Disturbance impacts on porosity and hydraulic properties of vesicular horizons
2020
Turk, Judith K. | Graham, Robert C.
Rapid formation of vesicular pores has been observed following disturbance of vesicular (V) horizons. This study investigates the post‐disturbance recovery of V horizons and the impact on hydraulic properties. At nine study sites, infiltration rates were measured using a tension disk infiltrometer, and intact samples were collected for analysis using high‐resolution x‐ray computed tomography (CT). The V horizon material was then removed, crushed, replaced, and left to recover for 1 yr before repeating the infiltration measurement and CT analysis. Some recovery of vesicular and vugh porosity was observed at all of the study sites. However, the V horizons formed in the first year after disturbance were thinner, with smaller pores, and with a reduction in vesicle and vugh porosity from an average of 2.9% before disturbance to 0.4% after disturbance. The saturated hydraulic conductivity of the V horizons was also significantly lowered, from an average of 20 cm d⁻¹ prior to disturbance to 6.6 cm d⁻¹ at 1 yr after disturbance. Vesicle and vugh porosity formed 1 yr after disturbance was positively correlated with predisturbance vesicle and vugh porosity (R² = .57; P = 0.02) and sand percentage (R² = .51; P = .03) and negatively correlated with silt percentage (R² = .51; P = .03). No relationship was observed between post‐disturbance formation of vesicle and vugh porosity and precipitation events during the recovery period, clay percentage, CaCO₃ percentage, or saline‐sodic classification. V horizons show incipient development at 1 yr after disturbance, but porosity and hydraulic properties are significantly altered from their undisturbed state.
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