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Summary To survive climate change, forest trees will have to shift seed production poleward. However, warming will not stimulate tree fecundity in the north if it is limited by other habitat variables.We evaluated the responses of tree fecundity to climate change for 292 tree species in North America and Europe, using response velocity, defined as (climate sensitivity) × (climate‐change rate). The sensitivities to climate were estimated for each species and combined with rates of climate change to quantify how temperature, moisture deficits, and late freeze are influencing biogeographic shifts in tree reproduction.The results show that moisture deficit and late freeze, not annual temperature, drive changing seed production. Unlike annual temperature, which is increasing generally, change in these climate variables is not driving poleward shifts in seed production.These findings do not challenge the expectation that forests might eventually shift poleward. Rather, they show why current efforts offer divergent interpretations. The changes happening now are not consistent with annual temperature trends. As warming continues, fecundity changes can best be anticipated from temperature interactions with precipitation and extremes that impact flowering and fruiting in winter and spring.
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This content will become publicly available on June 1, 2027
Fecundity and terrain‐climate interactions that shape tree niche differences across North America and Europe
Abstract If niche differences contribute to biodiversity, then landscapes must vary and species must respond differently to that variation. Terrain, through its effects on solar radiation and moisture, is an important contributor to habitat variation, but its effects on demography are largely unknown. Understanding fecundity responses to this landscape heterogeneity could provide insights on niche differences and on how terrain buffers climate change effects. Here, we use a hierarchical Bayesian state‐space model to quantify how topographic features buffer tree fecundity from intensifying climate change. We estimate the effects of slope, aspect and drainage on tree fecundity across North America and Europe while accounting for individual condition and climate.We analysed 2,874,955 tree‐years from 292 species across forest inventory plots spanning mountainous regions in North America and Europe. We fitted species‐specific fecundity responses to terrain variables and climate interactions, then constructed predictive distributions of terrain effects at landscape scales. We quantified community‐level hypervolume to assess how diversity in fecundity responses across species relates to topographic heterogeneity.Topography influences tree fecundity, with terrain as an important contributor for most species. In dry portions of their ranges, tree species in southeastern North America and south‐central Europe increase fecundity towards northeast aspects, while highest fecundity of species in southwestern North America shifts towards south‐facing aspects. Terrain‐sensitive species (terrain explains >20% of fecundity variance) are most abundant in southwestern North America (~42% of species), but southeastern North America shows the strongest terrain effects on fecundity and highest per‐species fecundity variance, despite having the gentlest slopes. Community hypervolume is exceptionally high in southeastern United States. Whether this variation maintains diversity depends on how fecundity combines with other demographic rates.Synthesis: Fine‐scale terrain variation creates reproductive differences through species‐specific fecundity responses. The effectiveness of topographic heterogeneity as a climate refuge depends on regional landscape structure and species sensitivity to terrain. In topographically diverse regions, species may buffer climate change through fine‐scale redistribution to favourable microsites. Quantifying these differences helps identify factors limiting reproduction and habitat features with greatest potential as local refuges.
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- PAR ID:
- 10708164
- Publisher / Repository:
- Journal of Ecology
- Date Published:
- Journal Name:
- Journal of Ecology
- Volume:
- 114
- Issue:
- 6
- ISSN:
- 0022-0477
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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