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Ecology and Evolution





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Global change is modifying species communities from local to landscape scales, with

alterations in the abiotic and biotic determinants of geographic range limits causing

species range shifts along both latitudinal and elevational gradients. An important

but often overlooked component of global change is the effect of anthropogenic

disturbance, and how it interacts with the effects of climate to affect both species

and communities, as well as interspecies interactions, such as facilitation and competition.

We examined the effects of frequent human trampling disturbances on alpine

plant communities in Switzerland, focusing on the elevational range of the widely

distributed cushion plant Silene acaulis and the interactions of this facilitator species

with other plants. Examining size distributions and densities, we found that disturbance

appears to favor individual Silene growth at middle elevations. However, it has

negative effects at the population level, as evidenced by a reduction in population

density and reproductive indices. Disturbance synergistically interacts with the effects

of elevation to reduce species richness at low and high elevations, an effect not

mitigated by Silene. In fact, we find predominantly competitive interactions, both by

Silene on its hosted and neighboring species and by neighboring (but not hosted) species

on Silene. Our results indicate that disturbance can be beneficial for Silene individual

performance, potentially through changes in its neighboring species

community. However, possible reduced recruitment in disturbed areas could eventually

lead to population declines. While other studies have shown that light to moderate

disturbances can maintain high species diversity, our results emphasize that

heavier disturbance reduces species richness, diversity, as well as percent cover, and

adversely affects cushion plants and that these effects are not substantially reduced

by plant–plant interactions. Heavily disturbed alpine systems could therefore be at

greater risk for upward encroachment of lower elevation species in a warming world.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Appendix_S1.pdf (371 kB)
Appendix_S2.pdf (394 kB)