Bioenergy is an important component of sustainable energy production. Obtaining biofuels from native grasslands may provide a more ecologically sustainable alternative than traditional sources, such as corn. For example, we know that pollinators are much more abundant in native grasslands. But how will bees and their floral resources respond to disturbances, such as grassland harvesting, that are necessary for bioenergy production?
In an upcoming issue of Ecological Applications, we describe the results of an experiment that tests this question. We found that harvesting had a positive effect on the grassland floral community. Harvesting opens space for new plant growth and knocks back competitively dominant species. The result is a greater abundance and diversity of floral resources for bees.
Although having more floral resources is typically good for bees, whether bees responded positively or negatively to harvesting depended on whether they nest above or below ground. The 80% of bee species that nest below ground in the soil (and thus safe from the harvester) tended to benefit from harvesting because they could take advantage of the more abundant resources. On the other hand, harvesting negatively affected the remaining 20% of bee species that nest above ground in e.g., hollow stems because their nests were destroyed in the process.
Our study supports the idea that bioenergy production from grasslands can promote pollinator conservation. However, steps will be needed to ensure the persistence of bee species that nest above ground.
This study was conducted in collaboration with colleagues in the labs of Claudio Gratton at the University of Wisconsin – Madison, Rufus Isaacs at Michigan State University, and the Great Lakes Bioenergy Research Center. Read more about our experiment here:
Spiesman, BJ, A Bennett, R Isaacs, and C Gratton. In press. Harvesting effects on wild bee communities in bioenergy grasslands depend on nesting guild. Ecological Applications doi: 10.1002/eap.1828