Physiological response and recovery from reduced soil moisture of an invasive palm species compared with native tree species of Ticino

Increase in global temperature has already increased the frequency and intensity of droughts, and is projected to escalate further by the end of the century. Droughts are thought to be one of the main contributors to recent increases in tree mortality at large scale. The ability of local species to resist climate change is questioned due recent changes in climatic conditions. Recent trends demonstrate increase in invasion of drought-tolerant species in new regions. Non-native species alter their new host environment in an effort to gain competition advantage which could cause serious ramifications to ecosystems. In Ticino, Trachycarpus Fortunei, a palm species originating from China, has showed tremendous spread in the understory of natural forests. T. fortunei’s impact ranges from growth inhibition of native woody species, alteration in soil composition and weakening of the protective function of forests. This study explores the role of hydraulics in the invasion of T. fortunei in Ticino, compared to co-occuring species (Ilex aquifolium and Tilia cordata). To do so, hydraulics parameters such as resistance to embolism (P50 and P80), leaf water potential at turgor loss point, and minimum leaf conductance have been assessed in a controlled environment at EPFL, Lausanne using various methods. The results of this study reveal the importance of hydraulic parameters in the invasion process of T. fortunei in Ticino. In addition, invasive T. fortunei is more drought tolerant than native I. aquifolium, notably due to its resistance to embolism events and its capacity to maintain physiological activies under high xylem tension. This study provides valuable knowledge on the role of hydraulic parameters in tree mortality and invasion processes of non-native species which could be of use in future climatic models.