Managing Prairie Remnants for Insect Conservation as a Means of Restoring Native Flora

Sara Adams
Ecology Project
December 8, 1999 

My research was conducted at Bernheim Research Forest in conjunction with Dr. Covell, Biology. professor and Lepidoptera expert at the University of Louisville, and under the direction of Margaret Shea chief administrator of research at the forest. Bernheim Forest is a nature preserve and as such it is crucial that the forest be preserved. Many projects have been implemented in order to restore Bernheim to its original floral and faunal conditions that existed before humans cultivated it more than three hundred years ago.

The main objective of the research is to successfully restore native floral and faunal conditions approximating those that existed centuries ago. This is not any easy task. Some things that are done to facilitate restoration is seeding with native grasses as well as flowering plants it is also important to remove any weedy and non-native grasses from the prairie. While this is being done over an extended period of time it is also very important to make periodical bioassessments of the prairies.

The project included two prairies one previously burned site and an unburned site. Bioassessments of both sites are done in order to assess the fauna of each remnant. This is a strictly qualitative assessment not quantitative it is done in order to get an idea of the species that are present in each area as well as the relative numbers of the species. Since the fauna consists mostly of insects, the insects are collected with a sweeping method with an equal number of sweeps performed on each site. The insects, before being taken out of the net, are closed in a jar where they are killed by toxic fumes. Next they are very carefully separated from the thicket that was inadvertently collected when collecting the insects. Much caution is used when doing this (often done under a scope) because many insects are invisible to the naked eye. Spiders and caterpillars are preserved small vials containing an alcohol solution. Large insects are pinned and labeled and small insects are put on card points and labeled. Finally the insects are to be identified via binomial nomenclature.

It is very important to manage prairie remnants because the species that inhabit them do so precariously. They are susceptible to extinction by extinction causing catastrophes because of their small populations, poor dispersal abilities, fluctuating population densities, and patchy distributions. The three main things to do to manage prairie remnants are 1) eliminate unnatural landscape 2) maximize habitat diversity 3) burn with restraint.

Maximizing habitat diversity means that insect populations when kept stable contribute to the diversity of the habitat furthermore there seems to be a strong correlation between habitat diversity and insect population densities. Also within the laws of complexity the more complex or diverse the area is the more stable the system tends to be as well. Many things were noted upon the first bioassessment Dr. Covell noted that there were many fewer nectar sources in the unburned area which was also made apparent by the lack of nectar gathering organisms, namely, Butterflies (also absent would be any other nectar dependent species). The unburned are also had much more dead grass and a lot less new grass, many more spiders were noted as well. There were however, more small bushes as well as saplings, which were not subjected to fire. These two factors contribute to why far less insects were gathered with the sweep of the unburned area: Thick dead grass as well as the presence of the saplings made it more difficult to obtain the insects. In conclusion burning seemed to foster prairie management by increasing its complexity. Bioassessments were done in order to determine how often burning should be prescribed. Also to do a qualitative assessment to make sure that extinction of small insect populations especially those that are burn-sensitive, does not occur. Comparisons of the progress of the burned and unburned areas can be monitored as well. The sites are well on their way to becoming just as they were three hundred years ago.