Macroecological patterns of vegetation change across a warming tundra biome

• Main Author: García Criado, Mariana
• Other Authors: Myers-Smith, Isla, Lehmann, Caroline, Fisher, Janet, Bjorkman, Anne
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Edinburgh 2022
• Subjects: climate change; tundra; Arctic; alpine; plant diversity; woody encroachment; functional traits; Climate change; Tundra
• Online Access: https://hdl.handle.net/1842/39076; https://doi.org/10.7488/era/2327

The climate is changing across the globe at unprecedented magnitudes, and temperatures in the Arctic are increasing at three times the rate of the global average. Climate change impacts are being felt across the tundra biome, both at northern latitudes and high elevations. Examples of these impacts include northward species range shifts, changing community composition and increasing shrub growth, height and expansion, a phenomenon also known as shrubification. While multiple reports of plot- and landscape-level transformations have been described from locations across the tundra biome, uncertainty remains about 1) the extent of climate as a driver of biotic change, 2) the identity and traits of species that are currently shifting their ranges, and 3) how precisely is plant diversity changing over time. By combining decades-long large-scale tundra datasets of community composition, abundance, change over time, functional traits, species distributions and gridded climate data, I delve into these key questions about how climate change is reshaping the tundra biome. My research has demonstrated that, while rates of woody encroachment do not generally correspond with rates of climatic change, climate is still a driver of shrub expansion in the tundra. I found that warmer and wetter sites have provided fertile ground for shrubs to expand across tundra landscapes. Increased precipitation at dry sites was also associated with greater woody encroachment in a structurally similar open biome, the savanna. Contrary to initial expectations, trait values and intraspecific variation in three key functional traits (plant height, specific leaf area and seed mass) were not consistently related to current and projected tundra shrub species ranges. Likewise, the identity of climate change ‘winner’ and ‘loser’ shrub species differed depending on whether they were considered through past-observed change or projected range shifts, highlighting discrepancies arising from the use of different methods. Additionally, I found that there is ...