Changes in soil chemistry after forest fires?

Al Stangenberger forags at nature.Berkeley.EDU
Mon Nov 24 21:04:17 EST 1997

Don Staples (dstaples at wrote:
: Al Stangenberger wrote:
: f.
: > 
: > Under some conditions fires can make a soil surface hydrophobic (presumably
: > some volatile organic compounds from combustion condense on the soil
: > surface).  This can affect infiltration.  Leonard DeBano of the US Forest
: > Service has done quite a bit of work on this in chaparral systems in
: > southern California.
: > 
: Interesting, have never found that in Texas, usually after a burn
: infiltration is increased (faster rate) do to the removal of the heavy
: litter, letting the water go through a more porous medium. This is all
: predicated on the burn being done correctly, and not a scorched earth
: attempt.   Would one suspect less volital waxes, oils, turpins, etc, to
: have condensed on the remaining layer?

That's the idea.  Actually I mis-spoke in my initial posting -- the 
hydrophobic layer forms a few inches down in the soil where temperatures
are lower.  In other words, the waxes, oils, etc from plant material and
litter are vaporized during the burn, the vapors penetrate down into the
soil, and the water-repellent material condenses on a lower layer of soil

The effect has been noted in chaparral soils of southern California.
For a brief description and some references, check

: My Ego Stroke:

Al Stangenberger                      forags at            
Dept. of Env. Sci., Policy, & Mgt.    145 Mulford Hall # 3114
Univ. of California at Berkeley       Berkeley, CA  94720-3114
(510) 642-4424  FAX: (510) 643-5438   

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