Department of Land Environment Agriculture and Forestry, University of Padova, Legnaro, Italy.
Icelandic Forest Research, Reykjavik, Iceland.
Glob Chang Biol. 2023 Oct;29(20):5896-5907. doi: 10.1111/gcb.16895. Epub 2023 Aug 1.
Current global change is inducing heterogeneous warming trends worldwide, with faster rates at higher latitudes in the Northern Hemisphere. Consequently, tundra vegetation is experiencing an increase in growth rate and uneven but expanding distribution. Yet, the drivers of this heterogeneity in woody species responses are still unclear. Here, applying a retrospective approach and focusing on long-term responses, we aim to get insight into growth trends and climate sensitivity of long-lived woody species belonging to different functional types with contrasting growth forms and leaf habits (shrub vs. tree and deciduous vs. evergreen). A total of 530 samples from 7 species (common juniper, dwarf birch, woolly willow, Norway spruce, lodgepole pine, rowan, and downy birch) were collected in 10 sites across Iceland. We modelled growth trends and contrasted yearly ring-width measurements, filtering in high- and low-frequency components, with precipitation, land- and sea-surface temperature records (1967-2018). Shrubs and trees showed divergent growth trends, with shrubs closely tracking the recent warming, whereas trees, especially broadleaved, showed strong fluctuations but no long-term growth trends. Secondary growth, particularly the high-frequency component, was positively correlated with summer temperatures for most of the species. On the contrary, growth responses to sea surface temperature, especially in the low frequency, were highly diverging between growth forms, with a strong positive association for shrubs and a negative for trees. Within comparable vegetation assemblage, long-lived woody species could show contrasting responses to similar climatic conditions. Given the predominant role of oceanic masses in shaping climate patterns in the Arctic and Low Arctic, further investigations are needed to deepen the knowledge on the complex interplay between coastal tundra ecosystems and land-sea surface temperature dynamics.
当前的全球变化正在导致世界各地的变暖趋势呈现不均匀性，北半球高纬度地区的变暖速度更快。因此，苔原植被的生长速度正在加快，分布范围也在不均匀地扩大。然而，木质物种响应这种异质性的驱动因素仍不清楚。在这里，我们采用回顾性方法，重点关注长期响应，旨在深入了解属于不同功能类型、具有不同生长形式和叶片习性（灌木与乔木、落叶与常绿）的长寿命木本物种的生长趋势和气候敏感性。我们从冰岛 10 个地点的 7 个物种（普通刺柏、矮桦、毛柳、挪威云杉、花旗松、欧洲花楸和银桦）中采集了 530 个样本。我们建立了生长趋势模型，并对比了年轮宽度测量值，同时过滤了高频和低频成分，以及降水、陆面和海面温度记录（1967-2018 年）。灌木和乔木的生长趋势不同，灌木与最近的变暖密切相关，而乔木，尤其是阔叶树，表现出强烈的波动，但没有长期的生长趋势。次生生长，特别是高频成分，与大多数物种的夏季温度呈正相关。相反，生长对海面温度的响应，特别是低频部分，在不同的生长形式之间存在很大的差异，灌木呈正相关，而乔木呈负相关。在类似的植被组合中，长寿命的木本物种可能对相似的气候条件表现出不同的响应。鉴于海洋对塑造北极和低北极气候模式的主导作用，需要进一步的研究来加深对沿海苔原生态系统与陆海表面温度动态之间复杂相互作用的认识。
