Southern Lessons

by Carl Strang

This year’s chapter in the series of annual bioblitzes organized by the Indiana Academy of Sciences took place at Eagle Creek Park in northern Indianapolis on June 2-3. This is early enough in the season that there were few singing insects for me to find, but I was able to gain valuable experience with two southern species that occur or have occurred in the Chicago region.

The first of these is the spring trig.

Female spring trig at Eagle Creek.

This species of tiny cricket first was described in 2014. That is surprising, given its abundance in southern Indiana and its extensive range beyond the state. It proved to be common in a range of habitats at Eagle Creek Park, from woodland edges to grassy meadows.

Spring trigs appear plain-faced to the eye, but bright light and magnification reveal a pattern of fine dark lines.

I learned more about the spring trig’s habitat, and found that I can hear them easily while driving at speeds of 30mph or less. This allowed me to get clarity on the species in the Chicago region. Driving in the southernmost counties, I found widely scattered small colonies in Fulton and Jasper counties, at road edges where wider bands of herbaceous plants were backed by woodlands. In the future I expect to find them in southern Pulaski and Newton counties, too, but not north of there.

Eagle Creek Park also has a large population of northern wood crickets.

The northern wood cricket is a forest species that is smaller and blacker than the spring field cricket, which could be heard chirping in the park’s meadow areas.

The spring field cricket is a few millimeters longer, typically has bronzy wings, and has a proportionately broader head and thorax.

Recordings I made during the bioblitz, and at home with a captive male, have provided further clarity on northern wood cricket song characteristics. Their chirps may never have 4 pulses (commonly 2 or 3), and almost never rise above 5 kHz in pitch, where spring field crickets often have 4-pulse chirps, and seldom drop below 5 kHz. Habitat also helps separate the two. I dug deeper into the literature, and learned more about historical records of the species in two Chicago region counties. Those observations were made in 1902, and I went to the sites in the weeks after the bioblitz. Northern wood crickets no longer occur there. I believe the records are correct, but that the crickets have gone extinct in those places. Northern wood crickets are reported to be sensitive to forest fragmentation, perhaps especially so in the northern fringe of their range, and such fragmentation clearly took place where they once were found in Lake and Marshall counties. I will continue to check the region’s larger surviving forest blocks, but it seems likely that the species no longer occurs in northern Indiana.

Incidentally, the other expected early-season singing insect, the green-striped grasshopper, lives in Eagle Creek Park’s meadows and prairie areas.

Next year’s bioblitz is expected to take place in one of my counties, and I am looking forward to the experience.

 

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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.

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