Twenty Years of Plant Monitoring at Nachusa Grasslands

Miles of waving grass punctuated with colorful flowers once covered Illinois. Birds and insects created a layered soundscape of song, chirps and buzzes. Deer, coyote, bobcat and bison wandered freely. This vison is Illinois’ ecological legacy. Although tallgrass prairie once covered most of Illinois, by the 1970s just over 2,000 acres of this habitat remained in total. Efforts to protect and restore tallgrass prairie across the state have been underway for decades. Sustaining and restoring diverse native plant communities is often a central goal for conservation projects. Diverse plant communities and variation in plant communities at the landscape scale are generally thought to support diverse animal communities. Monitoring plant communities over time is a relatively easy way for land managers to track if conservation efforts are reaching biological goals.

The Nature Conservancy’s Nachusa Grasslands preserve began in the mid-1980s as an effort to protect unplowed hilltop prairie and restore prairie into surrounding crop fields. At the preserve, located near Franklin Grove in north central Illinois, volunteers and staff remove invasive species, restore historic fire regimes, collect native seeds, and plant tallgrass prairie restorations into crop fields. Measuring plant community composition and diversity is vital to honing restoration approaches and building support for large-scale restoration.

Beginning in the mid-1990s, project manager Bill Kleiman established several permanent transects to evaluate plant communities on native prairies, planted prairies and savanna habitat at the preserve. These transects were resampled several times across the years as the preserve expanded. Recently, research scientist Dr. Elizabeth Bach synthesized the results of data collected from 12 of these transects between 1994 and 2016.

Plant communities on native prairies were made up of 80 to100 percent native plants. These communities have maintained their unique structure, including most of the rare plants that initially attracted the attention of conservationists. A few of the native prairie transects exhibited increases in total plant species present and mean coefficient of conservatism, a measure of plant rarity. Each of the four unique native prairies surveyed supported slightly different plant communities. Plants which distinguished native prairies included pussytoes (Antennaria neglecta), grass-leafed goldenrod (Euthamia gramminafolia), leadplant (Amorpha canescens) and prairie smoke (Geum triflorum).

Planted prairies reached 75 to 80 percent native plant species, achieving restoration goals of establishing plant communities dominated with native species. The oldest restoration on the preserve, planted in 1987, increased in the proportion of native species over 20 years. Plant communities in the two oldest restorations showed increases in more conservative plants, reflected in increased mean coefficient of conservatism. Key plants that drove that increase include pale purple coneflower (Echinacea pallida), stiff goldenrod (Oligonueron rigidum) and rosinweed (Silphium integrifolium). Reductions in “weeds” such as Queen Anne’s lace (Daucus carrota) and sweet clover (Melilotus sp.) were also observed.

Nachusa Grasslands includes savanna habitat as well. Savannas include some tree cover but maintain an open canopy and understory full of grasses, sedges and flowering plants. In this study, overall number of plant species and proportion of native plants did not change over the two decades studied, but plant community composition did shift. Savanna habitats have transitioned from shrub-dense communities including non-native honeysuckle (Lonicera mackii) to open understories dominated with native herbaceous plants such as joe-pye weed (Eutrochium purpureum), lopseed (Phryma leptostachya) and elm-leafed goldenrod (Solidago ulmifolia).

Active land management is central to the restoration practices at Nachusa Grasslands. The tallgrass prairie ecosystem developed over millennia with Indigenous people actively dwelling with the system. Numerous Indigenous cultures cultivated fields, planted trees, set fires to select plant communities and attract large game like bison, and harvested food, fiber, and shelter from the landscape. Their actions have been essential to shaping and sustaining this ecosystem. It is hardly surprising the plant communities at Nachusa have responded neutrally or positively to regular prescribe fire, aggressive invasive species removal, and active planting into former crop fields and degraded areas.

Today, Nachusa Grasslands covers 1,600 ha (nearly 4,000 acres), ten times the size of the original area. Volunteers, staff and scientists work side by side actively restoring the landscape. Many animals are also rebounding. Restoration efforts are recreating a medium landscape-scale habitat, large enough to support organisms ranging from tiny insects to the iconic bison. We continue long-term monitoring of plant and animal communities to evaluate how our efforts succeed and how they fall-short. We look forward to continuing to learn from our work and the work of colleagues engaged in restoration around the world.

For more information:

Bach, E M. and Kleiman, B.P. 2021. Twenty years of tallgrass prairie restoration in northern Illinois, USA. Ecological Solutions and Evidence (in press). This is an open access article which anyone can access for free.

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Dr. Elizabeth Bach is a Research Scientist with The Nature Conservancy in Illinois based at Nachusa Grasslands (Franklin Grove) where she works with scientists, land managers and volunteer stewards to investigate questions about tallgrass prairie restoration ecology. Her own research expertise focuses on soil ecology and botany.