The declining health of bee populations has been in the news lately, and no wonder since about 70% of the world’s 100 most important food crops are bee-pollinated. Oregon hosts more than 500 bee species, of which perhaps 300 species live in or use forest habitats. While most Oregon trees are wind-pollinated, many forest understory shrubs and flowers depend on bees and other pollinators to complete their life cycles. Forests also provide habitat for bees that pollinate agricultural crops. Until recently the role of forests as bee habitat has mostly been overlooked, but that is starting to change.
In general, forests provide two things for bees: nesting habitat, and floral resources (nectaries). Most bees nest in bare ground, but they are also found in stumps, old twigs, and even tree cavities, giving new meaning to the term “cavity nester”! This lovely infographic from the Oregon Bee Project provides some interesting examples of forest nesting habitat.
Many of our local shrubs and forb (wildflower) species provide abundant resources – nectar and/or pollen – for bees and a myriad of other pollinators such as butterflies, bats, hummingbirds, flies, and beetles. This publication provides a good introduction to native pollinator plants in the Klamath-Siskiyou region.
Currently there’s tremendous interest in the forestry world in the relationships between forest habitats and bees. But at this stage, surprisingly little is known about this topic. For example, a recent literature review in the Journal of Forestry by OSU’s Jim Rivers and others found only 14 papers across four countries that were relevant to pollinator use of managed forests.
One intriguing finding emerging from recent research is that disturbances such as fire and timber harvest may actually increase the abundance and diversity of wild bees. For example, a study after the Douglas Complex fires in southern Douglas County found 20 times the number bees and 11 times the number of bees species for the most severely burned sites compared to the least severely burned sites. Another study in NW Oregon found increased bee abundance and diversity following intensive biomass removal on a site after timber harvest. Recently disturbed sites often have exposed, bare ground suitable for nesting, woody nesting materials and open conditions favorable for growth of understory forage plants, both shrubs and forbs, so it makes sense that these sites would be good for bees. However, much remains to be learned about the relationships between forest management and bee populations.
Southern Oregon contains a diverse mix of closed and open conifer-dominated forests, mixed evergreen forests, oak woodlands, chaparral, and other vegetation types, often occurring in a patchy matrix with lots of “edge habitat” (where two or more habitat types meet). This should make for good bee habitat, but to my knowledge, there’s been little study of local forest-pollinator relationships.
On the new Collins Demonstration Forest, we’re hoping to sow a diverse pollinator seed mix in several areas as well as monitor local bee populations, to see what’s out there. If you’re interested in participating or finding out more, let me know. Meanwhile, join us for the Forest Bees presentation on Feb. 20.
A good place to start is the Oregon Bee Project’s Foresters page. Check here for pollinator forage plant lists and habitat guidelines.
I’d also recommend the OSU PolliNation Podcast interview with Dr. Jim Rivers, an OSU scientist who is engaged in research on bees in forests.