Relationship of Eastern hemlock (Tsuga canadensis) to the ecology of small streams in Delaware Water Gap National Recreation Area

Hemlock ravines in Delaware Water Gap National
Recreation Area (DEWA) are highly valued because of their
distinctive aesthetic, recreational and ecological qualities.
We conducted a comparative study designed to determine
the potential long-term consequences to aquatic
communities of the suspected transition from
hemlock-dominated forests to mixed hardwood forests as a
result of hemlock woolly adelgid (HWA; Adelges tsugae)
induced mortality. A landscape analysis of DEWA using
Geographic Information Systems (GIs) was used to select
14 hemlock and hardwood site-pairs that were similar in
topography (i.e., slope, terrain shape, aspect, light levels)
and stream size (first or second order) but differed in forest
composition. This paired watershed approach provided a
powerful means to discern the influence of hemlock forests
on stream communities. This study was designed to provide
an aquatic perspective on potential losses of biological
diversity should hemlock forests die.