American beech dominates, maple abundance declines due to climate change in Northeast forests
The composition of hardwood forests in the northeastern United States is changing significantly. Over the past 30 years in forested areas in four states, climate change has increased the abundance of American beech compared to three other hardwood species commonly associated with regional forests, according to the University of Maine research team.
The significant shift to American beech-dominated forests, Fagus grandifolia, in Maine, New Hampshire, New York and Vermont is associated with higher temperatures and precipitation, according to Arun Bose and Aaron Weiskittel at UMaine and Robert Wagner at Purdue University, the team that conducted the study — one of the first to examined broad scale changes over a long period of time in the northeastern United States and southeastern Canada.
The shift from beech-maple-birch forests to beech-dominated woodlands could have consequences for ecosystem structure and function, the researchers say. Beech is associated with a widespread bark disease and is known to limit the natural regeneration of other species. In addition, the wood has less commercial value.
The significant increase of beech over the past three decades has also led to a reduced incidence of sugarcane, red maple and birch. Factors in changing forest composition include the ability of beech to shade other species.
“Our results highlight the need for management strategies such as higher-intensity harvesting methods, vegetation control, and limiting browsing pressure to reduce beech dominance,” according to the researchers, who published their findings in the Journal of Applied Ecology .
The researchers used US Forest Service census and analysis data, 1983–2014, for Maine, New Hampshire, New York, and Vermont to study the occurrence and abundance of American beech, sugar and red maple, and birch saplings. Their assessment included seedling encroachment in new areas, as well as the abundance of American beech relative to the other three species.
They found beech-dominated forests particularly prominent in the Adirondack Mountains of New York, the Green Mountains of Vermont, and the White Mountains of New Hampshire.
Climate-related changes in forest composition often involve high mortality in sensitive species and disproportionate favoring of others that can better adapt to the new conditions, the researchers note. In the northeastern US, the presence and abundance of beech saplings is likely driven by additional factors, including the long absence of fire and clearcutting and species traits such as shade tolerance.
According to the researchers, forest management must include large-scale harvesting and canopy opening to prevent beech-dominated forests from growing over even larger areas.
Contact: Margaret Nagle, 207.581.3745
