Water use partitioning of native and non-native tree species in riparian ecosystems under contrasting climatic conditions

We aimed at evaluating water-source partitioning between native and non-native tree species coexisting in central Spain floodplains; determining the dependency on drought stress of such water-sources-use; and assessing if the reliance on deeper water sources relates with physiological and growth performance. We assessed water-uptake depth, leaf functional traits related to physiological performance and growth of native (<em>Populus alba</em>) and non-native trees <em>(Ailanthus altissima, Robinia pseudoacacia</em>) coexisting in riparian forests under different drought conditions (drier, intermediate and wetter). We analyzed δ²H and δ¹⁸O isotopes in xylem water and in soil water from top, mid and deep soil depths and determined the contribution of each water source to plant xylem water. Leaf traits related with resource use and secondary growth were assessed for each species.