Ecology and Evolution
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.
Chardon, Nathalie; Wipf, Sonja; Rixen, Christian; Beilstein, Annabarbara; and Doak, Daniel F., "Local trampling disturbance effects on alpine plant populations and communities: Negative implications for climate change vulnerability" (2018). University Libraries Open Access Fund Supported Publications. 91.
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