One of the primary challenges to restoring prairie habitat is the negative effects of intensive row crop agriculture. Intensive agriculture simplifies landscapes with plant monocultures that have little value to wildlife such as native bees.While research has shown that bee communities in restored prairies can be diverse, few studies have addressed the issue of how the surrounding agricultural landscape can affect native bee communities. To answer this question we sampled 16 Minnesota prairie restorations that varied in the proportion of row crop agriculture, such as corn and soybean, surrounding the site in a 1500m radius; forming a gradient of sites with surrounding agricultural land between 17–85%. We sampled restorations throughout the 2017 season from mid-May to mid-September. Bees were hand netted during timed transect walks. Local plant diversity and abundance was sampled using 60 1-meter 2 quadrats that evenly covered the sampling area. All specimens were identified to species and models were specified to predict how flower diversity and frequency (local factors) and proportion of row crop agriculture around the site (landscape factor) affect bee abundance and diversity.
Results/Conclusions
We collected a total of 7626 bee specimens from 131 species and recorded richness and abundance for 97 flowering plant species. Neither plant frequency nor agricultural land cover were significant predictors of bee abundance. Models for bee diversity indicate a significant positive effect of forb richness on bee diversity (slope= 0.05, P= 0.02), and a marginally significant positive effect of surrounding agricultural cover (slope= 0.004, P= 0.07). While our model found a weak relationship between surrounding agriculture and bee diversity, the model predicted a positive relationship which ran counter to our predictions. Local plant richness predicted a gain of about 7 bee species moving from our lowest value (1 flowering species) to our highest value (21 flowering species)., we found no evidence for the negative impact of surrounding agriculture on native bee diversity or abundance in tallgrass prairie restorations. We suggest the primary focus for restoration practitioners be on developing and maintaining diverse local forb communities.