喀斯特石漠化区不同植被恢复下土壤颗粒分形特征

Fractal characteristics of soil particle under different vegetation cover restoration in Karst rocky desertification area

【目的】研究喀斯特石漠化地区的土壤颗粒分布和分形特征,为石漠化地区水土保持和土壤评价提供科学依据。【方法】在贵州师范大学喀斯特野外观测研究站,选取石漠化治理区中火龙果(Hylocereus undulatus)、玉米(Zea mays)、核桃(Juglans regia)、柚木(Tectona grandis)和种植于坡上和坡谷的花椒(Zanthoxylum bungeanum)等6种植被作为研究对象,分析了雨、旱两季的土壤粒径分布,并基于单重和多重分形理论计算了土壤颗粒分形参数。【结果】(1)研究区土壤粒径集中在1.5~300μm,质地较细以粉粒为主,黏粒含量最少,粒径分布呈非均匀性;(2)植被和季节对单重体积分形维数D_(v)均存在显著影响(P<0.05),决定系数R^(2)表明D_(v)与黏粒关系最为密切。旱季D_(v)的均值(2.56)较雨季(2.64)相比有所下降,细粒物质流失程度在不同植被之间存在显著差异(P<0.05);(3)各样地土壤粒径分布以体积分数占比较大的颗粒为主,广义维数谱D_(q)的递减程度在指数q<0时要大于q>0时,稀疏区土壤颗粒对环境因子的影响更敏感;(4)D_(v)与黏粒和粉粒呈极显著正相关,与砂粒呈极显著负相关。容量维数D_(0)、信息熵维数D_(1)、D_(1)/D_(0)、关联维数D_(2)和土壤颗粒的相关性与D_(v)相反。土壤有机碳/全氮(SOC/TN)与粉粒呈显著正相关,而与砂粒呈显著负相关,这说明粉粒组分在发挥固碳功能方面发挥主导作用。【结论】土壤分形维数能够作为喀斯特石漠化区土壤物理结构改善效果的指标,为石漠化水土保持和土壤评价提供科学理论支持。

[Objective]This study investigates the distribution and fractal characteristics of soil particles in karstic rocky desertification areas,thus providing scientific basis for soil and water conservation and soil evaluation in rocky desertification areas.[Method]At the Karst Field Observation and Research Station of Guizhou Normal University,six vegetation covers including dragon fruit(Hylocereus undulatus),corn(Zea mays),walnut(Juglans regia),teak(Tectona grandis),and pepper(Zanthoxylum bungeanum)planting in valley and slope in the rocky desertification control area were chosen as the research objects.According to single and multifractal theory,fractal parameters of soil particles was investigated based on particle size distribution(PSD)measured in rainy and dry seasons[.Result]The results showed that (1)the PSD was concentrated in the range of 1.5-300μm and the distribution was non-uniform.The particle was mainly silt with fine textureand low clay content;(2)Both vegetation cover and season had significant effects on the fractal dimension D_(v)(P<0.05).The determination coefficient of R^(2) indicated that clay grains were most closely related to D_(v).From wet season to dry season,the mean value of D_(v) decreased from 2.64 to 2.56.Meanwhile,erosion degree of soil fines significantly differed among these vegetation covers;(3)The multi-fractal characteristics showed that the PSD range of each plot was dominated by particles with a large volume fraction.The decreasing degree of the generalized dimensional spectrum D_(q) was higher at index q<0 than at q>0.The PSD were more sensitive to environmental changes in the sparse area;(4)The D_(v) value showed significant and positive correlations with clay and silt contents,while significant and negative correlation with sand content.However,the correlations of capacity dimension D_(0),information entropy dimension D_(1),D_(1)/D_(0),and correlation dimension D_(2) with soil particles were contrary to those of D_(v).The significant correlation of soil organic carbon/total nitrogen(SOC/TN)ratio was positive with silt particles while negative with sand particles,which indicates that the silt fraction played a dominant role in performing the carbon sequestration function[.Conclusion]Soil fractal dimension can be used as an indicator of the improvement effect of soil physical structure in karstic rocky desertification areas.The research results provides theoretical support for soil and water conservation and soil evaluation in rocky desertification areas.