Geoscience Reference
In-Depth Information
Figure 8-30.
Smoke plume from prescribed burning of cattails and other emergent vegetation at the state Cheyenne
Bottoms Wildlife Area, central Kansas, United States. Such burning requires dry conditions and is usually carried out
in late winter or early spring in order to remove standing thatch from the previous year. Blimp airphoto by J.S. Aber.
peat i res covered Moscow with smoke for
weeks. In this case, the problem was com-
pounded by past drainage and mining of peat,
which left the remaining peat dry and especially
susceptible to i re (Pollowitz 2010). In the
western United States, extreme i re years are
related to Pacii c Ocean circulation anomalies
(Littell, Peterson and McKenzie 2010).
Regarding the peatlands of Alaska and north-
ern Canada, warmer and drier climate could
lead to lower water levels and more frequent
i res, which “could accelerate greenhouse gas
emissions and cause much of the stored soil
organic matter to be released back to the atmos-
phere” (Turetsky 2010). On the other hand,
removal of forest cover by i re leads to a long-
term increase in albedo, as the exposed ground
is more rel ective than forest canopy. In the case
of boreal forest i re, Randerson et al. (2006)
found that long-term increase in surface albedo
was more signii cant climatically than the release
of CO
2
, and they concluded that increased
boreal forest i res might not affect global
warming.
In a comprehensive investigation of boreal
peatland in northern Manitoba, Canada, Camill
et al. (2009) compared carbon accumulation
rates, i re severity, and vegetation composition
over the past 8000 years. They found that shifts
in i re severity and carbon accumulation lagged
behind changes in climate and vegetation and
concluded that i re severity and carbon accumu-
lation are mediated by changes in vegetation as
a consequence of climatic shifts. On the basis
of these examples, i res may have dramatic
impacts on wetland vegetation and soil, and
burning peat may generate spikes in green-
house gases. Over the long term, however, the
roles of i re, wetlands, and climate change are
less well understood and may have distinct
regional variations. What is abundantly clear is
that human-caused i res have accelerated the
release of greenhouse gases and conversions of
land cover that increase albedo. The climatic
consequences of these contradictory factors
remain to be seen.
8.6 Summary
Wetlands are dynamic environments that change
through time in response to internal (autogenic)
processes and external (allogenic) factors. The
balance between autogenic and allogenic effects
depends on magnitudes and rates of various
processes working within and upon wetlands.
Five primary factors for wetland development
and change are climate, geomorphology, geology
