Comparing the Effects of Two Tillage Operations on Beneficial Epigeal Arthropod Communities and Their Associated Ecosystem Services in Sugar Beets.

Beneficial arthropods provide important ecosystem services in terms of arthropod pest and weed management, but these services can be adversely affected by farming practices such as tillage. This study investigated the impact of two tillage operations (zone tillage and moldboard plow) on the activity density of several beneficial, epigeal arthropod taxa, and postdispersal weed seed and prey removal in sugar beet agroecosystems. In addition, four omnivorous ground beetle species were selected for a weed-seed choice feeding assay, whereas a single species was selected for a weed-seed age preference assay. Ground beetles were the most commonly collected taxon (via pitfall sampling), with only a few dominant species. Tillage operation did not affect ground beetle activity density; however, spider, centipede, and rove beetle activity densities were higher in the reduced-tillage treatment. Live prey consumption was similar between tillage practices, with more prey consumed during nocturnal hours. More weed seeds were consumed in the reduced-tillage treatment, whereas weed-seed preference differed between the four weed species tested [Setaria pumila (Poir.) Roem. & Schult., Echinochloa crus-galli (L.), Kochia scoparia (L.), and Chenopodium album (L.)]. In the weed-seed choice feeding assay, significantly more broad-leaf weed seeds (C. album and K. scoparia) were consumed compared with grassy weed seeds (E. crus-galli and S. pumila). No preference for seed age was detected for E. crus-galli, but Harpalus pensylvanicus (De Geer) preferred old C. album seeds over fresh seeds. Zone tillage is compatible with ecosystem services, providing critical habitat within agricultural ecosystems needed to conserve beneficial, edaphic arthropods.

A quarter of a century succession of epigaeic beetle assemblages in remnant habitats in an urbanized matrix (Coleoptera, Carabidae).

We studied the long-term (23-24 years) species turnover and succession of epigaeic beetle assemblages (Coleoptera: Carabidae, incl. Cicindelinae) in three remnant habitats [cottonwood (Populus spp.) and oak (Quercus spp.) stands, and old fields] that are embedded within highly urbanized areas in central Minnesota. A total of 9,710 beetle individuals belonging to 98 species were caught in three sampling years: 1980, 1981 and 2005 in pitfall traps in identical locations within each habitat. Results indicate that there were 2-3 times greater trap catches in 2005 than in 1980 (cottonwood and oak stands, and old fields) and 1.4-1.7 times greater species diversity of beetles in 2005 than in the 1980-1981 suggesting increased habitat association by beetles over time. Although there were no significant differences in catches between 2005 and 1981 (only cottonwood stands and old fields), there was a trend where more beetles were caught in 2005. At the species-level, 10 times more of an open-habitat carabid species, Cyclotrachelus sodalis sodalis LeConte, was caught in 2005 than in 1980. However, trap catches of five other abundant carabid species [Pterostichus novus Straneo, Platynus decentis (Say), Platynus mutus (Say), Calathus gregarius (Say), and Poecilus lucublandus lucublandus (Say)] did not change indicating population stability of some beetle species. These remnant habitats were increasingly colonized by exotic carabid species as Carabus granulatus granulatus Linneaus, Clivina fossor (Linneaus) and Platynus melanarius (Illiger), that were trapped for the first time in 2005. Species composition of epigaeic beetles was quite distinct in 2005 from 1980 with 39 species reported for the first time in 2005, indicating a high turnover of assemblages. At the habitat-level, greatest species diversity was in cottonwood stands and lowest was in old fields, and all habitat types in 2005 diverged from those in 1980s, but not cottonwood stands in 1981. As our sampled areas are among some of the last remnants of the original oak savanna habitats in central Minnesota, we hypothesize that conservation of these sites may be critical to maintaining epigaeic beetle assemblages under increased urbanization pressure.

Oil pipeline corridor through an intact forest alters ground beetle (Coleoptera: Carabidae) assemblages in southeastern Ohio.

Litter-dwelling ground beetle (Coleoptera: Carabidae) assemblages were monitored 1 yr after the construction of a corridor for installation of an oil pipeline along a xeric ridge-top forest in southeastern Ohio. After the creation of the corridor, three distinct habitats were evident in these sites: open corridor, ecotone areas around the corridor, and undisturbed forest interior. Carabidae were collected using directional pitfall traps that were placed parallel and perpendicular to the corridor in each of the three habitats. Results indicate that more carabids were present in the ecotone than in the other two habitats. Carabid diversity as estimated by rarefaction was highest in the corridor followed by ecotone and forest interior. Generalist and forest specialists such as Synuchus impunctatus (Say), Carabus goryi Dejean, and Pterostichus trinarius (Casey) were present in greater numbers in the forest interior and ecotone assemblages. In contrast, open-habitat specialists such as Harpalus pensylvanicus (DeGeer) and Selenophorus opalinus (LeConte) were present in greater numbers in the corridor assemblages. Carabid assemblages of the corridor were distinct from those of the ecotone and forest interior, whereas the latter two habitats had very similar assemblages. The successional pathway of the corridor carabid assemblage will therefore be likely different from that of the forest interior and ecotone. Overall, results indicate that construction of the oil pipeline corridor had significant short-term effects on the carabid numbers, diversity, and species composition because of ensuing habitat changes and fragmentation of the forest.