the closed canopy, late successional mixed-pine stands
dominated by long-lived red pine (Pinus resinosa) and
eastern white pine (Pinus strobus).
Although drastically different in terms of structure and
composition, these forest ecosystems share similar
sandy soils, a reliance on fire, successional states, and
many species of wildlife. However, differences in the
severity and the return interval of disturbances (the
latter often a result of management objectives) can
yield contrasting forest conditions. More frequent and/
or more significant disturbances (e.g., stand replacing
fires or clearcuts) yield different vegetation patterns
and habitats for different wildlife species compared to
infrequent surface fires or partial harvests.
Cautionary Tale of Warblers
The challenge of managing forests altered by changes
in the natural disturbance regime is particularly
acute in Michigan, where the endangered Kirtland’s
warbler breeds. This species evolved to breed within
a habitat influenced by wildfire. Fire opens jack pine
cones for seed dispersal and prepares the soil surface
for the seeds to germinate. Years of fire suppression
and other changes in land use have led to a loss in appropriate habitat and a dramatic population decline
of Kirtland’s warblers: In 1971, only 201 singing males
were counted in Michigan (Probst et al. 2005).
Although prescribed or managed wildfire would yield
the most “natural” breeding habitat for the birds,
changes in land use make broad-scale application of
fire untenable in Michigan’s northern Lower Peninsula, where most of the birds breed. Consequently, most
warbler habitat management involves clear-cutting
mature jack pine, then trenching and densely planting
these sites with jack pine seedlings in an “opposing
wave” pattern (see photo). Akin to the way natural
wildfire would move across the landscape and produce
large patches of burned-over land, these plantations
are managed as multiple-square-mile patches with a
rotation age that approximates natural return intervals
for stand-replacing fire events (Frehlich 2002). This
type of jack pine plantation management has resulted
in an unprecedented nine-year run in which the global
population of singing male warblers exceeds the
established recovery objectives of 1,000 singing males.
In 2009, nearly 1,800 singing male warblers were
counted in Michigan alone. Breeding birds are also
now found in neighboring Wisconsin and Ontario (see
photo on page 38).
Research has shown a downside to this single-species
approach, however. By placing such an emphasis on
habitat variables important for Kirtland’s warblers and
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not emulating patterns of natural disturbance, management has produced monotypic plantations with
drastically simplified structure compared to stands
generated by wildfire. Indeed, the typical biological
legacies of fire-produced stands—such as residual
live trees, dead standing trees or snags, and downed
coarse woody debris—are nonexistent or significantly
reduced (Spaulding and Rothstein 2009). Such
homogenized conditions do not bode well for many
ecological processes (LeDuc and Rothstein 2007).
Fortunately, because Kirtland’s warbler population recovery objectives have been met for the past nine years,
a more ecological approach to
the species’ habitat management may now be possible. We
suggest that the focus of future
management should be to
emulate patterns of wildfire. In
doing so, the judicious application of prescribed fire should be
used, especially in landscapes
with large contiguous blocks of
public land (Wilson et al. 2009).
It is also important to note that
plantations do not necessarily restore habitat, but instead
provide a surrogate condition
for breeding birds. Plantations
are therefore not a ‘silver-bullet’
for the management of jack pine
forest ecosystem types.
That said, plantation manage-
ment for Kirtland’s warbler
habitat will still be necessary,
and in this vein we suggest that future habitat man-
agement take the following approaches:
• Consider the dynamic nature of jack pine forests
and manage for the range of successional states and
associated structure of jack pine ecosystems. Of
these, perhaps the most imperiled is the openland-
dominated jack pine barrens (Houseman and
Anderson 2002).
• Set aside large-scale (hundreds of acres) openings
for the rotation age (estimated time of harvest) of
the nearby plantations, with both managed as a
shifting mosaic of barrens and plantations across
the landscape. Doing so would help restore pre-Euro-American landscape structure that has been
degraded by changes in land use. Such management
would also benefit many openland wildlife species,
such as upland sandpiper (Bartramia longicauda)
and sharp-tailed grouse (Tympanuchus phasianel-lus) (Corace et al. in press, a).
Credit: R. gregory Corace iii
With its bark
mechanically stripped
off in a process called
girdling, this pine will
die and create a snag—a
potential future home for
woodpeckers and other
wildlife in the Kirtland’s
Warbler WMa. Such
techniques help vary the
structure in monotypic
jack pine plantations,
mimicking historic
disturbance patterns
and enhancing species
diversity.
