Tom's Blog

Sunday, January 25, 2009

How many species in a planted prairie?

When we have visitors at Pleasant Valley Conservancy, we are sometimes asked how many species we have in our planted prairies. Folks are often surprised when I say there are over 100. I think this surprise arises because the USDA requires a much smaller number in prairies planted under the Conservation Reserve Program.

However, one of the watchwords of restoration ecology is "diversity", and this means as large a number of species as possible.

Another factor is that none of our former agricultural fields have constant characteristics. Because of slope and drainage factors, different parts of these fields vary from dry-mesic through mesic to wet-mesic, and even (in the case of the Valley Prairie) wet prairie. Thus, some of the species we have been planting grow in one area but not in another. With time they sort themselves out.

I have been making surveys in the all of our planted prairies, starting with the second growing season. In the three planted prairies that were planted the longest ago, I have detailed records.

Toby's Prairie: planted 1998, 10 growing seasons, 146 species.
Pocket Prairie: planted 1999, 9 growing seasons, 142 species.
Valley Prairie: planted 2002, 6 growing seasons, 136 species.

Toby's Prairie is on the ridge top and has the most dry-mesic habitat. However, part of Toby's Prairie slopes gradually to the north, and in this area there are wet mesic species, such as mountain mint and closed gentian.

Pocket Prairie has the most complex topography. It is in a basin below the white oak savannas and receives drainage from a ravine at the northeast corner. Hard rains pour down through one part of the Pocket Prairie and exit at Pleasant Valley Road. There is quite a bit of wet mesic habitat, as well as lots of mesic areas. But at the upper end of the Pocket Prairie conditions are really dry mesic, and this is where we see lots of little blue stem. We knew when we planted the Pocket Prairie that there was a lot of variability in moisture, and planted appropriate species in areas where they were most suited.

Valley Prairie actually grades directly into real wetland, and at its border is sedge meadow and cattails. It also receives runoff from the Pocket Prairie. During the heavy rains of June 2008 we had a real stream running for several days. Not surprisingly, cup plant, a wet-loving Silphium, grew very well along this stream.

When these three prairies were planted, we prepared three separate seed mixes, dry-mesic, mesic, and wet-mesic, and each was planted in its appropriate place. As the species developed, they sorted themselves out.

The most important tool we used when working out the species mixes was the DNR publication written by Rich Henderson called Plant species composition of Wisconsin prairies
(Technical bulletin. (Wisconsin Dept. of Natural Resources), No. 188) Madison, Wisconsin: Wisconsin Department of Natural Resources, 1995 58 pgs.

Although this publication is now out of print, it is available on-line through the UW-Madison Digital Collections (an outstanding resource for anyone interested in restoration ecology!).

Finally, I want to emphasize that we have never been satisfied with a single planting. In subsequent years we replant all of these prairies, as other species become available.


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