Phenology and growth of European trees in relation to climate change

Research topicsThe relationships between climate and both phenology and growth of some important European tree species were studied to evaluate the potential impacts of climate change on trees and forests in Europe. In order to make such assessments, insight is required on the mechanisms how climatic variables interact with plant processes. The topics addressed in this study were: (1) the modelling of phenology, (2) the consequences of climate change on spring frost damage, (3) the importance of phenotypic plasticity, (4) the importance of phenology on the effects of climate change on growth of monospecies deciduous forests, and (5) the importance of phenology on the effects of climate change on growth of mixed-species deciduous forests.Modelling phenologyTo evaluate the impacts of climate change on growth of temperate deciduous tree species, the onset and cessation of the growth must be accurately described. A review is presented on eight models predicting the date of leaf unfolding depending on temperature. These models were fitted using 57 years of observations on the date of leaf unfolding of Fagus sylvatica in The Netherlands, and used to predict 40 years of similar observations collected in Germany. As conflicting experimental evidence exist on the role of photoperiod on leaf unfolding of Fagus sylvatica, photoperiod was incorporated into each of these models.The timing of leaf unfolding could best be described by a model in which the effects of chilling temperatures (-5 to +10°C) and forcing temperatures (>0°C) operate sequentially in time, according to a triangular and logistic function, respectively. Including photoperiod reduced the predicting power of this model.Spring frost damageTwo studies presented in literature evaluate the effect of increasing winter temperature on the probability of spring frost damage to trees. However, one study predicted an increase, while the other predicted a decrease in the probability of spring frost damage. It is unclear wh