Oecologia http://doi.org/c2jk (2019)

Climate warming tends to extend the vegetative growing seasons through earlier spring activity or later autumn dormancy, or some combination of the two. Responses are often quite complex in practice however, due to modulating factors such as snow cover and because warming in many regions is inconsistent across the year. In Europe, for example, winter and spring months are warming twice as fast as months in the summer and autumn.

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Incamerastock / Alamy Stock Photo

Constantin M. Zohner at ETH Zurich, Switzerland, and Susanne S. Renner at Munich University, Germany, use an experimental approach to investigate the phenological response of several deciduous European trees to 4 °C of warming in winter and spring, summer and autumn, and all year.

The all-year warming treatment led to significantly delayed leaf senescence, but advanced the end of primary growth (bud set). The summer and autumn warming treatment delayed leaf senescence; and the winter and spring warming treatment advanced bud set and leaf senescence. This suggests that continued enhancement of warming in winter and spring will lead to earlier end-of-season growth cessation, even if leaf senescence is delayed.