Simulated global change: contrasting short and medium term growth and reproductive responses of a common alpine/Arctic cushion plant to experimental warming and nutrient enhancement

Abstract

Cushion plants are important components of alpine and Arctic plant communities around the world. They fulfill important roles as facilitators, nurse plants and foundation species across trophic levels for vascular plants, arthropods and soil microorganisms, the importance of these functions increasing with the relative severity of the environment. Here we report results from one of the few experimental studies simulating global change impacts on cushion plants; a factorial experiment with warming and nutrient enhancement that was applied to an alpine population of the common nurse plant, Silene acaulis, in sub-arctic Sweden. Experimental perturbations had significant short-term impacts on both stem elongation and leaf length. S. acaulis responded quickly by increasing stem elongation and (to a lesser extent) leaf length in the warming, nutrient, and the combined warming and nutrient enhancements. Cover and biomass also initially increased in response to the perturbations. However, after the initial positive short-term responses, S. acaulis cover declined in the manipulations, with the nutrient and combined warming and nutrient treatments having largest negative impact. No clear patterns were found for fruit production. Our results show that S. acaulis living in harsh environments has potential to react quickly when experiencing years with favorable conditions, and is more responsive to nutrient enhancement than to warming in terms of vegetative growth. While these conditions have an initial positive impact, populations experiencing longer-term increased nutrient levels will likely be negatively affected.

Vascular plant abundance and diversity in an alpine heath under observed and simulated global change

“…The increase in temperature is predicted to persist in the future, with warming continuing to develop fastest in the polar regions 3 . And this may affect vegetative growth, reproduction and phenology of plant in severe environments 18 19 20 .…”

“…As a result, short and medium term experiments indicate that global change may cause shifts in the hierarchical structure of plant communities 30 . There is also temporal variation in responses, as shrubs, cushion plants, and whole communities for instance, have shown differing short- and longer-term effects of nutrient addition 20 26 30 , whereas total communities may show contrasting responses to warming 31 . Finally, the initial conditions of the communities may determine response to global change, as well as biotic interactions 32 .…”

Vicariance, long‐distance dispersal, and regional extinction–recolonization dynamics explain the disjunct circumpolar distribution of the arctic‐alpine plant Silene acaulis

“…It is not clear what ecological factors may limit the distribution of S. acaulis , especially in northern areas. Alatalo and Little (2014) showed experimentally that S. acaulis is sensitive to nutrient levels, with declining cover under longer‐term increased nutrient levels. Atmospheric humidity and substrate type have been suggested as limiting factors for S. acaulis in parts of Britain (Jones and Richards, 1962).…”

Peer Review #1 of "Dominance hierarchies, diversity and species richness of vascular plants in an alpine meadow: contrasting short and medium term responses to simulated global change (v0.1)"

“…Another important functional group is cushion plants, which have great influence on ecosystems in polar and high alpine areas throughout the world as they often function as facilitator species across trophic levels (Cavieres & Arroyo 2002;Molenda, Reid & Lortie 2012;Roy et al 2013). Unfortunately, there are very few experimental studies on climate change impact on cushion plants, but the few that exist have shown contrasting responses to warming (Day et al 2009;Alatalo & Little 2014). The Reviewing Manuscript ability of functional groups to compete for light, nutrients, and other resources varies, and the responses may depend on interactions with co-inhabiting species; for instance, the most abundant ("dominant") species or functional group in a community can have a strong influences on the biotic conditions of the other species by either negative, competitive interactions or by positive, facilitative interactions (Grime 1998;Klanderud & Totland 2004).…”