Functional traits in arborescent Cactaceae: a guideline for their measurement

: The need to understand the impacts of global change on ecosystems has driven interest in studying functional traits, which represent morphological, physiological, or phenological adaptations that determine the ecological performance of organisms. Although standardized methods exist for assessing functional traits in woody and herbaceous plants, protocols for arborescent cacti are still scarce. Cactaceae is a tropical American plant family that reaches high abundance in tropical dry ecosystems and encompasses a great diversity of form and size. Cacti perform fundamental ecosystem functions, are on the list of the most endangered plants globally and represent economically-impactful invasive species outside of the Americas. Here, we propose protocols to measure 12 functional traits in cacti, which are grouped into structural (two traits), morphological (seven traits), hydraulic–mechanical (two traits) and biophysical (one trait) categories, so as to complement ecological studies of plants and improve the understanding of their life cycle and the main environmental challenges faced by cacti.