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Accueil du site → Doctorat → Australie → 2014 → Trees and groundwater on the water-limited Eyre Peninsula : an ecohydrological perspective

Flinders University of South Australia (2014)

Trees and groundwater on the water-limited Eyre Peninsula : an ecohydrological perspective

Swaffer, Brooke Aily,

Titre : Trees and groundwater on the water-limited Eyre Peninsula : an ecohydrological perspective

Auteur : Swaffer, Brooke Aily,

Université de soutenance : Flinders University of South Australia

Grade : Doctor of Philosophy (PhD) 2014

Résumé partiel
This thesis investigated the ecohydrological linkages between native and exotic tree species and karstic groundwater systems on Eyre Peninsula, South Australia. It focuses on two issues of global importance : the declining status of fresh water resources in water-limited environments and the rate of evapotranspiration from native and non-native trees encroaching across groundwater recharge areas. The work focussed on karstic groundwater systems, a geological setting where the water flux dynamics from the surface through to groundwater is a complex process involving storage in the unsaturated zone and diffuse and preferential recharge pathways. This geological complexity and the processes associated with this behaviour are not well understood, despite karst aquifers often being the source of drinking water supplies. As a result, uncertainty regarding the ecohydrological processes in this environmental setting remains large. In addition to the complex nature of the karst substrate, the presence of vegetation growing above the groundwater lens will further influence recharge and discharge dynamics. Water use by trees, as well as the partitioning of precipitation into interception, stemflow and throughfall, was considered to be an important ecohydrological process affecting this groundwater system. This study examined whether groundwater level decline could be attributed to changes in land cover, reflecting differences in evapotranspiration rates and pathways of water flux across morphologically distinct, locally common tree species. Pre-European settlement the region was characterised by a grassy woodland dominated by Allocasuarina verticillata (Lam.) L. Johnson (drooping sheoak). Since the establishment and subsequent cessation of grazing across groundwater recharge areas, Eucalyptus diversifolia ssp. diversifolia Bonpl. (coastal white mallee) has expanded in range. Furthermore, the non-native Pinus halepensis Mill. (Aleppo pine), originally planted as a wind-break, has since naturalised and invaded significant areas of the rocky, shallow, calcrete soils often characteristic of karstic systems. Invasion by an aggressive exotic plant species into this water-limited environments was commonly believed to further exacerbate water scarcity issues. Fundamentally, this thesis seeks to address concerns regarding the effect native trees, or encroachment by exotic trees, exerts over groundwater flux in a water-limited environment.

Mots clés : Evapotranspiration,water balance,sap flow,tree water use,ecohydrology

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