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Thursday, December 8, 2022

The Battle of the Aggressive Sunflowers

Oak communities in the tallgrass region are in serious decline. (Some say they're in trouble everywhere.)

Most of our surviving oak savannas and woodlands have lost - and continue to lose - species and diversity. In considerable part the slow deaths result from insufficient fire and the resulting gloom. Yet when we seek to restore better health by cutting brush and pole-trees, the increased sunlight may lead to a density of woodland sunflower sufficient to kill off most of the other wildflowers and grasses.

In 2018, we asked if woodland sunflower was “Savior or Threat?”. In February 2022 we described grim sunflower impacts on frustrating mid-savanna areas. It seems like a long time since then; experiments continue; we’ve learned so much. 

Oak ecosystem remnants with full biodiversity on good soil may not still exist. (But see: Wisconsin Discovery for an excellent, if little, newly discovered island remnant.) Quality woodlands and savannas certainly seem to be rarer than prairie remnants, but less appreciated. Their future depends on remedial care, which in turn depends on us understanding them better. 

At the relatively well-studied and intensively managed Somme Prairie Grove, ecosystem quality trends in some areas seem positive – in others, negative. One of the biggest lessons we’ve learned is that 34-years of monitoring data may reveal a lot – but even now, after 41 years, this experiment is far from finished. Thus this post is “news” – another interim report. 

Large areas of Somme Prairie Grove Nature Preserve are increasing dominated by woodland sunflower. Pretty, but does it kill diversity?

When we experimentally scythe these sunflowers, hoping to make way for the recovery of diverse associates, we are disappointed in what we find below its dense foliage.

Under the sunflower, in some areas that we hoped were recovering ecosystem health, the ground is now mostly bare.  

Many so-called “weedy” or “invasive” species are trivial. They just go away in time. But some, perhaps better called malignant species, can impede restoration - and even degrade or destroy high-quality areas. For a well-understood example in prairie restoration, tall goldenrod can shade out young prairie grasses so badly that burns fail. Then woody plants may proliferate under the goldenrod, gradually increase, and ultimately kill off everything else, including the goldenrod. Some stewards worry that woodland sunflower under some conditions may be similarly damaging to savannas and woodlands. 

 

Woodland sunflower impacts under some conditions may seem positive, as was suggested by the technical paper we published, based on those 34 years of data. For a long time we had been eager to share our woodland data and what we’d learned, but we hesitated, as we kept learning more each year. When we did finally publish it, in proper “academic” form in the journal PLOS, the article celebrated successful restoration. But there’s an implication when you publish, that the experiment is done. For many reductionist experiments, yes. For ecosystem experiments like this, not at all. Changes and lessons have continued apace. 

 

Biodiversity conservationists may need to recognize new approaches to ecosystem science. At Somme we've been trying various approaches for four decades, learning all that time, slowly. Not that everything we learned was slow; but much of what we learned more quickly turned out to be wrong. 


Somme Prairie Grove consists of prairie, savanna, woodland, and wetland. For this report, we’ll mostly forget the wetland, prairie, and very open savanna. We'll consider the somewhat-shadier savanna and woodland. 

 

In and near Vestal Grove, through which runs that 34-year transect study, we had burned, cut brush, and planted highly diverse seed. Early results looked hopeful. Workhorse turf plants as well as many rare and endangered plant and animal species were coming back. But after a few years, as light increased, we increasingly felt the need to try scything some areas of tall goldenrod, as its dominance seemed to deplete the fragile recovering ecosystem. Then, beginning about 2009, the “weedy” goldenrod was progressively replaced by conservative woodland sunflower as the most common herb species (see "Top 25 Species" in Endnotes). The fact that "high-quality" sunflowers were replacing "low quality" goldenrods helped deliver the impressive, apparently positive results in many of our statistical analyses. But how confident should we be that this "experiment" or "healing process" was continuing in the direction of restored biodiversity? 

 

Woodland Sunflower Total Cover in Study Transect from 1986 to 2019. 

Looking just at the graph, we might have been reassured that, as with the goldenrod, this sunflower's dominance would rise and then settle down. But we were not reassured. The Grove had been unnaturally dark (after a century without fire), with vastly more trees than the original (1839) survey showed. Though we initially removed the dense buckthorn that filled the understory, we did not cut most of the thin, young hickories, cherries, box elders, and others that were poking their tops up into the big, old, original bur oaks. In time we began thinning some of the young invaders, as herb vegetation declined when shade deepened. But we had not thinned trees near our sample plots, unsure about how that would impact the study. It was in the areas that we did thin, that we first noticed woodland sunflower busily wiping out not just goldenrod, but diversity, rare species, and all. Some of the sunflower patches seemed unstoppable, building dominance and expanding inexorably. We had to make a decision. Thinking narrowly, there was reason to continue the study of how just fire and time would impact our sampling plots. Thinking more broadly, those (initially random) plots, once we were treating them differently, no longer represented the overall community that we wanted to study. They did not represent the community we were working to restore. Thus, after 2019 we decided that the original experiment would continue for now, for some plots. But for others, we began scything sunflower and reducing canopy cover, as we've done away from the transect.


Case Studies


The first three case studies take place under the substantial shade of old oaks in Vestal Grove.The oldest trees here are mostly bur oaks. Trees of savannas and open woodlands are predominantly oaks because their thick bark is best for reproduction under a fire regime. But in the decades before burns returned to Vestal Grove, while buckthorn proliferated under the dappled light of the open oaks, so too had large numbers of other trees native to other nearby ecosystems, but largely alien to the savanna. We initially adopted the principle, "Let the fire decide." But our controlled and rather tepid fires had little impact on trees more than three inches thick. Belatedly we needed to face a fact that confounded the concept of our study: trees grow. We had imagined that this was the nature we were studying. But over the decades we increasingly noticed the loss of some of the brightness-requiring grass and wildflower species in areas where shade was increasing most. We became clearer that what we wanted to study and facilitate wasn't simply an abstract leave-it-alone "nature." Our goal was the recovery of the rare savanna and woodland ecosystems, the nature in which original biodiversity had thrived here. So we started cutting and girdling trees, at first cherries, elms, and bitternut hickories, but later all that had invaded or increased beyond what seemingly would have been natural under regular fire, including hop hornbeams, shagbark hickories, even Hill's and some bur oaks, where shade was growing toward closed forest levels. As sunlight increased, the woodland sunflower increased. It does not thrive in forests. Its habitat is the more open woodland and savanna. 

All the trees here are bur oaks.
One big old tree (back left) with large horizontal limbs, shows natural history.
The others are unnaturally dense, thin, and limbless ...  
... not what natural evolution designed this species to be. 

After 34 years of carefully restricting any specialized experiments from the areas in and around the transect of plots, we now learned from scything “thug” species (now including woodland sunflower) from a few other areas. Some such areas seemed to respond to the scything with increasingly diverse and conservative vegetation; others did not. Now including some of the areas of the long-sampled plots, our future sampling will benefit from the 34-years of earlier data as we try to understand the impacts of this next stage of experiments. The new studies in the long-sampled areas are only a couple of years old. The five case studies presented below are from areas without long term data. For now, all we can present are observations and judgments.

 

Case Study 1. Does coddling work?


Toward the west end of Vestal Grove is an area about 25 feet in diameter that seemed relatively rich.  Here we had scythed "thuggish" or "malignant" species for perhaps ten years - tall goldenrod, Joe Pye weed, briars, and more recently woodland sunflower. Below is a 2022 close-up of the spring vegetation in that scythed area. 

Species in the photo include:

 

Rue anemone

Big-leaf aster

Cut-leaf toothwort

Thicket parsley (Perideridia)

Dutchman’s breeches

Bloodroot

Pennsylvania sedge

Nodding wild onion

Elm-leaved goldenrod

Wild geranium

Cinquefoil

Unidentified grasses or sedges

 

But a thug is in the above photo too: Three vigorous-looking, paired-leaved re-sprouts of woodland sunflower are along the left edge of the photo; there is also part of one easy-to-see re-sprout in the lower-right corner. Though diminished, they come back each year. We’ll continue to scythe this test area and leave the “no action” and “less action” experiments to other spots, for now. Nearby "no action" areas have none of the above conservative species, or just one or two. 

 

It seems significant that, after all these years, a graminoid turf is absent here. Some conservationists suspect that a natural (high-quality) woodland historically had (and for sustainability should again have) a turf of grasses and sedges. Like in a prairie, perhaps graminoids should be a matrix in every square foot. Are they less here, despite all the sunflower control, because we have not seeded enough or waited long enough? (We will start honoring this test area with a diverse seed mix this year.)

 

Grasses and grass-like plants - that might ultimately resist the sunflower without help from the scythe and are found here and there within this long-scythed circle - include:

 

Nodding fescue

Wood reed

Silky rye

Wood rush

Bottlebrush grass

Awned woodgrass

Wide-leaved panic grass

Penn sedge 

Short-headed sedge (Carex cephalophora)

 

Some of these species have only recently reached here. Will they become more robust and luxuriant? 


(See Endnotes for scientific names and other details.) 


Case Study 2. Didn't learn much? Failure?


Large areas of eastern Vestal Grove now have the density of woodland sunflower shown below:
Five or ten years ago (haven't located the earliest records yet), in this area we chose a seemingly "non-special" spot. Here, in a square, about 20 feet on a side, marked by four tree trunks, we have annually scythed species that we thought could inhibit the "embryonic growth" of the recovering plant community - tall goldenrod initially, Joe Pye weed, briars, and more recently woodland sunflower. A corner of this square is shown below:

The northwest corner had been marked by a large hickory. Over the decades, as trees have grown larger and shadier, making the grove less valuable for our open oak woodland biodiversity goals, we have selectively thinned trees here and there including, as it turned out, the hickory that marked the northwest corner of this plot, which is now marked by a hickory re-sprout bush. (The other three corner-marking trees, bur oaks, are still there.)

Woodland sunflower and purple Joe Pye weed are now dense on the west and north sides of this square. The scythed area looks dull in this photo, and it looks dull most of the time. Perhaps it's recovering slowly. For years, its vegetation was sparse. It has gradually become denser and stayed relatively short. The vegetation is mostly common, non-conservative woodland species, unlike Case Study 1.  


If we step a few feet into the dense sunflower and push it aside, we see the scene below:

It's pretty much the same species as in the scythed square, just smaller. Perhaps this experiment will reveal some new truth in time. But so far all we have learned is that conservative diversity is not noticeably increasing. Now we'll try to seed conservative species appropriate to this area into both the scythed and adjacent un-scythed areas. We'll see what we learn from that. 


Case Study 3. Unexpected Conservatives


In 2022 we scythed sunflower here and there as sort of "exploratory surgery" - in part to get a better view of what was underneath. Occasionally we found patches like the one below:

This area, from which woodland sunflower had been scythed in early July, looked like this on August 13 after a month of growing in less-shaded conditions. Much of the ground is covered by big-leaf aster, which is flowering a bit (lower left). Nearby, under dense sunflower, this locally rare species produces few flowers. By September, big-leaf aster bloomed exuberantly here and in many of the areas we had scythed. Also in the photo are wood betony, golden Alexanders, elm-leaved goldenrod, meadow rue, hog peanut, Joe Pye weed, and some little sunflower re-sprout stems. There's little graminoid (grass or sedge) vegetation, although species such as those listed above are occasional nearby. Would graminoids increase with more light? More crucially, would "woodland sunflower scything therapy" facilitate sufficient biodiversity recovery here that further scything would be unnecessary? 

Nearby, in the photo below, exploratory scything of sunflower tops revealed a conservative plant we'd never found in Vestal Grove. It is shining bedstraw. Interestingly, it does survive (with woodland sunflower, white trillium, and other species) in along the highway at the southern edge of the Grove. The plants there seem to have benefitted from the increased light resulting from highway maintenance. We've had poor restoration results with shining bedstraw, probably because we find very little seed. In this case, unseen by us, it had been growing under the sunflower to a patch 26' by 16' - a fine surprise. 
The shining bedstraw is the whirls of thin leaves near the ground.
We decided to invest conservative seed in and around this patch, to see what we can learn about relations between this and other species. We'll scythe half and not scythe half. A diagram of the now-underway experiment is below. 




Case Study 4. Highly meaningful failure in brighter light


For this next case study, we walk out of Vestal Grove into the sunshine of an area we call West Point. It's the westernmost lobe of the glacier that covers much of the site. Here, along the main "Inner Loop" path is a U-shaped curve along which a series of experiments have been unfolding. Some visitors have watched them for years. This case study focuses on a seventy-six foot stretch, starting at a 7" diameter hickory (or, actually, a change since this report was first drafted, the stump of a 7" hickory) and running first south and then west. On the northwest side of this path we have scythed thugs from time to time, mostly years ago. We have left parts of the opposite side unscythed, as a control. 


Much of what we do seems obviously successful. But this area has continued to fail. A new experiment focuses on the 52 feet immediately north of the path, where solid sunflower increased and stood through 2021, when we began frequent scything here. It's an area where buckthorn had been cut decades ago and the ground planted to mostly prairie species. What grew instead was dense tall goldenrod, ironweed, Joe Pye weed, and other species that can behave "thuggishly" in this kind of situation. We scythed them from time to time over the years, hoping that the scattered young plants of quality species would, with help from the scything, establish a grassy, burnable, sustainable, diverse turf. It didn't happen. Over the last few years woodland sunflower crowded out the rest. That phase of the experiment was done.

 

Solid woodland sunflower! Really? Decades after the brush was cleared and rare seeds planted, there should be more to show for the effort. We scythed it all down in 202, in early 2022, and then hit the re-sprouts later.  In the fall we broadcast a rich mix of savanna species. 

This experimental area is unusual in that it has high quality both north and south of it. That may be why we found the time to come back every few years and take a whack at the thugs. South of the dense woodland sunflower here is the highest-quality area of Vestal Grove (including Case Studies 1 and 3). Heading north from the path, those first 52 feet (16 meters) consist of the sporadically-scythed area that, until a few years ago, was dense tall goldenrod and more recently woodland sunflower. The next 20 feet (6 meters) contain rather rich mid-light savanna vegetation - Seneca snakeroot, mountain mint, meadow parsnip, purple milkweed, Virginia rye, Maryland snakeroot and others but only scattered warm-season grass. Finally, north of that is high-quality open savanna grassland, thick with lead plant, prairie clover, little bluestem, dropseed, etc. for perhaps a quarter of a mile. 

 

In spring 2022, the sunflower was dramatically reduced, but there were still multiple small stems in every square foot. Though we looked hard in mid summer, we saw little evidence of the species we had planted. Maybe there were some; it's common not to be able to find newly sown species for two or three years. It's also possible that the sunflower poisons (allelopathy) in the soil excluded new seedlings of most species. Possibly any allelopathic chemicals will dissipate in time.


In late fall, we finally noticed a few prairie/savanna seedlings - lead plant, purple prairie clover, and Kalm's brome - perhaps an early sign of success. 

A young prairie clover (thin leaflets) with young daisies.


A young lead plant (small round leaflets) 
with quick-growing, vigorous dandelions. 


The quality species were few and far between, vastly outnumbered by unplanted "weeds." Next year we expect a glorious patch of pretty, non-native daisies here, along with weedy and dense fleabanes and dandelions. But, if the prairie/savanna species get established before the competition gets too dense, they would readily out-compete the weeds. We will continue to scythe. This experiment continues. But one experiment is done. All the desultory work we'd done here for decades had failed. We had wondered, is there something wrong with the soil here? Or is shade the problem? This area gets full sun during mid-day. But there are trees to the east and west. Is the partial shade in mornings and afternoons deterring the establishment of prairie species? Had we planted the wrong species? We didn't have to wait long for a partial answer.


Case Study 5. Glorious (if unintentional) Success.


The path through West Point was installed in 2003. Unnoticed by us, an unplanned experiment along the sides of this path had been under way for nineteen years. The occasional scything of Case Study 4 had started at this path and extended north about 50 feet. While we were evaluating (and recording failure in) that experiment, we ignored the edge of the path. There it would have been impossible to separate impacts of the occasional scything from path impacts. Instead we had looked in the heart of the experimental area, where results wouldn't be confused by "edge effects" and path maintenance. Trying to be "good scientists," we separated our use of scythes for lofty restoration experiments from that other scything for lowly trail maintenance. 


But in 2022 we did our second year of scything, and when we worked along the edge of the path we found ourselves absent-mindedly avoiding a few quality species that grew there. Oops! They did? We looked more closely: For about a width of one foot, on the north side of the path grew good-quality vegetation. The added light from trail maintenance, consistently for nineteen years, seems to have given some species an opportunity ... and gave us the opportunity to "discover" a successful experiment. Last year's scything likely helped them grow bigger. But these were not first-year plants. They'd clearly been there for many years. We now hypothesize that more frequent and regular scything may pay off in the long run. 

The above photo shows the path through the experiment, looking west. To the left is unscythed woodland sunflower.  To the right, heading right (north) for 52 feet, the aggressive vegetation has now been intensively scythed for two years and is covered with new, low vegetation, mostly temporary "weeds." But the right edge of the path, consistently scythed every year just enough to keep the path open, became the successful treatment. Many species now hugging the path seem not to survive anywhere under the never scythed "thugs" to the left or the occasionally scythed "thugs" to the right. (Because of the angle of the sun in the temperate zone, the south side of the path remained too shady for most of the species below.) 


Species along the north edge of the path:

Scientific Name

C

Common Name

Allium cernuum

7

nodding wild onion

Amorpha canescens

9

lead plant

Andropogon gerardii

5

big bluestem grass

Andropogon scoparius

5

little bluestem grass

Anemone virginiana

5

tall anemone

Aster ericoides

5

heath aster

Aster sagittifolius drummondii

2

Drummond’s aster

Aureolaria grandiflora pulchra

8

yellow false foxglove

Bromus kalmii

10

prairie brome

Cirsium discolor

2

pasture thistle

Euphorbia corollata

2

flowering spurge

Gentiana flavida

9

yellowish gentian

Hypericum punctatum

4

spotted St. Johnswort

Lespedeza violacea

7

violet bush clover

Liatris spicata

6

marsh blazing star

Lycopus americanus

5

common water horehound

Monarda fistulosa

4

wild bergamot

Muhlenbergia mexicana

5

leafy satin grass

Panicum virgatum

5

switch grass

Parthenium integrifolium

8

wild quinine

Pedicularis canadensis

9

wood betony

Penstemon digitalis

4

foxglove beard tongue

Pycnanthemum tenuifolium

7

slender mountain mint

Quercus coccinea

4

scarlet (or Hill’s) oak

Quercus macrocarpa

5

bur oak

Ratibida pinnata

4

yellow coneflower

Rudbeckia hirta

1

black-eyed Susan

Silphium integrifolium deamii

5

Deam’s rosin weed

Silphium terebinthinaceum

5

prairie dock

Smilacina racemosa

3

feathery false Solomon’s seal

Smilax lasioneura

5

common carrion flower

Solidago juncea

5

early goldenrod

Solidago rigida

4

stiff goldenrod

Solidago speciosa

7

showy goldenrod

Solidago ulmifolia

5

elm-leaved goldenrod

Sorghastrum nutans

5

Indian grass

Sporobolus heterolepis

10

prairie dropseed

Triosteum perfoliatum

5

late horse gentian

Ulmus americana

3

American elm

Vicia americana

7

American vetch

Zizia aurea

7

golden Alexanders

In addition to 38 prairie and savanna herb species, we found three bur oaks in that foot-side strip. These too were absent from the dense sunflower areas. 


A view of the un-scythed side of the path is below. 

Looking southeast from the path

A final photo shows an expanded new treatment area (to the west of where we began scything annually last year). It's clear after first year's scything of dense woodland sunflower here, how little green was left beneath it.

It's our impression that scything woodland sunflower (a conservative) has a much bigger impact than does scything tall goldenrod (a weed). Thus, our hope (and our hypothesis) is that diversity could sustainably establish with sunflower regularly reduced by scything for a few years. We will plant diverse seed and scythe, perhaps twice a year. We'll also seed some of the comparison un-scythed sunflower areas. After some years, we’ll study the vegetation in the various areas and compare. And at some point we'll stop scything. Will the impact be for the long term? 

 

Endnotes

Scientific names of woodland sunfowers: Somme Prairie Grove has four species that might be called "woodland sunflower" (and many other common names). For an additional complication, we find at least three of these to hybridize with each other shamelessly. In the wooded Vestal Grove most plants mostly seem to have the characteristics of Helianthus strumosus (with minor admixtures of Helianthus decapetalus). In brighter sun (savanna) areas, they seem to be mostly Helianthus hirsutus (with minor or major admixtures of strumosus). We have found only one patch that convincingly seems to be Helianthus divericatus. There seemed to be no "pure" Helianthus decapetalus, but then this "species" was found to be the most common of the bunch in eastern Somme Woods, when we started working there. As the light levels increased there, strumosus seems to be dramatically on the rise. Decapetalus has not increased much, in part because the overpopulated deer have consumed it hungrily. Photos comparing leaf shapes among three of these are in our first woodland sunflower post


Scientific Names generally: Scientific names for many of the species mentioned in this paper can be found below. Others can be found on line or in most plant books including Swink and Wilhelm's Plants of the Chicago Region, which we relied on for decades. More up-to-date scientific names can be found in Wilhelm and Rericha. We have mostly left scientific names out of this version of this report for three reasons: 1: The more professional or expert people know both the scientific and common names, especially if they want to converse with conservation stewards and advocates. 2: We want this blog to be broadly accessible and as easy as possible to read. Some people report that too many scientific names make their eyes glaze over, and they give up. We need more people to be learning and caring. 3: We're not the world's best spellers, and it takes a lot of time to check all those names. If people thought it was important, we could publish a "scientific names version" (if someone wanted to do the work).


Scything Strategies: How to do selective  or "surgical" scything

How to do this work is not settled science. This post describes experiments and early indications of how they’re going. In  trying to explain “surgical scything” I can remember telling people that expert scything depends on a sort of plant conservativeness computer in your visual field that averages the quality ratings of the plants that would be cut in various possible swings of the scythe. You make the cut that mows the most low-quality plants without cutting too many high-quality plants. I was vaguely aware as I said this that I didn’t really quite do it that way. It was sort of a metaphor. 

 

These days I describe it differently. I do have the C values in my head. But more importantly, I have inchoate RF values … if RF = Recovery Facilitation. That computer in my field of vision asks the question: “How much of an impact will these various species have on the evolving quality of the ongoing restoration?” To explain that for this post I try, below, to quantify some of the judgments that determine what I cull and what I protect.  I work especially hard to control species with an RF rating of -5. I try hardest to foster and protect +5 species. These "ratings" are very different from the familiar "native" and "non-native" categories. For example, in an area with a bluegrass and orchard grass (non-native) turf that was being invaded by (native) dogwood or goldenrod, I'd work to protect the bluegrass, because it's easy to foster quality prairie restoration by seeding into burned, thin bluegrass ... and hard to foster quality prairie in a goldenrod patch.   


The small sample of "values" below were hastily assembled to explain the concept. 

The RF numbers and RFV thinking would be different for woodland restoration.

 

Vestal Graph (again) and Vestal Species List

The sunflower graph seen earlier in this post - and repeated below for your viewing ease - shows how much woodland sunflower was recorded over the years in the woodland plots of the random transect in Vestal Grove. If you don't know what that sentence means, read the next paragraph. If you do, skip it.

Woodland Sunflower Total Cover in Woodland Plots of the Vestal Grove Transect from 1986 to 2019. 

Every two years from 1986 to 2019 - in 15 initially random circular plots of 1m2 each - we recorded how much of the ground was shaded by each of the plant species growing there. Computer programs can analyze that data to show us changes in plot diversity, the conservatism and Floristic Quality, cover by sedges or legumes or any other category of plants we care to define, and other information - thus informing our management. The above graph for one species was extracted from that data. The "Total Cover" figure is the sum of the amount of cover in all fifteen plots for that year. Thus, if woodland sunflower covered 25% of one plot and 50% of another and that species was found in no other plot, then the total cover for that year would be 75. If a plant covered 100% of all plots, its total for that year would be 1500.

Thus, we found no woodland sunflower the first year. Its total cover for the first ten years averaged about 50; over the next ten years its total averaged about 100; and then for the last ten years it jumped to the 400 to 600 range. But then again, over the last few years the general trend seems to be downward. 

The downward trend might reassure a person about the overall trajectory of this species. It does not reassure us. We've been watching the whole woods. Woodland sunflower seems to get established slowly. Little plants then grow inexorably denser and taller, as competition from other species is eliminated. In many places there is little left in its dense shade. In vast, growing patches in many parts of this woodland, 15 samples would result in that 1500 figure. Such areas "happened to be" little represented in the plots. Perhaps woodland sunflower may have been increasing less rapidly in the area of the 15 permanent plots because, with our (questionable, in retrospect) goal of interfering with these sacrosanct experimental areas as little as possible, we left them alone. But in the grove overall, where shade had been gradually increasing, as trees grew, and some valued species disappearing, presumably because of the gloom, we thinned trees as good stewards. The natural habitat of woodland sunflower (or at least the habitat in which it increases most rapidly at a site like this) seems to be sunnier spots where we've been reducing canopy. 

If you'd like to consider the principal grass and wildflower species in the 15 square meters of these plots in 2019, the 25 herb species with most leaf surface (cover) are shown in the table below.

Top 25 Species in Vestal Grove in 2019 

Common name

Scientific name

Cover

C

FR

Woodland sunflower

Helianthus strumosus

352

5

-4

False mermaid

Floerkea proserpinacoides*

228

7

5

Swamp buttercup

Ranunculus septentrionalis

197

5

2

Tall goldenrod

Solidago altissima

192

1

-5

Golden Alexanders

Zizia aurea*

190

7

2

Elm-leaved goldenrod

Solidago ulmifolia*

180

5

4

Hog peanut

Amphicarpaea bracteata*

155

4

-1

White grass

Leersia virginica*

135

7

4

Purple Joe Pye weed

Eutrochium purpureum*

130

7

2

Honewort

Cryptotaenia canadensis

109

2

1

Wild geranium

Geranium maculatum

104

4

4

Jack-in-the-pulpit

Arisaema triphyllum

74

4

4

Awned wood grass

Brachyelytrum erectum*

66

10

5

Wild hyacinth

Camassia scilloides*

56

6

5

Sweet black-eyed Susan

Rudbeckia subtomentosa*

52

9

3

Wood betony

Pedicularis canadensis*

50

9

4

Cow parsnip

Heracleum maximum*

49

5

4

Woodland puccoon

Lithospermum latifolium*

46

9

4

Wild coffee

Triosteum perfoliatum*

45

5

3

Davis sedge

Carex davisii*

40

7

5

Cut-leaved toothwort

Dentaria laciniata*

40

5

5

Black raspberry

Rubus occidentalis

40

2

-4

Early meadow rue

Thalictrum dioicum*

38

7

5

Short’s aster

Symphyotrichum shortii*

35

8

5

 

It's interesting to note that 17 of these 25 species (those marked with *) are growing here today because their seed was broadcast by us. The other species were here when restoration started, except for raspberry (likely brought here by birds), tall goldenrod (seed dispersed by wind and likely to pop up in any disturbed area with enough light), and woodland sunflower which, as stated above, was growing along the sunny road edge on the south edge of the Grove and over the decades somehow spread slowly over the site. There are no non-native species on this list, even though the transect was dominated by them in early years.

Currently at Somme Prairie Grove our relatively small patches (a few acres each) of higher quality savanna and woodland are isolated from each other, with "problem areas" in between. Here are three possible interpretations (hypotheses/prescriptions) of what we're watching in Somme Prairie Grove:

1. If we work to keep light levels more or less where they are, we may over time continue to see more conservative diversity and less dominance by a few species, especially those with low C. Under this hypothesis, perhaps woodland sunflower would stabilize as just another member of this community.

2. But many parts of woodland biodiversity seem to thrive here in the sunnier areas. Somme Prairie Grove is managed mostly to conserve savanna biodiversity, with woodland biodiversity better represented in Somme Woods, so perhaps here we should find successful prescriptions to foster the somewhat-brighter-light-dependent ("intermediate") species. Then prairie could gradually blend into open savanna and then into darker savanna and then open woodland.  

3. Maybe we should be more patient. Have we been watching the start of a 100-year or 1,000-year process - at the end of which our hopes for sustainably conserved prairie-savanna-woodland biodiversity would finally be realized? We don't mind waiting, in principle. But as wise conservationist Doug Ladd has emphasized, high-quality and diverse natural ecosystems aren't going to just wait around. Although they will be the ones best able to adapt and evolve in response to climate change and other stresses, without good management they would be lost.

Other Details

We have, of course, a lot more detailed info than this post includes. Some is omitted here because it would make the post too long. Other details are sadly omitted, because we don't have the time to find them in our vast piles of (pre-computer) paper records. Even this version of this post has taken a long time to assemble, and much other needed work is crying for attention. Our apologies. 


Dates and Species 

Some of the time periods and other details in the above report are less exact then we'd prefer:  "about ten years" or "thugs like X and Y species." We're well aware that more detail would be better. If anyone needs them, we have longer reports and vast data in our files. 


Other Experiments under way.

1. Scything solid sunflower in the open (with no warm season grass and no oak leaves).

2. Scything solid sunflower where there are sufficient oak leaves to allow annual or semi-annual fire. 

3. Scything thug species in combat areas – where diversity may or may not win out (in woodland, savanna, and prairie areas).

4. Selective scything in apparently diverse, gradually improving open grassland where sunflower (typically Helianthus hirsutus or grosseseratus) seems to be invading

5. Selective scything in apparently diverse woodland areas where sunflower seems to be threatening that diversity. 

6. Brute, unselective scything ("anyone can do it") in various situations

 Bonus photos

Above, just before the Outer Loop path enters Vestal Grove, we see unscythed sunflower (left of path) and, to the right, the two-year-scythed beginning of the Vestal Grove sampling transect. Here there was still a good quality (not high or very-high quality) turf of wildflowers, sedges, and grasses. The foreground on the right includes "intermediate" (not woodland) quadrats 1 and 2. In the background, big bur oaks indicate the beginning of the area of "woodland" quadrats that produced the graphs in the PLOS paper and the plant list labeled "25 Species with most Cover in Vestal Grove in 2019" above. We have also sampled these intermediate plots for the same 34 years, but we have not published results, because little seemed to be happening. Without sufficient oak leaves or grass to burn, they taught us little. We'll now see what we can learn here under scything. We'll sample again and analyze after a few years. 

The graphs below, parallel to those published in our PLOS paper, are based on data from quadrats 1 and 2. As a reminder, the published data showed quality increasing for 34 years in the fifteen woodland quadrats. The excluded intermediate quadrats were different in at least three ways 1) brighter light levels (perhaps 30-60% canopy cover), 2) lower fire frequency (Because of insufficient grass and oak leaf fuel, they rarely burned.), and 3) quality (It's changed little).  

These graphs may not be worth a lot of analysis (or blog post words) at this point. But a quick summary would be that:
    1. Species numbers increased for the first few years, then leveled off, then trended down.
    2. The three quality measures increased for the first few years and then leveled off. Most improvement was in 1985, immediately after the dense buckthorn was cut. After that, quality didn't improve much; FQI of 12 is not very good. 

It may be worth a reminder that there's vastly more going on here than we understand in detail. Plants do fight it out. Each individual may differ in its abilities to win or lose against an individual of another species, and the outcome of the struggle may depend on many factors that also differ from spot to spot – wetness, soils, soil biota (fungi, bacteria, protists and more), as well as the mix of other plant species present. We stewards may have a role in these battles when ecosystem recovery is threatened. Rare and compromised species and ecosystems sometimes deserve "intensive care ward" treatment. In that spirit, we started the new experimental treatments.

Dismal Start in some Open Savanna areas 

We had thought that, once a restoration was off to a pretty good start, success was pretty much preordained, given good stewardship. Perhaps the key question here is: “What is a pretty good start?” Our open grassland (prairie or savanna) restorations that started with old field vegetation have worked magically well. Soon (five years or so) after seeding, prairie clover, leadplant, dropseed, and their associates started outcompeting the Eurasian species; then just regular burns were sufficient to result in increasing quality and stability, decade after decade. (We did occasionally over-seed with missing species when we found them.) We only rarely found a malignant "weed" or two - and never did buckthorn or other invasive trees come back. Darker oak ecosystem situations (closed savanna and woodland) also seemed to progress well, as their ample oak-leaf fuel facilitated regular burns. 

 

But savanna restorations starting from brush were different. Here tall goldenrod and its ilk could suppress the warm-season grasses sufficiently to reduce or eliminate fire (under the moderate conditions of today's controlled burns) and brush may reclaim the ground there. Today in such areas we have many acres of what we'd have to call failure: Poor quality, not getting better, ultimately becoming brush once again. We have begun scything experiments with these areas too. 


It almost seems easier to see what's going on in the fall, when the crucial warm-season grasses stand out: 

Above, warm season grasses are solid in this "shrub prairie" or "open savanna."

In the photo below, two young bur oaks stand on an edge. Behind them is the high-quality diverse grassland. The foreground, until two years ago, was nearly solid woodland sunflower. It's been scythed, and quality vegetation seems to be increasing. 


But in the photo below, we're not so hopeful. 

Here, for decades, the edge, as best we remember it, has been static. The huge area in the rear was tall goldenrod and is now woodland sunflower. We're just starting to scythe and mow areas like this. For the true horror of this infestation, take a look just past the edge of the grasses:
No warm season grasses. Very little diversity. We do not feel we've been good stewards to this area. We have resolved to do better. 


Ambivalent Start in Open Woodlands


Above, buckthorn was cut and seed broadcast decades ago. Under occasional scything over the years, sparse diversity under tall goldenrod evolved toward sparse diversity under woodland sunflower. We decided to try harder in 2022. The foreground shows vegetation remaining after sunflower was cut earlier in the year. Here, under the sunflower, we found indications of quality that we couldn't easily see before: patches of zigzag goldenrod, big-leaf aster, wood betony, golden Alexanders, Short's aster, awned wood grass, and many others. In the center of the photo is un-scythed sunflower. 

Behind the sunflower is a bur oak with a big lower limb pointing west; there are two such trees in the Grove; both are here at the west edge of the area of old bur oaks - and approximately where the 1839 survey showed the west edge of trees. Beyond here was prairie (to the west, to the right in this photo) extending to the horizon. Behind that noble tree (looking south) is the "edge hedge" of un-cut brush that shelters Vestal Grove from Dundee Road.  
 
 
Would the quality vegetation under the sunflower have been slowly lost over time? Or would it have slowly succeeded to diverse high quality, with the sunflower as just another member of the community? In many other areas of Vestal Grove we'll be able to watch whether the community evolves in either of those directions - or perhaps in some very different one. Here, we're trying the scything-and-more-seeding experiment, where perhaps sooner or later restored to rich health, woodland will blend into savanna and then prairie. When we learn more, we'll let you know. The excitement is high, and the answers come slow. 

Acknowledgements

Thanks to Christos Economou and Eriko Kojima for helpful edits and to James McGee for pointing out annoying typos. 

29 comments:

  1. Humans have been scything to keep areas short and cutting trees for various used for thousands of years. Some of the earliest records of "lawns" are scythed meadows around dwellings in Japan (reference needed) and later Humans used grazing to further keep areas short. The Intermediate Disturbance Hypothesis suggests that natural areas with intermittent and regular biomass removal rabies biodiversity by creating heterogeneous habitats, etc. So, you have made a breakthrough in restoring the overcrowded areas with by removing the aggressive plant species that crowd out and shade more conservative species. Trail-side dynamics are very interesting to study and continuous graminoid cover could certainly change the trajectory of developing plant communities. So, what does scything mimic that is so beneficial to ecosystem balance - one of the largest missing biotic influences on the landscape, biomass removal and disturbance by browsers and grazers. Humans and machines are now filling that niche.

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    1. Will, thanks for the good thoughts. As to grazers: I'm doubting that bison ate much sunflower, as they generally focus on grass. Elk? Deer don't seem to like it much.

      It could be that the scything doesn't mimic anything natural. It could be that the explosion of sunflower is like a person getting sick when some normally simpatico gut bacterium becomes toxic after an operation or sickness messes up the balance. If so, maybe the scything will just inhibit the aggressive sunflower enough for conservative diversity to use up a lot of nutrients and root space, upon which competition will simmer down the sunflower. Or - I wonder if there's some missing parasite that we have to find?

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    3. The reason I don't think the population explosion of woodland sunflowers is a result of a lack of some bacteria or parasite is because as you state “It came in on its own, apparently from populations on the sunny roadside on the south edge of the preserve.” Since this is an existing native population expanding, the organisms that had been controlling the population should have been, and should continue to be, present.

      I look at the “mostly bare” ground visible in the image of a monoculture of woodland sunflower or where the woodland sunflower monoculture has been scythed. What I see is dry soil appearing to have a lower percentage of organic matter. In contrast, I look at the image under the heading “Does coddling work?” and see a dark-rich-moist soil. The images under “Unexpected Conservatives” appear to be intermediate between the soil shown in the images showing “mostly bare ground” and the image under “Does coddling work?”

      This leads me to believe the issue may not be a lack of Robert Paine’s analogous purple sea stars in the tide pool. Rather, the areas you are trying to restore to savanna may have been altered to the point that they no longer have the potential to develop into the same ecosystem. Conducting soil testing prior to restoration may be necessary to ensure the habit is in a state where it can achieve the desired restoration outcome.

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  2. From Frank P Lawrence via Facebook:
    Did you broadcast seeds of Woodland sunflowers through out the plots or have they expanded on their own ? After seeing this savanna 8 years ago and a similar restoration at Morton, I decided not to broadcast seeds far and wide on a client's 6 acre woods ( I feared the domination of 1 species ) but rather just incorporated them in to 2 separate but small groupings. Currently the groupings are larger but have not moved all that much through the woods . My biggest problems are with Wingstem and Joe Pye which have reseeded to the point of becoming a nuisance. I used only 1 species, Helianthus strumosus.

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    1. Frank, we planted no woodland sunflower of any kind. It came in on its own, apparently from populations on the sunny roadside on the south edge of the preserve.

      As to Joe Pye, we worried about that early on. For a few years it seemed too aggressive. But then the deer got a taste for it, and soon it was just another plant.

      Figwort (Scrophularia) also seemed like trouble for a while. We warned others about it. But then it simmered down all by itself. Perhaps it was just taking advantage of excess nutrients (like pokeweed does) and then fades back when it has used them up and there's more competition.

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  3. Interestingly, on our working list of native disturbance indicators (when in high abundance...often proliferate post clearing) for WI oak woodlands in addition to the woodland sunflowers and Canada goldenrod is hog peanut. One of our structural metrics for healthy communities, even mesic ones, is short vegetation (low cover of herbaceous vegetation over 2 ft./knee high throughout the growing season), often b/c of a lot of low graminoids, but in the case of Army Lake there is much higher cover of precious, low forbs than graminoids.

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    1. Dan - have you studied the nutrient dynamics of Graminoid dominance? Is it that nitrogen is depleted with increased Graminoid dominance, generally... Or?

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    2. I read a book "The Changing Prairie" where a nutrient cycle dynamic was described that suggested N decreases with fire and perennial warm season grass dominance. That is onecreason why N fixing legumes are successful in dry prairie and other tight knit grassland plant communities...

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    3. Dan, thanks, as always, for thought provoking comments. We all have a lot to learn. Army Lake is a good teacher.

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    4. Mr. Overbeck

      I used to think what you wrote above too. However, with further study I realized the nitrogen dynamic is more complicated. Burning decreases total fixed nitrogen but can increase available fixed nitrogen. The decrease in total fixed nitrogen is because a lot of it goes up in smoke. The increase in available fixed nitrogen is because without the duff, soil organisms have less carbohydrate food to consume with the result they also use less fixed nitrogen.

      I have seen this in my backyard sedge meadow planting. The sedges in the half I burned are a darker green color. Color is a way to measure nitrogen in leaf tissue. If burning is done consecutively then one study found available fix nitrogen decreases after the second prescribed burn.

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    5. Mr. McGee, how can we relate those nutrient cycles to the invasive species colonies? It it simply a physical competition? Does nutrient availability have a major role? Is light the main factor? I think it is a combination of these variables, plus the seed bank capability to produce new seedlings at the correct timing - after a disturbance opens a niche (bare soil patch) and then recruitment depends on that habitat being stable enough for establishment and gain of dominance before the other species out compete the newcomers. Allopathy and fungal/bacterial/microbial interaction might also have an important role, but are harder to study...

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    6. I believe you are right that it is “a combination of these variables.” The variables mentioned being intertwined and inseparable.

      I just worry if the labor-intensive practice of scything is stopped, that the ecosystem would revert to the previous state. Such a practice would be hard to sustain for long. This is what I have seen starting to occur in small areas of native plant gardens and reconstructions. I removed weeds from them for several years, but after I stopped putting work into them the tall goldenrod begins making inroads again.

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    7. Yes, no one proposes mowing forever. The hypothesis is that a period of stressing various malignant species would allow "the patient" - that is, the degraded natural ecosystem - to recover. At that point, competition from diverse species - if the hypothesis is correct - would be sufficient control of tall goldenrod or woodland sunflower. We have seen this hypothesis proven right in some instances for tall goldenrod control in prairie and open savanna systems. That is, once conservative and diverse species (including many somewhat conservative goldenrods) have established, the weedy tall goldenrod has faded out and is gone. We are testing whether scything or mowing will facilitate such a process for woodland sunflower.

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  4. How about throwing heaps of Cuscuta glomerata(?) at it?

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    1. Drew, thanks for the question. Yes, we do "throw heaps" of seed of dodder into over-abundant goldenrods, sunflowers, and mountain mints. Yes, it reduces them. In some cases it seems to lead to a more diverse community. In others it doesn't. We continue to study it.

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  5. Are you noticing the dodder killing the woodland sunflower in the diverse areas? I wonder if it would be more effective if you collected seed or even took cuttings where it's been successful and dispersed into other spots.

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    1. Drew, we have mostly what we're calling common dodder (Cuscuta gronovii), and it principally reduces tall goldenrod and sawtooth sunflower. Increasingly, rope dodder (C. glomerata) is also doing well. Where they succeed massively, they do also reduce woodland sunfowers - but so far only in sunny, open areas, not in the woodlands. They seem worth more experimentation, which we're doing.

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  6. Have you considered using a roller crimper instead of scything? This might knock down the woodland sunflower without having much impact on grasses and shorter forbs.

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    1. An interesting possibility, because scything is very exhausting. A small, engine driven, manual roller-crimper looks as if it would be able to handle the extensive areas of sunflowers shown in the photos above with a lot less time and tiring effort than scything would require. The use of such a piece of equipment would be an interesting experiment.

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    2. A board with some angle iron attached to the bottom held against an operator's foot by a rope would be enough to complete a test plot and proof the concept. If it works, then one powered by an engine could be purchased.

      I bet if the stems were crimped down to the ground, they would carry fire slowly.

      https://www.youtube.com/watch?v=EjcyoalaeAM

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  7. At MacArthur Woods in Lake County, goldenrod invaded an 80-90% canopy woodland from an adjacent old field. The ground layer before invasion included 20-40% bare soil. I noticed it invaded where there was bare ground or low density forbs, but avoided areas with decent sedge coverage. If graminoid establishment is the best way to stop rhizomatous plants like goldenrod & sunflower, I wonder if a dense strip of grass or sedge would act as a barrier? Also, would a Transline experiment be appropriate? It worked great on my goldenrod but I had no desirable natives to worry about.

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    1. Don, interesting reports and hypotheses. Yes, it would be good to compare Transline and mowing experiments. I'm dubious about the effectiveness of a barrier against tall goldenrod, as its seeds blow everywhere and fall everywhere. When we cut brush deep in the woods, far from invasive goldenrod populations, it comes in anyway. Other aster-family woodland plants (like Short's aster and zigzag and elm-leaved goldenrods) usually don't come in - although they might be among the best to fill that niche and out-compete tall goldenrod in the long run. As many of us carefully experiment, we'll learn more.

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    2. I see your point about wind dispersed seed. If a graminoid firebreak/footpath partially or wholly encircling a desirable uninvaded or Translined area is capable of stopping an advancing front of rhizomatous invaders, I wonder if the patches created by wind blown seed would be much easier to mechanically control than a monoculture and be more easily out-competed by natives because the isolated patch root system is not well developed. When an invasive monoculture is partially scythed, can it remain aggressive or possibly allelopathic in that spot since the roots are still getting resources from the nearby unscythed stems? I love your well designed experiments as we are all learning from them.

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  8. Here is a Facebook comment from Debbie Antlitz.

    ... The sunflower patches are also low on fuel, which limits ash, which affects the pH which affects the soil chemistry. Some suggested experiments: 1) Lay down grass thatch and let it work into the soil. 2) Lay down grass thatch and let it burn and let the ash work into the soil. 3) Collect ash and sprinkle it into the soil.

    Here is my response to Ms. Antlitz.

    The impacts of ash deposition, to the extreme, can be observed in old burn piles sites. In these locations, along the edges, garlic mustard grows to the size of a cabbage and in the burn scar itself tall goldenrod often eventually colonizes. I think the aggressiveness of tall goldenrod, woodland sunflowers, and other tall species that form monocultures is a result of elevated levels of phosphorus in the soil. Adding ash would increase pH making phosphorus less available, but also add more phosphorus that would stay in the soil as rain adjusted the soil pH over time. I think Mr. Packard’s success from thinning and burning is in part due to moving phosphorus from one area, resulting in improvement, with the other part being that phosphorus is concentrated in the location of the burn pile. Likewise, scything and removing material removes nutrients. Although, removing excess phosphorus is a slow process. The reason I think Vestal Grove is having issues with aggressive native species, when this is not a problem in other areas, is because Vestal Grove was used for grazing. Grazing means manure. If animals are being provided supplementary feed then manure would have built up excess phosphorus in the ecosystem.

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    1. I have seen degradation occurring in areas that are (or were) high-quality even if they escaped domination by common buckthorn. Increased phosphorus deposition could be a more recent development. Lawn companies often use blowers that put lots of dust into the air from heavily fertilized lawns. Dust is also made airborne when farmers disk fields. What is causing the problem could be contemporary. In addition to a legacy from past land uses.

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  9. Here is an older publication that synthesizes research on effects of fire. As I said previously, the impacts of fire on nutrients (specifically nitrogen) are complicated. Nutrients and in certain cases pH are dependent on fire temperature. The pH impacts of burning grasslands are “negligible.” However, I expect a large oak log burning would have a significant impact where ash has been deposited.

    https://wildlandfire.sd.gov/docs/Effect%20of%20Fire%20in%20the%20Northern%20Great%20Plains.pdf

    Likely, prairies at Somme Prairie Grove are being maintained because prairies with an overabundance of nutrients burn hot balancing nutrient levels. In contrast, the savanna areas burn at low intensity, if they burn at all. A low intensity burn can increase available soil nitrogen and available phosphorus. However, a hot burn will volatilize organic nitrogen, volatilize ammonia, and cause phosphorus to be lost in “fly ash.”

    If the problem is an increase of nutrients from a lack of hot fire with a self-reinforcing result that a species which will not burn dominates, in this case woodland sunflower, then the solution is simple. Cut and remove the above ground material during the dormant season to simulate what would be done by a very hot fire. Do this until enough fuel species have established that a hot fire can be achieved.

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  10. Despite the fact that woodland sunflowers at Somme spread from existing populations, I think it’s possible that some insect herbivores and/or Helianthus pathogens aren’t present due to fragmentation, with normal stochastic fluctuation extirpating local populations which can no longer be repopulated from other nearby sites.

    This post itself confirms that herbivory is an important part of the equation by mentioning that deer hold Helianthus decapetalus in check while strumosus and hirsutus multiply.

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  11. Here is an article I thought was amusing. What Mr. Packard works hard to scythe, a gas company in Vermont must transplant.

    https://www.burlingtonfreepress.com/story/news/2016/07/13/vermont-gas-transplant-rare-flowers-monkton/87039028/

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