After cutting down trees in a section of forest, logging crews can do their local bees a favor by sticking around to clear the debris and flatten the ground.
A recent from Oregon State University suggests that removing timber harvest residue 鈥� also known as 鈥渟lash鈥� 鈥� could help wild bee populations thrive in the wake of a clearcut logging operation.
The study was led by wildlife biologist Jim Rivers, principal investigator in . It was part of an effort to find out how the removal of slash to be used as biofuel might affect forest ecosystems 鈥� including the populations of many pollinators, like bees.
Bees have been in the spotlight recently due to concerns about pollinator shortage caused by . Cultivated bees are vital for agriculture; by some estimates, bees pollinate worth of U.S. crops every year.
But what about wild bees? Even far from farmland, insect pollinators are responsible for fertilizing up to . This promotes biodiversity and creates a healthy food supply.
Of these pollinators, wild bees may be the most important. Not only are they the most abundant, they鈥檙e the only ones that feed on pollen and nectar for their entire life cycles.
鈥淲hen bees are present, they鈥檙e helping to maintain plant populations, and those plants are producing fruits and nuts, which in turn support (small) mammals and up through the food chain,鈥� Rivers said. 鈥淲e call it ecosystem services.鈥�
That鈥檚 why Rivers and his team wanted to know how land management decisions might impact wild bee populations.
To find out, Rivers turned to a managed conifer forest in western Oregon, near Springfield. From 2014 to 2015, his team assessed bee populations on 28 one-acre clearcut plots. Each plot received a different level of management, ranging from minimal slash removal and no ground compaction, to complete slash removal and total ground compaction.
Against expectations, more land disturbance 鈥� that is, removing more slash and compacting more land 鈥� appeared to give greater benefits to wild bee populations.
鈥淚t was really surprising to me the diversity that was there, and also the number that was there,鈥� Rivers said.
Not only this, but the researchers also recorded a threefold increase in wild bee population in the second year of the study, suggesting the original population was thriving and that new bees were arriving, too.
Although 92 distinct species of bees were identified during the course of the study, the researchers found that soil-nesting varieties dominated. According to Rivers, this is normal; 70 percent of wild bee species nest in the ground.
This isn鈥檛 the first time ground-nesting bees have been linked to disturbed land; have been known to proliferate in forest patches that have recently burned.
On scorched land and in clearcuts, the absence of other varieties of bees like cavity-nesters 鈥� which make their homes in places like blackberry canes and in old beetle burrows 鈥� raises questions about the evolution of bee communities over time.
鈥淎t what point do these communities change?鈥� Rivers wondered. How does the forest evolve after these disturbances? There has been much research on old growth forests, but the early stages of forest regeneration have received relatively little attention.
鈥淎t this point, we just don鈥檛 know,鈥� Rivers said.
Across the United States, native bee species appear to be But Rivers and his colleagues hope their research may be able to help conservationists create more habitat for at least one kind of native bee. In clearcuts, burn sites, and other disturbed areas, these key pollinators could be a boon for the whole ecosystem, all the way up the food chain.
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Jim Rivers, College of Forestry
/Wild bees are more abundant than cultivated bees. That's one reason they are considered important pollinators.