Shifts in species geographic distributions in response to climate change have spurred numerous studies to determine which abiotic (e.g. climatic) and, less commonly, biotic (e.g. competitive) processes determine range limits. However, the impact of disturbances on range limits and their interactions with climatic and biotic effects is not well understood, despite their potential to alter competitive relationships between species or override climatic effects. Disturbance might have differential effects at contrasting range limits, based on Darwin's theory that biotic interactions set abiotically benign range limits and abiotic factors set abiotically stressful range limits. We predicted that plants at lower elevation (abiotically benign) range limits experience a net positive effect of disturbance, whereas those at higher elevation (abiotically stressful) range limits experience a net neutral effect. We examined plant populations along elevational gradients in the Colorado Rocky Mountains, in order to quantify the effects of human trampling disturbance at lower and upper elevational range limits of the common alpine cushion plants Our results are consistent with Darwin's theory. A disturbance‐mediated reduction of competitive effects increases the performance of cushion plants at lower elevations, suggesting a range limit set by biotic factors. At higher elevations, where biotic interactions are minimal, disturbance has neutral or negative effects on cushion plants.
High‐elevation plants are disproportionally affected by climate change. As temperatures rise, the amount of available alpine habitat in the Rocky Mountains will decrease resulting in potential local extinctions of plant species. In addition to the direct effects of climate‐driven habitat loss, alpine plants must also respond to indirect effects, such as changes in disturbance regimes. One notable shift is the increase of wildfire frequency in regions where fire was previously rare or absent, including the alpine. We hypothesized that direct climatic changes compounded with increased wildfire frequency will reduce the future suitable habitat of high‐elevation plants more than if climate was considered alone.
Rocky Mountain Floristic Region, western North America.
Our approach integrated historical herbarium records, field surveys, remote sensing, species distribution models, historic wildfire data, and predictive models.
Our results indicate wildfire has significantly reduced the abundance and increased the likelihood of extirpation for
Our evidence that increased wildfire frequency will compound the impacts of climate change on alpine taxa in North America led to the development of a new, general hypothesis on the fundamental interaction between direct and indirect effects of climate change on species range reductions.
- NSF-PAR ID:
- 10078119
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Biogeography
- Volume:
- 45
- Issue:
- 12
- ISSN:
- 0305-0270
- Page Range / eLocation ID:
- p. 2755-2765
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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