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Saturday, July 26, 2014

Nine Ideas: July 2014

Thinking about conservation goals and decisions, 
inspired by walks through Somme Prairie Grove 
in July 2014.

In an important study for Chicago Wilderness, Marlin Bowles found that a large proportion of our most important natural areas were deteriorating. For me the most surprising aspect of his results was the decline of shrubs in oak woodlands and former savannas

At Somme our biggest recent shrub success has been elderberry (white flowers, above). Kent Fuller gave us a big sack of berries from nearby Air-station Prairie; we added them to our savanna seed mixes; and just a few years later we have elderberry surging in many new plantings. How this shrub will integrate with competition and fire will be fun to watch in upcoming years and decades.


Our woodlands now are essentially devoid of shrubs. That’s fine, for one component of woodland conservation. Historic reports tell us that horses could gallop through some woods, and there’s a whole suite of bird species that thrive in a “two-layer community” (herbs and trees without shrubs). But other reports (and other birds) suggest that shrub components were also important in some woods (perhaps where hydrology and topography limited fires on most years).

The dead horizontal limbs on the oaks (above) remind us of what happened to this formerly open community. Shade kills. Mostly it was buckthorn that killed the understory; pole maples, ash, etc. killed the lower limbs of the ancient oaks. Even as recently as when we began our work here around 1980 – the dead wood of hazel, dogwood, Iowa crab, and sumac could be found under the oaks. (These species fortunately still survived on the edges of the site’s open pasture remnants.)

This “Prairie Grove’s” few wooded acres may or may not be sufficient for such restoration experiments, but work to begin this fall in the 250 acres of Somme Woods next door hopes to focus on at least some component of naturally shrubby woods.

On the edges between “wooded” and “prairie” parts of Somme, curious phenomena abound. One humongous blob of a plant (the dark leaves and purple flowers) fills the top half of this photo. This plant - showy tick trefoil - would not be that large in a fine prairie. But in the savanna, where trees come and go (and some were recently burned off here, leaving an opening for this short-term aggressive plant), we expect such unusual phenomena as a matter of course. Here, on the edge of a wet swale, New Jersey tea and silky dogwood also grow dense when years pass without fires. Such fluctuations are a part of the savanna dyanmic that likely provides opportunities for some species that may not thrive elsewhere. 

Carolina rose and prairie sundrops have increased enormously and seem “excessively dominant” (to the great pleasure of some photographers) in some areas. I wonder if changing patterns of “excessive dominance” will turn out to be a permanent feature of this savanna – or if increasing small-scale diversity is an inexorable trend (given regular fire), as it seems to be where restoration has been simmering the longest.


After thirty years of burning, this inter-seeded area appears to be increasing in diversity. We’ve random-sampled here every five or ten years, with steadily increasing diversity so far. Time for another sample. Will plant diversity here in the long run fall short of, equal, or exceed that of our “best” natural areas? Only time will tell. How long do we need for a good answer?


Tom Vanderpoel told me that white prairie clover (note its divided leaves, much wider that those of the purple in the foreground, above) is rhizomatous, unlike its somewhat less rare purple relative. After decades of barely surviving at Somme, white now seems to be on the increase. White is usually found only in the best parts of fine remnants. H. S. Pepoon, writing 100 years ago, claimed the white was everywhere more common.

We early on found only tiny amounts of seed for white prairie clover, with no nearby seed sources surviving at this point. If it comes to hold its own against the huge numbers of the purple, that would be evidence in favor of the idea that restored species may inexorably reach their natural equilibriums.


Two species of unusual tick trefoils emerged on site from our seed-gathering in the best nearby savanna remnants we could find (many now destroyed). We’re not sure of the identifications of either. The keys seem not to be decisive. We’ll take another crack when the (distinctive) fruits form. One species (glabellum? perplexum?) is increasing rapidly. The other (shown above, cuspidatum?) seems to survive as only a couple of isolated plants. Given that the open woodlands are changing as the restoration progresses, might it not be a good idea to protect these from deer until they have a chance to spread their seed around, seeking just the right niche? Or is that too much “gardening” for a recovering natural area?

Yellow coneflowers are favorites of new prairie restoration efforts. But they mostly don't last. Here they waved by the thousands a couple decades back. Now only an occasional one appears in the most mature parts of the site. The bulk of the vegetation in undisturbed prairie is made up of conservatives. Coneflower seed (or semi-dormant roots) lie in the soil waiting for a digging coyote, or buffalo, or off-road-vehicle. Coneflowers help damage heal.


Last photo, and idea number 9. Our bur oak woodlands have gone through too many stages to count (starting with buckthorn, then bare ground, then weeds as in our naiveté we waited to see what was in the seed bank, then seeding followed by evolving diversity, then – ). For a while the woods was dominated by tall goldenrod and white snakeroot (Eup rug). But beneath the stages of changing dominants, diversity has continually increased (a fact we wouldn’t have known without periodic random sampling). Now, starry campion (above) is exploding in many areas. But the “scary” one is woodland sunflower. Will this “thug” wipe out much diversity under its fierce dominance? Or will it rise and fall like the others, on the way to the high quarter-meter diversity that our “best” prairies and forests have led us to expect, or hope? It’s a good question, as far as I’m concerned.   

Your “Comments” and discussion are always appreciated by this blog.

There’s a different treatment of these same photos at http://vestalgrove.blogspot.com
where they’re described in a possibly more educational, or fun, or emotional way for the overall audience of people who like Somme Prairie Grove.

5 comments:

  1. In addition to the shrubs you mention, the following would be good candidates for restoration efforts at Somme Woods.

    Cornus alternifolia; Euonymus atropurpureus; Viburnum acerifolium, V. lentago, V. prunifolium, and V. rafinesquianum

    I especially think V. acerifolium would be worthy of restoration effort. It likes dry slopes and summits in closed savannahs. I’ve been told V. rafinesquianum is present locally. However, it so closely resembles V. recognitum and its habitat is so filled with this common invasive species that I have had trouble locating any of this native Viburnum. The Celastrus species (vines) can also be similarly difficult to distinguish on some individuals.

    The following are some invasive shrubs that have been taking over habitat and making our native shrubs increasingly rare.

    Berberis thunbergii, B. vulgaris; Cornus mas (cornelian cherry); Euonymus alatus; Viburnum opulus, V. recognitum; and of course Rhamnus frangula and R. cathartica

    I would remove the previously mentioned species quickly if they appear in your restoration.

    I must wonder if the increase in diversity of Somme’s prairies is due to seed of new species being added. I also wonder if diversity would have leveled off within a decade without the continued introduction of new species.

    I am glad Oenothera pilosella is doing well for you. I wish it was doing better in a local restoration. I have seen rescued plants produce seed but not a single seedling in a local restoration that was formerly in agriculture. This has been the case even after many decades have passed. One important factor in restoration seems to be luck. With some luck, each species will fluctuated within natural population ranges. This does not always happen. Sometimes one species dominates.

    I don’t know what to tell you about the Helianthus divaricatus. I have always thought of this plant as a woodland edge species. It seems savanna restoration has the explicit goal of making habitat for species that are now primarily restricted to edge habitats. Looking for possible solutions to the over abundance of Helianthus divaricatus will take some investigation. You might want to ask Doug Taron if he can provide you with some of his butterflies.

    http://articles.chicagotribune.com/2009-09-20/news/0909190216_1_checkerspot-adult-butterflies-plant

    The Silvery Checkerspot (Chlosyne nycteis), Gorgon Checkerspot (Chlosyne gorgone), and Painted Lady (Vanessa cardui) butterflies, along with a number of moths, host on Helianthus divaricatus.

    http://www.illinoiswildflowers.info/savanna/plants/wd_sunflower.html

    Cuscuta glomerata is also mentioned as a parasite. I have been able to establish Cuscuta glomerata in new locations by sowing seed. It definitely weakens the host and often will kill it. I am trying to use this species to reduce the over abundance of Solidago altissima in a local non-FPCC restoration.

    Below is a blog post that is encouraging regarding your issue with Helianthus divaricatus.

    http://www.timberhilloaksavanna.com/plants/gaining-insights/#comments

    I do not know if you will have the same experience at Somme. Ability to succeed at restoration depends on the degree of degradation and ability of organism to colonize from adjacent areas. As I said before, "With some luck"

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  2. Thanks for the good comments.

    We're eager to restore the almost gone shrubs and understory trees. There are some species we've stayed away from because they seem more typical of dark forest rather than open woodland or savanna. These include maple-leaved viburnum, black haw, alternate leaved dogwood and some of the others you mentioned. It could be we should be trying them, in case. But there's so much to do, and we at this point are focusing on hazelnut, American plum, nannyberry, bladdernut, wafer ash, and a few others.

    We'll have a chance to try some of those others in Somme Woods East.

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  3. In my experience, many of the shrubs I mentioned are still hanging on in low numbers. You are likely to find at least a few of the mentioned species are still present as you go about the work of eliminating invasive species. Of course, the natives cannot hang on forever and the faster "malignant" species get removed the better. Stewards need to be extra careful to make sure quality native species are not getting damaged or eliminated while removing the "malignant" species. Some mistakes are to be expected, but stewards need to be vigilant to minimize mistakes as much as possible.

    James

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  4. From Henry Eilers:

    Helianthus dominance: Our forest uplands have long been dominated over large areas by woodland sunflower (H. strumosus). This year and also in the past I have noticed occasional 'infestations' of dodder (Cuscuta ssp). Have you ever collected their seed? We have done so for control of Sericea, our most serious herbaceous invader. Successfully? - maybe not.

    A huge handicap is excessive numbers of White-tail, an awful plague here. But - other ungulates are woefully lacking, especially Bison. A herd resting in the shade of a savanna, trying to escape pesky insects, would profoundly affect structure and distribution of cover in ways that we perhaps cannot imagine. On one hand I am awed at what we can accomplish in our short human life cycle. Then I wistfully think how much more impact 800 years would have, instead of 80 years.

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    Replies
    1. Yes, we sometimes collect and broadcast seed of the parasitic dodder, attempting to control "unnatural" concentrations of some species (for example, saw-tooth sunflower and mountain mint). We then broadcast diverse seed into those areas. Too early to have a sense of the results. James MaGee has experimented with that too.

      As for the bison, this year at Nachusa - for the first time in over a century - the Prairie State will have a herd back on the eastern tallgrass prairie. I hope studies of their impact there will teach us a lot.

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