Tom's Blog

Sunday, March 13, 2016

Interesting prairie/savanna burn at Pleasant Valley Conservancy

We did our first burn this year on 11 March 2016. This was the earliest we have ever burned at Pleasant Valley Conservancy, although in 2012 (the infamous drought year) we burned on March 13. (The latest we have ever done our first burn has been 29 March.)

It doesn’t take long for the prairies and ridge-top savannas to dry out, if the sun comes out and the humidity drops to 45-50% and the temperature reaches 60 F. The important thing is to be ready to burn when good conditions do come. It takes Amanda and Susan (and helpers) about a week to get things ready. This means getting all the firebreaks ready, clearing around all the snags and special trees, and getting all equipment ready. (My job was to prepare and submit the spring burn plans to the DNR forester in February, and get the go-ahead on the day of the burn.)

Burning the south-facing slope these years is a tricky task, because the fuel is so lush. The photo shows what the slope looked like at the end of the 2015 growing season.

South-facing slope in October 2015. This was a very good growing year and the fuel is very tall and flammable.

The three dominant grasses (big bluestem, little bluestem, and Indian grass) are tall and lush, very burnable, and capable of producing really high flames. Although the bur oaks are fairly fire resistant, their upper branches are quite capable of catching on fire. Mop up could therefore be a real problem.

The answer is to carry out the whole burn as a backburn. The slope is steep and therefore more important than the wind, so the backburn has to start from the top. This year we had a crew of 13, mostly hired contractors, plus a few volunteers. Amanda ran the burn, as she has done the past three years.

The first photo shows the start of the burn, at the top end of the slope. We need very little water but lots of drip torches, especially to broaden the blackline and cover all the territory. (The total area burned was 27 acres.)

Start of the burn, 11 March 2016 at the top of the ridge.
The next photo shows a later stage when most of the top of the ridge was black and the fire line was starting to move down the hill. People with drip torches were making sure that the whole line was on fire.

After the whole top of the unit was on fire, and the fire breaks at both ends blackened, most of the time was taken with watching and waiting, while the backburn moved slowly down the hill. 

The next photo shows the fire line about half way down the hill.
Fire line gradually "backing" down the hill. The vehicles are being moved away.[Susan Slapnick photo]

A later photo from the bottom of the hill shows the fire line about to put itself out as it runs out of fuel. Most of the later stages of the burn occurred while the burn crew ate lunch, because there was nothing to do but wait.

Fire about to put itself out at the bottom of the hill.

After lunch we burned all the planted prairies that were adjacent to Pleasant Valley Road. These burns took place fairly quickly, as they were burned as conventional prairie burns, ending mostly as spectacular head fires.

The next photo is a view from the top of the ridge the next day, showing the black south slope and a couple of the planted prairies.

View from the top of the ridge showing several planted prairies that had been burned taken the day after the burn.

The final photo shows another view from the top, the day after the burn.

The fire break is visible at the left side of the photo

Although this was not a large burn, it was a complicated one. Because we are burning through an old-growth forest, with many venerable trees, we are especially careful to protect their branches from catching on fire.

In all, a very successful burn. We'll be burning the rest of our ridge-top savannas as soon as conditions permit.


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