One of the central questions
around regenerating oak is
how much light is needed
for the seedlings to reach
sapling stage and subsequently
become part of the over-
story (Rebbeck
et al. 2011).
In rural forest management,
thinning forested stands to
increase the amount of light
that reaches the forest floor
is a common practice that can
enhance oak regeneration. For
urban forest managers, cutting
mature trees is often illegal,
and usually frowned upon
by the public. Consequently,
in our study we capitalized
on existing, natural gaps
in forest canopy. Gaps are
created by the loss of large,
canopy-dominant trees due
to windstorms, insects and
disease, or old age (Figure 3).
Climate Adaptation and Assisted Migration
Forests are not static; trees disperse, and the range of each
species expands, shrinks, or migrates over time. In forests
of the Eastern U.S., the range of a species may only move
10 miles (16 km) per decade on its own (Fei et al. 2017). As
climate changes, many species may be challenged to keep up
with warming temperatures. As a result, trees in a given loca-
tion today may be maladapted to the climate of tomorrow.
One possible management strategy to combat these climate
change impacts is assisted forest migration, which may involve
moving (a) genes or provenances of a species within a range
(i.e. assisted population migration), (b) expanding migration
just outside of the natural range (assisted range expan-
sion), or (c) moving species to an entirely different location
(assisted species migration). Due to the Urban Heat Island
effect, cities are already 5-7 degrees warmer than nearby non-
urban landscapes (Figure 2). Consequently, cities provide a
dynamic testbed for assisted migration studies and findings
that may have relevance to future rural forest populations.
Figure 3. Max Piana surveying an existing canopy gap in New Haven, Connecticut.
30 CityTREES
