Demographic performance of European tree species at their hot and cold climatic edges

Abstract

Species range limits are thought to result from a decline in demographic performance at range edges. However, recent studies reporting contradictory patterns in species demographic performance at their edges cast doubt on our ability to predict climate change demographic impacts. To understand these inconsistent demographic responses, we need to shift the focus from geographic to climatic edges and analyse how species responses vary with climatic constraints at the edge and species' ecological strategy. Here we parameterised integral projection models with climate and competition effects for 27 tree species using forest inventory data from over 90,000 plots across Europe. Our models estimate size‐dependent climatic responses and evaluate their effects on two life trajectory metrics: life span and passage time—the time to grow to a large size. Then we predicted growth, survival, life span and passage time at the hot and dry or cold and wet edges and compared them to their values at the species climatic centre to derive indices of demographic response at the edge. Using these indices, we investigated whether differences in species demographic response between hot and cold edges could be explained by their position along the climate gradient and functional traits related to their climate stress tolerance. We found that at cold and wet edges of European tree species, growth and passage time were constrained, whereas at their hot and dry edges, survival and life span were constrained. Demographic constraints at the edge were stronger for species occurring in extreme conditions, that is, in hot edges of hot‐distributed species and cold edges of cold‐distributed species. Species leaf nitrogen content was strongly linked to their demographic responses at the edge. In contrast, we found only weak links with wood density, leaf size and xylem vulnerability to embolism. Synthesis. Our study presents a more complicated picture than previously thought with demographic responses that differ between hot and cold edges. Predictions of climate change impacts should be refined to include edge and species characteristics.

Climate warming causes mast seeding to break down by reducing sensitivity to weather cues

“…Widely available data on forest growth and mortality have allowed a good understanding of how tree growth and survival respond to climate fluctuations (Berdanier & Clark, 2016;Brienen et al, 2020;Manzanedo et al, 2020;McMahon et al, 2010;Young et al, 2017). By contrast, an understanding of climate change impacts on fecundity is less developed, as seed production is not directly observed for most species and habitats, and data accumulate slowly and with substantial investment (Clark et al, 2021;Kunstler et al, 2021). Thus, realistic estimates of tree fecundity and population growth rate are basically absent from most vegetation models (Kunstler et al, 2021;McDowell et al, 2020;Vacchiano et al, 2018).…”

“…By contrast, an understanding of climate change impacts on fecundity is less developed, as seed production is not directly observed for most species and habitats, and data accumulate slowly and with substantial investment (Clark et al, 2021;Kunstler et al, 2021). Thus, realistic estimates of tree fecundity and population growth rate are basically absent from most vegetation models (Kunstler et al, 2021;McDowell et al, 2020;Vacchiano et al, 2018).…”

Modelling Tree Growth in Monospecific Forests from Forest Inventory Data

“…Integral projection models (IPM) have also been parameterised with data from forest inventories to obtain a forest DBH distribution model, where the individual growth law used was phenomenological. For instance, Kunstler et al [58] used data from 27 species across Europe. Although they only used two data temporal series, they analyzed a wide range of DBH.…”

Climate change and plant reproduction: trends and drivers of mast seeding change

“…Another challenge is to unpack the consequences of changing synchrony for recruitment and wider community dynamics. Declining synchrony has been demonstrated to decrease individual plant fitness as measured by viable seed production [40], but the next step is to link this with tree regeneration and population growth [74,75]. Trophic consequences of changes in synchrony are potentially substantial but remain unexplored.…”