Research from Buckles and Harmon-Threatt explores how prairie management strategies can affect pollinator communities both directly and indirectly, highlighting why we shouldn’t ignore what’s happening below ground. Associate Editor, Guadalupe Peralta elaborates.

A Spanish version of this post is available here.

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A bumblebee enlarging her nest hole. If 80% of wild bees nest in soil, can we afford to ignore its affects on pollinators? Photo: Pahazzard.

Most efforts to preserve pollinators are focused on maintaining or increasing the range of flowering plants available. The reason behind this is clear: flowers provide pollen and nectar, which are essential for pollinators’ subsistence. However, pollinators also rely on other resources that also play important roles in determining the future of pollinator species. For instance, over 80% of wild bees nest in the soil, which makes soil conditions highly relevant for nesting success of these pollinators and therefore highly relevant for their survival. In addition, soils can indirectly affect pollinators via effects on the flowering community. Nevertheless, when the impact of habitat management on pollinators is evaluated, the focus is usually set on the pollinator community and the abundance and diversity of flowering species, whereas soil conditions are rarely taken into consideration.

In their recent study, Buckles and Harmon-Threatt explore the influence that different tallgrass prairie management strategies (burning, burning-haying, patch-burn grazing) have on both soil and floral resources. They also evaluate how these management strategies can directly and indirectly (via changes in soil and floral resources) affect nesting rates, richness, abundance and composition of bee communities. The authors show that different management strategies have different effects on soil and floral resources (burning having the overall lowest impact), and that these changes in turn alter the bee community composition and bee nesting rates. Specifically, greater bare ground, higher soil temperature, lower soil moisture and high flower abundance tended to favour bee abundance and bee nesting rates.

Although burning tallgrass prairie habitat is required to reduce woody encroachment and invasive species in these sites (Missouri, USA), additional management through haying and cattle grazing is used to simulate bison grazing by removing aboveground biomass. However, the inclusion of grazing and haying seems to have a negative impact on the resources bees rely on and on the bee community. Among the recommendations to make tallgrass prairie management strategies more bee friendly, the authors suggest a reduction of stocking rates. Moreover, they suggest ensuring prairie management does not increase soil moisture, or decrease soil temperature and bare ground, will be important for maintaining high bee nesting rates and hence promote the conservation of bee communities.

In conclusion, focusing solely on the maintenance of flowering resources might not be enough to reach pollinator conservation goals. The assessment of other resources, such as nesting resources, needs to be incorporated in the evaluation of habitat management strategies, as well as in global change impact studies and restoration planning. Taking into account multiple drivers of pollinators’ change will allow us to improve pollinator conservation strategies.

Read the full article, Bee diversity in tallgrass prairies affected by management and its effects on above‐ and below‐ground resources in Journal of Applied Ecology.