🚀 go-pugleaf

In article <1993Aug14.001119.5465@news.mentorg.com> jhurst@renfield.mentorg.com (Jim Hurst) writes:
>
>Fire regimes are funny things.  They vary widely in intensity and 
>frequency, even in a single valley.  Clearcuts most closely mimic
>fire in areas where stand replacement fires are common, ie, jack
>pine and lodgepole pine.  Clearcuts do not mimic fire in areas where
>some or most tree species are adapted to survive fires, ie, douglas
>fir or ponderosa pine.
_____________
Well, the subject is really a little more complex than that.  Fire
intensity and type affect the percentage of trees killed, the nutrient
loss and soil disturbance.  For example, low intensity ground fires in
interior B.C. Lodgepole pine forests were thought to be frequent in
history, and because of the frequency prevented large accumulation of
fuel.  Now that suppression is commonplace it is thought that fires are
more intense due to the extra fuel and damage consequently more severe. 
Since the bulk of the mineral nutrients in trees are stored in the
needles/leaves, Crown fires can have a greater effect on nutrient loss at
a local level.  Finally, more intense ground fires can consume ground
level organic matter to the detriment or benefit of the forest, depending
on whether the organic accumulation is itself to the detriment or benefit
of the forest.  It has been argued that fire, prescribed or otherwise, in
some coastal forests provides soil disturbance necessary for the best
regeneration on the site in the reduction of excessive organic matter
accumulation.

Forest fires and clearfelling are similar in that they cause disturbance
to forests.  It is important to recognize the differences in type of
disturbance between them, and the degree.

>The short answer is that site productivity goes down.  Most of trees
>are cellulose.  The mass for this is derived from atmospheric sources.
>It's the trace elements that get depleted:  nitrogen, sulfur, phosporus, etc.
>All very site specific, depending on climate and soils, of course.
>There Germans are the only ones to run this experiment for more than
>a few decades, to my knowledge, and even they didn't think to keep 
>very good controls.  8^)
____________
I have been told that over five centuries or so of hardwood forest
management in Europe foresters have recorded consistent declines in
productivity between rotations.  I gather that this is an ever increasing
problem in forests that are managed very intensively and where debris from
pruning and thinning is used in pulp or energy industry and final harvests
are of the whole-tree type.  The problem is twofold: the conservation of
organic matter in the soil which acts as a moisture and nutrient reservoir,
and the maintenance of site fertility or the management of nutrient
capital.  

Jim is correct when he suggests that the bulk of stemwood is cellulose. 
Most of the mineral nutrients in trees are stored in the leaves and may be
lost if the leaves are removed from the site, or when leaf litter is
burned in wildfire or prescribed fire, such as slashburning.  If there is
a true case of "mining" the forests, it is the example of whole tree
harvesting!  I have yet to speak with a forest ecologist that is not
concerned with this issue.

As far as organic material retention is concerned, forest companies in
B.C. have been and continue to be routinely condemned for "wasteful"
logging practices where uneconomic timber and slash is left behind after
logging.  It looks messy and it looks wasteful, yet it may be ecologically
beneficial.  I am very cynical on this subject as it has been an arrogant
battle cry for some environmentalists who have judged on appearance,
rather than science.  Forest companies do not deserve any credit for
possible benefits, though, as they have certainly not left debris for
ecological reasons either.

>>If it falls into the former category, is
>>it feasible to fertilize tracts of land the size of forests?  
>
>Well, technically, it's feasible from airplanes, ammonium sulfate is one
>thing I can recall getting dumped from planes.
>
>Economically, well, it's hard to justify in most cases unless the taxpayer
>is paying.  Too bad clearcutting and burning destroys all those good
>nitrogen fixing plants.
______________
Probably the best example of economically efficient fertilizer treatments
is in instances where forest sites are found to be lacking in one or two
nutrients but relatively fertile in general.  In these cases restricted
applications may show very good results.  In most cases, however, nitrogen
is the limiting nutrient and nitrogen in forms easily utilized by trees is
also easily leached from soils.

Does clearfelling really destroy N2 fixing plants?  The fixers I know of
are all adapted to suit early seral states (at least on the coast) such as
Red Alder.  What plants are you speaking of, Jim?

>Yeah, but it's mostly carbon, which is easy to come by.  There are more
>subtle effects, however, like starving out soil fauna by not allowing
>recruitment of downed woody debris.  Robert and I will be discussing 
>these in another thread.
_____________
Sorry Jim, I jumped the gun.  Looking forward to another of your colorful
replies, though........:-)


-- 
"There will always be an apologist for Business As Ususal. A pleasure to
meet you, Robert"  _Jim_Hurst_

....Robert Froese  VE7MOQ                          taganov@unixg.ubc.ca