Functional shifts in natural forests under environmental change over the last 65 years are faster in colder regions

Abstract

Global environmental changes have significantly impacted plant diversity and composition over many decades. Maintaining biodiversity and composition is critical for sustainability of ecosystem functioning and related services. While global environmental changes have modified plant species and functional compositions in forest ecosystems, it remains unclear how temporal shifts in functional composition differ across regions and biomes. Utilizing extensive spatial and long-term forest inventory data (17,107 plots monitored 1951–2016) across Canada, we found that functional composition shifted toward fast-growing deciduous broadleaved trees and higher drought tolerance over time; notably, this functional shift was more rapid in colder regions. Further analysis revealed that the functional composition of colder plots shifted toward drought tolerance more rapidly with rising CO2 than warmer plots, which suggests the vulnerability of the functional composition of colder plots against global environmental changes. Future ecosystem management practices should consider spatial differences in functional responses to global environmental change, with particular attention to colder plots that experience higher rates of warming and compositional changes.