I made a trip down to our Rulo Bluffs Preserve last week. I wanted to get down and see the results of the prescribed fire we conducted earlier this spring. We’re in a restoration mode at the site, trying to re-open the woodland and increase the amount of light hitting the ground. The day we burned the site this spring, the relative humidity was very low, so the fire was a little hotter and burned a higher percentage of the unit than we’d seen in previous burns. Killing small trees and brush with a nice hot fire was good for our objective. On the other hand, I worried a little that we might have cooked some of the bigger trees we wanted to keep.
A panorama (four photos merged together) along the edge of the burn unit. The area burned this spring is to the left and the unburned is to the right.
Overall, I was very pleased with what I saw last week. The fire, combined with some recent “hack-and-squirt” herbicide treatments on smaller trees has done a great job of increasing the amount of light hitting the ground. At the same time, the majority of larger trees were still alive and leafing out, maintaining a fairly complete canopy – but one that allows for mottled light to hit the ground throughout the day. We hope to continue annual, or at least very frequent, fires for the next several years to set the woodland back on the trajectory we want. Then we may back off on the fire frequency a little. Eventual success will be measured by whether we see an increased abundance of wildflowers, sedges, and grasses on the woodland floor, and – more importantly – regeneration of oak trees, which is crucial for the survival of the woodland itself.
Here are some photos of this year’s spring fire, as well as what I found during my walk through the site last week.
Firebreaks for the fire were mostly created by using a power leaf blower to clear out a narrow trail. Nelson Winkel is shown here making a final pass around the breaks of the 100 acre burn unit. Other members of the crew followed behind, raking out any other debris that needed to be cleared from the breaks.
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Anne Stine lights down a slope during the fire.
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The fire burned a little more intensively than most woodland burns we’ve done at the site, but nothing like a prairie fire – though it got pretty hot as it went up some of the steeper draws where leaf litter had accumulated and slopes helped drive the fire. Crew members patrolled the narrow breaks constantly during the burn, checking the fire, raking leaves and sticks in, and looking for dead trees burning along the edge of the unit that might need to be taken down.
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This stitched multi-photo panorama shows the largest of the prairies at Rulo Bluffs, along with some of the woodland. The photo(s) were taken from our neighbor’s pasture during the fire.
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This area burned fairly completely but there were still small unburned patches here and there.
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We were able to use ATVs to access some portions of the firebreaks, but others were too steep and/or narrow, and were accessible only on foot.
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This panorama shows approximately the same area as Anne was lighting in the earlier photo. The right half of this image was burned, the left was not. Note how much more open the burned area is.
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Burned on the left, unburned on the right. Wood nettles seem to be having a banner year in both burned and unburned areas. I’m not sure why that is.
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More wood nettles (and other plants) – this time on a southeast-facing slope that burned pretty hot. Note the dead (or at least top-killed) small diameter trees.
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Wood nettles were most abundant on lower slopes. Higher up, mayapples, sanicle, and other plants were more common. Here, mayapples grow with little company. That will change as the plant community adjusts to an environment with more light availability. The fire wiped out this year’s crop of garlic mustard. Hopefully, maintaining a high fire frequency in coming years will help suppress that invader.
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Here is a south-facing wooded slope with a lot of bare ground. Again, this will change over time as light-loving plants colonize and spread. Here, many of the small trees were dead prior to the fire (from the hack-and-squirt treatment.
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Columbine was blooming on north-facing slopes – mainly in places the fire skipped.
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A close-up of columbine.
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Yellow ladies slipper orchids seemed to weather the fire just fine. I found all four of the plants we marked with GPS last year, and three of them were blooming. All four were in areas that burned.
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Here is the same prairie (left) and neighbor’s pasture (right) shown in an earlier photo (during the fire). The prairie looks vibrant, and numerous dogwoods were knocked back (at least temporarily).
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The small prairie ridges scattered across the preserve are greening up very nicely. Most of the bur and black oaks in those areas appeared to escape the fire with little or no injury.
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This beautiful spreading bur oak was clearly thriving – as were the prairie plants around it. The top-killed shrubs will regrow, but frequent fires (and maybe some basal herbicide treatments) should keep them at bay.
The Prairie Ecologist 