When it comes to establishing prairies that support pollinators on reclaimed industrial land, a new study suggests native plant diversity matters less than seeding species with the ability to persist in poor soils.
Researchers found that flowering plants hardy enough to blossom and survive in about 6 inches of topsoil – including some non-native plants – were the best ecological bet for unmanaged plots designed to provide habitat for bees, butterflies, wasps and other pollinators for the long term.
The study produced a rare 10-year dataset on pollinator habitat plot experiments that Ohio State University scientists conducted at The Wilds, a conservation center in southeast Ohio located on the site of a former coal strip-mining operation.
As a group, the dozens of plots lost more than 75% of flowers over a decade, but the quality of the plantings stabilized after six years to provide a full season of blooms that were accessed by at least 120 species of bees. If the researchers hadn’t kept monitoring for a full 10 years, they would have finished the study with vastly different conclusions about what works – and what doesn’t.
“If you’re only monitoring a planting for three years, you’re going to overestimate how good that is in the long run. Between years four and six we had a massive decline in the abundance of flowers,” said Karen Goodell, senior author of the study and a professor of evolution, ecology and organismal biology at Ohio State Newark.
“On the other hand, some species stuck around. You need to plan to have flowers at the beginning, but you also need to plant species that might take a few years to get going and are going to last as long as a decade.”
The study is published in the January 2022 issue of the journal Ecological Applications.
Research shows that approximately one of every three bites of food we take is pollinated by bees – but bees and other pollinators are on a decline, to different degrees and for different reasons depending on the species.
Concern about that loss has prompted public and private efforts to support pollinators with widespread plantings of wildflowers in such settings as roadsides, garbage dumps and reclaimed mines. To be successful, these unmanaged plots need to be seeded with plants that have staying power, this research suggests.
In 2009, Goodell sowed native prairie wildflower seeds in 48 plots at The Wilds with one of three mixes – some with nine species and others with 18 – to test whether the quality of the floral community over time depended on the diversity or the composition of the species planted. Aside from occasional mowing around each plot, the plants were left alone.
“We were astonished to find a greater than 75% decline in flower abundance and loss of more than half of the species over 10 years,” Goodell said. “We played with species diversity, with some plots having more species than others. That had almost no impact on overall flower diversity after 10 years – time was the major factor that influenced what was growing in the plots.
