Journal Article Research Support, Non-U.S. Gov't climate change Arctic Arctic greening Meta-Analysis N762921K75 Nitrogen Research Support, U.S. Gov't, Non-P.H.S. Salix lanata Soil carbon cycle climate constraint dendroecology earth system model eddy covariance extreme events fitness gross primary productivity law of minimum meta‐analysis model-fitting model-selection nitrogen limitation ordinary differential equations photosynthetic seasonality plant-resource coupling rain‐on‐snow remote sensing stable isotopes