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Universidade do Algarve (2013)

Arid groundwater dependent ecosystem response to salinization processes in a coastal aquifer : deriving vegetation indicators of the aquifer condition

Aguilar Perez, Raquel

Titre : Arid groundwater dependent ecosystem response to salinization processes in a coastal aquifer : deriving vegetation indicators of the aquifer condition

Auteur : Aguilar Perez, Raquel

Université de soutenance : Universidade do Algarve

Grade : ERASMUS MUNDUS MASTER OF SCIENCE IN ECOHYDROLOGY 2013

Résumé
To maintain the groundwater quality represents a critical concern because of the increasing levels of groundwater contamination globally. This goal is particularly important in arid zones, where due to the scarce rainfall the groundwater is a significant source of freshwater supply to society and ecosystems. Here we follow an ecohydrological approach to derive effortless indicators of the aquifers condition, based on the monitoring of phreatohytic vegetation, a particular case of Groundwater Dependent Ecosystems (GDEs). This is the case of Z.lotus a deciduous arid shrub from North of Africa and Southeast Spain. This study aims to relate the biological condition of Z. lotus with the groundwater condition to explore the feasibility for using vegetation indicators to inform about the salinization levels of groundwater in coastal aquifers. With this goal we : 1) evaluate the salinization levels of an aquifer from the Cabo de Gata-Níjar Natural Park, by wells sampling ; 2) determine the brackish water distance gradient based on the use of Vertical Electrical Sounding (VES),the physiological condition of Z. lotus through leaf chemical analysis and spectral vegetation indices (NDVI and NDWI) along a salinity gradient. The results showed that the phreatic level, distance from the sea and therefore the salinity and freshwater available to GDE, are reflected in the leaf chemical composition of Z. lotus. However, salinity levels did not reflected clearly in vegetation greenness (NDVI) and vegetation water content (NDWI), probably because of Z. lotus showed salt tolerance within the range of salinity found in the aquifer. As a conclusion, we propose leaf ion concentration as a good indicator of groundwater salinization, while the spectral indices are good indicators of vegetation health but not for the groundwater salinization. Z.lotus is probably the only terrestrial GDE in the arid zones of Europe and its study is essential for the management and conservation of this ecosystem

Mots clés  : Geohidrologia Águas subterrâneas Qualidade da água Zonas áridas Vegetação Salinização Espanha

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Page publiée le 29 décembre 2015, mise à jour le 22 août 2018