The influence of vegetation on shallow soil and air temperature coupling: a Pan-Arctic data synthesis

Shallow soil temperatures influence ecosystem carbon cycling and the temperature of deeper soil layers where permafrost thaw occurs. Vegetation affects shallow soil temperatures via impacts on the surface energy balance, hydrology, and soil characteristics. Vegetation may influence the degree to which soil temperatures rise with increases in air temperature under global climate change. However, variability in vegetative influences on soil temperature are not well quantified at a pan-Arctic scale. We compiled data from 235 sites across high latitude permafrost regions to examine the influence of air temperatures and vegetation on shallow soil temperatures. Annual thermal regimes varied across vegetation types characterized by dominant plant functional cover. The overall magnitude of soil temperature maxima and minima varied across plant functional types. Ecosystems dominated by vegetation with tall statured canopies such as evergreen needleleaf boreal forests and tall shrub tundra tended to have warmer soil warmer temperatures than tundra sites dominated short statured vegetation such as graminoid or short shrub species. Soil temperatures increased with air temperature similarly within tundra vegetation types, and rising air temperatures from global climate change may result in similar increases in soil temperatures regardless of vegetation type in the tundra. Soil temperatures were highly variable and decoupled from air temperature in boreal forest sites.