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Charcoal hearth soils in Eastern US



Dear forest scientists,

I'm involved in a rather interesting project here at Penn State, and
thought I'd pass along some info to see if anyone out there in
computerland would have any thoughts or experience on the subject. 
First, some background. 

All through the 1800's and into the early 1900's in the Northeast US,
the charcoal-iron industry was operating.  Iron ore would be placed
into large, stone, open-topped furnaces (some of which still dot the
landscape) along with lime and charcoal, and the molten iron would be
collected out the bottom.  The iron companies would make their own
charcoal to fire the furnaces from the surrounding forests.  These
forests were clearcut at about 40 year rotations for 100 to 150 years. 
Up to 20 cords of wood were stacked in a conical pile, covered with
soil, and burned slowly for 2 weeks to produce charcoal.  Since it was
easier to transport charcoal than wood, this coaling process occurred
all throughout the countryside, where ever the timber was cut.  Today,
these "charcoal hearths" can be found quite readily, sometimes several
of them within only a few acres.  The hearths are recognized as being
flat, circular or elliptical areas about 10-15 meters across.  Kick
away the duff and one can see the charcoal residue and black soil. 

Vegetation surveys indicate that most tree species are very
under-represented on these hearths.  In fact, most of the hearths have
no woody vegetation at all.  The soils are up to 70% organic matter
from charcoal dust and fragments.  Tissue-water relations suggest that
trees may be water stressed, despite greater water holding capacity of
the soil. Other early test results suggest that there may be a Mn
toxicity. 

My question is, does anyone out there have any experience with the
effects of charcoal (perhaps from frequent wildfire) on vegetation? 
Any suggestions as to what may cause (possible) water stress in the
plants or the heavy metal toxicity? 

I look forward to any discussion this might produce.



Mark Kubiske                < MEK104@PSUVM.PSU.EDU >
School of Forest Resources
Penn State University




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