What allows diffuse treelines to respond to regional warming? The role of boundary layer micrometeorology

Our study on Pikes Peak shows that, compared to a treeless area at the same elevation, the interstitial spaces within the diffuse treeline had significantly higher soil surface and subsurface temperatures, higher net sensible heat flux into the soil, and higher air temperature in the boundary layer. The mechanism for the increased treeline heating was thickening of the boundary layer of air (36cm at treeline, 2.4cm in reference area). During up-slope winds the thickening of the boundary layer extended into the treeless area above the treeline. We are currently testing whether abrupt or island treeline morphologies generate different boundary-layer feedbacks.