Lessons from The Morton Arboretum’s ongoing restoration of its woodlands can be helpful to managers of other natural areas.
Strategy: Study the site
Restoration begins with research. Start with a good understanding of the site, including:
History: Through municipal public records and library research, learn who owned the land and what they did with it. Find maps, photos or historical accounts (including oral histories) to learn prior ecosystems. Aerial and ground photos, tree-ring dating and paleo-ecological evidence, such as fossil pollen and charcoal dating can be useful.
Regional planning issues: Learn how the land is related to neighboring lands. Map roads and highways (existing and proposed) and research the zoning laws. Understand how your site might benefit the region.
Identify current flora and fauna: Identify current problems, such as invasive species, loss of biodiversity, and soil erosion. Research why those problems exist.
Reference sites: Identify other sites to compare or measure your restored ecosystem against. These may include actual sites or written descriptions. Combine multiple reference sites into a composite model site.
Decide the mission. After collecting and analyzing the data, decide to what degree it is possible to "restore" the land. Options might include:
- Ecological restoration, an intentional, human-induced effort to initiate or accelerate the recovery of an ecosystem's health, integrity, and sustainability. It's an attempt to return an ecosystem to its historic trajectory.
- Re-establishment of one or a few plant species
- Creation of one habitat to offset or compensate the damage to another
Identify the path to correct the problem(s). As with all large-scale projects, prioritize problems and solutions.
Understand resources: paid and volunteer labor, equipment needed, timeframes and budget.
Inform your practices with current research. It's often difficult to access research and translate it into practice at your particular site. But the body of knowledge is growing as research and conservation organizations keep pushing forward.
Consider identifying research opportunities: They can be possible sources of funding and also a means of helping to develop best practices.
Set goals and objectives. Define measurable starting and ending points. Examples include:
- Facilitate savanna development in East Woods by decreasing canopy cover by __% throughout East Woods by 2011
- Increase light levels by __% by 2009
- Decrease understory/overstory stem density by __%
- Increase native, ground layer vegetation cover to 95% by 2012
Resources for study and planning:
Nature Conservancy's Conservation by Design program
Handbook of Ecological Restoration (Cambridge University Press, 2002)
"Ecological Restoration and other Conservation Practices: The Difference" by John Munro. Ecological Restoration 24:3 September 2006 pp 182-189
"Landscape pattern and structure of oak savanna, woodland, and barrens in northeastern Illinois at the time of European settlement," by Bowles, M.L., M.D. Hutchison, & J.L. McBride. 1994. Pages 65-73, Proceedings of the North American Conference on Savannas and Barrens. Illinois State University, Normal.
Interactive map of pre-european settlement vegetation in the Chicago region by Marlin Bowles and Jenny McBride
Strategy: Restore hydrology
Restoring the natural flow of water can be a good first step in restoring the land.
After the 1830s, settlers installed drain tiles to siphon water from wetlands to make way for logging, farming, and homesteading. In doing so, they upset natural processes that had worked for thousands of years. In the 19th and 20th centuries we saw the effects in increased flooding of rivers and loss of biodiversity. Today we see the value of wetlands in flood control, improved water quality, and wildlife and native plant habitat.
Play "Drain Tile Detective." Map the drain tile system. Generally, find tiles by examining…
Current topography. Many rural swales are part of drain tile systems. If there's a low spot that gathers water or drains surface water on the edge of a woodland or in the middle of the field, there may be a drain tile system below ground, but it's not always a given.
Historical use. If the land was used as farmland, drain tiles may have been installed. If it was always woodland, drain tiles are less likely.
Disable the drain tile system. Disabling methods include…
- Removal by trenching
- Installing valves
Strategy: Thin the canopy
One of the dominant trees of the Eastern U.S., white oak has diminished in numbers over the past two centuries. Why? There are many causes. One theory is the lack of fire (fire suppression).
Canopy thinning (by girdling or removal of trees) can allow more light in to help oaks and other native plants reproduce.
Factors to consider include:
- How many trees should be removed, if any? What's the goal?
- Which species should be removed and from which strata of the canopy? Understory? Overstory? Both?
The Arboretum's canopy thinning study seeks to answer these questions.
Resources on canopy thinning:
"The Decline of Oak Forests" by Craig Lorimer. BioScience October 2003. Vol. 53 No. 10 page 915
"Where has all the white oak gone?" Marc D. Abrams. BioScience. October 2003 53:10 pp 927-939
Strategy: Restore fire
Over thousands of years, oaks have adapted to fire, which helps to clear the forest floor to create light and space for oak seedlings. But humans have suppressed fire, opening opportunities for other species to take root.
- Can increase canopy openness over time
- Is less effective in reducing densities of stems larger than 5-10cm
- Increases ground layer diversity, leading to a greater abundance of summer herbs without loss of spring herbs.
Resources on prescribed burning:
"Long-term changes in an oak forest's woody understory and herb layer with repeated burning," Marlin L. Bowles et al, Journal of the Torrey Botanical Society 134(2), 2007, pp. 223-237
US Geological Survey guidelines on prescribed prairie burns
National Interagency Fire Center Communicator's Guide about wildland (natural and prescribed) fires
Strategy: Control invasive species
Invasive plants are aggressive competitors that out-compete other species for water, nutrients, sunlight, and space. As a result, invasive species can:
- Displace native species
- Reduce plant diversity
- Alter ecosystem processes
- Hybridize with native plants, changing their genetic makeup
- Destroy the habitats that support native animals, insects, and micro-organisms
- Create ecosystems that support aggressive, non-native plants, animals, and pathogens
Controlling invasive species is an ongoing, labor-intensive process. Methods include:
- Hand-pulling: for biennials, annuals, seedling shrubs, and trees in small areas or large natural areas, and where many volunteers are available to do the work.
- Mechanical control: for large plants or poisonous plants. Tools include chainsaws, mowers, pulaskis, brush cutters, hand saws, etc.
- Chemical control: for large or poisonous plants. Controls include herbicides, foliar spray, basal bark treatments, etc.
Resources on invasive plant management:
Invasive trees, shrubs and Vvnes, The Morton Arboretum
Exotic Species pages of the Illinois Department of Natural Resources
Invasive Species Network, a joint project of the University of Georgia and the USDA
Invasive Species Node of the National Biological Information Infrastructure (NBII)
These organizations and agencies that work in the area of conservation and ecological restoration can be helpful to land managers.
National and international organizations
Ecological Restoration, published by The University of Wisconsin-Madison Arboretum and SER International.