Forest [FAR1]

Distributions of many common species are expected to shift on the broader landscape, but persist in these moist lowlands. Some of these species are tightly linked to moisture availability. Future projections for species in this community may have greater uncertainty because many of these species are less common and there are challenges to modeling wetland habitats. Black ash and eastern hemlock are expected to lose a large amount of suitable habitat under low and high climate scenarios.

This diverse forest community occurs over a wide range of habitats and is widespread and common throughout the interior portion of the Mid-Atlantic region. In general, areas that are north-facing, at higher elevations, or are farther north in the region are expected to undergo less change compared to forests in warmer, drier, or more southerly locations, particularly where past land use, land development, fragmentation, invasive species, or other factors have already impaired the system.

Although prolonged flooding may exceed the saturation tolerance of some species, an increased risk of drought is also a serious threat which many species are not likely to withstand. Changes to the timing and intensity of precipitation events are expected to result in increased flooding, erosion, and sedimentation during precipitation events, as well as potentially increased risk of drought between precipitation events. Hotter and drier conditions could reduce water table levels and water availability to trees.

The physical structure and function of conifer communities create the shady, cool microclimates where they thrive and there are relatively few native conifers to fill this functional role.

Deer use conifer-rich lowlands to avoid severe winter weather, so even low deer populations can be damaging. Changes in herbivore populations may have substantial effects on forest growth and composition. Browsing pressure may increase on hardwood species as northern white-cedar and other conifers decline.

Climate change may amplify several major stressors that are already affecting this forest system. Warmer temperatures may dampen the effects of the eastern spruce budworm, but allow balsam woolly adelgid and hemlock woolly adelgid to increase and spread more easily . Tree susceptibility to insect infestations are expected to increase as trees become moisture-stressed. Studies suggest that insect pests may increase in northern forests due to increased metabolic activity in active periods and increased winter survival.

Peak streamflow is expected to shift to earlier in the spring and increased precipitation is expected to intensify spring peak flows. An increase in intense precipitation is likely to result in more frequent flooding. Reduced precipitation in the summer and fall is may result in drier conditions and a lower water table, which would negatively affect rain-fed ecosystems.

This community has relatively few species compared to other forest communities and many of them are threatened by insect pests. As the current dominant species decline, the functional identity of this ecosystem will be greatly challenged. Some tree species may be more likley to persist or increase through the end of the century , such as red maple.

Multiple forest impact models tend to agree that many species are more likely to decline in suitable habitat and biomass across a range of climate scenarios by the end of the century. These are largely northern species near their southern range limits in the Mid-Atlantic region. Yellow birch and red maple are projected to decline under the high emissions scenario only. Common associate species, such as American beech, American elm, and white ash, may not be able to increase as much as projected due to substantial impacts from insects and diseases.

This forested wetland community is limited to areas that remain wetter and cooler than adjacent uplands. They occur in a range of hydrologic and soil conditions which are expected to be disturbed through increased severe precipitation events and flooding, increased risk of drought, and changes in the water table or relative influence of precipitation versus groundwater. Historical land use has already resulted in altered hydrology in some locations; this legacy will likely continue to stress the system as the precipitation regime changes.