Long-term development of transition hardwood and Pinus strobus - Quercus mixedwood forests with implications for future adaptation and mitigation potential

•Forest development was examined for climate adaptation and mitigation potential.•Mixedwood stands had high diversity (functional, structural) and biomass.•Hardwood stands were compositionally stable, but mixedwoods transitioned.•Ingrowth are more vulnerable to future climate threats than overstory species.•Loss of mixed species stands reduces adaptability and associated climate benefits.