Fire behaviour researchers were measuring "woody fuel" before it became more
generally known as Coarse Woody Debris. The fact that we still call it
"debris" says something about its origins and our inability to come up with
a more appropriate term.

Snags play a role in fire behaviour as they can be struck by lightning,
shatter and spread burning material to the forest floor. They can also
smoulder for quite some time and thus start a fire several days after being
struck by lightning. Snags are often ignited from surface fires at their
base and then spread fire into the adjacent live tree canopy, creating a
crown fire.

Fine woody debris on the ground is responsible for fire ignition and spread,
while larger down debris burns longer, depending on the decay class and
moisture content, and contributes to the increase in temperature experienced
by the underlying soil horizons as well as determining the longevity of the
fire (known as "residence time").

Fire researchers have been interested in snags for quite some time but they
probably didn't quantify them as much as they did down dead fine fuels,
especially present as logging or thinning slash.

In our standard ecological inventories, snags are considered to be part of
the total deadwood but not inventoried as CWD per se. It's a somewhat
artificial distinction introduced to separate the sampling into components
and avoid double-counting a standing dead tree as CWD and as a standing dead
tree.

We have no minimum length criteria to define CWD but some have used 1.5 m
(and > 10 cm diameter). When we measure piece length it's to the nearest
0.1 m.

One of the first summaries on the role of snags is:

Thomas, J.W., R.G. Anderson, C. Maser and E.L. Bull. 1979. Snags. In J.W.
Thomas (technical editor). Wildlife habitats in managed forests: the Blue
Mountains of Oregon and Washington. USDA Forest Service Agricultural
Handbook No. 553. pp. 60-77.

but there doesn't seem to be a version of that chapter on the web. This is
useful but lacks a literature cited:

http://www.fs.fed.us/r6/nr/wildlife/animalinn/hab_wlsnag.htm

more topics on that site are listed here:

http://www.fs.fed.us/r6/nr/wildlife/animalinn/habitat.htm

Much of the literature on snags and snag management is from the Pacific
Northwest.

Regards,


John Parminter, RPF
Research Ecologist
Research Branch, Ministry of Forests

Phone: (250) 356-6810
Fax: (250) 387-0046

mailto:John.Parminter@...

P.O. Box 9519 Stn Prov Govt
Victoria BC V8W 9C2

Website: http://www.for.gov.bc.ca/research/