Fig. 1.

Synthesis dataset field site locations in (a) geographic and (b) climatic spaces. The synthesis dataset includes field sites from the sparsely vegetated High Arctic, moderately vegetated Low Arctic, mountainous Oroarctic, and forested Subarctic. (a) Bioclimatic zones were derived from several datasets^98–100 and clipped to north of 55°N. (b) Climatologies are for the period 1981 to 2010 based on the CHELSA dataset gridded at 1 km² resolution (version 2.1)^101,102. Growing degree days represent the heat sum above 0 °C. To improve clarity, panel (b) excludes the Subarctic, the warmest and wettest 2.5^th percentiles, and climate spaces (i.e., unique growing degree day and precipitation combinations) that covered less than 500 km².