The role of deep vadose zone water in tree transpiration during drought periods in karst settings -insights from isotopic tracing and leaf water potential

Le rôle de la zone vadose profonde pour la transpiration des arbres lors des périodes de sécheresse - apports du traçage isotopique et des potentiels hydrique foliaires

Simon Carriere (1, 2, 3) , Nicolas Martin-StPaul (4) , Coffi Belmys Cakpo (4) , Nicolas Patris (5) , Marina Gillon (1, 2, 3) , Konstantinos Chalikakis (1, 2, 3) , Claude Doussan (1, 4) , Albert Olioso (1, 4) , Milanka Babic (1, 2) , Arnaud Jouineau (4) , Guillaume Simioni (4) , Hendrik Davi (4)

1 EMMAH - Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes
2 AU - Avignon Université
3 SNO Karst - Service National d'Observation sur le KARST
4 INRA - Institut National de la Recherche Agronomique
5 HSM - Hydrosciences Montpellier

Karst environments are unusual because their dry, stony and shallow soils seem to be unfavorable to vegetation, and yet they are often covered with forests. How can trees survive in these environments ? Where do they find the water that allows them to survive? This study uses midday and predawn water potentials and xylem water isotopes of branches to assess tree water status and the origin of transpired water. Monitoring was conducted during the summers of 2014 and 2015 in two dissimilar plots of Mediterranean forest located in karst environments. The results show that the three monitored tree species (Abies alba Mill, Fagus sylvatica L, and Quercus ilex L.) use deep water resources present in the karst vadose zone (unsaturated zone) more intensively during drier years. Quercus ilex, a species well-adapted to water stress, which grows at the drier site, uses the deep water resource very early in the summer season. Conversely, the two other species exploit the deep water resource only during severe drought. These results open up new perspectives to a better understanding of ecohydrological equilibrium and to improved water balance modeling in karst forest settings.

Domains: Environmental Sciences; Biodiversity and Ecology; Global Changes; Environmental Engineering; Continental interfaces, environment; Ecosystems; Soil study; Silviculture, forestry; Hydrology

Simon Carriere, Nicolas Martin-StPaul, Coffi Belmys Cakpo, Nicolas Patris, Marina Gillon, et al.. The role of deep vadose zone water in tree transpiration during drought periods in karst settings -insights from isotopic tracing and leaf water potential. Science of the Total Environment, 2020, pp.134332. ⟨10.1016/j.scitotenv.2019.134332⟩. ⟨hal-02283729⟩