Tom's Blog

Sunday, February 5, 2012

Rettenmund Prairie work party

Yesterday we ran our monthly work party at Black Earth Rettenmund Prairie. The weather was ideal, we had a nice group of volunteers, and we got a lot done. This time of year we do brush control, and the weather this winter has been great.
Although most of the Rettenmund preserve is real prairie, the southwest corner has a small patch of woods which borders onto a much larger woods of other ownership. We burn through this area every year, and the tangle of brambles and brush at the edge of the woods always gives us problems, so our goal was to set a good fire break. Although we had some loppers and hand clippers, most of the cutting was done with a trusty Stihl brushcutter (strongly recommended for this sort of work). The brush cutter was followed by our volunteers, who treated all the cut stems with Garlon 4. (We use Garlon 4 in oil because it not only works on the cut stems, but can also be used to basal bark any stems that were missed by the brushcutter.)

We had five treaters, which is ideal for such tangled brush.
There were lots of brambles, scattered honeysuckle, mulberry, and a few buckthorn. Nearby, in the neighbor's woods, there was lots more buckthorn, including some large (old-growth) trunks. As those following these posts know, buckthorn is a calciphile and in the Driftless Area is most common in soils derived from dolomite. Although the soil of most of Rettenmund Prairie is derived from sandstone, there are two small areas with underlying dolomite, and the corner of this woods is one of them. (The other is a knoll in the North Unit.)

My knowledge of the finer geology of this area comes from ArcGIS. The Wisconsin Geological Survey kindly sent me a map layer with the bedrock geology of Dane County and I was able to overlay a recent air photo and use that to chart the dolomite here. There is a tiny area of the Black Earth Dolomite, a member of the St. Lawrence Formation (Cambrian age). Although I have not done calcium measurements here, my work on the same formation at Pleasant Valley Conservancy (just a few miles away) provides good soil chemistry data. It is interesting to note that as we move off the prairie and into the woods, buckthorn increases markedly. In fact, we cut one large buckthorn right at out property boundary (see photo of the cut stump). This was a real tree, and was probably 40-50 years old.


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