Decreased soil moisture due to warming drives phylogenetic diversity and community transitions in the tundra

• Published in: Environmental Research Letters
• Main Authors: Ruud Scharn, Chelsea J Little, Christine D Bacon, Juha M Alatalo, Alexandre Antonelli, Mats P Björkman, Ulf Molau, R Henrik Nilsson, Robert G Björk
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2021
• Subjects: Arctic tundra; long-term warming; soil moisture; vegetation change; shrubification; phylogenetic diversity; Environmental technology. Sanitary engineering; TD1-1066; Environmental sciences; GE1-350; Science; Q; Physics; QC1-999; Arctic; Climate change; Global warming; Tundra
• Online Access: https://doi.org/10.1088/1748-9326/abfe8a; https://doaj.org/article/77cd879df3814dd2b628a584d4d2a2b8

Global warming leads to drastic changes in the diversity and structure of Arctic plant communities. Studies of functional diversity within the Arctic tundra biome have improved our understanding of plant responses to warming. However, these studies still show substantial unexplained variation in diversity responses. Complementary to functional diversity, phylogenetic diversity has been useful in climate change studies, but has so far been understudied in the Arctic. Here, we use a 25 year warming experiment to disentangle community responses in Arctic plant phylogenetic β diversity across a soil moisture gradient. We found that responses varied over the soil moisture gradient, where meadow communities with intermediate to high soil moisture had a higher magnitude of response. Warming had a negative effect on soil moisture levels in all meadow communities, however meadows with intermediate moisture levels were more sensitive. In these communities, soil moisture loss was associated with earlier snowmelt, resulting in community turnover towards a more heath-like community. This process of ‘heathification’ in the intermediate moisture meadows was driven by the expansion of ericoid and Betula shrubs. In contrast, under a more consistent water supply Salix shrub abundance increased in wet meadows. Due to its lower stature, palatability and decomposability, the increase in heath relative to meadow vegetation can have several large scale effects on the local food web as well as climate. Our study highlights the importance of the hydrological cycle as a driver of vegetation turnover in response to Arctic climate change. The observed patterns in phylogenetic β diversity were often driven by contrasting responses of species of the same functional growth form, and could thus provide important complementary information. Thus, phylogenetic diversity is an important tool in disentangling tundra response to environmental change.