Predicting spatial and temporal patterns of bud‐burst and spring frost risk in north‐west Europe: the implications of local adaptation to climate

Abstract

The timing of spring bud-burst and leaf development in temperate, boreal and Arctic trees and shrubs fluctuates from year to year, depending on meteorological conditions. Over several generations, the sensitivity of bud-burst to meteorological conditions is subject to selection pressure. The timing of spring bud-burst is considered to be under opposing evolutionary pressures; earlier bud-burst increases the available growing season (capacity adaptation) but later bud-burst decreases the risk of frost damage to actively growing parts (survival adaptation). The optimum trade-off between these two forms of adaptation may be considered an evolutionarily stable strategy that maximizes the long-term ecological fitness of a phenotype under a given climate. Rapid changes in climate, as predicted for this century, are likely to exceed the rate at which trees and shrubs can adapt through evolution or migration. Therefore the response of spring phenology will depend not only on future climatic conditions but also on the limits imposed by adaptation to current and historical climate. Using a dataset of bud-burst dates from twenty-nine sites in Finland for downy birch (Betula pubescens Ehrh.), we parameterize a simple thermal time bud-burst model in which the critical temperature threshold for bud-burst is a function of recent historical climatic conditions and reflects a trade-off between capacity and survival adaptation. We validate this approach with independent data from eight independent sites outside Finland, and use the parameterized model to predict the response of bud-burst to future climate scenarios in north-west Europe. Current strategies for budburst are predicted to be suboptimal for future climates, with bud-burst generally occurring earlier than the optimal strategy. Nevertheless, exposure to frost risk is predicted to decrease slightly and the growing season is predicted to increase considerably across most of the region. However, in high-altitude maritime regions exposure to frost risk following bud-burst is predicted to increase.

Evaluating Biosphere Model Estimates of the Start of the Vegetation Active Season in Boreal Forests by Satellite Observations

“…According to field observations, the heat sum requirement for bud break of birch decreases from south to north in the boreal region [94,95] and also the temperature threshold for the NDVI-based greening-up decreases [28,77]. This seems to be in contradiction to our results for JSBACH DBF_SOS mod .…”

Spring temperature change and its implication in the change of vegetation growth in North America from 1982 to 2006

“…After the TP of spring NDVI, both browning and cooling are observed, particularly in the above-mentioned regions. Such negative effects of spring cooling on vegetation growth of northern ecosystems may be not only associated with the delayed vegetation greening (21-23) but also related to the increasing risk of spring frost or extreme low temperature (24)(25)(26). It has been suggested that spring frost may severely damage vegetation growth, particularly when it took place after budburst (24).…”

The ecological significance of phenology in four different tree species: effects of light and temperature on bud burst

“…In fact the regulation of the timing of growth onset and cessation is a fundamental feature allowing the syncronisation of the plant growth cycle with favourable seasonal conditions, and, similar to other characteristics, has been driven by selective pressure (Leopold 1996;Bennie et al 2010;Korner and Basler 2010). This process of adaptation has been seen as the result of stabilising selection caused by two opposite forces: protection against an unfavourable season (survival adaptation), and effective use of growing resources (capacity adaptation) (Hänninen and Hari 1996;Leinonen and Hänninen 2002).…”