太行山区中段旱季土壤含水量的影响因素

Factors influencing soil water content during dry period in the middle part of the Taihang Mountain

  • 摘要: 太行山脉为我国第二、第三阶梯的重要分界线, 海拔自西向东迅速降低, 在这种自然条件复杂的地理空间过渡带内, 土壤含水量(SWC)空间格局特征及其影响因素亦复杂而不明确, 限制了对山区土壤水文过程的认知。本研究通过在太行山区中段设置间距约85 km的两条样线(长度分别为140 km和164 km), 在旱季采集土壤样品, 测定SWC、容重、毛管孔隙度、非毛管孔隙度、有机碳含量、机械组成等理化性质, 详细调查样点的地形条件(坡度、坡向、海拔等)和植被条件(植被类型、枯落物情况等), 利用经典统计和地统计的方法, 并结合结构方程模型, 分析了表层(0~10 cm)和次表层(10~20 cm) SWC在海拔梯度上的变异特征, 探讨了其主要影响因素。结果表明, 太行山区中段两条样线均表现为表层SWC显著小于次表层, 两条样线之间没有显著差异。地统计分析表明, 表层和次表层SWC分别适用线性模型和指数模型模拟, 说明表层SWC影响因素更加复杂, 随机因素占主导地位; 次表层呈现出块基效应, 随机因素和结构因素共同起作用。两条样线次表层SWC块基比分别为48.01%和31.62%, 说明次表层SWC属中等程度的空间相关性。影响SWC的主要环境因子为海拔和降水量, 坡度、坡向及植被类型没有达到显著水平; 土壤性质中, 表层SWC主要受容重的影响, 次表层主要受毛管孔隙度和黏粒含量的影响。结构方程模型显示, 土壤性质是影响旱季SWC的直接因素, 环境因子是间接因素。环境因子对旱季SWC的影响超过80%是通过土壤性质产生的间接影响。以上结果有助于深入了解太行山区SWC特征, 为水-土过程的深入研究提供科学依据。

     

    Abstract: Taihang Mountain is an important natural boundary between the second and third steps in China. The elevation of this mountains decreases drastically from west to east. Owing to the complex environment in this transition zone, the spatial pattern of and the factors influencing soil water content (SWC) are complex and unclear. This limits further understanding of the soil hydrological processes. In this study, two line transects (140 km and 164 km long, respectively) were set in the middle part of the Taihang Mountain, which are 85 km apart. Both disturbed and undisturbed soils were sampled along two line transects during the dry period in the middle part of Taihang Mountain region. Soil water content, bulk density (BD), capillary porosity (CP), non-capillary porosity (NCP), soil organic carbon (SOC), and soil particle composition (sand, silt, and clay contents) were measured. Topographical conditions (including slope gradient, slope aspect, and elevation) and vegetation conditions (including vegetation type, vegetation cover, and litter information) were also investigated for each sampling point. Classical statistical, geostatistical, and structural equation modeling methods were used to study the variation and influencing factors of the SWC in the surface (0–10 cm) and subsurface (10–20 cm) layers along the two line transects in the middle part of the Taihang Mountain. The results showed that the SWC of the surface soil layer was significantly lower than that of the subsurface layer. No significant differences were observed between the two studied line transects. In geostatistical analysis, the most suitable SWC model was a linear model for the surface soil layer, but an exponential model for the subsurface layer. This indicated that random factors played a dominant role, and the influencing factors may be more complex for the surface soil layer. For the subsurface layer, an obvious nugget effect was observed, suggesting the coexistence of random and structural factors. The nugget to sill value of the subsurface layer was 48.01% and 31.62%, respectively, for the two-line transects. This indicated that both line transects showed moderate spatial dependence. Among the considered environmental factors, precipitation and elevation significantly influenced the SWC. Other environmental factors showed no significant effects. Among the studied soil properties, BD significantly influenced the SWC of the surface layer, whereas the CP and clay content significantly influenced the SWC of the subsurface soil layer. Structural equation modeling showed that soil properties were the direct factor, and environmental factors were indirect factors of SWC. Over 80% of the environmental factors acted through the soil properties. These results can be helpful in further understanding the soil water characteristics in the middle part of the Taihang Mountain and provide a scientific basis for studying soil hydrological processes in similar mountainous areas.

     

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