We conducted a 3-yr cropping systems experiment in central Pennsylvania, USA, to determine the effects of initial cover crop species, tillage and resulting environmental variables on the activity–density (A–D), species richness, community composition and guild composition of carabid beetles (Carabidae: Coleoptera) during the transition from conventional to organic production. We compared four systems in a factorial combination of a mixed perennial sod (timothy, Phleum pratense L.) and legumes (red clover, Trifolium pratense L.) or annual cereal grain (cereal rye, Secale cereale L.) followed by a legume (hairy vetch, Vicia villosa Roth) as initial cover crops, and soil management using full tillage (moldboard plow) or reduced tillage (chisel plow) implemented in soybeans followed by maize in the subsequent year. The experiment was established twice, first in autumn 2003 (S1) and again in autumn 2004 (S2) in an adjacent field, in a randomized complete-block design with four replicates in each Start. We collected a total of 2181 adult carabid beetles. Approximately 65% of the carabid beetles collected were from six species. Indicator Species Analysis showed that several carabid species were indicative of treatment, e.g., Poecilus chalcites was a strong indicator for treatments with an initial cereal rye cover crop. Eleven environmental variables explained variation in carabid A–D, richness and the A–D of species categorized by size class and dominant trophic behavior, respectively, but varied in significance and direction among guilds. Soil moisture was a significant effect for total carabid A–D in both S1 and S2. Redundancy analyses revealed some similar and some idiosyncratic responses among informative species for the cover crop×tillage treatments through the 3-yr rotation. The most consistent factors that distinguished species assemblages among years and treatments were the number and intensity of soil disturbances and perennial weed density. The consistent occurrence of soil disturbance indicators in multivariate analyses suggests that future studies that aim to compare the effects of nominal soil management treatments on carabid beetles and other soil-associated arthropods should quantify frequency and intensity of disturbance associated with crop management practices.

Although ecological succession is one of the principal focuses of recent restoration ecology research, it is still unclear which factors drive this process and positively influence species richness and functional diversity. In this study we sought to elucidate how species traits and functional diversity change during forest succession, and to identify important factors that determine the species in the observed assemblages. We analyzed species richness and functional diversity of ground beetle assemblages in relation to succession on post-industrial localities after habitat deterioration caused by spoil deposition. We selected ground beetles as they are known to be sensitive to landscape changes (with a large range of responses), and their taxonomy and ecology are generally well-known. Ground beetles were sampled on the spoil heaps during the last 30 years when spontaneous succession occurred. To calculate functional diversity, we used traits related to habitat and trophic niche, i.e. food specialization, wing morphology, trophic level, and bio-indication value. Ground beetle species were found to be distributed non-randomly in the assemblages in the late phase of succession. Ordination analyses revealed that the ground beetle assemblage was significantly associated with the proportion of forested area. Environmental heterogeneity generated assemblages that contained over-dispersed species traits. Our findings indicated that environmental conditions at late successional stages supported less mobile carnivorous species. Overall, we conclude that the decline in species richness and functional diversity in the middle of the studied succession gradient indicated that the assemblages of open habitats had been replaced by species typical of forest ecosystems.

The molecular detection of predation is a fast growing field, allowing highly specific and sensitive detection of prey DNA within the gut contents or faeces of a predator. Like all molecular methods, this technique is prone to potential sources of error that can result in both false positive and false negative results. Here, we test the hypothesis that the use of suction samplers to collect predators from the field for later molecular analysis of predation will lead to high numbers of false positive results. We show that, contrary to previous published work, the use of suction samplers resulted in previously starved predators testing positive for aphid and collembolan DNA, either as a results of ectopic contamination or active predation in the collecting cup/bag. The contradictory evidence for false positive results, across different sampling protocols, sampling devices and different predator-prey systems, highlights the need for experimentation prior to mass field collections of predators to find techniques that minimise the risk of false positives.