See how fast wildfire spreads - Texas Parks and Wildlife

Discussions of forest fires and fire management.

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edfrank
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See how fast wildfire spreads - Texas Parks and Wildlife

Post by edfrank » Tue Sep 13, 2011 11:00 am

See how fast wildfire spreads - Texas Parks and Wildlife [Official]

http://www.youtube.com/watch?v=vhJeDYQVtdQ&feature=player_embedded#!

Uploaded by TexasParksWildlife on Sep 6, 2011

Video shot September 5, 2011 on the north edge of Bastrop State Park near Austin. All but about 100 acres of the 6,000-acre park have been blackened by fire. Firefighters have been battling blazes for 3 days. At this point, historic CCC buildings are still intact. For more information, see http://www.tpwd.state.tx.us/

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jamesrobertsmith
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Re: See how fast wildfire spreads - Texas Parks and Wildlife

Post by jamesrobertsmith » Tue Sep 13, 2011 12:11 pm

Wow. That's really scary. I assume since the fire is so fast-moving that it's not necessarily killing the trees?

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Lee Frelich
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Re: See how fast wildfire spreads - Texas Parks and Wildlife

Post by Lee Frelich » Tue Sep 13, 2011 1:27 pm

James:

This might be more details than you want, but here it is anyway.

Basal scorch can kill a tree if most of the circumference of the cambium at the base is killed. For conifers and oaks with thick bark, the fire would have to last a long time for heat to penetrate the bark to living cambial tissue underneath (basically, number of minutes of exposure to heat from fire necessary to kill cambium = 2.9 x bark thickness in cm squared). so for 1 cm thick bark, thats 2.9 minutes, 11.6 minutes for 2 cm bark and 26 minutes for 3 cm bark. Based on that I would say the larger conifers in the video will survive.

However, there is also mortality from crown scorch--foliage killed by rising hot air above the flames. Foliar scorch is very important for evergreen species like pines and spruces with long leaf life spans (2-8 years), whereas its not very important for deciduous trees that will lose their leaves whether there is a fire or not. One minute at 60-70 degrees C will kill foliage. The height of foliar scorch is 0.094 I ^^2/3. Fireline intensity, I, in Kw/m is directly related to flame height. Based on the flame height and tilt in the video, I would say that scorch will occur up to about 20 feet, so that 30-50% of the crowns might be scorched. Based on relationships between percentage of the crown with scorched foliage and mortality, 30-50% crown scorch for pines means fairly low mortality on the range of 5-10%.

Its hard to tell what the extent of basal and crown scorch is until some weeks later. Lots of models have been published that predict mortality based on the extent of basal and foliar scorch in conifers, and based on height of trunk char in deciduous trees.

Lee

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Marcboston
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Re: See how fast wildfire spreads - Texas Parks and Wildlife

Post by Marcboston » Thu Sep 15, 2011 10:17 am

That was awesome! So is Lee's response.

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jamesrobertsmith
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Re: See how fast wildfire spreads - Texas Parks and Wildlife

Post by jamesrobertsmith » Thu Sep 15, 2011 5:23 pm

Thanks, Lee! Very informative! Now I know!

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