There's always a certain amount of agonizing as burn seasons approach. Will we get an excellent fire that will do all the good we hope for? Or might various things go wrong?
What follows are photos - not of flames - but of the ecosystem after the burn - and some thoughts on what these images mean.
Checking out a controlled burn at Somme Prairie Grove on April 7, 2014.
No fire on the path because there was no fuel there.
The burn here looks fairly complete, as the main fuels were warm-season grasses and oak leaves - both "born to burn."
But elsewhere there are different stories.
Here's our first concern. A hot fire on a good burn day would have burned these logs. A good thing? Or not?
For the ecosystem, burning up these acres of jumbled trunks would be a plus. Almost all of these are (recently over-abundant) invasive trees that were killed by previous fires (or girdled by us stewards long ago). Natural oak woodlands burn so often that most downed wood is consumed. This kind of ecosystem is not adapted to lots of trunks lying helter skelter.
Yet the practical challenges for resource managers are also a concern. For the burn crews, it would be a plus to get rid of all these logs. But if the fire had been hotter, most of the logs would have caught, and (with current Cook County Forest Preserve burn practices) they'd all have to be extinguished before the burn crew got to go home and rest up for the next day.
Notice that some of these logs here have previously been cut into sections. Long before the burn, they should have been carried to a bonfire to get them out of the way, but we ran out of time when we last worked here. The stewards try to do as much of this "fuel reduction" as we can, because otherwise the burn crews may be reluctant to choose this needy site on the best burn days. Yet cleaning up all those logs is a lot of work for us, and while we're doing that, other needs go unmet.
Here's a related issue. Though they may be hard to see, a few feet behind the somewhat charred red oak (front tree) are three bur oaks, each about 3" in diameter (one to the left and two to the right).
They all have dead limbs leaning against them and are a bit charred. The middle one rises out of the main helter skelter in the mid upper right. Bur oak was the main tree in this savanna area, but this species is poorly represented among young trees here now, because in the decades before restoration, there'd been too much shade, which bur oak can't survive. Thus we want to give extra protection to the now-too-rare young burs during this "remedial restoration" period. We ought to have cut the mess of fuel away from those young trunks, so they would get big enough to be pillars of this community in a few decades. The red oak with the blackened trunk in the middle left of this photo is much less adapted to fire. It's likely to burn out in time given the frequent conflagrations needed to maintain a bur oak savanna. Oak savanna is the community that the conservation-priority species of plants and animals depend on at this site.
Another goal is the restoration of hazelnut, formerly a major shrub of the savannas and oak woodlands. Loss of native shrubs is a major problem for community structure and for some rare animal and plant species. The barely visible green fence protects young hazels from the deer (that would otherwise eat every one, at their current levels of overpopulation). The ground around this pampered patch was raked mostly free of fuel before the fire, protecting the young stems from burning. In time, with sufficient "remedial" help, the hazel populations should build up enough to both feed the deer and burn off naturally from time to time. But without help, they were almost gone. Before we started protecting and replanting them, we had watched them dwindle to only a few sprigs left on the entire site. At Somme Woods, across the street, they're now entirely gone.
This hazel clump didn't fare so well. Despite a narrow raked break, the fire got through and burned every stem. It will have to start again from its roots. Why did we fail? There are too many tasks, and two few stewards. Perhaps someone will read this and take over some of the hazel and young oak protection?
This patch around two scarlet oaks didn't burn. It was perhaps a bit too wet and the fuel too meager. Is this is a spot where the hazels would do better? We're hard at work planting what hazel nuts we can rescue from the squirrels in various areas that seem to have potential.
Yet way too many areas didn't burn. In this "mesic intermediate" patch, a thin sprinkling of savanna herbs struggles to out-compete the invasive species. Rare natural ecosystem components would win out if burned frequently enough, but if the site is burned only on days mild enough that the downed logs won't catch, these areas will never recover.
Savannas consist of a mosaic of:
We started to realize this when we noticed that we needed "open," "intermediate," and "closed" seed mixes to get good results in savanna restoration. The "open" patches are easy to restore, as they burn readily from their "prairie grasses." The "closed" patches burn somewhat readily thanks to the oak leaves. The "intermediate" (and most distinctive of the savanna) patches are the hardest to burn, until the natural vegetation robustly re-establishes. Unburned patches like this won't benefit from this year's fire. Such areas will tend increasingly to become ever-less-burnable stands of tall goldenrod, briars, and young brush.
Why didn't this patch of woods burn? Usually the problem areas are the "intermediate" ones - because they lack the dense prairie grasses and oak leaves, our best fuels. But here the trees are mostly ash, box elder, and cherry (all invasive in unburned oak woods). When brushy, the trunks and branches can burn explosively during extreme burn conditions (when we wouldn't have a controlled burn). But the leaves of these trees are adapted more to rot than burn, so this year's rather cool fire skipped this area too.
As we walked the site, studying the results, we agonized over what to do with the downed wood. Then - we saw smoke in the distance. Is there a problem?
That's when we found exactly what the burn crew had wanted to avoid. They put a lot of work into extinguishing any burning trees they find. This dead ash must have been imperceptibly smoldering. Now it's out-and-out burning.
Is this tree a danger?
We'll keep an eye on it while we do our other monitoring.
This sedge was partly burned. Sedges are a critical part of the ecosystem. Have we damaged it? Our answer is "no." We've seen this before. It will be lush and luscious in a few weeks. The species of the savanna are adapted to fire.
When we return to that burning ash tree, it has fallen and continues to burn. Do we put in a call for the fire crew, or would we be wasting their time?
Stepping back, it's easy to see that all the fuel around this smoker has been burned. Perhaps it would concern people if it could be seen from the road. But it's certainly safe.
Returning the next morning, we find it entirely consumed. A ghost log. If there was more understanding and support from the public, this is what would happen to all those helter skelter piles of dead invasives. Then subsequent burning would be easier and better.
During our last burn at Somme Prairie Grove, in fall 2011, this vegetated pond was dry, and the whole pond area burned. But spring burns are different from fall burns. Today the water has chorus frogs singing. Every kind of fire helps the savanna, a little or a lot.
In the long run, we're looking forward to "pyro-diversity" - all kinds of fires occurring as they would have - when nature ran the show. In the meantime, we staff and volunteers will work to heal the ecosystem as best we can.
Comments and questions very welcome.