Warming-driven shifts in dominant tree species potentially reduce aboveground biomass in northeastern United States forests

Abstract

Forest ecosystems play a critical role in the global carbon cycle. However, climate change may shift the geographic distribution of numerous tree species and alter the capacity of forest ecosystems to store carbon. The forests in the northeastern United States, characterized by their diverse tree species and complex structures, have experienced climatic changes in recent decades and are particularly vulnerable to these changes. Given that tree species vary in their carbon storage capacities, understanding how forest composition influences aboveground biomass (AGB) is crucial for assessing the impact of climate change on forest carbon storage. In this study, we synthesized plot-level forest inventory records (n = 27,858) to evaluate the influence of forest composition on AGB in the northeastern United States. Our results indicate that dominant tree species are the primary feature of forest composition most strongly correlated with AGB across all successional stages, exceeding the influence of species diversity and evenness. Projected climate warming in this region is likely to alter these dominant species. Although this shift may increase the abundance of hardwood species, which generally have higher wood density, the plot-level AGB is projected to decrease due to changes in forest structure introduced by the new dominant species. These findings highlight the important role of dominant tree species in determining forest biomass and suggest that warming-induced shifts in dominant species could reduce the carbon sequestration capacity of forests in the northeastern United States.