TY - JOUR

T1 - Anisotropy of intensity-capacity parameters on Aquands with contrasting swelling-shrinkage cycles

AU - Zuniga, Felipe

AU - Horn, Rainer

AU - Rostek, Jens

AU - Peth, Stephan

AU - Uteau, Daniel

AU - Dörner, Jose

N1 - Funding Information: The lead author wishes to thank all the researchers and students of the “Ñadi Soils Team” for their assistance with the fieldwork, to Mónica Díaz for her support during laboratory analysis, to Christoph Haas and Anneka Mordhorst for laboratory support and dataset analyses in Kiel, to Margit Rode for her support in Witzenhausen, and for the hospitality of the landowners (Don Alfredo, Sra Elba and family). We also thank the National Commission for Scientific and Technological Research (CONICYT) for supporting the doctoral studies (Scholarship N° 21140263) and the ‘Dirección de Estudios de Postgrado, Universidad Austral de Chile’, for supporting the internships of Mr. Zúñiga in the ‘Institut für Pflanzenernährung und Bodenkunde at Christian Albrechts Universität zu Kiel” and “Fachgebiet Bodenkunde at ‘Kassel Universität zu Witzenhausen” in Germany.

PY - 2019/10

Y1 - 2019/10

N2 - The Ñadi soils (Aquands)are volcanic ash soils with an iron–cemented layer that are subject to different hydraulic stresses caused by high levels of exposure to weathering agents and high water–tables. Two Aquands pedons with high (ALC)and low (CHA)hydraulic stresses were evaluated to consider their capacity and intensity parameters, the effect of shrinkage on carbon stocks and the anisotropy of their physical functions. In undisturbed soil samples, water retention curves and air permeability (K a)were measured. C stocks were calculated using bulk density corrected for shrinkage. Air conductivity (k a), gas diffusion anisotropy of (AR)and X–ray computed tomography (μCT)were used to assess soil structural changes and the related modifications of pore anisotropies. Both pedons showed andic properties (Al o+½Fe o≥2%)dominated by organo–mineral complexes (Al p/Al o≥0.5). The (ALC)pedon exposed to high hydraulic stresses has 58% more volumetric water content compare to waterlogged (CHA)pedon after shrinkage, however, the air permeability decreases similarly in both soils (ΔK a = 0.40 – 0.36). Shrinkage depends of SOC (R 2 = 0.69)and it determine the differences in soil C stocks (6.6 – 7.6 Mg C ha −1). Convective and diffusive horizontal air fluxes were reported on the surface for ALC (k a = −3.0 log cm s −1; AR = 3.1)and at depth (k a = −2.6 log cm s −1; AR = 2.4)for CHA. With the μCT, the highest Euler numbers were used as indicator of intricate pore matrix in ALC (−1.92 × 10 5)and CHA (−2.35 × 10 5). The two Aquands pedons responded differentially to shrinkage and was considered in the C stocks calculation. And horizontal anisotropy is well defined in A and BCr horizons and are analogous with the pore connectivity evaluated with μCT.

AB - The Ñadi soils (Aquands)are volcanic ash soils with an iron–cemented layer that are subject to different hydraulic stresses caused by high levels of exposure to weathering agents and high water–tables. Two Aquands pedons with high (ALC)and low (CHA)hydraulic stresses were evaluated to consider their capacity and intensity parameters, the effect of shrinkage on carbon stocks and the anisotropy of their physical functions. In undisturbed soil samples, water retention curves and air permeability (K a)were measured. C stocks were calculated using bulk density corrected for shrinkage. Air conductivity (k a), gas diffusion anisotropy of (AR)and X–ray computed tomography (μCT)were used to assess soil structural changes and the related modifications of pore anisotropies. Both pedons showed andic properties (Al o+½Fe o≥2%)dominated by organo–mineral complexes (Al p/Al o≥0.5). The (ALC)pedon exposed to high hydraulic stresses has 58% more volumetric water content compare to waterlogged (CHA)pedon after shrinkage, however, the air permeability decreases similarly in both soils (ΔK a = 0.40 – 0.36). Shrinkage depends of SOC (R 2 = 0.69)and it determine the differences in soil C stocks (6.6 – 7.6 Mg C ha −1). Convective and diffusive horizontal air fluxes were reported on the surface for ALC (k a = −3.0 log cm s −1; AR = 3.1)and at depth (k a = −2.6 log cm s −1; AR = 2.4)for CHA. With the μCT, the highest Euler numbers were used as indicator of intricate pore matrix in ALC (−1.92 × 10 5)and CHA (−2.35 × 10 5). The two Aquands pedons responded differentially to shrinkage and was considered in the C stocks calculation. And horizontal anisotropy is well defined in A and BCr horizons and are analogous with the pore connectivity evaluated with μCT.

KW - Andisols

KW - Shrinkage

KW - C stocks

KW - Air fluxes

KW - Computed tomography

UR - http://www.scopus.com/inward/record.url?scp=85066461933&partnerID=8YFLogxK

U2 - 10.1016/j.still.2019.05.019

DO - 10.1016/j.still.2019.05.019

M3 - Article

VL - 193

SP - 101

EP - 113

JO - Soil & tillage research

JF - Soil & tillage research

SN - 0167-1987

ER -