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黄土丘陵区长期种植柠条坡地土壤饱和导水率及其影响因素

Soil saturated hydraulic conductivity and its influencing factors on the slope with long-term plantation of Caragana korshinskii in the loess hilly region

  • 摘要: 在坡面进行人工灌木种植,是黄土丘陵区控制水土流失、恢复脆弱生态系统的重要举措,但其对土壤饱和导水率(Ks)的影响仍不明确。以黄土丘陵区带状种植3个不同年限的柠条坡地和对照荒草地为研究对象,研究5个坡位0~100 cm土层Ks变化特征及其主要的土壤影响因子,并利用土壤传递函数进行模拟分析。坡地Ks变化范围为6.81~60.77 mm/h,柠条种植年限和坡位对其有显著影响(P < 0.05)。随柠条种植年限的增加,0~40 cm土层的Ks先升后降,40~100 cm土层的Ks则持续增加。坡下Ks最高,坡顶和坡中次之,坡肩和坡上最低。选取的6个土壤传递函数模型模拟结果表明:除考虑土层深度的Wösten模型拟合相对较好外,其他模型预测值均小于实测值。通径分析得到有机碳、饱和含水量和土壤密度等是影响坡面Ks的关键土壤因子,据此构建的土壤传递函数模型可以更准确地预测Ks变化。综上,坡地长期种植柠条总体可以提高Ks,但这种改变受柠条种植年限和坡位的共同影响。

     

    Abstract:
    Background The saturated hydraulic conductivity (Ks) can characterize the strength of soil water conductivity, which is an important indicator of soil water conductivity and is closely related to eco-hydrology and soil erosion. Artificial shrub planting on slopes is an essential measure for controlling soil and water loss and restoring fragile ecosystems in the loess hilly areas, but the effect on Ks remains unclear. Soil transfer functions are constructed by integrating easily measurable or obtainable soil indices to estimate Ks accurately.
    Methods This study focused on the sloping land planted with Caragana korshinskii for 15, 25, and 35 years and a control wasteland with wild grass in the loess hilly areas of Ningxia. Three random sample plots were set up along the horizontal slope surface, each with three replicates. The characteristics of Ks variation were investigated and its main soil influencing factors at five slope positions, including top-slope, shoulder-slope, up-slope, mid-slope and low-slope were studied, from 0 to 100 cm (0-40 cm with 10 cm intervals, 40-100 cm with 20 cm intervals). Six common soil transfer functions, Cosby1, Cosby2, Weynants, Saxton, Wang, and WÖsten, were used to fit Ks.
    Results The Ks range was 6.81-60.77 mm/h, and C. korshinskii planting duration and slope position had significant effects (P < 0.05). With the increase of C. korshinskii planting years, Ks first increased (15 years of planting) and then decreased in the 0-40 cm soil layer, while Ks continuously increased in the 40-100 cm soil layer. The highest Ks was at the slope bottom, followed by the slope top and middle, and the lowest at the slope shoulder and upper slope. The simulated results of the six selected soil transfer function models indicated that, except for the WÖsten model considering soil layer depth, the predicted values of other models were all lower than the measured values. Correlation analysis showed that Ks was closely related to other physical and chemical properties except capillary porosity. The influence of soil properties on Ks was mainly closely related to the formation and stability of soil structure. Path analysis identified organic carbon, saturated water content, and bulk density as the key soil factors affecting Ks on the slope, and the constructed soil transfer function model based on these factors can predict Ks changes more accurately.
    Conclusions In summary, long-term C. korshinskii planting on slopes may generally increase Ks, but this change is jointly affected by the sea buckthorn planting duration and slope position. The Ks soil transfer function constructed in this study may provide a reference for simulating and predicting Ks on slopes in the loess hilly areas.

     

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