Journal Article Research Support, Non-U.S. Gov't climate change conifers wood density Northern Hemisphere conifer cambial activity cambium cell differentiation cell production cell wall thickening dendroclimatology generalized additive models (GAMs) growth kinetics of tracheid development meristem photoperiod process-based model quantitative wood anatomy radial stem growth ring width secondary wall formation spring forcing tracheid anatomy tree hydraulics tree rings tree-ring network tree-ring structure winter chilling wood formation