Non-crop habitats in agro-ecosystems provide habitat for insects that perform valuable ecosystem services including pollination, pest suppression, decomposition, and seed predation. The loss of natural habitat as the human population grows and the area for food production increases threatens the persistence of biodiversity in agro-ecosystems. Recently, farmer initiatives such as Wisconsin Healthy Grown® potatoes have been developed to protect and restore natural habitats within agro-ecosystems to preserve these services. Working on potato farms in central Wisconsin, the objective of this study was to examine how one ecosystem service, predation of weed seeds, is influenced by adjacent non-crop habitats that are targets of restoration through the Healthy Grown program. We hypothesized that (1) seed predation is higher in adjacent non-crop habitats, including oak savanna, forest, and grassy field margins, than within crop fields, (2) seed predation within crop fields varies as a function of these adjacent habitat types, and (3) seed predation rates are correlated with ground beetle (Coleoptera: Carabidae) diversity and abundance.

To test these hypotheses we placed seed cards in potato fields and adjacent habitats at 10 and 50 meters from the edge of the crop/non-crop interface. Seed cards were left out for one week intervals four times from June through August 2007. Pitfall traps were also set in order to determine ground beetle abundance and diversity in the different habitats.

Results/Conclusions

The results were examined separately for small (<1.25 cm) and large (>1.25 cm) predators. For small predators, mainly beetles, we found that (1) seed predation rates were 4 times higher in non-crop habitats than within the crop field (p<0.01), (2) there was no difference in predation rates within the crop field as a function of adjacent habitat type (p=0.7), and (3) seed predation rates are positively correlated with both ground beetle abundance (p<0.001) and diversity (p<0.02). In contrast, for larger predators we found that (1) seed predation rates were on average 25% higher in crop fields than in non-crop habitat ( p=0.004), and (2) there was no difference in predation rates within the crop field as a function of adjacent habitat type (p=0.48). Overall predation rates by large predators were between 3- and 10-times greater than predation by small predators in both crop and non-crop habitats (p=0.0001). Non-crop habitats may provide resources not found in potato fields resulting in higher diversity and abundance of ground beetles which in turn consume weed seeds.