High chloride concentrations in the soil and groundwater under an oak hedge in the West of France: an indicator of evapotranspiration and water movement

Abstract : Chloride is a major anion in soil water its concentration rises essentially as a function of evapotranspiration.Compared to herbaceous vegetation, high transpiration rates are measured for isolated trees, shelterbelts or hedgerows.This article deals with the influence of a tree hedge oil the soil groundwater Cl(-) concentrations the possibility of using Cl(-) as an indicator of transpiration water movements near the tree rows.Cl(-) concentrations were measured over 1 year at different depths in the unsaturated zone ill the groundwater along a transect intersecting a bottomLandoak hedge.We observed a strong spatial heterogeneity of Cl(-) concentrations.with very high values up to 2 g l(-1) in the unsaturated zone 1.2 g l(-1) in the upper part of the groundwater.This contrasts with the low homogeneous concentrations (60-70 mg l(-1)) in the deeper part of the groundwater.Cl(-) accumulation in the unsaturated zone at the end of the vegetation season allows us to identify the active root zone extension of trees.In winter, upslope of the tree row, downwards leaching partly renews the soil solution in the root zone, while the slow water movement Under the trees or farther downslope results in Cl(-) accumulation leads to a salinization of the soil groundwater.This salinization is of the same order as experimental conditions produce negative effects oil oak seedlings.The measurement of Cl(-) concentrations in the unsaturated zone under tree rows Lit the end of the vegetation season Would indicate whether certain topographic, pedological or climatic conditions are likely to favour a strong salinization of the soil, as observed in the present Study.Copyright (C) 2009 John Wiley & Sons, Ltd.
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C. Grimaldi, Zahra Thomas, M. Fossey, Y. Fauvel, P. Mérot. High chloride concentrations in the soil and groundwater under an oak hedge in the West of France: an indicator of evapotranspiration and water movement. Hydrological Processes, Wiley, 2009, 23 (13), pp.1865-1873. ⟨10.1002/hyp.7316⟩. ⟨hal-00729222⟩

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