Data from: A three decade assessment of climate-associated changes in forest composition across the north-eastern USA

1. Climate-associated changes in forest composition have been widely
reported, particularly where changes in abiotic conditions have resulted
in high mortality of sensitive species and have disproportionately favored
certain species better adapted to these newer conditions. In the
northeastern USA and southeastern Canada, few studies have examined
climate-related influences associated on forest composition, and none have
considered broad-scale changes over a long temporal (>25 years)
period. 2. We used US Forest Service Forest Inventory and Analysis data
from 1983-2014 across four northeastern states (Maine, New Hampshire, New
York, and Vermont) to assess temporal and spatial changes in the
occurrence and abundance of American beech, sugar maple (Acer sacharum
L.), red maple (A. rubrum L.), and birch (Betula spp.) saplings. We also
tested the effects of biotic and abiotic factors on the distribution of
the four studied deciduous species over the entire studied period. 3.
Occurrence and abundance of American beech have increased substantially
over the past three decades, whereas the occurrence and abundance of
three-other deciduous species have decreased in all ecological provinces
of the northeastern USA, except the Midwest Broadleaf ecological province.
Consequently, a clear shift in species composition is currently underway
in the beech-maple-birch (BMB) forests of the northeastern USA, with
uncertain consequences for future ecosystem structure and function. 4. In
the studied region and over the entire studied period, the distribution of
increased occurrence and abundance of beech relative to three-other
deciduous species were associated with the higher temperature and
precipitation as well as higher conspecific basal area and dead tree basal
area. 5. Synthesis and applications: The change from BMB forests to
beech-dominated forests and beech encroachment to new forest areas across
the northeast may expand in areas where higher intensity
harvesting/disturbances (i.e., large-scale canopy openings) do not occur,
which would be a management concern as the beech is associated with the
beech-bark disease. Our results emphasize the need for management
strategies such as higher intensity harvesting methods, vegetation
management, and controlling browsing pressure to reduce the beech
dominance.