Friday, July 17, 2009

The Slip

A slip occurs when an unstable hillside soil becomes saturated with water to the point of acting like a liquid and flows down hill. An old slip is marked by a very steep uphill portion transitioning into a fairly level section that goes back to very steep before resuming the original slope. This slip at Blue Jay Barrens is old and is now relatively stable. The area of the slip is clearly visible in a 1938 aerial photo and, except for being surrounded by much thicker vegetation, seems to have changed little since that time.

One factor contributing to slips such as this is a subsurface flow of water along the interface between the soil mass and an underlying layer of rock or impermeable clay. The water acts as a lubricant and the soil does as the name describes and slips. There are still several areas along the upper slope that seep water for a big part of the year, thus creating the only wet barren at Blue Jay Barrens. These conditions give rise to many grasses and sedges that I have yet to identify. One day I’ll have the time to give this site enough attention to figure out what some of these plants are.

Much of this is Little Bluestem, but I can see a Panicum species, a little sedge and several broadleaved species mixed in.

Here’s one of the deer highways crossing the slip. Sometimes these trails are as much as two feet across and can lead to some severe gully erosion. If a problem does develop on a section of deer trail, you can usually alter the path by throwing down a couple of tree limbs on the trail, then giving the deer an easier way around. Deer will always choose the easiest route.
One winter, in order to section off a field for some intense maintenance, I used DR Brush to mow a grid pattern. Instead of pushing through the tall grass and plant stalks, the deer would follow the paths, making 90 degree turns as necessary to reach their destination. When several deer got going in different directions, it looked like a model of Downtown traffic.

Some deer just don’t know the rule about staying on the trail. This hoof print illustrates the size of this Common Dropseed, Sporobolus vaginiflorus, an annual grass that often becomes quite thick on the barrens.

This wet barren is a favorite site of the Tiger Beetle, Cincindela rufiventris. This is a fairly common species that is relatively easy to approach and photograph.

A female Eastern Pond Hawk. This is described as one of the most aggressive of the Dragonflies. This species often rests on or near the ground and is hard to see in grassy areas. They’re hard to miss when sitting on bare ground like this.
Although this is a portion of what I described as a wet barren, you can see that the ground is already drying and starting to crack. This is an area of high clay and once it dries, it’s like brick.

As the slip pushes back into the trees, the shade allows for the moist conditions to persist for a longer time. Indiangrass is becoming established here.

Looking at the slip from the woods, you see the branches of a young Beech. When I cleared this area, I would like to have removed this tree, but it’s the largest Beech on the property and I decided to leave it here.

My favorite greenbrier is this little Upright Smilax, Smilax ecirrata. Normally found near the edges of clearings, it’s one of those plants that seems to possess an inner glow that calls for your attention. The Blue Jay Barrens specimens are all short plants that end in a tight whorl of leaves. Not at all like some of its spiny relatives.

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