A Good Burn

by Carl Strang

The Forest Preserve District of DuPage County has invested a welcome amount of effort in restoring the forest at St. James Farm, where I am volunteer steward. Early this spring a large group of trained staff came in and conducted a successful burn of accumulated leaf litter in the main part of the forest. The point of the burn is to kill or at least weaken invasive plants such as garlic mustard and barberry.

The contrast between the unburned trail and the burn area reveals the intensity of the burn.

The burn coverage was about as complete as one could expect.

No burn is complete, however. Some forest floor invertebrate species will need a few years to recover, but there will be plenty surviving in small spots missed by the fire, as well as surrounding areas not included in the burn.

A smaller burn on an earlier date in the area we are clearing of buckthorn was not as complete, because the leaf litter accumulation was relatively shallow and spotty.

I didn’t take any photos of the main burn as it was taking place because I was busy. Our forests historically burned very infrequently, and some of the plants cannot be assumed to be as fire-adapted as the ones characteristic of savannas and woodlands. In particular I was concerned that blackhaws (Viburnum prunifolium), the dominant shrub layer species, might be harmed. So, I worked ahead of the flames, frantically raking dead leaves away from the bases of as many blackhaws as I could reach in the two hours that I had. I did not have time to cover the entire forest, so there were some areas where the flames reached the bases of blackhaw shrubs.

Some blackhaws were heavily scorched.

Other blackhaws were lightly scorched.

Blackhaws I cleared by raking away the leaf litter were unscorched.

In subsequent weeks the forest leafed out, and the blackhaws bloomed.

Blackhaw flower cluster

I spent part of an afternoon assessing scorched vs. unscorched blackhaws. The scorched ones nearly all had plenty of leaves, though a few were killed. Most scorched plants had some flowers, though almost all were limited to 1-5 clusters.

Unscorched blackhaws had abundant flower clusters.

A little less than two-thirds of the scorched shrubs flowered at all, and again, those that did had few. Nine-tenths of the raked blackhaws bloomed, for the most part with many more flower clusters. Sample sizes were large enough to support a strong statistically significant difference. I will continue to watch this, as I am concerned that the scorched plants may have been partly girdled by the flames. I will be recommending that other forest stewards take measures to work with the fire crews and protect the native shrub layer of our woodlands by raking away fuel from shrub bases.

In the meantime, the part of the forest that we have been clearing of buckthorn and other invasive shrubs is showing first fruits of our efforts.

Even in this first year, our treatment area showed an encouraging growth of spring ephemeral herbaceous plants.

One long-term goal will be to promote blackhaw and other native species, so as to restore the shrub layer in the area we have cleared.


I Stand Corrected!

by Carl Strang

In a recent post I identified a shrub at Mayslake Forest Preserve as blackhaw (Viburnum prunifolium). Fortunately I have an excellent botany backstop in Scott Namestnik. In his comment he pointed to the possibility that the plant might instead be the closely related nannyberry (V. lentago), pointing to some characteristics he could see in the photo. I checked my own principal reference, Plants of the Chicago Region by Swink and Wilhelm. They emphasize two characteristics, leaf tip shape and petiole structure, that separate blackhaw from nannyberry.

Blackhaw leaf tips should be “abruptly short-acuminate,” i.e., blunt. Nannyberry leaf tips are long-acuminate, meaning that they are somewhat pinched and drawn out in a longer point, as the above photo from the shrub in question illustrates.

On the petiole, or leaf stem, nannyberry has distinct wings or flanges that are undulate, or wavy, as the photo confirms. Blackhaw petioles, if a little winged, would then be straight and not wavy.

I want to make a couple points, here. First, botanical identifications often require wading through some terminology. If you are not familiar with the terms they can be intimidating at first, but it’s simply a matter of slowing down and looking up definitions. The Swink and Wilhelm book, which I recommend for anyone serious about Chicago region botany, has an excellent glossary with drawings that make meanings clear. The only caveat is that sometimes comparisons are relative. In this example, what is the boundary between “short-acuminate” and “long-acuminate?” Here I used another tool, the Internet search. I found photos of both plants with close-ups of their leaves, and that allowed me to see the distinction.

The second point is that science works best when the scientist is egoless. This time it was easy. I had no ego invested in this identification, and I know that Scott is a topnotch field botanist. I’m a vertebrate ecologist. At the same time, however, I had the plant and all he had was a compressed photo. It was important that I go back and confirm his suspicion, both to make the correction and to learn the difference so my own botanical knowledge would be improved.

I’ll finish by pointing to Scott’s own blog, Through Handlens and Binoculars, which he and his wife Lindsay produce. It’s on the short list of blogs I follow regularly.

Happy New Things

by Carl Strang

However familiar a landscape has become, there always is something new to discover in it. I have begun my second year at Mayslake Forest Preserve, and still I am finding rather large organisms I completely missed last year. Recently I noticed a conspicuously flowering shrub I did not see in 2009.

Unless I miss my guess, this is a blackhaw, one of the native viburnums. Fungi are an entire group with which I have only spotty, passing familiarity. Here is one of the common ones, Polyporus squamosus, which appears on the trunks of several different tree species in spring.

The scaly looking shelves of these reproductive structures are worth taking some time to enjoy. Novelty and surprise certainly are among the factors that draw me again and again into wild places, even ones with which I am reasonably familiar.

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