Tom's Blog

Wednesday, February 16, 2011

Dealing with brush piles

Almost any prairie or savanna restoration project ends up creating lots of brush piles. One or two piles might be left as wildlife habitat, but if you have a lot of piles you must get rid of them by burning.

This is the time of year to burn brush piles. Here is the regulation, copied directly from the Department of Natural Resources web site: "For areas where the ground vegetation is completely snow-covered and will remain so for the duration of the burn, a DNR burning permit is NOT required. You may burn at any time, on any day."

We had four rather large piles that were created late last fall along the fence line in Unit 13, which is a fine open white oak woodland. These piles were created when removing several large dead oaks that were right along the property boundary. We needed to clear out all this dead wood so that when we burned in the spring, there would be no standing dead smokers. Fence lines are always a problem, since they are difficult to clear, and make lousy fire breaks. The photo at the top shows one of these piles that, thanks to Integrated Restoration, was well built. (Note how tight and compact this pile is.)

We also had about a dozen smaller brush piles that were left over from the East Basin restoration. These were easier to deal with.

The safe way to light such a pile is with a good supply of drip torch fuel (2-3 diesel to 1 gasoline). We carry the fuel in a stainless steel sprayer which can be pressurized and has a long brass wand. A little fuel is first dropped inside one edge of the pile and a lighted match tossed in. Since the fuel is mainly diesel, it isn't too flashy, although the person with the match must be quick to pull back. Once the starter is lighted, fuel can be sprayed farther into the pile, driving the fire with it.

With dry snow-free wood, a pile usually starts burning quickly. The pile in the photo to the left, for instance, was lighted about 10 AM and after lunch was mostly burned down.

It is good to get all the piles started in the morning since it takes quite a while in the afternoon to consolidate the remains of each burning pile. It helps to have a pitch fork or heavy shovel to pick up any burning pieces and toss them into the center of the pile. (Leather gloves are essential!) Usually, if all the burning pieces are piled in the center, the following day there should be nothing left except ashes.

I am often asked what effect the fire has on the soil underneath. Is the soil sterilized, and will any plants grow? Actually, there is little harm. Soil is a poor conductor of heat so that only a thin area on top gets very hot. The main problem is the residue of ashes, which keeps seeds from reaching the underlying soil. We use a good leaf blower to scattered the ashes, and then plant the burn scars with a good prairie or savanna seed mix. Within a year or so, there will be no trace of the burn sites.


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