Disturbance impacts on porosity and hydraulic properties of vesicular horizons

Abstract

AbstractRapid 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.