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.

中文翻译：

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Aciphylla glacialis 死亡率、生长和抗冻性：田间增温实验

预计高山地区积雪深度的减少和融雪的提前将使植物暴露于更大范围的极端高温环境中。因此，矛盾的是，除了增加平均温度外，季节性霜冻可能会成为气候变暖下植物生存和发育的主要决定因素。通过使用开顶室，我们评估了模拟升温对高山草本植物 Aciphylla glacialis (F.Muell.) Benth 幼苗的影响，该植物来自热特性不同的来源。我们假设在高温下生长的幼苗会降低存活率和降低抗冻性，但存活下来的个体会显示出生长增加。此外，我们假设幼苗来自温度变化更大的低海拔地区，与来自温度范围较窄的地点的死亡率相比，在温暖条件下的死亡率较低。温暖的条件显着增加了幼苗死亡率，但那些存活下来的幼苗长得比周围环境中的对应物略高，对叶片生产或光合效率没有影响。尽管加温处理不会影响最低温度，这将使我们能够评估季节性霜冻的影响，但对抗冻性没有影响。与我们的预期相反，几乎没有证据表明来源之间存在差异。我们的研究结果表明，气候变暖和更多极端事件可能导致幼苗建立和存活率下降；然而，确实存活和建立的幼苗不太可能表现出任何挥之不去的有害影响。