‘A better toolbox’: Winter presents unique opportunities for restoration work in forest preserves
Winter, the dormant season for most plants in the Chicago area, presents unique opportunities for restoration work targeting larger, woody invasive species at suburban forest preserves.
The large-scale restoration work of removing aggressive, invasive species and helping native ones flourish follows seasonal changes across the collar counties.
Restoration work can be arduous when it comes to removing larger plant species, especially with the tens of thousands of acres the preserves have to work with, and winter conditions provide an ideal environment for targeting these varieties.
Woody, invasive, aggressive species, such as buckthorn and honeysuckle, are targeted across the forest preserves using equipment like forestry mowers, chain saws, clearing saws and large rubber-tracked skid loader machines often used on construction sites. The brush and trees are cut down, piled and burned.
These species are typically cleared during the winter because the ground is frozen, so heavier equipment can be used without compacting the soil and disturbing any seeds or sprouts within it.
“When you're out chainsawing down trees and dragging brush, it is super physically intensive, and so you are not cold because you're working so hard,” said Shaela Rabbit, natural resources specialist with the Forest Preserve District of DuPage County. “When it's not very cold and the ground isn't frozen, that means that we can't have large equipment helping us clear, and we can't get as much done as during the winter.”
With the goal of increasing native plant cover and providing habitats for native animals, crew members across Cook, DuPage and Lake forest preserves collect seeds from native species – bur and white oak trees, hickories and herbaceous species such as butterfly milkweed and cardinals – and spread them throughout the forests, along with planting plugs of native plants.
Plant diversity is necessary for ecosystems to thrive in the face of threats, Rabbit said.
“The more diverse in plant and animal species an area is, it's almost like it has a better toolbox,” Rabbit said. That way, when something like a tornado comes in, the ecosystem has more options on what works best for it to move forward, he further explained.
For herbaceous non-native species – such as phragmites, teasel, crown vetch, birdsfoot trefoil and non-native cattails – if they cannot be removed by hand, tractors and equipment with mowers are used to cut the plants down and stop them from making seed.
A lot of the invasive species are annuals or biennials, so they grow for a year or two and die once they release seeds. If these species are controlled early on, the growth of herbaceous invasive species that are perennials – long-lived – can be better contained, Rabbit explained. Crews also utilize targeted herbicide sprays that are designed to kill specific plants.
During the growing season, warmer months, crews at the forest preserves focus more on targeting vegetative, herbaceous invasive species as this is when they are growing. Crews work every day. During dangerous winter days that are too windy and tree branches start to fall, crew members usually stay busy making seed mixes indoors, Rabbit said.
Planting seeds, though it may take time to see results, is an effective way of replenishing forest diversity, since the seeds will wait for the right conditions to germinate, whether it’s the right amount of sunlight or hydrology patterns in the soil, according to Troy Showerman, resource project manager at the Forest Preserves of Cook County.
“What's unique to the nation, the areas around here, is that seeds can survive in soil for a long period of time,” Showerman said. “By doing this stuff large scale, we're trying to give as much opportunity as possible for what's in the seed bank to show itself.”
The work completed in the winter has a follow-up component with the work completed in the growing season to ensure what is removed in the winter does not resprout, Showerman said. Herbicides are used to treat resprouting, he added.
All forest preserves have volunteer opportunities for residents to help with the clearing of invasive species by hand and with hand tools, along with other stewardship opportunities. Even on cold days, volunteer work is available and crucial to the larger-scale work occurring in the forests, Matt Ueltzen, manager of restoration ecology at Lake County Forest Preserves, said.
“This restoration work is important year round, and winter is no exception. And we don't take winters off, this is an important time of year to accomplish these woody brush control projects,” Ueltzen said.