Enriching Log Landings to Benefit the Native Bees of Indiana

Aliza Boles Fassler, Cheryl Coon, and Lauren Pile Knapp

Aliza Boles Fassler is a graduate student, University of Massachusetts-Amherst, 160 Holdsworth Way, Amherst, MA 01003.

Cheryl Coon is an Economic Partnership Coordinator, Shawnee and Hoosier National Forests, 811 Constitution Avenue, Bedford, IN 47421

Lauren Pile Knapp is a research ecologist, U.S. Department of Agriculture, Forest Service, Northern Research Station, 202 Anheuser-Busch Natural Resources Building, Columbia, MO 65211.

Meet the native bees of Indiana

While everyone knows the European honey bee (Apis mellifera), many don't know about the 430 species of native bees pollinating Indiana’s flowering plants! They range from robust carpenter bees (Xylocopa virginica), which reach an inch in size, to tiny fairy bees (Perdita spp.), smaller than a grain of rice. Native bees can be red, green, brown, black, yellow, and even blue like the blue orchard bee (Osmia lignaria). Unlike the European honey bee, a non-native species, most of Indiana’s native bees live solitary lives. These hard-working female bees build nests and care for their offspring alone. Native bees nest in the ground, hollow plant stems, wood, or in existing cavities such as rodent burrows or snail shells. By pollinating plants, native bees contribute to clean water, oxygen, and healthy soils. Native bees also pollinate agricultural crops and may increase crop yield. While the European honey bee faces health risks and colony losses, native bees such as the rusty patch bumble bee (Bombus affinis) are federally endangered. The rusty patch bumble bee has disappeared from over three-quarters of its historic range and was the first bee listed on the US Fish and Wildlife Service (USFWS) Endangered Species Act. The USFWS is currently considering listing the American bumble bee (Bombus pennsylvanicus). Both species still occur in Indiana. Threats to native bees include diseases, parasites, habitat loss, pesticides, and climate change.

Figure 1.  American bumble bee (Bombus pennsylvanicus)

What do the native bees need and what can we do for native bees?

Of all the threats to native bees, habitat loss is the greatest because it means losing the food and nesting resources they require. Most bees get all their food from flowers. Adult bees rely on nectar from flowers as an energy source, and female bees collect pollen to feed their offspring. Not just any flower will do! Some bee species are specialists meaning they feed their offspring on pollen from one native plant species or a group of closely related plants. Bees such as the spring beauty mining (Andrena erigeniae) bee rely on forest spring ephemerals (spring beauty, Claytonia virginica) as a source of pollen to for their offspring. You can recognize these mid-sized brown bees in the spring by the pink pollen coating their legs.

Similarly, not just anywhere is suitable for nesting! Many bee species prefer to nest in areas of bare warm soil. While others need large pieces of woody debris or hollow stemmed plants such as raspberries, blackberries, sumacs, and elderberries.

Forests are essential habitats for native bees. They provide resources not found in other habitats such as dead wood and flowering trees. Some bee species are strongly associated with closed canopy forests while others rely on open forest habitats with flower-filled understories. Over the last 200 years, the midwestern US lost 75% of open forest habitats such as savannas and woodlands. Forest management that creates open forest habitats by mimicking the effects of natural disturbances (e.g. windfall gaps) and indigenous management (e.g. fires) can encourage the growth of flowering understory plants and provide important nesting habitat for these vulnerable pollinators.

Why enrich log landings for native bees?

Log landings from active forest management can provide semi-natural habitat to support native bee populations. Research in the Poconos Mountains of Pennsylvania has shown that log landings are important habitats for bees. Log landings can support 14 times as many floral resources and twice as many bees compared to timber harvest areas (Lee et al 2021). However, managers face challenges with soil compaction and getting native vegetation to re-establish on log landings. Forest managers at Hoosier, Shawnee, and Mark Twain National Forests shared a desire to actively promote pollinator habitat. Together with the Forest Service Northern Research Station the collaborative Pollinator Habitat in Log Landings (PHiLL) project was born (described in the 2024 Volume 33, Issue 1 of the Indiana Woodland Steward). Two of the main goals of this project were to 1) test a seed mix of 31 native plant species to see which plants establish well in log landings and 2) test whether seeding log landings enhances the quality of the pollinator habitat they offer.

How to pick native plants for seed mixes?

Since log landings are highly disturbed, pollinator-friendly plants that prefer disturbance are the best options for enriching log landings for native bees. When the PHiLL project began, a team of experts decided on a broad list of plants that would be competitive in environments with disturbed and compacted soils, germinate quickly, adapt to a range of soil moisture and light levels, and would compete well against invasive plants such as stiltgrass (Microstegium vimineum) and sericea lespedeza (Lespedeza cuneata).

Selecting a seed mix for pollinators requires multiple considerations: 1) providing season-long nectar sources, 2) selecting plants that already grow in the area and 3) purchasing species that are locally sourced. Planting a mix of species that flower early, mid, and late in the growing season, with overlap, ensures nectar availability throughout the season. Common native roadside and field species that can grow and flower quickly in disturbed areas are ideal choices. Rare plant species may have limited seed availability, higher costs, and a lower success rate due to restrictive habitat needs. Most important is to buy native seeds that were collected within the region they are being planted. If native seed is not available locally, buy from a region that has similar environments (seasonal changes, elevation, soil types) or what we could expect with climate change. For the PHiLL project in southern IN, we sourced our seed from a supplier in Kentucky.

The plant perspective -- what we learned about seeding log landings with native plants.

By year three of the PHiLL project, we learned that of our diverse native seed mix, only a few plant species performed well – meaning they were abundant and flowering across most of our landings within the first few years of seeding. Successful flowering species included Coreopsis species, blackeyed susan (Rudbeckia hirta), bergamot (Monarda fistulosa), slender mountain mint (Pycnanthemum tenuifolium), partridge pea (Chamaecrista fasciculata), narrow-leaved sunflower (Helianthus angustifolius), and showy tickseed (Bidens aristosa) (Figure 2). Other species in our seed mix were often slow to establish and flower, and several we did not see at any of our landings. We also seeded several grasses to improve habitat conditions, and both little bluestem (Schizachyrium scoparium) and river oats (Chasmanthium latifolium) performed well with gains each year since initial seeding. One of the most important lessons learned from the project was that selecting an economical seed mix that could be broadly applied requires an iterative and deductive processes to select the bee-beneficial plant species that would work best across a range of ecological conditions. Remaining questions include how to increase performance of our native species when invasive plants are 1) present but not well-established and 2) the dominant species. We are working on our next iteration for native seeding of log landings by experimenting with seeding rates and pre-seeding herbicide treatments.  

Figure 2. Seeded log landing on the Hoosier National Forest.

The native bee perspective -- what we learned about seeding log landings with native plants.

Preliminary results from the PHiLL project show that log landings seeded with native pollinator plants support abundant and diverse wild bee populations. The PHiLL project has found over three times as many bees on log landings as we initially anticipated. Seeded plant species were among the plants used most often as food sources by native bees on Hoosier National Forest log landings. Ground-nesting bee nests were commonly found in log landings indicating they can provide important nesting resources.

Among the bee species collected on log landings in Hoosier National Forest were species of conservation concern such as the American Bumblebee (Bombus pennsylvanicus). Other bees found included specialist species that rely on plants in the Asteraceae (daisy) family such as the Colorado miner bee (Calliopsis coloradensis). Many nest parasitic species, including several species of sharp-tailed bees (Coelioxys sp.) were also collected. Nest parasitic species lay their eggs in the nests of other bees like a cuckoo bird. Abundant nest parasitic bee species can be an indicator of healthy populations of their host species.

Managing forests for native pollinators

How we manage our forests has profound effects on native bees. A bee may spend its whole life within a couple of hundred square feet of forest. Actions such as keeping forested land forests, restoring open forest conditions through active thinning and burning to promote favorable conditions for native ground flora, leaving snags and coarse woody debris, and enriching log landings as open pollinator habitats can benefit our native bees.

References:

Lee, M. R., McNeil, D. J., Mathis, C. L., Grozinger, C. M., & Larkin, J. L. (2021). Microhabitats created by log landings support abundant flowers and insect pollinators within regenerating mixed-oak stands in the Central Appalachian Mountains. Forest Ecology and Management, 497, 119472. https://doi.org/10.1016/j.foreco.2021.119472

For more information on the PHiLL project, please visit: https://www.fs.usda.gov/research/nrs/projects/phill#overview