In reply to David Martell's posting with the following comment from
J.P. Kimmins: "They concluded that in many forests,
clearcutting, done appropriately, provides the closest mimic to
natural disturbance."
I am not aware of comprehensive investigations comparing clearcutting
with natural fire either, but I think it's possible to get a pretty
good answer to the magnitude of the issue by thinking it through.
Fire differs from clearcutting by leaving standing snags (and future
logs) on site, by not compacting the soil, and often by removing much
of the forest floor. Are snags and logs important to wildlife and
site productivity, is compaction a problem, or do litter layers limit
plant establishment? To the extent that the answer is yes, and you
care about it, then clearcuts are different from fires. Beyond that,
the differences depend on "typical" fire patterns and logging methods.
Often fires do not kill all the trees on site, providing onsite shade
and seed sources. The difference between fire and clearcuts for
onsite nitrogen will depend on fire intensity, whether clearcuts are
burned, and whether whole-tree harvesting removes nutrient-rich
foliage. If all you're interested in is growing trees in the short
term and your species don't benefit from "dead shade" or decayed woody
substrates, then clearcuts are pretty good mimics. I hate to conclude
that "it depends", but your land-use objectives, your natural
disturbance regimes, and your harvest systems will determine what
"mimic" means.
It's important to add, however, that "natural disturbance" is not
limited to catastrophic wildfire, and that clearcutting is in no way
similar to wind-throw, beetle-kill, landslide, flood, drought-induced
mortality, etc. that can be very important for particular species in a
forest system.
I do have citations for studies of the effect of different harvest
methods (e.g. burn or no burn), and of the role of structural legacies
following natural disturbance in coastal Douglas-fir if they would be
relevant to your boreal systems.
Andrew Gray
Oregon State University
graya@fsl.orst.edu
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