On the need to report the variability and data used in the determination of xylem vulnerability curve parameters

Abstract

Vulnerability curves to cavitation (VC) and their derived parameters, such as P50, are increasingly used and reported to assess forest vulnerability to drought and predict forest responses to climate change. Forest practitioners and policy-makers are encouraged to rely on these parameters to support species selection based on their sensitivity to drought. However, in the majority of studies, we consider that the variability of VC parameters is not clearly reported nor considered, which can lead to counterproductive decisions. In this opinion paper, we demonstrate the importance of precisely reporting the variability around VC parameters and the sources of this variability (plant materials, methods, etc.). We also identify the information that should be provided when reporting mean values of VC parameters. To support our argument, we built VCs for three Picea species and Pinus strobus, using different methods, and compared the value of P50 determined in our experiments with values from a literature review.