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Friday, January 16, 2015

Re-discovering the Composition of Oak Woodlands

Scientists don’t know the natural state of our woodlands.
A lot of great research has been done on the original character
of prairies and savannas.
But the problem with woods has been that most people
thought the answer was obvious.
They were wrong.

Yesterday I had a wild and unexpected time reading through an old manuscript. Higley and Raddin’s Flora of Cook County (1891) seems to have been mostly ignored, perhaps because some of their identifications have been questioned by later botanists. But what seemed so powerful about their catalog was the new perspective on the habitats of many easy-to-ID species.

Why is it exciting to discover how things were? New insights into the past suggest new possibilities for restoring ecosystem health. When we rise to that challenge, we need models of what we’re striving toward. They’re just one tool, but valuable. A model is a hypothesis to be tested. For each project, trying to restore health to our badly degraded natural communities, for all plants and animals dependent on this work at each site, we have to make choices. Thus we roll a lot of experimental dice, for example: a) selection of site; b) fire regime; c) selection of wildflower and grass species to restore by seed and plugs; d) what woody species to cut or restore; e) how open to make the canopy; f) management of animal communities; g) what kind and how much resource to put into which possibly malignant species; and h) what kinds of special care to give what selected plant species that may possibly be key – to name just a few decision that we have to make for each site.

Then we cut, plant, burn, watch for some years, and if the community seems to be moving in the direction suggested by the model, then (all else being equal) we continue what we’re doing. Or if some parts of the model are not being approached, and we can figure out why, then we change. Perhaps we do more or less of one of the measures above according to our understanding of the effects. Or perhaps some unexpected results lead us to re-evaluate our goals and expectations, and we change the model.

This is where Higley and Raddin (H&R) come it. I had assumed that the natural composition of woodlands was more or less what experts had identified in our “best” (least obviously degraded) remnants. But what if oak woodlands (the forest glory of the tallgrass region) had been very different for thousands of years. Could we have been misled in the last few decades, when most scientific sampling was done?

Dr. Robert Betz, our greatest prairie conservation entrepreneur, always reminded us that every prairie remnant today is profoundly changed and degraded. How about the woodlands?

The first surprise in H&R was the number of species that are now thought of as completely or mostly prairie species but which H&R identified as being more characteristic of woods at that time.

Consider H&R’s comments on the following five species that most experts today would say are clearly prairie species:
Astragalus canadensis. Milk Vetch. “Moist woods along streams and lakes”
Ceanothus americanus. New Jersey Tea. “Open woods”
Monarda fistulosa. Wild Bergamot. “Rather dry banks, open woods and fence-rows”
Pedicularis canadensis. Lousewort. “Open woods, banks, etc.”
Phlox glaberrima. Smooth phlox. “Prairies and open rich woods”

The second surprise was how many plants that rare are today were common then. H&R list the conservative prairie plant Yellow Star Grass as common in lawns, roadsides, and woods. Lawns and roadsides have fundamentally changed. From the examples below, woods have too.

The species below are listed in the order provided by H&R, as samples that seemed worth commenting on. The quotations following the common name are from H&R. The words following the quotes are my comments on the basis of four decades of conservation work in northeastern Illinois.

These samples don’t add up to a prescription or model in themselves; they just provide hints that should come to influence our models and goals. Many species of animals and plants may require that at least some of our “conserved” woods be much more open and sunny than the rarely and mildly burned state they’re maintained in today.

Viola sagittata. Arrow-leaved Violet. “Moist and rich open woods; infrequent.” This species today is found in prairies and savannas.

Silene nivea.  (Snowy Campion) Infrequent.  “Evanston. Niles. Riverside.” This species would probably do well in restored wet savanna. But we’ve never tried it because we’ve found it only twice in Cook County in recent decades. One time was just a couple of plants in a thicket edge on the Plank Road Prairies (Rich Township). The other time was just a single plant in Spring Lake Nature Preserve (Barrington Hills). In neither case did we manage to secure any seed.  

Silene virginica. Fire-pink. “Damp open woods; frequent.” Not frequent today. Too dark and too many deer? Only feeble results in restoration so far.  

Oxalis violacea. Violet Wood Sorrel. “Moist woods and banks; not common.” Not found in moist woods today. A characteristic plant of fine prairies.  

Ceanothus americanus. New Jersey Tea. “Open woods; frequent.” Very rare in woods today; most frequently cited as a prairie plant.  

Staphylea trifolia. American Bladder-nut. “Wet and rather dark woods; not rare.” The comment “rather dark woods” is interesting. H&R seem attuned to the varied amounts of shade in various woodlands.

Astragalus canadensis. Milk Vetch. “Moist woods along streams and lakes; frequent.” Not a woodland plant today. To be healthy, do some types of woodland need enough thinning to support milk vetch, violet wood sorrel, New Jersey tea, etc. etc.?   

Desmodium dillenii. (Smooth Tick Trefoil) “Open woods; frequent.” (Perhaps this is the species that Swink and Wilhelm call D. glabellum.) I know of no woods where this and the next two tick-tre-foils are frequent. Sadly, this and the next species don’t survive in prairie either, so we’re likely to lose these important legumes if woodland habitats can’t once again be made hospitable to them.

Desmodium paniculatum. (Panicled Tick Trefoil) “In open woods; frequent.”

Desmodium canadense.  (Showy Tick Trefoil) “Rich woods; frequent or common.”

Lespedeza violacea. (Violet Bush Clover) “Dry open woods and copses.” This species is almost gone. It survived in a mowed, wooded campground near Barrington. It came back after decades when mowing stopped in a lawn at Barbara Turner’s house adjacent to Reed-Turner Woodland Nature Preserve. In the darkness of the nature preserve, it was entirely gone. This species was restored and is now spreading by the thousands in Somme Prairie Grove.

Vicia caroliniana. (Carolina Vetch) “Banks of streams and shaded places; common.” Really? Common? I’ve only seen it twice in my life. The first was one plant on a ridge in Black Partridge Woods Nature Preserve. The other was a plant or two in Moraine Hills State Park in McHenry County. We should find some populations of this species, harvest seed, propagate it, and restore substantial populations before we lose it.

Vicia Americana. American vetch. “Moist banks, woods and copses; frequent.” Swink and Wilhelm characterize its habitat today as “grassy places, prairies, and woodland borders.” It’s still rather common but, perhaps a temporary refugee from its real woodland home.

Lathyrus ochroleucus. (Pale Vetchling) “Railroad banks and shaded bluffs; frequent.” Far from frequent, today it’s a threatened species in Illinois. In the case of one oak woods, it appeared and flourished once we’d started burning. There’s no reason it couldn’t be frequent again. In one Lake County site it seems to be thriving in a burned woods, but only inside a deer-exclusion cage.  

Lathyrus venosus. (Veiny Pea) “Open woods, copses and shaded banks; not common but widely distributed.” Swink and Wilhelm report that “In our area this is a plant of dry prairies and savannas.” Yes, it is, today. But it has vanished from many of them.  In one Cook county site with a heavy deer populations, it wasn’t found for decades, but a few leaves were spotted after a deer reduction program was established. The plants remained as just a few leaves until caged, after which they grew into great rambling vines, flowered, and set seed.

Prunus americana. (Wild Plum) “Moist open woods and banks of streams; frequent.” Still a common plant along some roadsides but almost completely gone from the interiors of woods.

Prunus serotiina. Wild Black Cherry. “Woods; infrequent.” Today the most invasive canopy tree in the oak woodlands according to the Chicago Wilderness Woods Audit. Its numbers need to be controlled if oaks are to reproduce.

Epilobium angustifolium. Fireweed. “Usually in copses and low grounds; frequent.” It is said to thrive after fires. I’ve never seen it in our region.

Daucus carota. Carrot. “Occasionally spontaneous in waste places and old gardens, but usually dies out in three or four years.” An interesting statement on how our flora has changed since 1891. Today “carrot” or “Queen Ann’s Lace” is a common plant in most disturbed situations.  

Galium circaezans. Wild Liquorice. “Dry woods and copses; common.” Our woods would have to be very much ore open for this plant to be common.  

Vernonia fasciculata. Iron-weed. “Prairies, open woods and banks; common.” Still common in prairies but no longer found in woods.  

Solidago speciosa. (Showy goldenrod) “Woods and shaded banks, frequent.” Today thought of as a species of sand savannas and prairies. But we found this species surviving on the edge of a forest preserve on Devon Avenue in Chicago, where a road cut allowed in extra light.   

Solidago juncea. (Early Goldenrod) “Banks of streams, open woods and moist fields; frequent.” Like the next three, no longer found in most woods.

Solidago serotina (gigantea). (Late goldenrod) “Woods; common.”

Solidago rigida. (Rigid Goldenrod) “Prairie, open woods, fence-rows; frequent or common.”

Cirsium altissimus. Tall Thistle. “Fields and newly-cleared lands and in open woods; frequent.” Today this fine plant is rare. It was restored and now thrives in the bur oak woodland at Vestal Grove.  

Gentiana alba. Whitish Gentian. “Low grounds and open woods, glades, etc.” Many people have thought of this one as a prairie species, but it fades out there over time.  

Phlox glaberrima. (Smooth Phlox)“Prairies and open rich woods; frequent.” Many experienced people will find it easier to believe that “prairie” species were also in dry woods. But this is a species of mesic and wet-mesic prairies (and woods?). Such a “rich open woods” is a community I’d dearly like to see.

Phlox pilosa. Hairy Phlox. “Prairies and open woods; common or abundant.”

Lithospermum canescens. Hoary Puccoon. “Prairies and open woods; abundant.”

Veronica virginica.  Culver’s Physic (Culver’s Root). “Rich woods, moist banks and prairies; frequent.”

Pedicularis canadensis. Lousewort. “Open woods, banks, etc.; common.”

Pedicularis lanceolata.  (Swamp) Lousewort. Wet open woods and swamps; frequent south, infrequent elsewhere.

Monarda fistulosa. Wild Bergamot. Rather dry banks, open woods and fence-rows; common.

Cypripedium pubescens. Yellow Lady’s Slipper. “Moist rich woods and bogs; frequent.” This fine plant deserves to be common again. Often I’ve seen it common in Wisconsin under occasionally mowed power lines (and uncommon in adjacent woods). Like so many, it needs more light.  

Hypoxys erecta. Star-grass. “Meadows, lawns, roadsides, woods, etc.: common or abundant.” Another almost unbelievable comment on how plant associations have changed. Common in lawns? Woods? This is a dominant spring plant in many fine prairies, but that’s about it.  

Tradescantia virginica. Common Spiderwort. “Moist open woods, prairies and fields; common or abundant.” (probably T. ohiensis).

by William K. Higley and Charles S. Raddin. 1891.
Bulletin of the Chicago Academy of Sciences.

Available electronically at:;view=1up;seq=183

Caution: Higley and Raddin used different scientific names than the most recent ones. Yet, between the scientific name (given first, in italics) and the common name, it’s usually easy to figure out which species they probably meant. Common names given within parentheses were omitted by H&R and supplied by me. Note: if you happen to be an expert and can correct any misleading species identifications, by all means let us know, and we’ll make corrections.

Comment on the scientific significance of such a list:
Some people think that conservationists, as scientists, ought to do our management experiments by controlling one variable and one species at a time – extensively replicated. At this stage of our understanding of ecosystem management, this is a fool’s errand for trusting graduate students. No one can try 10 different 100-acre patches each for 10 different soil/hydrology/topographic conditions, planting 10 different seed mixes, with 10 different burn regimes, watching each for 20 years. For that you need 10,000 similar ten-acre patches, for this one experiment.

We’re in a somewhat comparable position to medical doctors trying to restore health to human patients. In some ways we’re worse off, because human medicine has so much longer a history. In other ways we’re better off, because in all likelihood, ecosystems are so much more complicated that feedback loops may do a lot of our work for us, if given original conditions and diversity.  Also, in the very degraded systems we so often work with, we can be satisfied by a wide variety of outcomes. If the choices turn out to be good for half the species we’re concerned about on a given site, then we can celebrate a victory, as 50% of our goal is so much better than the 0% that we’d get if we didn’t try.


  1. The manuscript is dated 1891 when Cook county already had a population of over a million people so I would assume that fire suppression was already a well established practice so isn't it possible that the areas in question were in fact prairie prior to the writing of the manuscript but with the absence of fire that by 1891 those area had developed in to various stages of woodland ?

    1. I agree that this is one legitimate concern about the document. It's important if we can to find earlier observations on the composition of woods. Perhaps we will. "Prairie" growing up rapidly to woods seems less likely than "savanna" doing so. But the the theoretical concerns are similar. It's possible that H&R's "open woods" may refer to what today we might call savanna. It would be interesting to analyze the list to see if a better picture emerges of what they meant by their categories. And of course we want to continue to look for good sources. I once stumbled across a pressed plant collection from someone's property, now a level, mesic oak woods (but with many trees formerly having "woodland grown" rather than "open grown" or "forest grown" lower branches). According to "grandmother's herbarium" - the woods of her youth included scarlet painted cup, Seneca snakeroot, and many other species that we're not seeing in mesic woods today.

    2. There is a great study by Marlin Bowles and Jenny McBride 2002 entitled Pre-European Settlement Vegetation of Cook County, IL. In the study they, "...mapped and analyzed the landscape pattern and composition of vegetation described by the U.S. Public Land Surveys of Cook County Illinois which were conducted between 1821 and 1840. Their conclusions include "Cook County was 73% prairie, wet prairie and marsh, with fragments of timber essentially restricted to the eastern sides of watercourses or steep topography, which offered protection from eastward-moving prairie fires driven by prevailing winds. The largest blocks of timber occurred.......east of the North Branch of the Chicago River. Forest tree densities of >100/ha predominated i timber along....the North Branch." In addition, they state, "Woody understory vegetation was not systematically sampled by the PLS, but the small sample indicates that hazel and oak brush dominated this time of vegetation and that it had greater linear cover at higher tree densities." In reference to wood vegetation composition they state, "Species richness and diversity, as measured by the Simpson's index........species richness and Simpson's index were higher (>16 species) North Branch. The North Branch is referred in the study as a, "wet-mesic forest on lake plain along the North Branch." They state "Elm, poplar, walnut, bur oak and ash apparently had minor representation in mesic forest. Line summaries indicate that woody undergrowth had 100% occurrence, with dominance by hazel and oak." Further on the study states. "Mesic and wet-mesic forest in The Big Woods along the North Brnch reached the highest richness and diversity of any forest type, probably due to a comparatively high degree of fire protection, as well as a diverse habitat gradient ranging from well drained beach idges to poorly drained lake plain soils. Mesic forests were dominated by white oak and bur oak with subdominance by red oak and hickory. A wet-mesic maple-basswood component (NOTE: this currently exists in part of Midway Woods) occurred locally alonog the North Branch, while wet elm-ash-soft maple-basswood forest occurred throughout much of the area. Woody undergrowth was apparently not sampled regularly in the Big Woods, but was recorded from about 50% of the exterior lines of Township 41 North Range 13 East, as well as part of the Indian Boundary. Hazel, oak, ash, willow and paw paw were frequent species. These forests also had high richness of herbaceouos species (HIgley and Raddin 1891, Greenberg 2002)." The study includes an awesome table that indicates 18 species of trees being included in the North Branch survey! I do all this quoting to first establish that the North Branch was in fact a wet-mesic forest before European settlement, but to also raise the question of whether or not we are including the actual tree diversity that was there when the woods were virginal. I think we need to consider whether we only retain oak trees when the orirginal forest included 7.04% hickory, 4.46% elm, 9.59 percent ash, 2.3% soft maple, 1.23% basswood, .52% sugar maple, 2.12% aspen, .33% white ash, .18%Walnuut., .72% cottonwood, .20% swamp ash, .16% cherry, .16% thorn and .15% ironwood. It appears that the rich species diversity in the North Branch was not only on the forest floor as Stephen points out as stated in Higley and Raddin, but the diversity was also in the forest canopy! I have a cop of another study from the State of Illinois Natural History Survey (February1926) of "Brownfield Woods: A Rremnant of the Original Illinois Forest". This study seems to confirm the richness and diversity of the woody vegetation in the North Branch. While oaks may predominate, the forest was also rich in other types of trees. Thanks for taking the time to read this. I will provide access to studies if requested! John Cherry

    3. John, I very much agree with most all your points. The Bowles and McBride (PLS) data make it clear that the diversity of the forests was also diversity in types of forests. Some likely tolerated a good deal of shade. In the case of those, we have less to worry about. But some forests had major components of bur oak. This tree reproduces only with a good deal of sun. It's likely that in the bur, swamp white, and white oak areas that we had a lot of the so-called "prairie" species. Both they and the bur oaks are so highly "sun loving."

      The point I'd question is the implication that conservationists believe in leaving "only" oak trees when thinning these forests. From what I've seen, the functioning goal and plan is to retain the full diversity of trees as well as animals and other plants. It's just that some species need more control than others to even out the balance.

  2. Here is a link to the Marlin Bowles and Jenny McBride study:

    John Cherry

  3. I think in many cases the plants you are considering still occur in the mentioned habitats in other regions or states. For example, I have seen Viola sagitatta in high quality woodland on course sandy/fine gravel soil in New Hampshire. Ceanothus americanus is similarly a species of both woodlands and more open areas on dry gravel further east. The University of Wisconsin lists Astragalus canadensis in the same habitat as Higley and Radin.

    Before I moved from the Northeast to Illinois I considered Lousewort to be a woodland species. Phlox glaberrima is listed as being found in “openings in bottomland woodlands” among other habitats by Illinois Wildflowers. “Phlox: A Natural History and Gardener’s Guide” also list various wooded habits for Phlox glaberrima. Illinois Wildflowers lists Monarda fistulosa as inhabiting sandy black oak woodlands, savannas, and woodland borders along with the habitats where we most often see it locally.

    I’ll touch on a few others. I have seen Oxalis violacea under Quercus marcrocarpa on a hill prairie. There still are fine stands of Silene virginica in the area. I’ll have to check if the seed that was spread around many year ago into adjacent habitat cleared of buckthorn ever grew into plants. I also found some Vicia caroliniana in open woodland. This is really an attractive species. This woodland became more “open” after the Rhamnus cathartica was cleared, but Rosa multiflora continues to be a problem at this location.

    My thoughts on having more frequent fire is it can only help. This is especially true in areas where the prairie transitioned into savannah and woodland. However, I think our fires just are not as intense as they were historically. The Rhamnus cathartica and Asian Lonicera keep their leaves well into the fall. This extra leaf cover during prime burn season shades the fuel considerably significantly reducing the intensity of a fire. I think invasive species control really needs to be done simultaneously with prescribed burning to restore and maintain our woodlands.

    I think we do not only need frequent fire, but also need intense fire. I think intense fire is especially important for savannah and open woodland. I have been thinking about the reason those trees are so widely spaced in savannah. I think tree spacing is a function of fire intensity. When conducting prescribed burns, packing of the fuel is an important consideration. I think the trees tend to grow just far enough apart that they do not also become fuel for a fire.

    Another thought provoking post.

  4. Thanks for the helpful comments, James. Seeing these species in wooded situations elsewhere may help people envision them in the woodlands under restoration here. Many people are not surprised to see these species in sandy or very dry woods. Those survived longer than the mesic woods for a number of reasons. But perhaps our wetter woods will have some features in common with them, if diverse competition and effective fire can be restored.

    1. Through the magic of the internet I found you some pictures.

    2. Here is some more evidence in favor of your argument. Annual fire allowed these species, that people traditionally consider to be limited to only prairie, to move into woodland. It has also allowed oak savannah to begin development in an area that had formerly been closed woodland.

  5. Steve, thanks for sharing. Despite its shortcomings, another piece to the puzzle. Pete

  6. Stephen,

    I was wondering what your thoughts are on the restoration work being done at Portwine, Dam 1 and Willow-Sanders preserves, per this press release:

    It sounds like they'll be doing precisely the amount of intensive tree thinning needed to get those sunlight dependent plants to return, and open up the woodlands. I assume this work is being documented before/after as a study for how the ecology improves?
    Is this a pilot program for similar work to be done in other preserves?

    I'd love to see a series of before/after photos when this work is all done.

    Aaron Andrews

    1. Aaron, I very much share your interest in the Portwine project. It would be great to look at the plan. Yes, it could be helpful to study the documentation. Judging from what I've seen there so far, the plan may be to rely on a hypothetical seed bank to provide the bright-sun-dependent plants that the ecosystem needs to thrive. Some studies and many conservationists' experience suggest that seed banks make substantial contributions in wetlands but result in very few species in long-shaded-out woods and prairies. From what I've seen at Portwine, a ton of shrubs are doing well, but not much in the way of mesic woodland, savanna or prairie forbs or grasses.

    2. Stephen,
      Is anyone in your area surveying the ectomycorrhizal fungi in oak savanna restorations? In the 22 years since we began restoring our oak and hickory woodland I have observed a marked increase in the number and diversity of fungi that have a symbiotic association with plant roots. This has been particularly true of the boletes, fungi with pores instead of gills. Of the 27 species that fruit regularly on our 200 acres almost half are state records. Gastroboletus turbinatus is reputed to fruit only in coniferous or mixed woodlands. It is common here although we have no conifers. Boletus dupainii, another species abundant here is extremely rare in the continental US. The last time I checked it had been collected only in North Carolina and Florida. The relationship between woodland restoration and the fungi is fascinating. I think it is a better indicator of success than the plants.

      Sibylla Brown

    3. Sibylla, thank you for good comments and questions. (Thanks more, of course, for your years of fine restoration of the Timberhill Savanna.) Sadly, we have little systematic data on our fungi. We did make a start some years ago in cooperation with a young Field Museum mycologist. Many stewards (myself included) made scientific collections of fungi and sent them to the museum. The mycologist (who sadly moved away and discontinued the study after just a year or two) informed us that most every site was submitting rare fungi - and that they were nearly all different. You are inspiring me to cast around for people interested in pursuing this important component again.

    4. Stephen,
      Mushrooms surveys are being done at Cedar Creek and at Ha Ha Tonka in Missouri. But they aren't comparing them with the floristic surveys. Working with the ISU mycologists I assigned COC's to the Timberhill ectomycorrhizal fungi and found the that the most conservative species were found only in sites with the most conservative plants. Looking at the ECM fungi adds another pair of eyes into the understanding of the ecosystem. I wish more information was available.