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Root-Induced Variations in Electrochemical Properties of Soil Colloids Influence Rill Flow Detachment on the Loess Plateau
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DOI：10.1002/ldr.70390.png)
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Abstract
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Plant root-induced variations in soil-colloid electrochemical properties contribute to changes in rill flow detachment on the Loess Plateau. This field-based study was conducted to examine the influence of various electrochemical properties of soil colloids caused by roots on rill flow detachment on the Loess Plateau, because this phenomenon has not gotten much attention. A total of 288 samples of undisturbed soil were collected from two soil layers (0–10 cm and 10–20 cm) across eight typical vegetation plots. The samples underwent scouring with six flow discharges (0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 L s−1) on a slope of 15°. The findings showed that plant roots had a marked influence on the electrochemical properties of soil colloids. The electrochemical properties of soil colloids for the respective 0–10 and 10–20 cm layers over the different sampling sites were soil surface electric field (1–22 × 108 and 4–23 × 108 V m−1), |surface potential|(94–160 and 114–162 mV), surface charge density (0.1–1.6 and 0.3–1.7 C m−2), specific surface area (17–201 and 14–89 m2 g−1), surface charge number (7–13 and 6–10 cmol kg−1), and exchangeable sodium percentage (0.3%–0.6% and 0.5%–0.8%). These properties showed either a linear or exponential relationship with root length density (R2 of 0.4 to 0.5; p < 0.01). Fine roots (0 < d ≤ 2 mm) played a prominent role in this process. Moreover, the electrochemical properties of soil colloids had marked effects on the rill detachment rate, with rates across the sampling sites ranging from 8 to 62 g m−2s−1 in the 0–10 cm soil layer and from 29 to 59 g m−2s−1 in the 10–20 cm soil layer, and showing either linear or exponential relationships with soil-colloid electrochemical properties (R2 of 0.5 to 0.6; p < 0.01). Soil specific surface area explained most of the variations in the rill detachment rate (46%). In conclusion, plant roots were found to alter soil-colloid electrochemical properties by providing charge and ion-binding sites, which in turn control rill flow detachment by regulating soil internal repulsive forces. Assessments of soil-colloid electrochemical properties should therefore be a form part of strategies to prevent and control rill erosion.
Keywords:
colloidal charge
fine roots
rill detachment rate
soil internal forces
specific surface area
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