Saturday, September 17, 2011

Some Diggings

Here’s an interesting little clearing. It’s a dry knob covered with gravely soil, but instead of supporting the expected short grass community, the dominant grass is Big Bluestem. The Big Bluestem wasn’t here when I first cleared off the cedars. I was expecting the existing Little Bluestem and Sideoats Gramma to fill in the newly created opening. It just seems odd to have vigorous Big Bluestem plants that normally inhabit moist sites, coexisting with plants that are only found growing in the driest of soils.

I discovered this excavation in the middle of the area. Looks like some small animal has been searching for food. Skunk is usually the first animal that comes to mind when I see something like this.

Could this be the prize? A Yellow Jacket nest might have offered a good meal to a skunk. But, the cells are all filled with dirt. That means the skunk did quite a bit of digging after removing this nest. It could be that the skunk ate this section first and then dug out the rest of the nest, which it then carried off to eat elsewhere. Or the skunk might have been after something else and the nest was just pushed back with the loose soil.

It’s also possible that it was some other animal doing the digging. A Fox or Coyote could leave a hole like this after excavating a mouse or grub. The hole gives a good view of the extensive root system developed by the grasses. The soil is quite loose and easy for roots to penetrate. Moisture is the limiting factor here.

The scattered soil material partially buries several plants. The loose soil provides conditions favorable for the development of new plants from seed. Some managers encourage soil disturbance in hopes of stimulating the germination of seeds from a persistent seed bank. A seed bank refers to a store of viable seeds that lay dormant in the soil. Excavation such as this could expose those seeds and allow them to grow into new plants. I hold little hope that there is such a seed bank at Blue Jay Barrens.

There were also several smaller digs scattered about. About 20 years ago, I collected a large number of soil samples by pushing back the upper half inch of the soil layer and collecting the soil down to about six inches. I took each sample and spread it lightly over the surface of gridded plots in a large planting bed. The idea was to see if any plants would emerge that indicated the presence of a seed bank. The only plants that developed were a few that already existed at the collection sites plus several weedy species that grew near the planting bed. Nothing suggested that there were any dormant seeds residing in the soil.

A bit of thought made me realize that a seed bank was highly unlikely. Topsoil on this site would have taken many thousands of years to develop and it would have been within that topsoil layer that a seed bank could possibly have existed. Poor land use practices over the last 200 years have effectively allowed the topsoil to erode and be carried away in the runoff water. With the topsoil went the seed bank. I’m afraid that there’s nothing left to expose in the soil now left on site. Excavations may create opportunities for recently produced seeds to germinate, but I don’t think I’ll be seeing any resurrection of past prairie components.

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