Journal Article Research Support, Non-U.S. Gov't 059QF0KO0R Water sapwood Allometry Arctic amplification Research Support, U.S. Gov't, Non-P.H.S. allocation calibration carbon allocation climate change climate-growth association conduit widening functional balance heartwood hydraulic conductance hydraulic model leaf area night-time transpiration plant architecture ring width sap flux density sapflow structural balance thermal dissipation probes transpiration tree and shrub tree growth tundra vegetation