Vegetation effects on soil pore structure and hydraulic properties in volcanic ash soils of the high Andes. Issue 9 (2nd September 2022)

• Record Type: Journal Article
• Authors: Páez‐Bimos, Sebastián; Villacís, Marcos; Morales, Oscar; Calispa, Marlon; Molina, Armando; Salgado, Silvia; de Bievre, Bert; Delmelle, Pierre; Muñoz, Teresa; Vanacker, Veerle
• Is Part Of: Hydrological processes. Volume 36:Issue 9(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-02
• Subjects: Andosol -- hydrological services -- infiltration -- páramo -- root growth -- soil hydrology -- vegetation species -- water retention; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.14678
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: Soil hydraulic properties control the provision of hydrological services. Vegetation and topography influence these properties by altering soil structure and porosity. The underlying mechanisms are not yet fully understood for the high Andean region. In this study, we examined how vegetation and topographic attributes are related to soil hydraulic properties and soil pore structure in young volcanic ash soils, and further correlated them to soil texture, organic carbon, and root characteristics to explain these relationships. In a 0.7 km 2 study site located in the Andean páramo of northern Ecuador, we measured soil water retention, saturated hydraulic conductivity, bulk density (BD), and pore size distribution parameters on eight soil profiles with contrasting vegetation types (cushion‐forming plants vs. tussock grasses) and topographic positions (summit vs. hillslope). We observed significant differences in soil hydraulic properties and soil pore structure in the uppermost horizons by vegetation type, whereas topography had a minor effect. In the A horizons, we found higher water retention at saturation and field capacity (10%–14%), higher total available water (8%–15%), and higher saturated hydraulic conductivity (4–12 times) under cushion‐forming plants compared to tussock grasses. The elevated values under cushion plants were attributed to the presence of larger pores, lower soil BD, and higher soil organic carbon content as a result of coarser root systems. Total available water was generally high (0.34–0.40 cm 3 cm −3 ), and locally not associated with any soil property. The higher water retention in soils under cushion vegetation can enhance soil water storage for plants and the regulation of water flows during prolonged rainfall events. The saturated hydraulic conductivity of the surface horizons is high compared to rainfall intensities resulting in high infiltration capacity; whilst its decline with depth reveals the potential for generation of subsurface stormflow, especially below cushion‐forming plants. Our findings highlight that soil hydraulic properties differ among vegetation types, and show the significance of vegetation types for soil hydrology. Abstract : In volcanic ash soils of the high Andes, vegetation has a significant effect on soil hydraulic properties in the A horizon. Water retention, total available water, and saturated hydraulic conductivity are higher under cushion‐forming plants than under tussock grasses due to differences in soil pore structure. Such differences are associated with coarser roots and higher soil organic carbon. Under cushion‐forming plants, this can enhance infiltration capacity, and soil water storage, and result in subsurface stormflow at prolonged rainfall events.