Root vulnerability to embolism and lack of physiological recovery limit the competitive ability of an invasive palm

Climate change and invasive species both threaten forest ecosystems. While exacerbated droughts drive tree mortality, species invasion alters forest composition. Invasive plants may be more vulnerable to drought due to acquisitive traits and low embolism resistance, but their potentially superior recovery capacity raises key uncertainties in predicting future species distributions.

We compared the drought resistance and recovery of an invasive palm ( Trachycarpus fortunei ) with two native species ( Ilex aquifolium & Tilia cordata ) from the Southern Alps. Saplings were exposed to increasing intensities of drought-induced xylem embolism, then rewatered for 45 days. Among others, we tracked net assimilation (A _net ), stomatal conductance (g _s ), and leaf water potential (Ψ _leaf ) before and after the drought, and modeled the time to hydraulic failure in leaves, stems, and roots.

While the invasive palm had exceptionally drought-tolerant leaves, its roots were the most drought-sensitive among all species. The palm maintained positive gas exchange until Ψ _leaf of -4 MPa, as some native species; however, it failed to recover from the most severe drought, with simulations showing root embolism preceding leaf failure, unlike native species.

Invasive plants may match or exceed natives’ drought resistance, but their inability to recover from extreme droughts could limit their future spread.