Crown Fires and Greenhouse Gases

We don’t have as much decomposition on the
outside of the tree as opposed to the inside Charred logs, Standing dead tree trunks and
decaying branches mark the site of the Hochderffer Fire that burned hot near Flagstaff. Northern
Arizona University forest ecologists Mike Stoddard and Matthew Hurteau are looking for
a sign, any sign of ponderosa pine seedlings some 15 years after the 16,000 acre fire. We’re concerned about ponderosa pines not
regenerating after these wildfire events. But it’s the invisible damage that the scientists
are learning more about. We have a site here that is not taking up
carbon dioxide and storing it at all right now. We all know trees breathe in carbon dioxide,
but how long they can hold it affects the amount of greenhouse gasses in the atmosphere. This is something that is called an eddy covariance
system. As air flows through the fingers of this claw
like device, NAU tree physiologist Tom Kolb can measure the carbon dioxide that is moving
between the air and the land. The fire has had a long term legacy effect
on the capacity of the site to take in carbon dioxide and store carbon dioxide. Prior to
the fire, this was a dense forest that would take in somewhere between 100 and 200 grams
of carbon per square meter per year. After the fire, now it is actually releasing CO2
to the atmosphere. Remains of intense fires dot the southwest.
This is the site of the Cerro Grande fire that burned 48,000 acres near Santa Fe New
Mexico 11 years ago. Greenhouse gasses were emitted during the fire and live trees that
used to store carbon in the wood are now dead trees releasing carbon dioxide years later. If we reduce the amount of trees per acre
and return fire as a process to the system to manage the surface fuels, the carbon that’s
left in the forest in the live trees is much more stable. Carbon flux research shows that trees in this
thinned forest are inhaling carbon dioxide and less likely to burn up in a high severity
fire, which has scientists breathing a little easier. For Inside NAU, I am Bonnie Stevens with the
Ecological Restoration Institute.

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