After 30 years the densest taller KR is on a yard plot that is mown once annually.
|Mown once per year, 29 July 2007|
At the other extreme are old KR areas that have never been disturbed. The typical pattern seems to be that as thatch develops, the resulting shade inhibits germination as well as lateral tiller extension of older tufts. With senescence, the tufts lose vitality and produce few flowering culms, few seeds, and eventually die out. In older plots there are generally empty spaces between tufts (and their thatch). Plants that otherwise could not survive in the dense KR, often manage to emerge, perhaps even benefitting from the thatch as mulch; such plants include greenbriar (Smilax bona-nox), wild petunia ("Ruellia nudiflora"). One forb that manages to penetrate even dense KR is gay feather (both Liatris mucronata and L. punctata on our land).
Those competing grasses which also need light to germinate don't seem to fare any better than KR under this condition — and seeds from competing shade area grasses would not be immediately available. KR does yield to other grasses at the edges to shady areas (e.g., to dropseeds (Sporobolus clandestinus and S. compositus var. drummondii). One exception is the highly versatile little bluestem (Schizachyrium scoparium), which does well in all but the darkest shade, and has culms often exceeding 4 feet tall from which to disperse seeds into nearby areas. It has gradually been replacing adjacent KR regardless of exposure.
|Old KR area with greenbriar and regularly mown lane, 29 July 2007||Area detail|
The apparent death in the KR thatch area below may have been precipitated by heavy seasonal moisture.