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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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This content will become publicly available on October 1, 2026
Marked tree demographic variation along subtle elevation differences partially explains species' habitat associations in an Amazonian forest
It is widely recognized that large‐scale topographic variation affects the distribution of tree diversity, yet the effects of topography at smaller scales are less appreciated but can be no less consequential. We evaluated how small‐scale topographic variation affects tree demography and diversity in a hyperdiverse Amazonian forest where species distributions respond strongly to elevation differences as small as 22 m. For topographically structured species distributions to arise, species should grow and survive (perform) better in the topographic habitat they are associated with, and they should outperform other species that are found, but not strongly aggregated, in that habitat. Here, we tested these demographic hypotheses using data on the growth and mortality of 79,911 trees (352 species) among three topographic habitats (valleys, slopes and ridges) in the 25‐ha Amacayacu Forest Dynamics Plot.Despite the small variation in elevation, there was significant community‐level variation in growth and mortality among topographic habitats: trees growing in valleys, where soil moisture is higher, had significantly higher growth and mortality rates than those growing on slopes and ridges. However, tree growth rates did not depend on, and mortality rates varied inconsistently with, species' habitat association. Our results partially support the resident‐advantage hypotheses for valley‐associated species, which grew best in their home habitat (valleys) than elsewhere and had lower mortality there compared to slope‐associated or generalist species (foreigners). For slope‐ and ridge‐associated species, our results did not support these hypotheses at the community level. Species‐specific analyses revealed that 73 out of the 352 species analysed at the community level supported either hypothesis. Our findings show that even small differences in elevation can lead to biologically meaningful variation in resource access that translates into significant differences in tree growth and survival. However, resource access could not fully explain the patterns of topographically driven demographic variation we observed. While certain species may still exhibit home and resident advantages in specific habitats, even when community‐level averages partially reflect this pattern, alternative hypotheses are likely driving the patterns observed at the community level.
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- Award ID(s):
- 2020424
- PAR ID:
- 10665248
- Publisher / Repository:
- British Ecological Society
- Date Published:
- Journal Name:
- Journal of Ecology
- Volume:
- 113
- Issue:
- 10
- ISSN:
- 0022-0477
- Page Range / eLocation ID:
- 2860 to 2874
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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