Effects of silvicultural operations in a Mississippi River bottomland hardwood forest on ground beetles in the genus BrachinusThis article is part of a larger document. View the larger document here.
Little information is available on how insects are affected by anthropogenic influences in the bottomland forests of the West Gulf Coastal Plain. This study investigates one genus of ground beetles that lives in managed forested landscapes to discover which species are positively and negatively influenced by human disturbances. Ground beetles (Carabidae) were collected from a bottomland hardwood forest in the Mississippi River floodplain that received three harvesting treatments in 1995 (three replicates each of clearcut, selection, and control). Beetles were analyzed to assess the effects of forest disturbance over time. Four species in the genus Brachinus accounted for about 66 percent of all specimens collected. Brachinus larvae are ectoparasites on the pupae of water beetles, and the adults prefer moist habitats. In 1996, the year after applying treatments, the selection cuts yielded almost three times as many Brachinus (63 percent of 3,696 total) as the control (19 percent) and clearcut (19 percent) treatments. One year later, in 1997, both the control (45 percent of 2,572 total) and selection cuts (40 percent) yielded almost three times the number of Brachinus than the clearcuts (14 percent). In 2000 (an exceptionally dry summer), both the control (44 percent of 465 total) and selection cuts (45 percent) yielded four times the number of Brachinus than the clearcuts (11 percent). The steady loss of beetles during the study is believed to be due to several summer floods followed by several summer droughts. Nonetheless, this study demonstrates that the selection cuts continued to provide the habitat needs of these beetles, and the clearcuts continued to provide less suitable habitat, despite a lush growth of plants in 2000.