Tom's Blog

Wednesday, March 23, 2016

After savanna burn: good time to see old-growth forest structure

On Monday March 21 2016 we had a great burn of the oak savannas at Pleasant Valley Conservancy. The next day Kathie and I returned to assess the burn coverage and take pictures. It turned out to be an excellent time to see the forest structure in all its simplicity. Before leaf out of trees and shrubs, before forbs and grass growth. The black forest floor provides an excellent contrast with the trees.

Our bur and white oak savannas are excellent examples of old-growth forests.

How is an old-growth forest characterized? These are the keys, as taken from the forestry literature:

  • Mix of young and old trees
  • Many fallen and decaying trees
  • Light gaps
  • Trees in various stages of decline
  • Wide diversity of plant species
  • No or only minimal past disturbance from logging or agriculture
  • Coarse woody debris on the forest floor
According to the experts, in Eastern United States it takes 150 years or longer to reach old-growth character. According to our minimal evidence, our white savannas are between 150-200 years old and many of our bur oaks are older than 200 years.

Here are a few selected photographs:

Predominantly white oaks; note the downed timber, snags, and scattered oak grubs, ready to start the next stage
A fairly level area of mixed white and bur oak, with shagbark hickory. This trail is
an excellent approach through what we call the Ridge-top savanna

This large open-grown bur oak is growing at the edge of what we call the Basin Savanna
The burn coverage here was over 90% but the standing tall grass stems did not burn;
only the basal leaves burned

One of the princely open-grown white oaks dominates this section of the forest

Incidentally, right through the middle of this savanna burn the red-headed woodpeckers remained active. And the next day they were on the ground feeding on what they could find. 

Also, we had a large flock of red-winged blackbirds on the ground among the black. I counted over 50 birds.


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