Aciphylla glacialis mortality, growth and frost resistance: a field warming experiment.

Decreasing snow depth and earlier snowmelt in alpine regions are expected to expose plants to a greater range of thermal extremes. Thus, paradoxically, in addition to increasing mean temperatures, aseasonal frost is likely to emerge as a major determinant of plant survival and development under a warming climate. Through the use of open top chambers, we assessed the effects of simulated warming on seedlings of the alpine herb Aciphylla glacialis (F.Muell.) Benth, sourced from provenances that vary in thermal characteristics. We hypothesised that seedlings grown at elevated temperature would have reduced survival and lower freezing resistance, but that individuals that did survive would show increased growth. Further, we hypothesised that seedlings sourced from the lower-elevation sites, where temperatures are more variable, would exhibit lower mortality at warmed conditions than those from sites with narrower thermal ranges. Warmed conditions significantly increased seedling mortality but those that survived grew slightly taller than their ambient counterparts, with no impact on leaf production or photosynthetic efficiency. Although the warming treatment did not influence temperature minimums, which would have allowed us to assess the impact of aseasonal frosts, there was no effect on freezing resistance. Contrary to our expectations, there was little evidence of variation among provenances. Our results indicate that a warmer climate with more extreme events may lead to a reduction in seedling establishment and survival; however, seedlings that do survive and establish are unlikely to express any lingering detrimental effects. Climate change impacts (reduced snow and increased temperatures) have been predicted to detrimentally influence alpine plants. Simulated warming of alpine herb (Aciphylla glacialis), resulted in a reduction in seedling establishment and survival. However, seedlings that survived and established exhibited no lingering detrimental effects, regardless of the climatic conditions at the site of origin. There is little within-species variation and impacts of warming are highly developmentally dependent. For slow-growing alpine species climate change research should take a long-term and spatially-broad perspective. [ABSTRACT FROM AUTHOR]

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