New work on the impact of the historic 2018 heatwave published in Nature Communications
Richard L. Peters worked on a study within the DenDrought2018 initiative, an international team of researchers, to understand the impact of the 2018 heatwave on trees growing across Central and Atlantic Europe. Results of their joint effort have been published in Nature Communications under the title “The 2018 European heatwave led to stem dehydration but not to consistent growth reductions in forests”. As expected, tree species responded very differently to the 2018 heatwave, and – surprisingly – the drought stress did not necessarily translate into growth limitations, at least not on short notice. This was likely explained by the timing of the heatwave, which was quite late during the growing season at many locations when most trees had already achieved most of their stem growth. But this does not mean that trees did not suffer from temporary stress. Many trees ran into trouble, as stems showed considerable shrinkage. The inability of trees to refill stem-water reservoirs during the night suggests limited resilience to heatwaves and droughts. In particular, conifer species were more sensitive to the 2018 heatwave than broadleaf species. While a single stress event might not be problematic, repeated heatwaves cause problems for some species under certain site conditions. Trees might also be negatively affected by carryover effects in the years after the extreme event, which must be further explored. Our high-resolution dendrometer network was suitable to disentangle the effects of a severe heatwave on tree growth and desiccation at large-spatial scales in situ, and provided insights on which species may be more vulnerable to climate extremes.