Old-growth, or primary forests, are classified as having very little human disturbance — and thus they provide a unique opportunity to study life in relatively unchanged settings. Previous research suggests that these ecosystems may provide critical habitat for sensitive species that are absent or rare in other places.
However, past studies comparing bee biodiversity in primary and secondary forests have not consistently found this to be the case.
A recent study led by USDA Forest Service research entomologist Michael Ulyshen and Tall Timbers Research Station collaborators Scott Pokswinski and Kevin Hiers sought to address this discrepancy by comparing bee populations between primary and mature secondary longleaf pine (Pinus palustris) forests in the southeastern U.S. Secondary forests are forests that have regrown after human disturbance. In this case, mature refers to secondary forests that are more than 100 years old.
Converting natural bee habitats to agricultural land is a major cause of pollinator declines. Studying bee communities in secondary forests — habitats that have experienced historic disturbance such as agriculture — can provide critical information about how pollinator communities change as forests age and how they compare to bee populations in primary forests.
“From a functional perspective, bees are really the workhorses that dominate the provision of pollination services,” says Ulyshen. They are “a good representation of the pollinator community.”
Apart from a previous study researching how a history of tillage agriculture has affected bee communities in secondary longleaf pine forests, little is known about disturbance effects on bees in this ecosystem.
In the study, bees were sampled at seven locations within the historic range of longleaf pine. The sample sites were on the Eglin Air Force Base in Florida and in the Red Hills region on the border between Georgia and Florida.
All locations have been managed with regular prescribed burns to maintain the health of the forest and the open conditions characteristic of longleaf pine ecosystems.
To catch bees, the researchers installed eight sampling plots 100 meters apart at each forest location. The sampling plots consisted of three pan traps and were left out for about half a week. The sampled bees were counted and cataloged according to species. The team repeated the sampling various times from March to October.
The scientists found no significant difference in either the abundance or diversity of bee communities in primary and mature secondary longleaf pine forest habitats. Bee species did vary by location, but there was no evidence suggesting that primary forests provide critical habitats to bee species unable to live in mature secondary forests.
The findings are consistent with previous research that found no difference in bee communities on adjacent plots of forest that had or had not been previously tilled for agriculture.
“It’s really encouraging to know that these secondary forests can support bee communities comparable to the least disturbed forest remnants,” says Ulyshen, noting that “because the secondary forests we studied were really old, it would be nice to compare results across more age groups.” There could be differences between secondary forests and primary forests when the secondary forests are young.
For more information, email Michael Ulyshen at firstname.lastname@example.org