In the high Arctic, plant community species composition generally responds slowly to climate warming, whereas less is known about the community functional trait responses and consequences for ecosystem functioning. The slow species turnover and large distribution ranges of many Arctic plant species suggest a significant role of intraspecific trait variability in functional responses to climate change. Here we compare taxonomic and functional community compositional responses to a long-term (17-year) warming experiment in Svalbard, Norway, replicated across three major high Arctic habitats shaped by topography and contrasting snow regimes. We observed taxonomic compositional changes in all plant communities over time. Still, responses to experimental warming were minor and most pronounced in the drier habitats with relatively early snowmelt timing and long growing seasons (Cassiope and Dryas heaths). The habitats were clearly separated in functional trait space, defined by 12 size- and leaf economics-related traits, primarily due to interspecific trait variation. Functional traits also responded to experimental warming, most prominently in the Dryas heath and mostly due to intraspecific trait variation. Leaf area and mass increased and leaf δ¹⁵N decreased in response to the warming treatment. Intraspecific trait variability ranged between 30% and 71% of the total trait variation, reflecting the functional resilience of those communities, dominated by long-lived plants, due to either phenotypic plasticity or genotypic variation, which most likely underlies the observed resistance of high Arctic vegetation to climate warming. We further explored the consequences of trait variability for ecosystem functioning by measuring peak season CO₂ fluxes. Together, environmental, taxonomic, and functional trait variables explained a large proportion of the variation in net ecosystem exchange (NEE), which increased when intraspecific trait variation was accounted for. In contrast, even though ecosystem respiration and gross ecosystem production both increased in response to warming across habitats, they were mainly driven by the direct kinetic impacts of temperature on plant physiology and biochemical processes. Our study shows that long-term experimental warming has a modest but significant effect on plant community functional trait composition and suggests that intraspecific trait variability is a key feature underlying high Arctic ecosystem resistance to climate warming.

中文翻译：

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种内性状变异是北极植物群落对气候变暖具有高抵抗力的一个关键特征

在高北极地区，植物群落物种组成通常对气候变暖反应缓慢，而对群落功能性状反应和生态系统功能影响知之甚少。许多北极植物物种的缓慢物种更替和大分布范围表明种内性状变异在对气候变化的功能反应中起着重要作用。在这里，我们比较了分类学和功能群落组成对挪威斯瓦尔巴特群岛长期（17 年）变暖实验的反应，该实验在三个主要的高北极栖息地进行了复制，这些栖息地由地形和对比雪情形成。我们观察了所有植物群落的分类组成随时间的变化。仍然，Cassiope和Dryas heaths）。栖息地在功能性状空间中明显分离，由 12 个大小和叶经济学相关性状定义，主要是由于种间性状变异。功能性状也对实验性变暖有反应，在仙女木荒原中最为突出，主要是由于种内性状变异。叶面积和质量增加，叶片 δ ¹⁵N响应于升温处理而减少。由于表型可塑性或基因型变异，种内性状变异占总性状变异的 30% 至 71%，反映了这些群落的功能恢复力，这些群落以长寿植物为主，这很可能是观察到的北极高海拔地区抗性的基础植被对气候变暖。我们通过测量旺季 CO _{2进一步探讨了性状变异对生态系统功能的影响}通量。环境、分类学和功能性状变量共同解释了净生态系统交换 (NEE) 变异的很大一部分，当考虑到种内性状变异时，NEE 会增加。相比之下，尽管生态系统呼吸和生态系统总产量都因栖息地变暖而增加，但它们主要是由温度对植物生理和生化过程的直接动力学影响驱动的。我们的研究表明，长期实验性变暖对植物群落功能性状组成具有适度但显着的影响，并表明种内性状变异性是北极生态系统对气候变暖具有高抵抗力的关键特征。