Résumé
1. Understanding the water-use of plants is timely under increasing
drought stress due to climate change. Despite the crucial role of roots in
water uptake, relationships between water-use and root traits are seldom
considered. 2. Combining a functional traits-based approach with a water
balance model, we tested whether root functional traits are related to
spatial and temporal water-use among 12 Mediterranean rangeland species
grown in common garden monocultures. Soil water content was monitored for
10 months, and the dynamics of water uptake of each species was modelled
at a daily time step. Root functional traits were measured at two soil
depths (shallow and deep soil). 3. Species with fast resource acquisition
strategies in shallow soil, i.e. thin roots, maximised water uptake in a
short period and consumed large amounts of water during periods of low
water availability. Conversely, species with a more conservative root
strategy, i.e. coarse roots, took up less water during the peak-growing
season, maintained water uptake over a longer period of time and consumed
less water during periods of low water availability. Deep root traits are
strongly related to species’ ability to take up water from deep soil. Deep
roots with large diameters and low specific root length improve species’
ability to reach water from deep soil. Biomass investment in the deep soil
layer was positively related to the amount of water consumed during
periods of low water availability. 4. Our results highlight that root
functional traits influence a range of spatial and temporal water-use
among Mediterranean rangeland species. They account for the amount of
water taken up during dry periods but not during the entire growing
season.