The role of plant traits in climate warming responsiveness of tree species

Climate warming is mostly advancing the onset date of spring phenology, yet milder winters with higher temperatures may in fact delay this date, as chilling requirements of species are not fully met in time. The spring phenology of trees and forests is interconnected with ecosystem functions and services, thus the responses of single species to climate warming may have significant implications at the economic and ecological levels. Despite the numerous studies which have been conducted during the past decade on the responses of plant spring phenology to climate warming, the relative importance of various factors, such as phylogeny, floristic status, climate of the native range, life strategy and plant traits, is still not well understood. In this study, twigs from 53 different tree species with two different natural-chilling treatments were forced in climate chambers at 20°C/day and 15°C/night until budburst, and the onset of budburst was monitored 3 times per week. The forcing requirements until budburst were linked to phylogeny (genera), life strategy (pioneer to climax), climate of their native range (oceanic to continental), floristic status (native, ornamental, and invasive) and eight important plant traits from the TRY database. The aim of our study is to answer the following questions: Are pioneer species more responsive to warming compared to later successional strategies? Is the climate of the native range, floristic status and continent of the species related to responsiveness to forcing? Can plant traits indicate the degree of species’ phenological responses to climate warming?