[permaculture] questioning Douglas-fir thinning

Toby Hemenway toby at patternliteracy.com
Thu Mar 13 14:45:15 EDT 2008


Marimike6 at cs.com wrote:
> Not certain of the status of Douglas firs on the West Coast. But lodgepole 
> pine along the continental divide are nearly all dying or dead by now due to the 
> practise of allowing uninhibited dense growth. Near-monocultural stands of 
> these trees has encouraged the mother of all pine beetle infestations. Forest 
> rangers have told me it could be a couple of centuries before the natural 
> succession again returns these lodgepoles to the top of the ecological heap.
I've been re-reading my copy of Panarchy (by Lance Gunderson) and the 
pine-beetle infestation above reminded me of their story of the spruce 
budworm "damage." Forestry in much of North America is only old enough 
to have been through one cycle of the spruce budworm, which takes about 
40-140 years, so when it happened everyone thought it was the end for 
spruce-fir forests, since it defoliated a good 80% of the trees in some 
places, with kills nearly as large.

It turns out that in young forests the budworms are visible to predators 
and are kept in check.  This state is stable for many decades, but as 
the trees grow and foliage fills in, the larvae have more places to 
hide. They build to numbers that suddenly "release," in the language of 
complex adaptive systems, and kill large swaths of trees. This recycles 
enormous amounts of carbon into the soil, and in many ways sets the 
stage for the next generation of forests. The density of tree farms 
probably speeds up this cycle. Researchers are finding this kind of 
exploitation/release cycle in many places, such as the honey mushrooms 
that can kill hundreds of acres of forest. We see it as devastation, 
while it appears to be a very benevolent cycling that is on a scale a 
little too big, in both space and time, for us to grasp.

Toby
http://patternliteracy.com





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