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Saturday, February 10, 2018

The Somme Prairie Grove Experiment

Most Recently Updated: November 22, 2023

A Science and Conservation Summary

Beginning in October 1980, a team of volunteers and staff has worked here to restore a thought-to-be-extinct component of nature here – the tallgrass savanna – including its hundreds of endangered, rare, or uncommon plant and animal species. Was the tallgrass savanna extinct – or just badly degraded? Endnote 1 wrestles with this question. Benefitting from the encouragement and mentoring of experts in many fields, we (mostly the volunteers) have carried out a wide variety of informal and formal experiments. This area gained sufficient savanna quality that it was dedicated as an Illinois Nature Preserve in 2021.

Initially, some experts told us it wasn't worth our time. Though these 85 acres included what seemed to be remnant patches of prairie, savanna, and wetland, they were all too small or degraded to be included in the Illinois Natural Areas Inventory. The "high-quality" (Grade A and B) remnants that were accepted by the Inventory were all small. Most very high quality ("Grade A") prairies were just an acre to two. No Grade A black-soil savannas were found. 

Initially we had been impressed by the "prairie" species we found in the least shady areas of Somme. And indeed other experts told us this was a degraded prairie, worth nursing back to health. But as we worked, we gradually figured out that tallgrass savanna was the original ecosystem for most of this site. (The book Miracle Under the Oaks: the Revival of Nature in America by New York Times science writer William K. Stevens tells that story.) Since then we have experimented with restoring the best remnant parts of this Cook County Forest Preserve including prairie, woodland, sedge meadow, and marsh - but most of the land was savanna, and that's where we put most effort.

What would become the Somme experiment was launched in 1977 as the “North Branch Prairie Project” with goals and methods coached initially by Roland Eisenbeis, Chuck Westcott, Prof. Robert Betz, Ray Schulenberg, Dr. William Beecher, George Fell, Jerry Paulson, and many more over the years. At all stages, our work required authorization by Forest Preserve staff, but in early years we were encouraged to rely principally on Dr. Betz and Illinois Nature Preserves Commission staff for details as we drafted plans and developed techniques.

We were inspired by Dr. Betz, who had written:

“It is surprising how little is known about the natural world … In order to carry out meaningful research in this area, it is necessary to have relatively natural landscapes … to serve as standards to evaluate the changes that have occurred elsewhere and their effects on men and other biological organisms… Even if there were no scientific values in a prairie, its aesthetic appeal alone would warrant its preservation. It is one of our links with the past – a tie with the natural world. It seems immoral to destroy an integral and important part of the biological world from which mankind arose.”

From “What is a Prairie?” in “The Prairie: Swell and Swale.” 
Photos by Torkel Korling. Essay by Robert F. Betz. 1972.

We benefitted from Betz' detailed suggestions and exchanges about our ongoing work. His initial focus has been high-quality remnant prairies. He considered even the best of them to have been at least partly degraded, which had moved him to experiment with ways to restore quality and expand their dimensions. In little cemetery prairies, he pulled weeds, burned, and carried seeds from the best remnant areas to degraded ones. Then Betz began expanding the high-quality few acres of the Gensburg-Markham prairie to hundreds of acres of adjacent land. His concern? The small populations of most plant and animal species that comprised most prairies were vulnerable to genetic, disease, and other problems while having reduced capacity for maintaining evolutionary fitness as hydrologic, climatic, rain acidity, and other conditions changed. 

Across the railroad tracks from Somme Prairie Grove were two acres of Grade A (very high quality) original prairie. We had worked there first, removing invasives and spreading seed in what, with our support, soon became Somme Prairie Nature Preserve.    

Our initial plan for Somme Prairie had been simple. Pull invasive weeds, cut invasive brush, and move seed from high-quality to depauperate areas. At Somme Prairie Grove, with much less remnant quality prairie, Betz encouraged us to gather seed from diverse nearby natural populations. Betz impressed on us his judgment that all prairies, even the best remnants, had been subject to degradation – most obviously in the loss of animals – but almost certainly in the loss of many plant species and genetic alleles as a result of lack of fire, fragmentation, grazing, drainage, and other impacts. He emphasized two ecosystem conservation strategies: first, save and restore health to the little high-quality remnants and, second, do our best to restore full diversity to larger landscapes, where animals, fire, competition, evolution, and time would have the opportunity to restore a more complete, diverse, and sustainable whole.

Initially, we saw Somme Prairie as the remnant and Somme Prairie Grove (SPG) as part of the larger prairie landscape to which full diversity would be restored. To restore missing plant species, we found we could locate nearly all original prairie species in spontaneous populations within fifteen miles of the North Branch Prairies. Once we recognized that the larger, eastern part of SPG was originally savanna,[1] we began to look for savanna seed sources and found them even harder to locate. We expanded our search area for savanna and woodland species to 25 miles.

Thus, Betz, Eisenbeis, and other advisors encouraged us volunteers to begin an experiment[2], a specialized sub-set of the overall forest preserve experiment. We were – in the words of the Forest Preserves’ charter – “to restore and restock … such lands together with their flora and fauna as nearly as may be, in their natural state and condition …” We sought to assemble larger work crews and more focused expertise than were available for most preserves. We would record the work and the results, for comparison with differently managed areas.

Side by side with that science and conservation experiment is an ongoing human community experiment. There should be reports on that too. For one, describing recent initiatives in Somme Woods, check out

Initial State of the Preserve

A deeper history of this preserve is detailed in the book Miracle Under the Oaks by William K. Stevens. Briefly, it had been under the glacier until about twelve thousand years ago, then hunting and gathering land for Native Americans until about 1830, then owned by Euro-American farmers who used most of it to graze cattle but also plowed parts for corn and other crops. It was acquired as a Cook County Forest Preserve in the 1930s. 

When ecological restoration was begun in 1980, the site was mostly brush or young woodland but with scattered "old field" openings. About 250 native plant species were recorded as "original" or "spontaneous" here. Most of these were in small upland areas including a railroad edge, street edges, former fence lines, and in the old-field openings. Later when we paid more attention to the wetlands, we found many remnant wetland species there. 

Basic research questions

Through our ongoing discussions with Forest Preserve and Illinois Nature Preserves Commission staff along with Betz, Schulenberg, and many others, we had the sense that we were doing “battlefield medicine” - ecosystem triage and first aid. We accepted a hypothesis from Betz, as worthy of testing: 


That complex, natural ecosystems have a regenerative power such that, as we cut brush, controlled invasive weeds, planted diverse rare seed, and burned frequently, ancient interdependent relationships among species would re-emerge, and diverse quality vegetation (and interdependent animals) would gradually, increasingly take over and become self-sustaining. 

Three basic research questions underlay our planning and work: 

  • How well is it possible for a damaged ecosystem[3] to recover, and how much apparently missing biodiversity will spontaneously come back in response to remedial care?
  • How much missing plant biodiversity can be re-assembled and re-introduced into a damaged remnant through restoration by seeds, plugs, and otherwise?
  • What is the impact of this restoration work on the animals?
Over the years, these three questions led us to many sub-experiments and many ways of measuring the results, as described below.


Aside from a bit of weed pulling, which started in 1977, we began the restoration of Somme Prairie Grove (then called "Somme Woods Prairie") in October 1980. In the early years, work was on a rotating schedule with other North Branch sites; volunteer crews of fifteen to twenty people worked at this site roughly once a month during the eighties and nineties. In later years, as resources increased, work here was two or three large-group “workdays” per month and additional small-group sessions. The patch size of our early efforts reflected what a group could accomplish in three hours (typically a tenth acre or less). We initially sought to restore these “workday-sized plots” through cutting brush away from the most promising-looking plant associations on the site and planting diverse seed where the brush had stood. Since the best examples were scattered, we soon had little centers of “biodiversity restoration” to study that included dry-mesic to wet savanna and prairie scattered over the eighty-five acres. It may have been significant to our results that we never impacted any large area all at once. All work was in small scattered patches, bit by bit, year after year.


Fire was the exception. On average, half the flammable parts of the site have been burned every year. Unburnable parts included non-oak thickets, weed patches (e.g. tall goldenrod), and low areas that may have been too wet on burn days.

When we expanded burning from grasslands to the oak woodlands in 1983, we found that there was typically a non-burned zone in between our two best fuel types, dense "prairie" grass and dense oak leaves. Thus the woodlands and grasslands tended to stay separate.

Brush control

From the beginning we prioritized work according to the quality of remnants. Initially, there were many isolated “old field” patches among the more extensive areas of brush and trees. We worked to rescue and expand areas of greatest quality along with any areas that retained flora not found elsewhere.

The site had, and still has, many (now seemingly inappropriate) tree species planted in an earlier era. Forest Preserve staff introduced such species as pine, birch, post oak, rock chestnut oak, chinquapin oak, silver poplar, black locust, honey locust and others. In most areas, the major problem species that we thinned included buckthorn, tartarian honeysuckle, green ash, white ash, and box elder.

Bur oak, Hill’s oak, and shagbark hickory seemed to be consistently the major species of the higher quality wooded areas. There were many old bur oaks but few other old trees. We prioritized protection of existing young bur oaks and cut away trees shading them, including at times Hill’s oak and shagbark hickory. But in most areas, for many years, we left most Hill’s and shagbarks, watching to see how they responded to repeated fire.

All or nearly all the white oaks stood in the old tree-planting areas. (Large areas of natural white oaks occur in Somme Woods, which had apparently experienced less frequent or intense fire.) No white oaks at SPG were old. But we mostly did not cut or thin the white oaks as a) we had higher priorities, b) it seemed like too much work, and c) these areas were stable, not promoting the growth of noxious species. Indeed they increasingly became a good source of woodland seed (after we planted it where burning made good habitat under the oaks). We did control the white oaks where their shade was damaging high quality prairie or savanna remnants or recovery.

We gradually recognized the need to protect some shrub species, especially hazel and wild plum. Some shrub thickets are now quite diverse but do not seem to develop hoped-for self-sustainability under the influence of fire. 


Initially, we followed the guidance of Robert Betz, Ray Schulenberg, and Harold Rock[4]. We raked our seed mixes only into areas denuded by brush, after we cut the brush. We restored some other species by “plant plugs” or “rootlings” grown in greenhouses or gardens. In time we learned that we would get better results more easily from seed broadcast into turf areas that were being burned, and that became our standard method.

For any given area, we tried to broadcast our seed mixes for two or more years, because we found that some species would be established only in some plantings in some years. Our suspicion was that in non-establishment years, perhaps weather conditions or pest predation in the previous year resulted in poor quality seed, or perhaps weather conditions in the first growing season following planting were not favorable. Thus, repeat plantings in the same area over a number of years may have increased the likelihood of a larger number of species succeeding in a given area. We also suspected that the overall diversity benefitted from the scattered plot approach. Species planted in one plot had the potential to move into adjacent plots over the years. And many areas were never planted, so that the existing species mix there could evolve without sudden competition from the whole list of species in the seed mix, over time and according to its own unguided dynamics.   

Most of the species planted were already present on the site, but in small numbers. Although their genetic diversity may have been badly reduced, these species may have the advantage of surviving associated symbiotic bacteria, algae, diseases, invertebrate animals, etc. Species not surviving at Somme Prairie Grove but surviving across the railroad and river in Somme Prairie may in time have such associates restored by unaided dispersal. (One indication of this process is the appearance in Somme Prairie of a species, cream gentian, not originally found there but very common at Somme Prairie Grove. It originally appeared at Somme Prairie only along the entrance trail, suggesting that it was introduced in mud clinging to the footwear of people who visited both.) Species not surviving at Somme before our restoration efforts may have had some associates brought with the seeds in the chaff, which we included when broadcasting the seeds. But their associated species may be much reduced at this new site.

We later summarized our approach and gave details about our basic seed-mix lists in the Tallgrass Restoration Handbook[5]. We gather more than 200 species of seed annually and have more than a dozen different mixes according to how shady and how wet the various planting areas are. 

Current Status of the Preserve

Roughly one half of Somme Prairie Grove Nature Preserve is now of good or high quality. The plant list has increased from about 250 to about 500 species. Most acres of former brush are now savanna – with smaller acreages of prairie, woodland, and wetland.  

The main goal of Nature Preserves is to protect, restore, and maintain now-rare, high-quality natural communities of animals and plants. Less than 1/100th of 1% of Illinois prairie survives as high-quality. For savanna, the amount is still lower. Bur oak savanna on good soil was a major community in Illinois; it has been little understood or studied until recently and is extremely rare. See Endnote [14].

Assessing vegetation quality is not hard science. It requires judgment. If you'd like to know Stephen Packard's assessment of areas that are generally good or high quality, they are mapped below. The little  "good and high quality" outlier to the northwest is original prairie that is being nursed back to good health. Perhaps it should be expanded considerably to increase the prairie habitat for animals dependent on Somme Prairie Nature Preserve (which is essentially adjacent, across the railroad tracks to the west). Or perhaps the area to the east of that prairie patch (which now has planted oak trees) should be restored as savanna to increase the habitat of savanna animals in this Nature Preserve. Forest Preserve staff, stewards, and other experts are watching developments to help make that decision. (There is much former savanna habitat under restoration essentially adjacent, for some animals, like birds and butterflies that can cross a four-lane highway, to the east across Waukegan Road.) That little "good and high quality" outlier to the southwest is also former prairie.  

Some individual studies - and what we learned from them

There are and have been many sub-experiments – some aimed at solving various problems and some aimed at facilitating species or community recovery. We will not attempt to list them here, but a few are worth mentioning as examples.

We were initially counseled by our advisors (especially Betz and Schulenberg) that prairie seed could not compete against an established turf of weeds. Because we did not have the resources to plow up the weeds as they had done in their experiments, they encouraged us to grow young plants in greenhouses, to give them a good start, and then plant them in our degraded prairies. We did this with partial success in the early years and planted other seed in the bare dirt that was all that was left in some areas after we removed the invasive shrubs and trees. 

The belief that prairie seeds could not compete in turf turned out to be erroneous. It had just been assumed, and no one had checked. We tried various approaches, found that some worked, and published the results.[6] As it turned out, Dr. Betz had made similar experiments and found the same. One challenge of this approach is that it takes five or longer years for many species to become apparent. Using the plowed field method, big bluestem and many other species were robust after two years. On the other hand, many species, especially those typical to high-quality prairies, often failed to establish by that approach. But we found that “inter-seeding” into turf did establish them readily. The successful conservative species included shooting star, prairie betony, prairie dropseed, Leiberg’s panic grass, prairie gentian, prairie violet, cream false indigo, purple prairie clover, and many more.  

In early years, we laboriously incorporated the seeds into the dirt by tearing up the top inch to quarter inch of soil with four-pronged rakes. In 1993 we decided to test whether that was needed – or whether would it be sufficient to merely broadcast the seeds in the fall and let the freeze-thaw cycle work on them. We marked plots, kept careful notes, took random samples in both experimental and control plots, and found that prairie species established well in open “old field” turf by simple broadcast alone. We published the results of that study in “Restoration and Management Notes”[7].

Restoring populations of endangered plants
We had no expectation or intent when we started, but it turned out that strategic "intensive care" could revive populations of more than a dozen plant species on U.S. or Illinois Threatened or Endangered lists. See, for example, our reports on the eared false-foxglove at: and the prairie white-fringed orchid at: .

Caging species threatened by animals
We found some plant species of concern being badly depleted from some areas by white-tailed deer. "Sapling" oaks were one foot tall, because their tops were so often eaten by those same overpopulated deer.  We began protecting some of them with wire cages and found them increasing dramatically. In some cases, such species became common or robust enough that continued caging was no longer needed.

Edge hedge
In the early years, Somme Prairie Grove was badly torn up by vehicle recreation. We decided to stop cutting brush near the edges so as to promote a physical barrier to exclude vehicles. In time, the hedge also became an appreciated visual and sound barrier as well as a habitat for some animal species. We control female buckthorn to lessen berry-production and resulting reproduction on the site. In some areas we have made some progress in replacing buckthorn with shrub and tree species native to these habitats.

Vestal Grove transect
The stand of bur oak along a part of the southern border of the site is one of the first areas of the Midwest where efforts have been made to restore full plant diversity to a “closed savanna” or “oak woodland” ecosystem. Initially, little grew under the oaks other than dense buckthorn. We burned for two years and watched for signs of understory recovery. When we found not much appearing (beyond alien thistles and dandelions), we began to plant a mix of seeds designed for such a woodland[8]. In cooperation with a larger study[9], we began sampling the herbs in the grove every second year, beginning in 1985 and continuing thus far through 2017.


Some results are mixed in with the discussions above. It just seemed easier that way.

Other results are reported below. In some cases, the conclusions are based on scientific data. In other cases, the statements are just judgments from observations. Lest this approach concern some people, let us point out that if a plant species was not found on the site for many years, then appeared in good numbers where seeds of that plant had been broadcast, then spread to be common over a wide area, it seems reasonable to report that result without apologies for the lack of numbers. There is not time for random sampling of everything. And we can draw practical conclusions without it, in some cases. We will start with some general answers to the three basic research questions posed earlier and follow up with examples of data sets that along with observations and judgments informed those conclusions.

How well will a damaged ecosystem recover, and how much apparently missing biodiversity will just come back in response to remedial care?

Very few plant species that were not on our initial inventories came back from the seed bank or otherwise appeared. This was disappointing. On the other hand, many conservative species that had been present in small numbers increased dramatically. A few species (notably the endangered Bicknell’s geranium) did seem to emerge in response to the burns.

How much missing plant biodiversity can be re-assembled through restoration?

As best as we can determine, 345 native plant species seem to have survived on the site (some in very small numbers) when we started. Today, the list includes 487 native species. That overall increase in species diversity may or may not persist over time. Whether it will continues to be an ongoing part of the experiment. Many rare or conservative species seem to be increasing in numbers and extent. Random sampling in many areas shows gradual increases in plot diversity in the areas sampled.

What is the impact of this restoration work on the animals?

Five species of snakes and five of amphibians were found on the site when we began. All seem to be doing as well or better than they did then. In contrast, there are many unmanaged areas along the North Branch that once supported those species where, as the invasives increased, populations have been lost. Few conservative invertebrate species have been found; data on the somewhat conservative species has not been analyzed sufficiently to evaluate trends. Birds have made an impressive comeback; many savanna species of conservation concern have returned and reproduce annually.

The following four data sets are quick-ish examples of how we have monitored success and failure at Somme Prairie Grove.

Six circles data 1994 – 2017

In 1993, we drove six stakes into the ground to mark six previously unplanted plots that looked similar to us. In all six we scattered seeds, and then in three of the circles chosen by flipping a coin we raked the seeds into the turf. Within the six plots we recorded existing plants in quarter-meter quadrats and followed up to measure changes in 2003 and 2017. Summary data is shown below.

Our initial purpose was to check whether we needed to rake the seeds into the turf. That turned out to be a waste of time, in this case.

But we've continued to sample the plants in those plots. The results show that quality and diversity in the quadrats continue to increase. The overall number of species (and of native species) is not increasing, at least for now.  

Species quality
Quality plus diversity
Number of native species
Number of species

Species quality (also called conservatism)
Notice that the quality (average coefficient of conservation) continues to increase in the data taken 37 years after the restoration began and 23 years after the experimental seeding. Indeed, the quality rose as much during the first nine years of this study as it did in the subsequent 14 years, suggesting sustained increases slowing only slightly. We expect that the quality will continue to rise with good management.

Quality plus diversity (also called Floristic Quality Index)
These numbers represent a formula based on both the quality of the species and the number of species.

Number of native species
Increased about 15% between the first and second samples. Between the second and third samples (2003 - 2017), the number of native species has hardly changed.

Number of species
Declined slightly. What is happening here is that, as the number of “quality” species is increasing, alien and native “weedy” species are dropping out because they compete less well in a high-quality community. We would not be surprised to see the total number of species in these plots slowly rise over the decades. As the quality of the vegetation improves, niches may open up for yet more conservative species, but that is not happening so far.

For more detailed explanation and additional data, see Endnote[10].

Vestal Grove data

So far as we knew (or know), no one else had worked much on full plant biodiversity restoration for tallgrass oak woodlands when in 1983 we began restoring Vestal Grove. This bur and Hill’s oak patch with a dense understory of buckthorn on the south edge of the preserve is typical of unburned oak areas, probably all of which have suffered minor to almost total loss of the plant species (and, less studied, animals) of oak woodlands. At the Morton Arboretum and in the DuPage forest preserves, Gerould Wilhelm and Wayne Lampa had begun working together to study burning as restoration in good quality woodlands. They advised and influenced our work, but at that time they were burning only, rather than burning and broadcasting seed.

Actually, for our first two years of woodland burning we too only burned, but as little revived from the hoped-for seed bank, we began broadcasting seed in the fall of 1985. As it turned out, the herb sampling transect we began here in the fall of 1985[11] allowed us to track the progress of plant recovery and restoration in considerable detail. A fuller account of this study was published 2021; the study and a popular summary of it from the University of Illinois Somecan be reached through this link.

Some earlier lessons of this study are described below:

Degradation and Recovery

In the graph above, the red line shows the average floristic quality of the plots[12] in the bur oak woodland. Quality rose substantially for the first few years, but a severe overpopulation of white-tailed deer (documented at more than 160 per square mile by Forest Preserve staff) here and nearby prompted a deer culling program by both the Forest Preserve and Village of Northbrook staff. During 1990 to 1993, the years of greatest deer density, the floristic quality of the oak grove dropped substantially. Following the deer culling program, begun in 1993, quality rose again, until progress was reversed by a moratorium on all restoration activity, imposed by the Forest Preserve board president[13] (ending deer culling, prescribed burns, invasives control, and more). When burning and other restoration of the grove was resumed in 2003, quality began to rise again. 

The colored lines above graph the abundances (total cover) of four different types of plants from 1986 to 2015.

The red and yellow lines track rank weeds (red) and fairly weedy species (yellow).

The green line tracks the highest quality species (that is, the most conservative).

But the blue line is probably the one that deserves most attention in this brief account. It shows the amount of cover by plants of “relatively high-quality” (coefficient of conservatism of 4 to 6). These seem in this case to be the species most responsive to good care, or its lack. They increase to double their abundance in the first few years – then lose half their gains. Following deer culling, they rise again to four times their former abundance only to plunge again when restoration is paused. With the return to good management, these relatively high-quality species increase to about 800% of their original level. (That's as of 2015. The 2017 data is still being processes. Stand by!)

Note that the very high quality species (green) were hardly represented when we began - but by 2015 were more robust than the two weedier categories combined (yellow and red).

Three of us published a more technical paper based on this data in 2020. Links to a good popular summary of this paper by the University of Illinois News Bureau and to the paper itself are here.

Site-wide Vegetation Quality

Beginning only in the year 1996, we began random samples of the overall site every four years. We started this monitoring in part because the moratorium was still hampering us, and it seemed valuable to have hard scientific data to contribute to the case for good conservation management. It would have been better to have started earlier, but there’s only so much time in a day. Actually, to some extent, we have a form of “before” data in that parts of the site are still hardly managed, and we can compare the managed to the unmanaged areas. (Potential bias is introduced to the "grassland" areas by the fact that we managed first the best prairie-like areas first, but they were a very small part of the site, and few or no random points landed in them during this sampling.) These graphs also help us compare how the woodland areas are doing compared to the grasslands (that is, prairie and savanna).

The above graphs represent 113 random ¼m2 samples taken in 1996 and 2000. Some simple messages illustrated by the graphs above are:
  • Restoration works, in that floristic quality and plot diversity is dramatically improved in the areas under restoration.
  • Grasslands and woodlands responded remarkably similarly.
  • We still have a long way to go, as a high-quality grassland has Floristic Quality scores in the high teens or low twenties, and our averages don’t even reach 10.

The above graphs represent about 55 random ¼m2 samples taken in each of every fourth year from 1996 and 2012. These results may look like a "nothing-burger" - but may in time be among our most compelling graphs - if we're right. Our "hypothesis" is that this ecosystem will progressively heal in terms of what we understand as quality - over time, given good stewardship. When we compare the trends over the first twelve years of this study (begun during the stewardship moratorium), we notice the following:

1. We have not yet analyzed the data from 2016, though that should be done sooner or later, and this graph will be updated.
      2. Quality was still falling during the 2000 – 2004 interval. The explanation, we believe, is that the recovery from the moratorium took that long. Brush and noxious invasive weeds had spread dramatically, and it takes years to reverse degradation, especially when areas are in the “intensive care” phase of recovering from "major surgery" following the cutting of dense brush.
      3.  It may seem curious that the “unmanaged” areas also decreased in quality from 2000 to 2004. But the "unmanaged" (less managed?) areas had been benefiting from some control of invasives (because they would otherwise re-invade the recovering areas) and some fire. Thus, before the moratorium, we had been providing some benefit to otherwise-unmanaged areas. 
Challenges and Priorities Ahead

Drafts on this component are circulating. They’ll be added here when a draft is ready.

Summary and Conclusion

Expert judgment and data on many groups of species suggest that the restoration of Somme Prairie Grove has achieved substantial gains and is heading in the right direction. Overall site-wide gains suggest that after four decades the site overall may be about half way toward our goal of recovered high-quality natural ecosystems.


It would be truly impossible to list everyone, but some of the major Somme Prairie Grove contributors who may not be listed in the text include:
Jane and John Balaban, Karen Glennemeier, Eriko Kojima, Linda Masters, Lisa Culp Musgrave, Sai Ramakrishna, Jerry Sullivan, Gerould Wilhelm,  Steve Thomas, John McCabe, Trow Showerman, Joel Rosario, Steve Ochab, and Deborah Antlitz.

Restoration and study of all the Somme preserves in recent years have benefitted massively from the dedication of Eriko Kojima who initiates projects, coordinates new volunteers, plugs leaks, and finds ways to help make other people’s time more valuable.

Many thanks to Kathy Garness for patient proofing and good questions.  


[1] An important Phd scientist at an important planning seminar encouraged conservationists to forget the tallgrass savanna because it was "gone! gone! gone!" That was true of many minor ecosystem types, but the savanna had covered millions of acres. Ecosystems can be damaged and then recover. The real question was whether the savanna had been so badly damaged that recovery was impossible. We resolved to do our best to demonstrate that restoration and recovery was possible. Our evolving awareness of the savanna at that time is summarized in “Just a few oddball species: restoration and the rediscovery of the tallgrass savanna” in Restoration and Management Notes 6(1): 1988. A more technical treatment of our perception of the savanna at that time can be found in "Rediscovering the Tallgrass Savannas of Illinois," Proceedings of the Tenth North American Prairie Conference, Denton, Texas, 1986.

[2] Some people have charged us with not doing real science because we did not have control sites to compare our efforts with. While there’s some value to this concern, we have argued that we have actually been doing a larger and more challenging experiment than the ones our critics preferred. To start with, our experiment has lasted four decades, which few comparable experiments do. And our focus was a plot of more than 80 acres (more than 30 hectares). To paraphrase Stuart Pimm, most ecology fails to elucidate many ecological phenomena because it studies a few species in a few acres for a few years, but most ecological process require more, bigger, and longer to truly function.

Of course, we do many little controlled experiments, and we publish some of them. But the main thing we’re trying to do at Somme is to restore diverse quality to a savanna. With the resources available, we couldn’t possibly do that on many large sites. So we’re learning what we can as best we can. If we’re successful, and the patient survives and revives, it may be one of the few of this level of diversity that will be available over the years for black-soil savanna study.

Part of the problem with some critics is that our story has been sensationalized in the press as one of those American “rugged individual” or “lone rebel” stories. Those dramatizations are off base. We relied on broad expertise, from the beginning. One added special advantage accrued to the Somme preserves when Stephen Packard became Nature Conservancy director of science and stewardship – and focused on savanna conservation here. Many visiting experts provided advice when they looked at Somme or when he visited their comparable sites or through other exchanges. Special thanks go to Kim Alan Chapman, Doug Ladd, Jack White, Kat Anderson, Rich Henderson, Jerry Wilhelm, Paul Nelson, Bill Jordan, and many others.  

[3] Somme Prairie Grove contained remnant prairie, savanna, and wetland. Though the good quality remnants comprised only a few of the 85 acres, the fact that the rare plants survived likely meant that many remnant populations of animals (especially invertebrates), soil biota, and other species and processes likely survived as well. Thus, this experiment was one of restoring what was partly still there, rather than starting from nothing but a corn field.

“Prairie flora” that survived included prairie dropseed grass, hoary puccoon, smooth and downy phlox, porcupine grass, short green milkweed, New Jersey tea, prairie violet, yellow stargrass, and many more. Note that all these species, that we originally perceived as evidence of prairie, would also be present in savanna. Species present that are more typical of savanna included wild columbine, wild hyacinth, woodland puccoon, purple vetch, Maryland snakeroot, small sundrops, and others. Quality wetland species included American slough-grass, Wolf’s spike rush, the sedges Carex atherodes, buxbaumii, crus-corvi, vesicaria, Sullivant’s milkweed, and others.

[4] Betz provided ongoing mentoring. Schulenberg sent written guidance based on his work in the Morton Arboretum. Harold W. Rock had in 1971 published the Prairie Propagation Handbook. Boerner Botanical Gardens, Milwaukee, Wisconsin. In introductory comments he had mentioned that the restoration pioneers at the UW Madison Arboretum had found that the seeds of some prairie species would grow successfully if merely broadcast in an old field turf. These comments suggested that we might test the contrary views of our mentors, which let to “inter-seeding” as our major propagation method.

[5] Packard, S. and Cornelia Mutel eds., 1997, Tallgrass Restoration Handbook: for Prairies, Savannas and Woodlands, Island Press. Techiniques used at Somme are most specifically reflected Chapters 4, 5, 11 and Tables 5.1, 11.1 and 11.2.

[6] Packard, S. 1994. “Successional Restoration: Thinking like a prairie,” Restoration & Management Notes, Volume 12, Number 1.

[7] Packard, Stephen and Linda Masters, 2008, “Restoring Conservative Prairie Plants to an Old Field Turf,” Restoration & Management Notes, Volume 26, Number 2. (This journal today is called Ecological Restoration.)

[8] “Restoring the Herb Layer in a Degraded Bur Oak ‘Closed’ Savanna,” Stephen Packard and John Balaban in Proceedings of the North American Conference of Savannas and Barrens, James S. Fralish, Roger C. Anderson, John E. Ebinger, Robert Szafoni, eds. Illinois State University, Normal, IL 1994.

[9] The study was proposed and supervised by the Illinois Nature Preserves Commission and funded by the Illinois Department of Natural Resources. The study was designed by Gerould Wilhelm, Marlin Bowles, Steven Apfelbaum, and Alan Haney. Along four transects that spanned the width of the site from east to west, the study recorded trees, shrubs, herbs, lichens, small mammals, birds, and some invertebrate animals.

[10] The area where this experiment was conducted was typical of the “old field” areas of this site. Although no seed had been planted here, it had been burned many times and such invasives as white sweet clover weeded many times in its 14 years of previous stewardship. Thus the 1994 data may be typical of a burned, weeded, unseeded old field here.

So that we could re-find the plots we installed metal stakes at their centers and marked their edges by temporarily inserting flags in circles with radii equal to our four-pronged rakes, resulting in plots of 6.15 m2 (or 66 square feet). We recorded the positions of the stakes (and easily re-found them decades later) by triangulating to recognizable trees in the grove to the east. (The plots ranged from 17 meters to 32 meters west of those trees.)

In the chart below, the numbers represent the sampling inside the planted circles. We identified species within six 1/4 m2 plots (placed regularly inside the circumference of each circle).

Mean C
Native Mean C
Native FQI
Native Species #
Species #

See Swink and Wilhelm (1994). For a technical on-line explanation of terms see: [[[]]]

The six species with highest Relative Importance Value (RIV) – a measure combining frequency and how much ground the species covered – in 1994 were rigid goldenrod, early goldenrod, field hawkweed, a sedge (Carex hirsutella), meadow fescue, and Canada bluegrass. These species suggest a relatively common old pasture in a former prairie or (especially given this sedge) savanna.

In 2003, only one of the original six highest RIV species held their leads. Then the big six were big bluestem, prairie dropseed*, gray dogwood, early goldenrod, rattlesnake master*, and wild quinine*. The species with asterisks had been in the planting mix nine years earlier. Big bluestem was not in the seeding mix. But in the early 80s after our first burns, one remnant large plant of it stood above everything else in that part of the preserve. Under the burn regime, it was spreading on its own (too much, in our view).

In 2017, the six species with the highest RIV were big bluestem, prairie dropseed, wild quinine, gray dogwood, Carolina rose, and nodding wild onion. Thus, we have four of the 2003 species and two new ones. Change seems slower.

Two tidbits of observations about the Six Circles results:

1. White prairie clover

A small amount of the seed of this highly-conservative species was in the planting mix but not recorded nine years later. (The slightly less conservative purple prairie clover was plentiful after nine years.) However white prairie clover was found in the center of one of the plots in 2017. Did it really take more than nine years to be noticed? Had the seed lain in the ground for some years before it germinated? Had the deer eaten down this very palatable species repeatedly, so that we only managed to record it by chance on a year when the deer had missed it?

2. Woody invasion

Although these six plots represent an interesting planting experiment, they don’t well represent the surrounding area. In respect for the original experiment, we did little restoration in the part of the preserve where these circles are, which has been largely on its own for decades. But notes remind us that in 2004, after we had triangulated and found the circles again, we cut out and herbicided buckthorns, bur oaks, Hill’s oaks, and shagbark hickories “in and adjacent to” the plots – so that the trees wouldn’t interfere with the herb planting experiment. Arguments could be made either way on what approach would most have benefitted the experiment, but we chose removal of the trees. The note doesn’t mention gray dogwood. Perhaps there was little. Perhaps we forgot to list it. Or perhaps we decided that that species, present originally, was indeed part of the experiment. Its “total cover” of 107 in 1994 increased to 316 in 2003.

In any case, to our surprise (shock?), when we came to sample the plots in 2017, it was apparent that woody plants were dramatically increasing. (See photo, below.) Dogwood was much denser in all directions. Inside the plots its cover was 185 (perhaps reflecting our woody plant control?), but in our sample immediately outside the plots it was a whopping 519. Bur oaks, scarlet oaks, and shagbark hickories were frequent, in the plots and to the east and south. Young trees in the grassy areas typically have their tops burned back every few years, but in this area (perhaps because of shade from the east and south), they seem to have been sprouting back bigger and bigger. As this is a savanna restoration, the return of these trees to this formerly cleared field would be considered by many (including us) a plus. But the dense dogwood may represent a management challenge. If it increases just a bit more than it has (given modest fuel because the shaded grasses aren’t supplemented by plentiful oak leaves), the dogwood may start to shade out the herbs and grasses and further reduce burnablity by all but the more intense fires. This is a challenge worth thinking about.

Dogwood brush and young oaks seem to be increasingly dense in the Six Circles study area. Nearby, however, are similar areas with dense, good-to-high-quality grassland vegetation with few shrubs. The area of this mosaic of brushy/non-brushy patches has burned on the average of once every two years during the last three decades. 

[11] A permanent transect marked by metal stakes was installed here as part of a study initiated by the Illinois Nature Preserves Commission in 1986. One of the four east-west transects (selected at random by principal investigators Steven Apfelbaum and Alan Haney) happened to fall just a meter north of the transect we had sampled in the fall of ’85. This fortune of randomness allowed us to continue the INPC experiment with the benefit of the ’85 data. Since, typically, a spring sample misses some fall species and a fall sample misses some spring species, we decided to sample the transect twice each year (in June and September) and combine the results so that the sample would include as much of the flora as practical.

[12] In the Illinois Nature Preserves Commission study, plants were identified and how much ground they covered was estimated in circular plots of one square meter each. These permanent plots were ten meters apart on an east-west transect. The data given here reflects the “weighted floristic quality index” (see

[13] See “And then … the Moratorium” sub-head in

PS: Other studies underway

There are so many other studies underway that it would weigh down this paper just to list them in detail. Perhaps that should be a future paper. 

Subjects include amphibians, dragonflies, butterflies, fungi, lichens, varied seed mixes and planting times, spread of species by roots, spread of species by seed, “Land Audit” plots, “Woods Audit” plots, macro-plot comparisons, seeding-plot monitoring of various kinds and purposes, and many individual rare plant species. 

In 2017 two new sampling regimes were initiated by the Illinois Natural History Survey (quality woodland baseline study) and Forest Preserve District staff (quality savanna baseline study). 

Need for additional studies
The studies done so far are a pitiful scratching of the surface of what should be. We have little direct study of soil organisms, most animals, and even the plants of most parts of the preserve. We also need more thinking about the kinds of monitoring and studies most worthy of doing. 

Need for additional stewardship 
As much as we love the data and the science, the stewardship seems more important. People can study later what has survived, healed, and been restored. Priorities today include seed harvest and broadcast, raising and transplanting plugs of key species that don’t do well by seed, control of reed canary grass, teasel, crown vetch (especially nearby “feeder” populations), oak rescue, shrub thicket experimental maintenance, brush clearing,

[14]  In his seminal Vegetation of Wisconsin (1959), John Curtis wrote: “The oak openings not only varied in average density but also in the spatial distribution of the trees, with extreme aggregation the rule.” (Page 331.) Curtis also wrote that original Wisconsin had 5,500,000 acres of savanna, making it the most extensive community in the southern half of the state but that, “Beyond question, an oak savanna with an intact ground layer is the rarest plant community in Wisconsin today.” 
The Illinois Natural Areas Inventory’s Technical Report (1978) begins its discussion of savannas this way: “Savannas are communities with a grassy groundcover and an average tree canopy cover less than 80% but greater than 10%. A savanna may have shrubby areas, and the tree canopy may locally be greater or less than the above limits. ... They were among the most widespread and characteristic communities in Illinois, but few high quality stands remain.” 
The Illinois Natural Areas Inventory became a national model when it was completed in 1978. The "surviving prairie" figure of 1/100th of 1% (mentioned above) comes from that study. Statewide, the Inventory found 274 acres of high and very-high quality mesic prairie (the type with average soil moisture, not very dry or wet). For comparison, if we compare the amount of mesic savanna (which is what we mostly have at Somme) found by the Inventory, the state-wide total was 2 acres. High-quality savanna is very rare. To qualify for that original inventory, such a rare site had to contain at least one-quarter acre of very high quality or at least two acres of high quality. 
How high is the quality of the savanna at Somme today? When updating the Illinois Natural Areas Inventory here recently, the initial expert assessment proposed the south half to be high quality, and the north half to be good quality. Other experts questioned that assessment on the grounds that some parts had fewer trees than classic savanna - while other parts had too many. 
The tree variability at Somme today is mostly result of past farming and recent restoration. The areas here with denser tree canopies might best at this time be classified as bur oak woodland (another very rare community). Nearby areas may look superficially like little prairies, but they include many bur or scarlet oaks which are shrubby "grubs" because the tops are frequently burned off. More and more of these are getting big enough to survive fires, and sooner or later these trees will have fire-resistant trunks and canopies. But even as they are, these areas have many distinctive savanna animals and plants and represent one phase of natural savanna vegetation. 

However the details are mapped and graded, the Illinois Nature Preserve Commission judged that a consensus had emerged for dedicating this site as high-quality savanna. 
One short-term management question for the future of Somme Prairie Grove is how much to thin the oaks where they are especially dense and how much to protect oaks from fire in areas now lacking in mature trees. For the longer term, most trees gradually grow larger. Old trees die. Nature is not static. 


  1. Your results are remarkable. However, they are not totally unexpected. When things that are as completely destructive as buckthorn, bush honeysuckles, white sweet clover, extremely over populated deer etc. are removed; native species are seeded; and natural processes like fire are reintroduced then the quality is going to improve. Unfortunately, I still think there are factors that cannot be mitigated that will affect the ultimate outcome. I don’t think Somme Prairie Grove or Somme Woodland will be restored to the condition it was when Baker or H.S. Pepoon was surveying. Restoration is a moving target and we do the best we can under changing conditions.

    Still, I am hopeful. At Deer Grove Pete has discussed the sluffing off of top soil in a patchy manner from the woodland slopes. I hope the removal of buckthorn and its effects on soil chemistry might allow for a slow recovery. However, there are other factors. I do not know if what we are able to change will be what is needed to stop future deterioration.

    1. James, I agree with your concerns. On the other hand, our goal here is not to replicate some previous time. Our goal is to restore and conserve biodiversity. It's just fine if different relationships and patterns evolve. Plant associates are often very different from site to site. Niches may form for that are different from how things were 200 or 2,000 years ago. But diverse species may use their diverse genetics to adapt to each other. Surviving animal and soil biota species may adapt to new plant associations. It's a long term experiment, perhaps an "island" experiment (although perhaps not, as we have bags, vehicles, and shovels, and biota can be moved). Like you, many of us are interested and hopeful.

    2. The island issue is a pretty big deal, in ways I hadn't really understood till recently, and one reason I ask about fauna. I'm starting to understand insect dispersal, and dispersal genetics. If species formerly existing in metapopulations get completely isolated, they may lose the genetic variability that allowed for occasional longer-range dispersal and gene flow. At that point the metapopulation structure is unrecoverable and patch-by-patch extinction may be inexorable.
      But who really needs one more thing to worry about. It's just one interesting issue I recently became aware of and thought I'd share.

    3. Chris Helzer posted the following on his “The Prairie Ecologist” blog.

      Some of the comments to the above post mentions Theseus’ Paradox. I do worry that in the pursuit of increasing biodiversity irreplaceable nature could be lost. Although, this is probably not of much concern where you work because so much loss has already occurred.

  2. The are fascinating, amazing and hopeful.

    I can understand the many reasons behind a focus on flora.
    Still, I can't help but be interested in more commentary on the fauna. I'm sure there's an idea that most of the larger animals can find their way back once habitat is available.
    But what of the snails and slugs, moles, salamanders, frogs, millipedes and even flying insects whose dispersal is short-range? Is there a periodic full census? Has there been thought to restoring populations of animals that may not have a natural path back?

    1. Ryan, we share your curiosity. It needs to be a focus for the future. Restoring hundreds of plant species is challenging, but we know it can be done. There are said to be about ten animal species for every one plant species in high-quality ecosystems. That makes the animal challenge at least ten times as big, but many have demonstrated that restoring an animal population is often much more difficult than restoring a plant population. Even a "periodic full census" of invertebrate animals is beyond the current ability and resources of science. When Dr. Ron Panzer did Somme's one ambitious invertebrate survey, he chose to deal with only (potentially) representative groups (as I remember leafhoppers, butterflies, katydids, and a few others). Doing "just all the beetles" would be an enormous job requiring many experts. We have only preliminary info on ants. No one has done the bees. To become proficient at this, a person has to focus very hard on one group to learn to identify and census. Yet more and more people are doing it. We have at least preliminary data on fungi, dragonflies, lichens, frogs, salamanders, birds, and butterflies. But it would be valuable and exciting to have so much more.

    2. Thanks for the answer. Yeah, there's more than enough to do, so you cover what you can.
      By the way, I completed a contact form with the Illinois Butterfly Monitoring Network a month ago, asking to sign up as a monitor, and didn't get a reply. They list 8 training classes for March-May, 2017; none for 2018. It's getting close to March. Does anyone know what's up?
      My guess is you've got Somme butterflies covered, but I was thinking of a site closer to me. Maybe when my daughters grow up, I'll tackle a more difficult taxon. For now, I think butterflies is what I can do, and what might inspire the girls to help.

  3. The fauna census is unfortunately dependent on having an array of expert monitors available. Having followed Steve's efforts with Somme over a number of years, I am aware of significant improvements in nesting birds, amphibians, butterfly diversity, dragonfly diversity, etc., at Somme. However precise data can be difficult to accumulate. Much of it is due to the efforts of talented amateur photographers associated with the site. And the lack of volunteer entomologists in any meaningful numbers to assess regional sites is just an unfortunate fact of restoration life. One can hope that eventually the apparent increase in overall site quality will entice the level of professional fauna research the habitat deserves.

    1. Mark, I was with you fully, until your sixth-to-the-last word. I do not believe that we will EVER have PROFESSIONAL (paid) capacity to do all this science. We can work to get vastly more than we have. Indeed, increasing public interest and support can move us in that direction. But there are just too many species and groups of species. I'd go with you if you could revise your comment to reference "professional quality" fauna research. Yes, we need to fund many more experts. But they need to mentor many volunteer (amateur - in the classic sense) scientists. In previous centuries, the best science was frequently done by amateurs who had the resources (principally time) to do it. These days most people have enough - if they didn't spend their resources on unsatisfying consumerism (ever bigger houses, more airplane flights, thousand-dollar watches and phones, etc. etc). I say - let's use water or cheap wine to toast the future mostly-volunteer "Society for the Understanding of Nematodes" and its many fellow societies.

    2. Steve, point taken! In fact in hindsight I would strike the word "professional" altogether, and say "comprehensive" instead.

  4. Steve,
    Creating a written record of your work is very valuable. Well done.

    Two thoughts: 1. You mention acid rain as a possible cause of change. Considering how highly buffered are soils are, it seems unlikely, but the steady fall of fertilized farm dust, may be a significant factor, especially with respect to nitrogen. 2. You don't address red oak. Isn't it a significant consideration?

    Kent Fuller

    1. I have been reading about the issue of increased nitrogen deposition after it was recently mentioned in Chris Helzer’s blog “The Prairie Ecologist.”

      Acid rain and the amount of nitrogen deposited are linked because NOx emission turn into nitric acid in the atmosphere before falling with rain. Sulfur dioxide is another potentially more potent contributor to acid rain. Both receive EPA regulation to limit the harm to human health and the environment.

      An interesting aspect of soil ecology is buckthorn has been found to alter soil so it is both high in nitrogen and alkaline.

      The increased alkalinity and fertility of the soil can cause problems when trying to restore our oak ecosystems (scroll to pp. 16).

      The above is one of the reasons I have advocated for leaving dead wood to decompose. Other reasons include dead wood is wildlife habitat, leaving it is less work, and burn scars often are colonized by invasive species.

      Some people actually spread sulfur before beginning restoration of lawn areas to reduce soil nutrients and favor native species (see “Garden Revolution: How Our Landscapes Can Be a Source of Environmental Change”).

      Here is a paper where the authors have found increased low-level chronic nitrogen levels decrease diversity, but the level of diversity can mostly return if the deposition rates of nitrogen are returned to the original level and a nearby seed source is still present.

      In contrast, here is a paper where the authors have found additional nitrogen applied when restoring cropland to prairie can increase the cover of native prairie plants. I have also personally observed the benefit of fertilizing native plants when they are getting established in my garden. The difference is especially apparent when plants from my garden are compared to plants that were introduced into restoration areas and did not receive fertilization.

      In conclusion … it’s complicated.

  5. Thanks, Kent, for the good comments. As for acid rain and nitrogen deposition, etc., these are far beyond any expertise of mine. I mention acid rain mostly as an example of the many ambient changes. How well species will be able to adapt to them is a research question, and the answers may take many years to unfold (supposing that studies can be mounted for the species in question). But the overall point I'd make in this regard is that species have a much better chance to adapt if they have large populations with as much as possible of the richness of their original gene pool intact. We don't have to be experts in this. We just have to restore the gene pools, at least on some sites, as much as practical.

    As for red oaks, yes, I agree. In savannas and woodlands that haven't been burned for many years, red oaks may be said to have invasive qualities. At Somme we thin them quite a bit in some areas.