Tom's Blog

Sunday, April 21, 2013

Savanna and woods burns

Yesterday afternoon we burned 31 acres of savannas and oak woodlands, thus finishing our upland burns for this season.
Fire line just starting to move into a white oak woods.
The burn will be speeded up by interior lighting. Note how brush-free this woods is.

Oak savanna and woodland burns are challenging. Oak leaves, the principle fuel, burn at lower temperatures, with lower flame heights and slower rates of fire spread. This makes for safer burns, since you can usually walk up to and step over the flaming front. However, burn coverage is often spotty, since fallen logs often block the movement of the burn front. This is why a good, steady, but fairly stiff wind is desirable. However, if the wind is too strong, flame heights can get out of hand, and standing dead trees get ignited.
Flaming fronts of an oak woodland burn. The two lines joined in about 15 minutes. The unit on the left has already burned.
 Yesterday, the weather conditions were ideal for the burns we were doing. There was a steady west wind, the humidity was low but not too low, and the strong sunlight had dried out the fuel. When we first ignited at noon, we were unsure how the woods would burn, but we soon realized we had ideal conditions. Although we had intended to burn only about 10 acres, we ended up burning 31 acres.
The woodland here is mostly in a north-facing gully. Two weeks ago there was still lots of snow here.
 I returned today to assess the burn coverage. Most of the burn units had 90-100% coverage. The only areas that did not burn was where the fuel was spotty or absent. Some of these areas had been sprayed with glyphosate last fall and then overseeded. (We did not want these to burn anyway.)

This spring we burned a total of 80 acres, which includes prairie remnants, planted prairies, savannas, and oak woodland. Considering the challenging weather, we are delighted that we have been able to accomplish so much. We owe this success to excellent burn crews, including a number of dedicated volunteers.


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