为土壤的基本物理特性,对土壤结构、力学性质、肥力特征等均有明显影响。降雨径流、波浪和重力等多重营力作用下的消落带土壤侵蚀过程导致表层土壤颗粒发生了重新分布。为了研究水库消落带土壤颗粒组成的空间分异特征,以三峡水库典型消落带为研究对象,在不同海拔位置分别采集了0—10 cm和10—20 cm层的土壤用于测定颗粒组成,并利用分形理论计算出体积分形维数。结果表明:(1)三峡水库消落带土壤颗粒组成以粉粒为主,占总体积的72.6%～86.5%,且随着海拔的增加而升高; 从不同土层深度来看,0—10 cm层黏粒含量明显低于10—20 cm层。(2)消落带不同海拔位置的土壤体积分形维数具有明显异质性,且与海拔呈正相关(R²=0.74),而在不同土层之间具有弱变异性(C_v<2)。(3)体积分形维数与黏粒、粉粒含量均呈显著正相关(p<0.01),与砂粒含量呈显著负相关(p<0.01),且与黏粒的线性相关性最强。综上,消落带土壤颗粒组成在不同海拔存在较大差异(p<0.01),但在土层深度上无显著差异(p>0.01); 150～160 m海拔区间和0—10 cm层土壤具有明显的粗粒化现象。

Fractal Characteristics and Spatial Variation of Soil Particle Composition in the Reservoir Riparian Zone

As the basic physical properties of soil,particle composition has obvious effects on soil structure,mechanical properties,and fertility characteristics.The periodic flooding and exposure process resulte in the redistribution of surface soil particles in the reservoir riparian zone.In order to study the spatial differentiation characteristics of soil particle composition,the Three Gorges Reservoir was taken as the research object and the volume-based fractal model of soil particle was evaluated.The results suggest that:(1)the soil in the reservoir riparian zone of the Three Gorges Reservoir is dominated by silt,accounting for 72.6%to 86.5%of the total volume,and it increases with the increase in altitude;from the perspective of different soil depths,the clay content in the 0—10 cm soil layer is significantly lower than that in the 10—20 cm soil layer;(2)the volumetric fractal dimension showes significant heterogeneity at different elevations,and is positively correlated with elevations(R²=0.74),while the weak variability between different soil layers is found(C_v<2);(3)the volumetric fractal dimension has a significant positive correlation with clay and silt contents(p<0.01),and a significant negative correlation with sand content(p<0.01);the linear correlation between fractal dimension and clay is the strongest.In summary,the composition of soil particles in the reservoir riparian zone differs greatly at different elevations(p<0.01),but there is no significant difference in soil depth(p>0.01).The soil coarse-grained phenomenon is obvious in the elevation range of 150~160 m and soil layer of 0—10 cm.