Greenspace: Study offers insight into grassland restoration
A University of Minnesota study was intended to predict how plants return to native fields. Its findings may help future restoration projects.
Lauren Sullivan, the study’s lead author, does postdoctoral research in the university’s College of Biological Sciences.
Most past seed dispersal studies focused on one species, she said, their authors trying to determine why certain species are invading a given area.
This paper set its sights on post-agricultural areas, where farmers had spent years tilling and controlling the plant growth.
The researchers looked at several species — ones that might move into an abandoned farm field or agricultural area after plowing and spraying ended.
Seed dispersal is the most important factor in plant movement, according to the study. It’s how species travel long distances and find new habitat.
We know that some seeds can be transported by animals, like birds and mammals that eat fruit and leave the seeds elsewhere, or humans, who can seed areas to create favorable landscapes.
However, the limitations of many plants to disperse seeds naturally (by dropping seeds or seed pods that would be moved by wind alone) hadn’t been studied.
The researchers went to the Cedar Creek Ecosystem Science Reserve, where they measured the seed release height, the mass of dried seeds, and the fall speed of 50 co‐occurring plant species.
With these numbers, they calculated the average movement of the seeds away from parent plants.
In a grassland setting, these numbers would predict the expansion of the plants into an abandoned, empty area of land.
The findings were mixed. The seeds from perennials tended to disperse farther, Sullivan said, and many of the native Minnesotan plants the group hoped would colonize the empty areas fall into that category.
Something like milkweed, a native perennial, is therefore likely to show up quickly in an abandoned area, as will daisies and other plants with light, small seeds.
However, annuals, many of which are invasive, non-native plants, are very good at taking over a small area around their base, she added.
"They’re not as good at spreading, which is what you kind of want to see," Sullivan said.
And there is some application for restoration projects, where organizations may try to return a section of abandoned land to its native, grassland state.
Some native plants, like prairie clover and any type of legume, have dense, heavy seeds that won’t spread far on their own.
Those are the ones grassland restorers will want to seed personally, Sullivan said.
"If you need to, focus your efforts on plants that aren’t going to spread as far on their own," Sullivan said.