Abstract

Aim Tree mortality is increasing world-wide, leading to changes in forest composition and altering global biodiversity. Nonetheless, owing to the multifaceted stochastic nature of tree mortality, large-scale spatial patterns of mortality across species ranges and their underlying drivers remain difficult to understand. Our main goal was to describe the geographical patterns and drivers of the occurrence of mortality (presence of a mortality event) and the intensity of tree mortality (amount of mortality related to that mortality event) in Europe. We hypothesized that the occurrence of mortality represents background mortality and is higher in the margin than in core populations, whereas the intensity of mortality could have a more even distribution according to the spatial and temporal stochasticity of die-off events.Location Europe (Spain, France, Germany, Belgium, Sweden and Finland).Major taxa studied More than 1.5 million trees belonging to 20 major forest tree species.Methods We developed binomial and truncated negative binomial models to tease apart the occurrence and intensity of tree mortality in National Forest Inventory plots at the range-wide scale. The occurrence of mortality indicated that at least one tree had died in the plot, whereas the intensity of mortality referred to the number of dead trees per plot.Results The highest occurrence of mortality was found in peripheral regions and the climatic trailing edge linked with drought, whereas the intensity of mortality was driven by competition, drought and high temperatures and was scattered uniformly across species ranges.Main conclusions We show that tree background mortality, but not die-off, is generally higher in the trailing-edge populations. It remains to be explored whether other demographic traits, such as growth, reproduction and regeneration, also decrease at the trailing edge of European tree populations.

Keywords

background mortality; climatic edges; die‐off mortality; drought; European forests; hurdle models; National Forest Inventory; tree mortality

Published in

Global Ecology and Biogeography
2021, Volume: 30, number: 7, pages: 1356-1374
Publisher: WILEY

SLU Authors

• Dahlgren, Jonas

  • Department of Forest Resource Management, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Forest Science


Publication identifier

DOI: https://doi.org/10.1111/geb.13301

Permanent link to this page (URI)

https://res.slu.se/id/publ/111878