Tom's Blog

Thursday, November 17, 2011

Late fall burn

We had planned to do a late fall burn but conditions had not been favorable until today. We needed a couple of hard freezes to set back all this year's vegetation and then a warm sunny day with relatively low humidity. We got the hard freezes, the sun, and the low humidity, but not the warmth, but it appeared that if we didn't burn now, we would lose our chance.

Our principal goal was a good burn of the Sandhill Crane Wet Prairie, and this we got. This prairie had a very lush stand of Indian grass this year, and this species carries a fire quite well. However, we had a strong wind out of the west, and because the Crane Prairie runs NW/SE, the wind was blowing across the narrow part of the prairie, making the burn a bit tricky. The map below shows the Crane Prairie outlined in orange, and the wind direction. (Double click to enlarge the map for more detail.)
One drip torch backburned down from Pleasant Valley Road and the second drip torch created a big series of short head fires from the west fire break. We did not want to light a single fire line along the west fire break because this would create a huge fire. As can be seen in the map above and the photo below, upwind of the Crane Prairie was our whole south-facing slope, with about 20 acres of very flammable prairie grass. We certainly did not want to burn this!

In order to keep the fire relatively small, we lighted in strips. This worked, although it was time consuming. (It took us almost three hours to burn this 3-acre prairie!) We had a crew of seven.

Doing a burn in such cold weather is tricky. The temperature during the night had fallen to the mid 20s and when we arrived at 9 AM the temperature was still only 30 F. Since we needed a lot of water, we reactivated our water pump which had been drained in September. Since well water has a temperature of about 50 F, we did not have to worry about our backpack water cans freezing up. We started to light about noon, at which time the temperature had increased to 37 F and the relative humidity was in the upper 40s. An hour later the temperature was still the same but the R.H. had dropped into the 30s. By the time we finished at 3 PM the sun was starting down and the R.H. was on its way back up. Fortunately, we were able to get our burn finished during this narrow window.

Another problem we had was that there were several buildings at the downwind end of the Crane Prairie, and we had to protect them. Therefore, the first thing we did was to burn around these buildings. Even with extreme caution, we still almost came to grief, as a shingle on the roof of the historic corn crib got hit by a burning ember. Fortunately, it could easily be put out.

One of our reasons for wanting to burn the Crane Prairie this fall was that there had been a large infestation of pale Indian plantain, the clonal and highly invasive composite that we are trying to eradicate. This species appears early in the spring, producing large rosettes, which will be very visible in the bare prairie and easily herbicided. If we had not burned, the plantain would have been hiding under all the prairie debris and would have been lots more difficult to spray.


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