Tom's Blog

·       You can’t let things get out of hand. During the early stages, shrub establishment may seem benign and not worth worrying about. This is obviously wrong. At first, shrubs and trees are easy to remove. However, once the explosive phase of growth has set in, not only is the biomass needed to be removed much larger, but the whole population is growing at a vastly increased (quasi exponential) rate.

·       The importance of frequent fires. Fire is now a widely accepted component of prairie and savanna management systems. However, there is a tendency to assume that fire on a three- to four-year cycle may be sufficient. This is a mistake. Beginning at the time of TNC acquisition, burns have been conducted on the various units on the average every second year. Despite this frequency, shrub growth remains a problem. Sumac, prairie willow, brambles (Rubus spp.), and gray dogwood in particular continued to thrive. Aspen shoots continue to appear in former aspen areas. In those areas where the legacy of shrub growth remains, annual fire should be considered. The historical GIS data will help locate the areas where annual fires should be carried out.

·       However, burns alone are not enough. At Black Earth Rettenmund Prairie, with its biennial burn cycle, sumac, gray dogwood, prairie willow, etc. have remained or have developed into problems. There are strong reasons to believe that all clonal shrubs, even if they are native, should be eradicated by a multi-year program of herbicide use. If the prairie is burned in alternate years in the spring, then the shrubs should be treated with herbicide in the late fall of the second year after the burn (that is, before the upcoming spring burn).

·       Eradication of clonal shrubs is essential, even if native, because annual stewardship cannot be guaranteed to continue into the indefinite future.

·       Legacy effects must be taken into consideration when planning management strategies. Areas that were woody in 1986, when restoration began, continue to inhibit the established of true prairie species, especially graminoids. These areas not only need tree and brush removal, but planting with seed collected elsewhere on the site.

·       Significance of herbicide use. The prejudices against use of herbicides remain. The first seven years of restoration work at Black Earth Rettenmund Prairie were wasted by trying to control shrubs without the use of herbicides. (The State Natural Area Board had refused permission to use herbicides.) Although trees can often be controlled without herbicide (by girdling), shrubs, with their paramount ability to resprout, cannot be controlled without herbicide.

·       Seed collecting and overseeding are essential. A site that has been wooded for an extended period of time almost certainly has lost most or all of its warm season grasses, as well as some of the more light-demanding forbs. The seed bank for such a site is uncertain, and probably highly variable. Without overseeding, restoration of such a site may take years. Even if there is a good seed source near by, spontaneous overseeding will be random and, depending on the quality of the seed, the success will be highly variable. Even 25 years after the initial restoration work, formerly wooded areas at Black Earth Rettenmund Prairie still remained impoverished, even though they have been reseeded with native grasses and forbs. Although each restoration project must be analyzed individually, if the site was wooded it can safely be assumed that overseeding is advisable. In fact, why not plant? Unless this is a research site, it seems better to plant than to wait and see what happens. Overseeding is easy and relatively inexpensive, and the sooner it is begun the better. The only reason not to overseed may be if a local seed source is not available.