Gossamer Tapestry

Reflections on conservation, butterflies, and ecology in the nation's heartland

Friday, March 23, 2007

Ecological Restoration

I've blogged before about some of the work that we do at Bluff Spring Fen, but there's one part I've never discussed. We are trying to preserve this remarkable piece of land, but in doing so we remove a lot of brush and some trees. We even use chainsaws. This might seem counterintuituve at first. The answers have to do with what makes an ecosystem healthy, and biodiversity.

Consider the picture below:

To the untrained eye, this might seem to be a beautiful natural setting, but there are actually serious environmental problems here. There is actually very little biological diversity. The ground under the trees was, for a long time, bare soil. In the 1980's and 1990's a terrible non-native weed called garlic mustard began invading. Neither of these situations is natural. For milennia, this piece of land would have been subject to the influence of frequent fires. Large fire-resistant trees like bur oak and hickory, would have been able to grow in areas where the shape of the land caused fires to burn a bit slower and cooler. All of the trees in this picture are very young and are species not tolerant of fire. They have sprung up since about 1940. The shade that they cast kills off the herbaceous plants that grow under them, and prevents the oaks from reproducing. The space that's left is ripe for invasion by non-native weeds.

We know that Bluff Spring Fen was, until very recently, much less wooded than it is today because we have aerial photos that document the invasion of trees. For the last 25 years, our management efforts have begun to reverse this damage, and the aerial photos document this as well. Here is a series. The roads at the top of the picture allow you to orient them.

1939. Trees are only on the downwind sides of hills.

1975. The entire wetland is choked with trees and shrubs.

1995 (most recent aerial photo) The advance of the trees continues on the periphery of the preserve. Management efforts have again opened the central wetland. Endangered orchids, butterflies and dragonflies now thrive there.

Over the years, we have refined our management techniques. Today, we no longer stack our brush into piles for later burning, but rather begin small bonfires which we then expand with the brush as we cut it. This both saves time and reduces the number of ash piles that we create.

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At 00:14, Blogger Ur-spo said...

you butch things; chainsaws!
thank you for the lesson as they 'looke like OK trees to me"


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