Assessing climate impacts on tree phenology and growth rates

The PheGro-Clim project (PHEnological and GROwth responses to CLIMate) aims at increasing our knowledge about past trends in leaf phenology and growth rates of trees by combining long-term phenological observations, tree-ring measurements, meteorological data, and site data. It also intends to shed light on the drivers behind tree phenology and growth rates as well as their specific importance, according to species and ecogradient.

In the first part of the project we will analyse past trends in leaf phenology in the data of the Swiss phenology network of MeteoSwiss. First, we will conduct a species- and elevation-specific trend analysis of leaf unfolding, leaf colouring and the length of growing period. Second, we will evaluate past trends in bioclimatic conditions during the growing period of trees using interpolated daily data of sunshine duration, temperature and precipitation. This will allow us to determine and discuss the influence of shifts in leaf phenology on these bioclimatic conditions, as these shifts alter the timing and length of the growing period.
The second part of the project will focus on models for leaf phenology. We will analyse how the model-specific goodness of fit changes between different strategies of calibration sample selection and between different tree species. Thus, we aim to identify models and calibration sample selections that are best suited for predicting leaf phenology under changing climate conditions. Furthermore, we plan to apply these models to discuss predicted changes in leaf phenology and in the length of the growing period under different climate change scenarios.
For the third part of the project, we collect increment cores from trees observed in the Swiss phenology network. Thus, we will be able to measure the tree-ring widths and reconstruct site and species related growth rates. We will analyse trends of these growth rates per species and per ecogradient. Thereafter, we will discuss relationships between growth rates, phenological observations, temperature, and precipitation.
In the fourth part of the project, we will investigate the effects of late spring frost on tree phenology and growth rates. By applying different frost indices in combination with phenological observations, growth rates, and meteorological data, we will search for correlations between frost and anomalies in phenology and growth rate.

Funding

This project is funded by the Swiss National Science Foundation SNF.

Project status

The project takes place from August 2018 until July 2022.

Contact

For further information, please contact Michael Meier, Christof Bigler, or Harald Bugmann.