Warming-induced changes in bud dormancy and their effects on leaf phenology in common European tree species

• Applicant: Dr. Andrey Malyshev
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 403176259

The timing of leaf-out in the spring and plant senescence in the fall largely determines the length of a plant’s growing season and plays a major role in the net productivity of an ecosystem. Warmer spring and fall temperatures have been closely linked with advanced spring leaf-out and delayed plant senescence, respectively. However, a recently observed reduction in the rate of advancement of spring green-up per degree of warming over the last decades reflects a nonlinear response of plant phenology to climate warming. Future projections indicate that for certain species, advancement in spring leaf-out can stop or even be delayed. Fall senescence is much more unpredictable, with new evidence showing that it can be advanced following an earlier budburst in the spring and be delayed by warmer fall temperatures. Understanding the mechanistic causes of species-specific shifts in phenology in response to climate change is thus essential to better project future changes in ecosystem functions, plant community compositions and plant-animal interactions. To date changes in plant phenology under climate change have mostly been addressed in an observational manner, correlating historical phenological dates with temperature records. Recently, a better understanding of bud dormancy has provided an improved explanation for the biological controls behind bud burst dates. For example, warming during bud dormancy induction can increase bud dormancy depth and lead to a delayed spring budburst. As a result, bud dormancy changes have started to be incorporated into phenological models and have led to improved budburst date predictions. The species-specific photoperiodic and/or temperature control of bud dormancy induction is not known however and needs to be quantified. Plant phenology is not simply driven by fall and spring temperatures. Bud dormancy depth, photoperiod sensitivity and seasonal as well as yearly carry-over effects have been shown to be important drivers of plant phenology. The experiments in this project will thus primarily focus on a) the relative influence of photoperiod and temperature on bud dormancy depth, b) warming-induced changes in bud dormancy depth and c) legacy effects of spring phenology timing on subsequent leaf senescence and spring budburst dates. Among- as well as within-species variation will be quantified by conducting the experiments on common European tree species and ecotypes of Fagus sylvatica, arguably the most important native tree species in Europe. Taken together, manipulation of temperature and photoperiod will be used to quantify among- and within-species variation in warming-induced bud dormancy changes and subsequent leaf phenology. Experimental results where phenological changes are not merely left to temperature-driven "black box" effects but are linked to specific changes in bud dormancy will deepen our mechanistic understanding of plant phenology and will be a valuable basis for future phenology models.

• DFG Programme: Research Grants