East Savanna ridgetop
Continuing the discussion of Timberhill plant communities, I noted last month how plants first appear only in one site, gradually increasing until they become dominant. They then spread to the surrounding ridges and decline somewhat in the original site. The final stage is a balanced plant community where the most conservative species gradually increase and become more abundant.
The ridgetop east of driveway is the best example of this. White and hybrid oaks (Quercus alba, Q. X bebbiana, Q. X hawkinsiae) in this opening are very widely scattered with full sunlight available to plants much of the day. Despite the lack of sunlight and fire, when we purchased the property we found that a remnant native plant community had persisted in this site. Interestingly two conservative species, cream wild indigo, B. bracteata, and scaly blazing star, L. squarrosa, were the most abundant. Also, there were few exotics.
After we cleared the midstory brush and red cedar and implemented prescribed burns in 1995, the cream wild indigo and scaly blazing star began spreading. Cream wild indigo has now spread in all directions, even to the next ridge south. Scaly blazing star moved downhill under the denser canopy north and south of the ridgetop.
By 1998 native plant diversity increased with purple milkweed, Asclepias purpurascens, prairie coreopsis, Coreopsis palmata, and leadplant, Amorpha canescens, becoming well established. Bastard toadflax, Commandra umbellata, was so abundant that one could not help but step on it. Legumes growing on this ridge (besides leadplant and white prairie clover, Dalea candida,) include slender bush clover, Lespedeza virginica, violet bush clover, Lespedeza violacea, and panicled tick trefoil, Desmodium paniculatum. Rockrose, Helianthemum bicknelli, and rough blazing star, Liatris aspera, are also abundant. In 2003 I was surprised to find round-stemmed false foxglove, Agalinis gattingeri, growing under a couple white oaks. From a few plants this threatened forb has spread over an acre of open woodland. Two blue asters, A. azureus and A. laevis, round out the season each fall.
Little blue stem has always been the dominant grass, although we began seeing Indian grass here after three burns and finally some big blue stem which is always the last of the warm season grasses to return. In 2000 I noticed the first June grass, Koehlaria macrantha, clumps of which are now present throughout the site.
June grass, Koeleria macrantha, with rough blazing star on the right
The less conservative forbs did not find their way to this ridgetop until 2002. Now partridge pea, a common annual, fills in bare spots each summer and clumps of spiked lobelia, Lobelia spicata, bloom in late spring. Kentucky bluegrass, common yarrow and Korean clover represent the non-natives.
Many ectomycorrhizal fungi fruit in this site. The season begins with brittle caps (Russula), milky caps (Lactarius), and death caps (Amanita). The boletes, mushrooms with pores instead of gills follow: Gastroboletus turbinatus which is usually found in coniferous woodlands fruits from the base of white oak each year, Boletus dupainii, and B. rhodosanguineus also appear if there is adequate rainfall. All three of these are Iowa records.