Doane Rock: Prescribed Burn 5

Our fifth prescribed burn took place in the afternoon of the same day we conducted our fourth. Tactically, it was considerably more involved than the burn in the morning. Again, we split into two groups and walked the two flanks of the burn area laying down boxes of flame in tandem. However, this time we also lit point ignitions in the interior of the burn area. This strategy, coupled with our use of a backing fire throughout the burn, led to a much more complete burn than we achieved earlier in the day.

Our flank of the burn area. Like the first burn of the day we spread the flame by making consecutive rectangles of fire. Each rectangle, once its center had burned out, contributed to the line of black earth insulating the active fire from the area we did not intend to burn.

Our flank of the burn area. Like the first burn of the day we spread the flame by making consecutive rectangles of fire. Each rectangle, once its center had burned out, contributed to the line of black earth insulating the active fire from the area we did not intend to burn.

It was remarkable to me how efficient “drawing” the rectangles on the ground with the drip torch was at creating a solid black perimeter. Once the rectangle is drawn the heat from the flames causes the air in its center to rise quickly, air from outside the rectangle then blows in to fill the space. This constant inwards wind creates head-fires all around the rectangle. As I may have mentioned, head fires (fires in which the flames are bent over unburned fuels) burn faster (though less completely) than backing fires. Since the rectangle strategy creates a ring of head-fires, it creates the desired black perimeter faster than the alternative.

The slowly advancing flame front was carefully guided around the botanical signposts within the burn site.

The slowly advancing flame front was carefully guided around the botanical signposts within the burn site.

The alternative to the rectangle strategy is simply lighting a long line of fire using the drip torch. On the one hand you use less than half the fuel, but on the other it doesn’t burn nearly as quickly (nor, in my incredibly limited experience, so well).

This is what our flank of the burn looked like after the fires had been put completely out. This burn, because we relied on a backing fire rather than a head fire, removed more of the fuel (the dead wood, leaves, and flammable loam) than the first fire of the day did.

This is what our flank of the burn looked like after the fires had been put completely out. This burn, because we relied on a backing fire rather than a head fire, removed more of the fuel (the dead wood, leaves, and flammable loam) than the first fire of the day did.

Hopefully, now that Winter is gone (at least as far as the calendar is concerned) we’ll be able to do more of this, it beats the snot out of shoveling.

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Posted on March 26, 2013, in Americorps Cape Cod and tagged , , , , , . Bookmark the permalink. 1 Comment.

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