Virginia’s Piedmont grasslands: floristics and restoration

Jordan Coscia is a PhD student in the Restoration Ecology Lab at Virginia Tech and a graduate fellow at Virginia Working Landscapes, a program of the Smithsonian Conservation Biology Institute. She describes her research goals and includes a preliminary species list for natural and semi-natural grasslands on the northern Virginia Piedmont.

You may have heard the legend that before European colonization, a squirrel could get from the Atlantic Coast to the Mississippi by hopping from tree to tree. While the pre-European landscape of the eastern United States was indeed quite different from what we see today, the idea of a vast, all-encompassing forest is misleading. Particularly in the Southeast, open, grassy habitats such as meadows, pine and oak savannas, glades, and barrens were interspersed with hardwood forests. This mosaic of forests and open savannas was maintained by grazing elk and bison, variation in soil types and depth, and regular fires set by both lightning strikes and Indigenous peoples. All of these grassland-maintaining processes were disrupted by the introduction of European development and agricultural practices.

As a PhD student in the Restoration Ecology Lab at Virginia Tech and a graduate research fellow with the Smithsonian’s Virginia Working Landscapes program, I am researching native warm-season grasslands in Virginia. I have three main goals:

(1) To describe the plant species that characterize native warm-season grassland communities on the Virginia Piedmont;

(2) To determine which ecological processes and environmental conditions allow these grasslands to thrive and persist in tandem with forests; and

(3) To determine the best methods to restore and reconstruct these communities where they have been lost.

I am accomplishing the first of these goals, the description of Virginia’s Piedmont grassland communities, by surveying the plant species found in existing Virginia grasslands. Today, most high-quality grassland sites in Virginia are in areas where routine maintenance prevents the growth of shrubs and trees and keeps the habitat open for the sun-loving grassland plants. Many highly diverse sites, for example, are found in powerline rights-of-ways that are maintained by annual mowing.

Jordan Coscia surveys grassland plant vegetation in an experimental restoration in northern Virginia. Photo credit: Charlotte Lorick.

By surveying native grassland fragments such as those found in rights-of-ways, we can determine the plant species that are characteristic of these habitats. We can then include these species in planted grasslands and native grassland seed mixes to create more ecologically accurate restorations. In the summer of 2020, the Restoration Ecology Lab at Virginia Tech partnered with the Clifton Institute and Virginia Working Landscapes to identify and survey remnant and semi-natural grassland plant communities across northern Virginia. The results of these surveys will inform future grassland restoration projects in the area, including my own grassland restoration experiment that will test the effectiveness of different grassland installation and management techniques. While a full report of the survey results will be available in a future publication, you can find a sneak peak of the full list of the species recorded in our 2020 surveys below.

A semi-natural grassland bursting with scaly blazing star (Liatris squarrosa) blooms in a powerline right-of-way in Fluvanna County, Virginia. Photo credit: Jordan Coscia.

Across 34 sites, we identified 354 taxa (including subspecies and varieties), with an additional 53 groups only identifiable to genus or family. Of those identified to genus level or better, 330 (81%) are considered native, 41 (10%) are introduced, 11 (3%) are invasive, and 25 (6%) are of uncertain status in northern Virginia. The three most commonly recorded species were little bluestem (Schizachyrium scoparium), narrowleaf mountainmint (Pycnanthemum tenuifolium), and tapered rosette grass (Dichanthelium acuminatum).

Our species list is available for download below.

The final column is a count of occurrence, or how many sites a plant was recorded in, with a maximum possible value of 34. Plants are listed alphabetically by Latin species name in descending order of occurrence.

We are continuing this work in 2021 through a collaborative effort with the Center for Urban Habitats. This year, we have expanded our grassland discovery and characterization to an eight-county area centered on the city of Charlottesville in the central Piedmont. With a larger team and a refined protocol, we have already discovered more than 300 remnant grassland fragments this growing season. Both the 2020 and 2021 surveys are generously supported by research grants from the Virginia Native Plant Society.

A prairie resurgence?

James Faupel is the urban ecology restoration supervisor at the Litzsinger Road Ecology Center, a suburban outdoor education site managed by the Missouri Botanical Garden. The property is a mix of reconstructed bottomland prairie and restored riparian woodlands in St. Louis County, Missouri.  

North American prairie remnants are invaluable pieces of a once vast grassland ecosystem, critical for the survival of so many plants and animals. Prairies are one of the most endangered ecosystems in the world, removed from existence by our agricultural development for crop production. According to the National Park Service, less than 1% of original prairies now remain in North America. The Missouri Prairie Foundation states that less than half of 1% of pre-settlement prairie is left here in my home state. These few remaining North American prairie remnants are vital seed banks for local ecotypes of thousands of native plant species, such as the federally endangered Mead’s milkweed (Asclepias meadii), and they are home to many species of animals that just cannot be found in any other type of habitat. Most prairie specialist species cannot survive once a fragmented prairie has been plowed or bulldozed under. Species such as the regal fritillary butterfly (Argynnis idalia) only occur on remnant prairies in Missouri and have not appeared in our human-made prairie reconstructions.

A now rare, prairie horizon view. This one is visible at the National Tallgrass Prairie Preserve in Kansas. Photo Credit: James Faupel.

Undiscovered remnant prairies are generally only spared thanks to practices such as consistent haying or grazing, and have sometimes been found protected in unused areas of historical sites, such as old cemeteries. Unfortunately, remnant prairies are now mostly found in rural settings far from the eyes of our growing urban populations. These sometimes small patches of prairie habitat do not have large dramatic features, such as mountains or canyons that draw vacationers’ attention from states away. Most remaining prairies are also no longer large enough to host their once charismatic herds of grazing megafauna, the American bison. The amazing views of these smaller, modern-day prairies must be experienced up close and personal. This is a problem if you want to educate the public on the importance of protecting these fragile habitats, that are now fragmented and spread far from each other across such a vast continent.

Middle school children getting to know prairies up close and personal, at a prairie managed by the Missouri Botanical Garden. Photo credit: James Faupel.

My home city of St. Louis was once 61% prairie pre-European settlement. The only remnant prairie still existing here is a small plot at Calvary Cemetery, which has had to have extensive restoration work done to remove trees, shrubs, and exotic invasive plants from smothering it out of existence.

The prairie remnant at Calvary Cemetery in St. Louis City looking very open after some much needed restoration work, consisting of tree and shrub removal. Photo credit: James Faupel.

Many organizations in St. Louis have begun to reconstruct prairies here over the years, to help regain this lost habitat for local wildlife and to be able to get these valuable grasslands back in view of the public. Some of the earliest prairie reconstructions in the Greater St. Louis Region started in the 1970s and 80s. Specifically within St. Louis City & County, this practice didn’t begin until the 80s. I have the pleasure of working on one of those prairies reconstructed in the 1980’s, at the Litzsinger Road Ecology Center, a prairie started and managed by Missouri Botanical Garden staff. The ecology center is a private education site dedicated to working with K-12 teachers, to improve upon their ability to engage their students in place-based education, using our local ecology as the framework.

Recent work at the Litzsinger Road Ecology Center suggests that St. Louis prairies are making a comeback. Our 2021 spring intern, Lydia Soifer, began work on an independent research project looking at prairie habitat connectivity within St. Louis City & County. Through this project Lydia and I generated a count of 58 small-scale, urban prairie reconstructions managed by various entities within this highly populated area. There are also many more prairie reconstructions in the 7 surrounding counties within Missouri and Illinois.  

With an increase of 58 small prairies slowly over 40 years, this may seem like a time to celebrate, but this prairie resurgence should not be taken lightly. Some of these new prairies are now at risk of failure. Prairie reconstructions cannot be left to their own devices in our modern, highly human influenced world. Investment in both ongoing habitat maintenance and the continued education of staff is a necessity, or these prairie reconstructions can quickly turn into fields of exotic invasive weeds or full of aggressive trees and shrubby growth. Even at 32 years old, the urban prairie I work at still needs continued maintenance to keep it a “native prairie”.

Challenges facing urban prairie stewards range from intense seed pressure from surrounding invasive plants, severe runoff and volatile urban waterways, minimal funding and educational resources, fire & smoke restrictions that limit the chance of using prescribed fire, and heavy browsing from oversized whitetail deer populations. Many businesses and organizations outsource with private contractors for their prairie maintenance, which can have some beneficial and detrimental outcomes. There is not a constant visual presence overseeing the land they hold, but it can be much more affordable than permanent staff. Sometimes the only maintenance is periodic visits from dedicated volunteers. The decision to reconstruct a prairie should be well thought out and planned for optimal long-term care. Placement should be targeted for areas where a new prairie could help connect existing fragmented habitats to improve urban wildlife corridors.

A prairie planting reclaims some space previously occupied by turf grass on a steep hillside at Bellerive Park, a St. Louis City Park. Photo credit: James Faupel.

Are these human-made prairies working?

So, it appears prairie reconstructions are gaining some ground within St. Louis and surrounding areas of the Midwest. How do we know if these reconstructions are being successful? What is success? Data collection of any kind is minimal to non-existent across these local sites, so assigning a value to these lands could be considered speculative at best.  

When I transferred to the Litzsinger Road Ecology Center in 2018, I took notice of data previously collected there relating to pollinators (I have a passion for animal associations with native flora.). There were collection records from around the year 2000, of the now federally endangered rusty patched bumble bee (Bombus affinis), the endangered (IUCN Red List) Southern plains bumble bee (Bombus fraternus), and the vulnerable (IUCN Red List) American bumble bee (Bombus pensylvanicus). This is the only confirmed record of the rusty patched bumble bee in St. Louis, and its range has now shrunk considerably in recent times and can only be found much farther to our northeast. After surveying the reconstructed prairies at my work, I was able to find these two latter bumble bee species of concern. I was curious. Could more of the prairies around St. Louis be supporting the potentially declining populations of Southern plains and American bumble bees?  

Left image – A Southern plains bumble bee queen nectaring on spider milkweed (Asclepias viridis). Right image – An American bumble bee worker visiting great blue lobelia (Lobelia siphilitica). Photo credits: James Faupel.

Previously, not much was known specifically about the rare Southern plains bumble bee in the St. Louis region. According to the Checklist of the Bees of St. Louis, MO (Camilo et al. 2017) only two records within the city had been collected, in addition to the collection I mentioned earlier from the Litzsinger Road Ecology Center in St. Louis County. According to many local bee specialists, the American bumblebee used to be commonly seen all around St. Louis, but the Checklist notes only 3 sites that it was recorded at during their recent surveys. After spending a lot of my free time surveying St. Louis prairies, woodlands, and gardens over the last three years, I have found very promising results in the prairies.  

Six of the larger and older prairie reconstructions in St. Louis City and County, with moderately rich species lists of native plants, were found to contain and support the Southern plains bumble bee, sometimes two to three years in a row. Many more of the prairies I visited supported the American bumblebee. Shutterbee, a local citizen science project I partner with, has recorded 3 Southern plains bumble bees and over a hundred American bumble bees from bi-weekly bee surveys in private home gardens in St. Louis City and County over the last two years. This shows there may be increased value in native plant gardens placed near prairies, for enlarging the foraging areas of bumble bees. 

I am also beginning to see a trend with these two species’ floral choices. These two species of conservation concern seem much more reliant on native prairie plants than some of their more common bumble bee counterparts, that are flexible enough in their diets to visit many more exotic flowers. For the moment, this is just observational data, but at least it is showing that there is value in the hard work being done bringing these grasslands back to urban spaces. There are many other ways we could begin to assign value to man-made prairies, but more data collection needs to be done across the board on urban prairies. 

All of these same prairie reconstructions containing milkweeds, blazing stars, sunflowers, asters, or goldenrods have also been recorded to attract in the majestic, migrating monarch butterfly (Danaus plexippus). Last December, the monarch was nearly put on the U.S. endangered species list. The US Fish and Wildlife Service put off this decision for a few years and will revisit it. If the well-known monarch butterfly does indeed get listed as endangered in the near future, will there be a vast new interest in prairie reconstruction? Will there be more investment in prairie protection and reconstruction from municipalities, utilities, corporations and other large land holders? If a quick surge of interest arises, education about these unique ecosystems and their management will be needed more than ever. 

There are current opportunities to capitalize on the revitalized interest in the outdoors that the pandemic brought about, and with urban populations projected to outpace their rural counterparts in the future, native ecosystems will need to be brought to the people, to spark their curiosity and passion with nature. Without urban prairie reconstructions, we won’t be able to inspire the future volunteers, donors, conservation voters, and land stewards needed to care for and protect remnant lands. Urban prairie reconstructions are therefore integral in the process of preserving our rural remnant prairies, while also being ecologically biodiverse and important in their own right. We need more prairie reintroduced into North America and we need continued investment in their long-term care and monitoring. We aren’t just hoping to save endangered species, we are also hoping to save our continent’s most endangered ecosystem.

A monarch butterfly visiting New England aster (Symphyotrichum nova-angliae) at the Donald Danforth Plant Science Center’s 5-year-old prairie reconstruction. Photo credit: James Faupel.

Conserving and restoring Missouri bladderpod, a US Midwestern endemic

Matthew Albrecht is a Scientist in the Center for Conservation and Sustainable Development at Missouri Botanical Garden. Here he describes a recent fieldtrip to the Ouchita Mountains to study outlying populations of the federally threatened Missouri bladderpod, Physaria filiformis.

Situated between Rocky Mountains to the west and the Appalachians to the east lies the often overlooked Ouachita (pronounced WAH-shi-tah) Mountains of central and western Arkansas and adjacent Oklahoma. Unlike the Rocky and Appalachian Mountains, the Ouachitas are a relatively small mountain chain that trends primarily east-west. Despite occupying a relatively small area, the Ouachitas harbor a large proportion of the region’s plant diversity and represent a remarkable center for endemism including many rare plants species with extremely narrow distributions.

On a recent spring afternoon, Christy Edwards and I had the opportunity to visit the relatively rare and poorly studied shale outcroppings of the Ouachitas with botanists Brent Baker and Diana Soteropoulos of the Arkansas Natural Heritage Commission. In the Ouachitas, shale formations outcrop on gentle to steep south- or west-facing slopes and occasionally on gently sloping drainages. Upon first glance, these outcroppings with exposed fragments of thin, black shale and patches of sparse vegetation cover appear somewhat other worldly. Upon closer inspection, one finds tucked between shale fragments a number of xeric-adapted herbaceous species capable of surviving in this harsh environment, where the dark, sun-scorched shale at the surface creates extreme ecological conditions.

Ouachita shale glade and barrens. Photo by Matthew Albrecht.
Xeric-adapted species specialize on the thinnest soil portions of shale outcrops. Photo by Christy Edwards.

Shale barrens and glades are mosaic plant communities consisting of a remarkable number of endemic, rare, and narrowly-distributed species. According to NatureServe, 36 plant species of state conservation concern and more than 20 globally critically imperiled, imperiled, or vulnerable species occur in this system. New species are still occasionally discovered and a few species remain undescribed in the Ouachita shale barrens. For example, we saw a striking purple-flowered undescribed species of wild hyacinth (Camassia sp. nova) during our visit.

An undescribed wild hyacinth (Camassia sp. nova) growing in a shale glade and barren complex owned and managed by the Ross Foundation. Photo by Matthew Albrecht.

The star of the show that day and the focus of our research expedition to the Ouachitas was the federally threatened Missouri bladderpod (Physaria filiformis).  Many members of the genus Physaria – commonly known as bladderpods due to their inflated seed pods – are recognized for their narrow distributions and edaphic endemism, or restriction to unusual soils. As a small-statured winter annual, Missouri bladderpod showcases brilliant yellow flowers in early spring and specializes on thin-soiled calcareous (dolomite and limestone) outcrops in northern Arkansas and southwestern Missouri. However, at its southern range limit in the Ouachitas, Missouri bladderpod is known from just a few isolated shale glades and barrens.

A profusion of flowering Missouri bladderpod (Physaria filiformis). Photo by Christy Edwards.
Missouri bladderpod (Physaria filiformis) displaying inflated fruits on a shale outcropping. Photo by Matthew Albrecht.

Prior to visiting the Ouachitas I wondered how a presumed calciphile like Missouri bladderpod existed on shale formations, which typically produce acidic soils. Perhaps like a few other species of rocky outcrops in the region – such as Sedum pulchelum (widow’s cross), and Mononeuria patula (lime-barren sandwort) which occur on both acidic and calcareous substrates – I surmised MO bladderpod may also tolerate a broader range of edaphic conditions than previously thought. However, I soon learned the shale outcroppings we visited were interbedded with limestone and supported other calciphilic indicator species such as Ophioglossum engelmannii.

A case of cryptic speciation in the Ouachitas

Once known only from limestone glades in southwestern Missouri, botanists over the years have discovered populations of Missouri bladderpod on limestone, dolomite, and shale outcroppings in scattered locations throughout Arkansas, denying Missouri’s claim of its only endemic species. A recent study led by Christy Edwards at the Missouri Botanical Garden examined range-wide (Arkansas and Missouri) genetic variation in Missouri bladderpod and the degree of genetic differentiation among populations on limestone, dolomite, and shale. Interestingly, genetic data showed isolation by distance – meaning that as geographic distance increased among populations so too did genetic differentiation. Most strikingly, the geographically isolated shale populations in the Ouachitas were highly genetically divergent from dolomite and limestone glade populations further north in Arkansas and Missouri. This strong pattern of genetic differentiation points to a possible cryptic speciation event in the Ouachitas and a previously unrecognized extremely rare species. On one hand, the genetic data was somewhat surprising given there are no obvious morphological differences among Ouachita shale populations and P. filiformis. Conversely, the data do support the remarkable pattern of narrow-endemism observed throughout the Ouachita Mountains. 

As we trekked across Arkansas for a few days – along with Brent and Diana who generously shared their time and expertise – collecting fresh material of Missouri bladderpod for a deeper research dive into whether morphological traits differentiate this previously unrecognized cryptic species in the Ouachitas, the need to conserve and restore glade habitat became ever clearer. At present, there are only three known Ouachita populations, making this cryptic species extremely rare and vulnerable to extinction. Many shale glade and barrens systems are now severely damaged or have been destroyed by mining activities. Fortunately, the largest population we visited consisted of thousands of plants scattered across a shale glade and barrens complex that has been restored and managed with fire and woody thinning by the Ross Foundation. In the absence of periodic, appropriately-timed prescribed burning, glades and barrens slowly become encroached with woody species that eventually choke-out sun-loving plants like Missouri bladderpod.

A large, restored shale glade and barrens complex in the Ouachita Mountains.

Other populations of Missouri bladderpod eek out an existence on small stretches of outcrops on roadsides or private property maintained as cattle pasture. These sites prove challenging to conserve and restore. Sadly, we did visit some sites where populations were barely surviving due to degraded habitat conditions. However, two sites we visited gave us a glimmer of hope that Missouri bladderpod will continue to survive and thrive. First was a newly discovered dolomite glade population on private property in north-central Arkansas. The property owners recently thinned woody vegetation and began prescribed burning to restore their glade and woodland ecosystem. When we visited, Missouri bladderpod was thriving after a recent prescribed burn. Similarly, the second site we visited on public property had been thinned and burned in recent years, resulting in a diverse plant community and flourishing Missouri bladderpod population. These success stories illustrate the importance of restoring degraded habitat to conserve our rarest components of biodiversity.

Population of Missouri bladderpod growing on a roadside dolomite outcropping and pasture in north-central Arkansas.
A degraded site with woody encroachment and a small, declining population of Missouri bladderpod.
A restored hillside glade with a thriving population of Missouri bladderpod.

To learn more about the Missouri bladderpod, read the new, open access paper by Christy Edwards, Matthew Albrecht and others.

Torrey’s mountain mint – an oddball species?

In a state whose flora has been studied for hundreds of years, grassland conservation and restoration are still hindered by a need for better understanding of basic plant ecology and systematics. Leighton Reid, Jordan Coscia, Jared Gorrell, and Bert Harris contributed to this post.

All ecologists deal with puzzling groups of plants. In eastern North America, sedges (genus Carex) and panic grasses (genus Dichanthelium) are notorious for having many species with similar characteristics. In Central America, tree seedlings in the avocado family (Lauraceae) can be tricky to separate.

Sometimes we also encounter oddballs – plant species that it’s hard to see where they fit into the contemporary landscape.

Torrey’s mountain mint (Pycnanthemum torreyi) is a bit of both – an oddball species whose relationships to other mountain mints is not yet worked out.

Late-season aspect of Torrey’s mountain mint. Photo credit: B. Harris.

Like others in its genus, Torrey’s mountain mint is an aromatic herb that grows (mostly) in more-or-less open areas. Its crushed leaves have a delightful minty smell. In summer, it produces clusters of small, white flowers that are visited by a variety of pollinators.

Unlike some other mountain mints, Torrey’s is also rare. NatureServe ranks it as a G2, meaning that it is imperiled throughout its range – which extends sporadically from New Hampshire to Kansas.

Virginia has more Torrey’s mountain mint populations than the other states. The Flora of Virginia describes its habit as “dry, rocky, or sandy woodlands and clearings.” In some places, like the Piedmont, it occurs mainly on basic soils, whereas in other places, like the Coastal Plain, it lives in sandy, acidic soils. In the mountains it has been found also in limestone seepages.

An oddball species

While restoring natural areas in Chicagoland in the 1980s, Stephen Packard described some of the plants he saw as “oddball species”. Species like purple milkweed (Aslcepias purparescens) and cream gentian (Gentiana alba) grew neither in closed forest nor in open prairie, so where did they belong? These species preferred intermediate levels of light, such as would be found beneath a spreading burr oak. Packard’s observation that these species preferred savanna conditions sparked his realization that savanna had once been a frequent component of the Chicago landscape.

Matthew Albrecht has considered a similar possibility in Tennessee for Pyne’s ground plum (Astragalus bibullatus). This species grows on so-called cedar glades around Nashville, but it does not grow right in the middle. It prefers the edges where there is intermediate light. This suggests that these cedar glades may once have had softer edges that tapered slowly from exposed, rocky glade into open woodland. With modern fire suppression, these edges have become hard; many glades are now bordered by dense forests of eastern red cedar.

Could our own Pycnanthemum torreyi fall into the same category? An “oddball species” with a preferred niche that is neither full sun nor full shade? In our fieldwork on the northern Virginia Piedmont, we encountered several populations of Torrey’s mountain mint, all of which were growing in edgy sites, like powerline right of ways, or the edge of an old apple orchard.

A small population of Torrey’s mountain mint grows along one edge of this field near the forest edge, not in the open center of the field. Is this typical of this species’ preferred light environment?

Last summer, one of us (Leighton) tested P. torreyi’s habitat affinities inadvertently and with a very small sample size. He planted three seedlings in his small, Blacksburg, Virginia yard – one in an exposed spot on the south side of the house and two in a partially-shaded spot on the north side of the house. The plant in the more open, southerly spot grew okay, but it was somewhat stunted – like a spider plant that has been left out in the sun. Its stem and leaves grew short and tough. In contrast, the two plants on the north side of the house grew full and spread out, both flowering and fruiting in their first season. They also remained green late into the season, even after nearby P. tenuifolium and P. incanum had senesced. If this was a species desirous of full sun, shouldn’t it be doing better in the exposed position in the back by the parking lot?

Two Torrey’s mountain mints growing well and flowering in partial shade on the north side of JL Reid’s home in Blacksburg, Virginia.

Clearly Leighton’s sample is way too small to draw any conclusions, but it does make us wonder if Torrey’s mountain mint prefers and intermediate level of light, such as would be found in a savanna or an open woodland. These disturbance-dependent habitats were once widespread but are excluded today in much of the eastern United States. Maybe Torrey’s mountain mint is an oddball species whose habitat preferences will eventually lead us to design new restoration targets in Virginia, but we’ll have to study its ecology in a bit more detail first.

A “Problematic Species”

The Flora of Virginia also highlights that Torrey’s mountain mint is a “problematic species”, whose interpretation is “confounded by its similarity to Pycnanthemum verticillatum and its hybridization with other species.”

During our fieldwork in 2020, we were able to positively identify all of the individuals that we encountered, differentiating P. torreyi from P. verticillatum by characteristics of their flowers and leaves. Still, the possibility that Torrey’s mountain mint is not a well-differentiated species is troubling. Several landowners in our area are conserving open habitat in part because this rare species occurs there, so it would be nice to know if it is a good species.

I asked Gary Fleming, a Vegetation Ecologist for the Virginia Natural Heritage Program, for his thoughts. “Well, the entire genus Pycnanthemum is a bit problematic!” Gary wrote me in an email. He explained that the problem is that nobody has studied this genus using molecular phylogenetics, that is, using DNA to reconstruct the evolutionary relationships between species. As a result, our understanding of how species in this genus relate to each other is pretty fuzzy.

“Personally, I think P. torreyi is a good species,” Gary continued, “Over the years, I’ve observed it in numerous places state-wide and it appears to be morphologically very consistent.”

In a state whose flora has been studied for hundreds of years, apparently the Pycnanthumum nut has not yet been cracked. Hopefully some enterprising botanist will take this up soon (and maybe Packera while they’re at it).

Torrey’s mountain mint flowers. Photo credit: JL Reid.

How a rare plant provided clues to restoring a degraded ecosystem

Dr. Matthew Albrecht is an associate scientist in conservation biology in the Center for Conservation and Sustainable Development at Missouri Botanical Garden. He describes the ecology of the endangered Pyne’s ground-plum (Astragalus bibullatus).

Formed from the fossilized remains of an ancient tropical sea, the Nashville Basin encompasses the geographic center of Tennessee, stretching north to southern Kentucky and south to northern Alabama. Celebrated by some as the “home of country music,” many of us prefer to revel in the region’s unique flora and fauna associated with the globally rare limestone glades, or limestone cedar glades. Here, thin, rocky soils interspersed with flat, exposed limestone bedrock support sun-loving herbaceous plants adapted to the scorching temperatures and parched soils of summer followed by near-permanently saturated soils in winter. Trees and other woody vegetation struggle to take hold here, creating an open, desert-like ambience.

Limestone Glade in the Nashville Basin with Oenothera macrocarpa (Missouri evening primrose), a rare disjunct species, in bloom. Photo by Matthew Albrecht

Treasured for their unique flora, limestone glades feature over two dozen endemic or near-endemic species along with several unusual disjuncts – known mainly from grasslands far west of Mississippi River. Glade endemics such as Nashville Breadroot (Pediomelum subacaule) and Gattinger’s prairie clover (Dalea gattingeri), occur in open, shallow-soil communities dominated by C4 annual grasses and C3 winter annuals, including several members of Leavenworthia spp. Most of these glade-restricted species are widespread throughout the Nashville Basin. However, several of the disjuncts and endemics are extremely rare, such as the federally endangered Pyne’s ground-plum (Astragalus bibullatus). Known from just a few sites in a single-county, Pyne’s ground-plum teeters perilously close to the brink of extinction.

Gattingers prairie clover (Dalea gattingeri; top) and Nashville breadroot (Pediomelum subacaule, bottom), characteristic glade species in the Nashville Basin.
Pyne’s ground-plum in flower (top) and fruit (bottom). Photos by Matthew Albrecht

Why are Pyne’s ground-plum and a few other endemics and disjuncts so rare? At first glance, the obvious culprit appears to be habitat loss from the unrelenting sprawl of Nashville. Just take a drive from Nashville to Murfreesboro on I-24 and you will encounter an uninterrupted sea of strip malls and tract housing. In the late 1800’s, famed botanist Augustine Gattinger collected a specimen of Pyne’s ground-plum much farther north than where present-day populations are found, in a spot now inundated by the J. Piercy Priest Dam and Reservoir near Nashville. Constructed on the Stones River in the 1960s, the dam flooded thousands of acres for “recreational enjoyment” and hydroelectric power generation. Undoubtedly, other rare plant populations, unknown at the time, faced a similar fate. Over time, humans have abused many glades, using them as trash dumps or for off-road vehicle recreation, which could have also led to their demise.

Trash dump at a limestone glade with a Pyne’s ground-plum population. Photo by Matthew Albrecht.

Our long-term research with Pyne’s ground-plum also points to additional factors. In 2010, we began a demographic monitoring study on Pyne’s ground-plum populations to understand how we could reverse this species’ decline. Most remaining populations occupy slightly deeper soil pockets on glade edges where perennial C4 grasses and forbs form narrow, linear bands that abruptly transition into impenetrable thickets of woody vegetation – mostly of eastern red cedar (hereafter “cedar”). In a few cases, Pyne’s ground-plum grows in small, rocky openings surrounded by dense, dark cedar-hardwood forest.

Monitoring Pyne’s ground-plum populations located in a glade edge (top) and small opening of a cedar-hardwood forest (bottom).

At the time, the long-standing paradigm was that Pyne’s ground-plum – and some other extremely rare plants like Trifolium calcaricum – thrive in the partial shade cast by these adjacent cedar trees and woody vegetation at the glade edge. As the story goes, some endemics were less hardy and required some shade as a buffer from the extreme microclimate on the thin-soil outcrops. Much of the early, pioneering work on glade ecology by Elise Quarterman and her students – described stable plant communities under edaphic control of the thin, rocky soil. As was typical of that era, they described plant communities on deeper soils according to classical climax theories of eastern deciduous forest succession.

However, several years of careful monitoring and experimentation in my lab began to reveal other factors at play. Initially considered an outlier, one of our monitored populations occurs beneath a utility right-of-way, which rapidly succeeds to woody vegetation in the absence of periodic mowing. Our data showed that plants here grew larger and usually produced far more flowers and fruits compared to shaded sites. After measuring soil properties, light availability, and other vegetation properties in permanent plots, our analyses indicated that the amount of woody vegetation cover rather than edaphic conditions drove growth and reproduction in Pyne’s ground-plum. Follow-up experiments conducted by then REU student, Rachel Becknell, confirmed light-conditions that mimic cedar resulted in reduced growth of Pyne’s ground plum.

Top: Pyne’s ground population growing under a utility line kept open by periodic mowing. Bottom: Permanent monitoring plot with Pyne’s ground-plum and associated species.  Photo by Matthew Albrecht.

With fresh eyes, we began to scrutinize the dense thickets of cedar at our study sites. Upon closer inspection, we noticed the occasional, gnarled, and open-grown (i.e., wolf tree) chinkapin or post oak jutting above the younger, even-aged thickets of redcedar. Chinkapin and post oaks grow slowly in these thin, rocky soils, but their low-lying branches in multiple directions suggest these wolf trees once grew in conditions more open in the distant past. Historical aerial imagery dating back to the 1950’s confirmed that some of these forested sites were once more open, with far fewer cedars.

We speculate that disturbances from prior land-use activities probably kept these deeper soil areas around glade openings in a more savanna-like or open woodland state. In their absence, opportunistic woody vegetation – especially fast-growing cedar – colonized all but the thinnest soils in the limestone glades. Over time, this led to the development of multilayered forests and dense shrub layers that now surround the thin-soil glade openings at many of our study sites.

Dense cedar thicket behind a small remnant population of Pyne’s ground-plum. Photo by Matthew Albrecht.

To dig a bit deeper in time, my colleague, Dr. Quinn Long, and I also examined early land survey records dating back to the late 1700’s. Surveyors would delineate property boundaries based on the tree species (i.e., witness trees). If no tree species were present, surveyors used stakes (or sometimes stacks of rocks) to mark off the property boundary. In the records we examined, eastern redcedar represented just 2% of all witness tree species while oaks and stakes represented a majority of the records. Now, cedars are probably the most abundant tree in the Nashville Basin.

Although we interpret historical data with caution, these multiple lines of evidence imply a historically more open landscape in the Nashville Basin with far fewer cedars. Cedars are fire intolerant, and we hypothesize that periodic fire – naturally set by lightning and Native Americans – maintained historically lower densities of woody vegetation and promoted grassland species surrounding the glade pavement openings. Genetic analyses by our collaborators Dr. Ashley Morris (Furman University) and colleagues show widespread admixture among populations of Pyne’s ground-plum, which also supports a historically open landscape mosaic that facilitated gene flow among remnant populations via pollinator or animal movement.

Prescribed fire at Couchville Cedar Glades and Barrens Natural Area. Photo by Todd Crabtree.

Admittedly, we were not the first to propose a paradigm shift in the ecology of the Nashville Basin. We soon realized a few other astute botanists long before us advocated for the use of fire management to create more open habitat around glades, but with limited data these recommendations never gained widespread traction among land managers or found their way into the scientific literature. Another issue was that ecologists and botanists tended to focus almost exclusively on the plant communities of open, thin-soil glades – which are clearly not fire-dependent – rather than on the matrix plant communities of slightly deeper soil surrounding them.

Not surprisingly, our ideas faced much skepticism and many questions: Hasn’t cedar always been the dominant tree of the Nashville Basin? After all, the Cedars of Lebanon State Park and State Forest – the largest remaining tract of Nashville Basin Glades and Woodlands under public protection – was named after the towering eastern red cedars that reminded early settlers of the Biblical cedar forests around Mount Lebanon.

At about the same time of our research discoveries, Dr. Dwayne Estes, botanist and Director of the Southeastern Grasslands Initiative, also began developing transformative ideas about the Nashville Basin. Like us, he hypothesized that the glades were historically embedded in a savanna and open woodland landscape rather than dense forests as they are now. Unfortunately, there are few historical descriptions of the Nashville Basin before early settlers radically altered the landscape via farming, pasturing, and logging. Estes speculates that lack of detailed naturalist descriptions of the Nashville Basin prior to the Civil War resulted in a misunderstanding of its historical condition. The earliest reports after the Civil War describe a largely forested region with large cedars, which could have easily developed over the 80-year period between the time of settlement and the mid-1800’s.

Long before settlement, we know that American bison and other large mammalian grazers also crisscrossed this landscape along ancient traces or megafauna highways that connected mineral licks and water sources. Formerly known as French lick, what is now present day downtown Nashville contained a large salt lick, once visited by herds of bison and elk according to early accounts. Disturbance associated with grazing and large-animal activity combined with periodic fire and drought probably kept the Nashville Basin in a more open state. Interestingly, Pyne’s ground-plum’s presumed closest relative, Astragalus crassicarpus, is widespread throughout grasslands in the Great Plains. Commonly known as buffalo pea, it also produces large plum-colored fruits eaten by Native Americans and presumably bison. In many years of monitoring, we rarely find that animals eat Pyne’s ground-plum fruits, which slowly dehisce releasing their hard seeds next to mother plants. Seeds contain a double seed coat making them challenging to germinate. After years of experimentation, we have found that exposing seeds to high concentrations of sulfuric acid followed by a short period of cold stratification results in consistently high germination compared to other treatments. We now wonder whether this germination strategy might be linked to ancient relationships with mammalian grazers who possibly dispersed the fruits and scarified the seeds.

How does Pyne’s ground-plum inform restoration of degraded woodland and savanna-like systems in the Nashville Basin? Thanks to the prodigious efforts of conservation agencies, several remnant limestone glades have been protected. However, until recently, the dense, cedar-hardwood forest surrounding open glades received little attention from land managers. In 2012, we along with collaborators at the Tennessee Department of Environment and Conservation (TDEC) and United States Fish and Wildlife Service began thinning woody vegetation in the most shaded Pyne’s ground-plum populations. After a few years, we noticed increased flowering at the most shaded sites. To reestablish a more open woodland and savanna-like structure in protected areas throughout the Nashville Basin, TDEC began widespread thinning of woody vegetation around glade openings and reinitiating the key ecological process of fire.

A recently restored area at Flat Rock Cedar Glade and Barrens Natural Area.  Pyne’s ground-plum (inside cages) was reestablished at this site in 2016 after mechanical thinning and fire removed woody vegetation at the glade edge.

On a warm, sunny afternoon this past October, my colleague, Noah Dell, and I set out to survey restored areas that might be suitable for establishing Pyne’s ground-plum populations. Hiking through recently restored areas we noticed grassland- and savanna-associated species slowly beginning to rebound and increase in abundance. Compared to previous years, it was much easier to find open, deeper soils on well-drained sites that are needed to reestablish Pyne’s ground-plum. With time and continued restoration of ecological processes, we are optimistic that this and many other rare species will continue towards path of recovery in the Nashville Basin.

Restoring Tallgrass Prairies across Iowa

Andrew Kaul is a new Restoration Ecology Post-doc in the Center for Conservation and Sustainable Development at the Missouri Botanical Garden. Here he describes some projects from his dissertation work conducted with Brian Wilsey at Iowa State University.

Tallgrass prairies once covered most of the central United States, but much of this historic ecosystem was lost to agriculture during the 19th and early 20th Centuries. Iowa sits at the heart of the tallgrass prairie range and lost more of its prairie than any other state except Illinois.

Throughout the Midwest, prairie restoration efforts have become increasingly common, and after several decades of research, the practice of prairie restoration has become increasingly complicated. We now know that restoration outcomes can be highly variable, and it is difficult to predict the outcome of any given restoration because there are so many factors that have been documented to influence restoration success, in terms of species diversity and establishment of target species from the seed mix.

Nodding lady’s tresses (Spiranthes cernua) at Doolittle prairie in Story Co, Iowa. Conservative taxa from groups like orchids are common in remnants, but are often missing from restored prairie communities.

For my PhD at Iowa State I studied 93 grassland restoration projects across Iowa. Previous work on grassland restoration had included careful experiments and thorough investigations of novel restoration techniques. What hadn’t been done before was to treat existing restorations each as their own little experiment and to sample broadly across the wide diversity of restorations in the real world. This approach allowed us to describe general patterns across many sites and to investigate which of the many potentially important processes tended to drive restoration outcomes.

With this project, my advisor Brian Wilsey and I sought to test which factors are the best predictors of restoration success in terms of species diversity, degree of invasion, and establishment of sown species. We considered factors including management history, the diversity of the seed mix, land use history of the site, site size and shape, soil characteristics, and weather during the first couple years of vegetation development. We took a retrospective approach to answer these questions, using existing restorations, which were highly variable in their age and how they were undertaken. We sampled vegetation at 93 restoration sites across Iowa over two summers and interviewed the managers of each of those sites afterwards to get information on when the restoration was started, what seed was used, and how it had been managed. We also sampled 5 prairie remnants, as a reference.

Here I am squinting on a sunny day in July of 2015, posed next to a glacial boulder at one of the remnants in our study – Cayler prairie in Dickinson Co, Iowa. (Photo credit: Brian Wilsey)

We found that by far the strongest predictor of plant diversity and recruitment of species from the seed mix was the degree of invasion by exotic species, where the more heavily invaded a site was, the lower the plant diversity and recruitment of target species. The influence of exotic species was more important than soil type, site management, restoration age, or any other aspects of the restoration, indicating control of exotic species is key to restoring prairies, and other temperate grasslands. The degree of invasion was higher in more linear shaped sites, sites with higher soil organic matter, and sites with fewer species in the seed mix, so we found that these variables were negatively related to our restoration success measures because of their indirect effects through exotic species. More linear habitats tend to have more “edge effects” where there are more colonization opportunities for exotic species. The higher invasion rates we found in sites with greater soil organic matter indicate the exotic species are better able to take advantage of nutrient availability. The lower invasion rates in sites seeded with more prairie species indicate that these mixes contain species that together, occupy more niche space and leave less open niches for exotic species to colonize. We also found that sites mowed during the first two years of establishment had higher diversity and establishment of sown species. This practice is supposed to suppress the annual weeds, which start growing before the seeded prairie species can establish.

Roadside prairie plantings have become a common example of restoration in Iowa.
Sown natives, purple coneflower (Echinacea pallida), and beebalm (Monarda fistulosa) are seen in this roadside prairie planting, which has become mostly dominated by European smooth brome (Bromus inermis).

Another goal of this project was to examine the ecology of milkweeds in prairie habitats. Milkweeds are obligate host plants for larvae of the monarch butterfly (Danaus plexippus), and in recent years, conserving and restoring milkweed populations in service of monarchs has become a major conservation priority in North America, especially in the Midwest, where many of the migratory monarchs breed. We counted milkweed stems within a meter of our sample quadrats at each prairie, and used these count data to examine what prairie habitats have the highest milkweed abundances, and what features of a prairie habitat best predict stem density. Specifically, we tested whether stem densities were different between remnant prairies, roadside restorations, and the non-roadside “conservation” restorations, most of which are managed by the Iowa Department of Natural Resources.

Common milkweed (Asclepias syriaca) is abundant in roadsides, and often establishes in restored areas as a volunteer native.

Milkweeds were far more abundant in remnants than restorations. Among restorations, roadsides had higher milkweed densities. Remnant prairies also had a higher diversity of milkweeds, so they are clearly an important habitat for this forb assemblage. Most of the milkweeds we sampled in restorations were common milkweed, even though it is rarely planted. On the other hand, Swamp milkweed (Asclepias incarnata) and butterfly milkweed (Asclepias tuberosa) are often included in restorations seed mixes, but were not nearly as abundant as volunteer common milkweeds.

Across all the restorations, we tested whether milkweed stem density was related to management (burning and/or mowing) or environmental variables including soil characteristics, plant diversity, degree of invasion, and site shape (linearity). We found that milkweeds were more abundant in more linear and invaded sites, and sites with lower soil density, and higher soil pH. These factors indicate that milkweeds are more abundant in areas with more soil disturbance. This is not surprising, considering the “weedy” ruderal nature of many milkweeds, especially common milkweed. The relationship with pH was a novel discovery, and future work will be needed to experimentally test whether milkweed germination or growth is higher in more basic soils, which is what our study indicates.

I am continuing my research on tallgrass prairie restoration with new projects examining plant functional traits to help understand why certain species are under- or over-represented in restorations. We have collected data on plant and leaf functional traits for over a hundred prairie plants and will test how the mean traits of plant communities differ between seed mixes, restorations, and remnants. Additionally, I am working with the Wilsey Lab on a related project examining phenological differences between plant communities in remnant and restored prairies.

Bottle Gentian (Gentiana andrewsii) is being measured for plant height at Doolittle Prairie (Story Co., Iowa) as part of an ongoing project to examine how traits of prairie plants differ between remnants and restored communities.

To learn more, follow me on Twitter @andrew_kaul and check out our milkweed paper in Restoration Ecology. The prairie restoration study was recently accepted in Ecological Applications, under the title, “Exotic species drive patterns of plant species diversity in 93 restored tallgrass prairies.” Look for it to come out soon!

Botanizing a Central Appalachian Shale Barren

Leighton Reid describes a field trip to a unique, natural community with Tom Wieboldt, retired curator of the Massey Herbarium at Virginia Tech.

From southwestern Virginia to central Pennsylvania, ancient shale formations jut out of the mountains at wonky angles. Loose and crumbly, the rocks bake in the sun. Surface temperatures can reach 60° C (140° F) – comparable to a desert. Rocks slip and tumble easily on the steep slopes. Few eastern plants are tough enough to hack it under these conditions. Among those that can, a few are globally unique.

On a warm day in August, I had the opportunity to botanize one such place – a central Appalachian shale barren in Craig County, Virginia – with Tom Wieboldt, retired curator of the Massey Herbarium at Virginia Tech (VPI), and a leading authority on shale barren flora. As we hiked and photographed plants, we talked about the conservation and potential for ecological restoration of these rare communities.

Shale barren wild buckwheat (Eriogonum allenii), a central Appalachian endemic whose relatives are mostly west of the Mississippi.

The gems of the shale barrens are the endemics. Amazingly, 22 species are found mostly or exclusively on central Appalachian shale barrens. Another seven species are rare or disjunct from the rest of their range – typically far to the west. For example, the closest population of chestnut lip fern (Cheilanthes castanea) outside of Virginia and West Virginia is in Oklahoma.

Virginia white-haired leatherflower (Clematis coactilis), a Virginia endemic and one of three leatherflowers endemic to central Appalachian shale barrens.
Shale-barren ragwort (Packera antennariifolia) had already finished flowering by August, but its leaves lived up to their name, looking very much like pussytoes (Antennaria sp.). This plant is strictly endemic to shale and metashale barrens.
Kates Mountain clover (Trifolium virginicum) was long thought to be a shale barren endemic, but it also occurs (rarely) on other substrates.
Shale barren evening primrose (Oenothera argillicola), a strict shale barren endemic.
The teeny-tiny flowers of mountain nailwort (Paronychia montana), a plant that is not quite endemic to shale barrens. It also occurs on a variety of other substrates.

Shale barren plant communities exist in a dynamic equilibrium. The steep, brittle shale formations often are under-cut by rivers, which carry away rocks and cause further erosion. In essence, the entire slope is constantly slipping downwards. Successful plants find the most stable areas and send down deep roots to try to keep their place on the rocky conveyor belt.

Why do shale barrens occur only in the Central Appalachians and not also in the Southern Appalachians? Tom gave me two reasons. First, the shale deposits in the Central Appalachians get thinner south of Montgomery County, Virginia, where Virginia Tech is located. Second, the high Allegheny Mountains in West Virginia create a rain shadow over parts of the Central Appalachians, more so than the more southern and shorter Cumberland Mountains. Drier conditions in the Allegheny rain shadow contribute to the shale barrens’ uniquely western ambiance.

Inhospitable as they are, shale barrens are not immune from human pressures. They are sometimes crossed by roads or utilities, and shale banks are sometimes quarried for road-building material. Livestock and overpopulated white-tailed deer browse the plants and catalyze erosion, while also adding nitrogen and foreign seeds to the sparse soil.

Craig Creek undercuts several shale bluffs, hastening their erosion and creating the conditions for shale barren plants to flourish.

Can disturbed shale barrens be restored?

When Reed Noss visited a Virginia shale barren for his book Forgotten Grasslands of the South, he found traversing the slippery slopes, lurching from one scattered red cedar to another, “close to suicidal”. I had similar thoughts following Tom up the mountainside. He climbed like a mountain goat, wandering out on thin ledges to collect interesting looking mosses.

Tom Wieboldt collects an interesting-looking moss from the side of a crumbling cliff.

As we walked, Tom wondered aloud whether it would even be possible to restore such a fragile plant community if it was destroyed. Wouldn’t it be better just to leave these places alone?

Undoubtedly leaving these places alone would be better. But I enjoyed thinking about how one might restore a shale barren that had already been destroyed – by quarrying, for instance. A first step might be to recontour the slope, aiming to reestablish a dynamic equilibrium with some areas eroding more actively than others. Perhaps this could be done by a skilled operator with some of the same quarrying equipment that had previously exploited the loose shale.

To revegetate such a place would require a source of propagules. I am teaching a course on Plant Materials for Environmental Restoration, so I put it to my students to find out whether shale barren plants were available from two major conservation seed suppliers. The results were not promising. Out of 86 native, non-woody angiosperms found in central Appalachian shale barrens*, less than a quarter (23.3%) could be purchased from any major seed supplier, and only 2.3% were available as seed collected from Virginia. None of the endemics were available.

As far as I can tell, few shale barren restorations have been undertaken, but I did read about one attempt in a shale barren in Green Ridge State Forest, Maryland. Whereas some shale barrens are actively threatened by acute pressures, like quarrying, this small (0.6 ha) barren was passively threatened by steady encroachment from the surrounding forest. Trees, especially pignut hickory (Carya glabra), were growing into a formerly open barren, stabilizing the soil and cutting off direct sunlight to plants closer to the ground. Managers restored the site in 2010-2011 by removing some of the pignut hickories and by burning the area during the winter. Together, these actions resulted in greater herbaceous vegetation cover and greater species diversity.

Central Appalachian shale barren, Craig County, Virginia, with a mix of shale barren wild buckwheat (Eriogonum allenii) and hairy lip fern (Cheilanthes lanosa) dominating the foreground.

Thanks to Tom Wieboldt for a fun field day, an excellent guest lecture, and stimulating discussions about botany, conservation, and restoration. To learn more about this unique natural community, read Tom’s co-authored chapter about shale barren communities in Savannas, Barrens, and Rock Outcrop Communities of North America, or Reed Noss’s chapter on shale barrens in Forgotten Grasslands of the South.

*For the seed availability exercise, we used the list of plants recorded by the Virginia Natural Heritage Program in their description of Central Appalachian Shale Barren (Shale Ridge Bald / Prairie Type) CEGL008530. We excluded woody plants, non-native plants, and ferns.

Plant diversity, soil carbon, and ecological restoration in Virginia grasslands

Kathlynn Lewis is an undergraduate researcher in the School of Plant and Environmental Sciences at Virginia Tech. She is studying soil carbon storage as part of a larger project on grassland floristics, conservation, and restoration in northern Virginia. Keep up with her research on Twitter by following @KathlynnLewis.

How many rare or “cool” plants do you drive by every day without noticing? Do you brake for Buchnera americana? Do you pull over for Pycnanthemum torreyi? This is something not a lot of people think about, and I didn’t think about either until very recently. The answer is that there are more cool plants along roadsides than you would think. Some of the rarest grassland plants in Virginia have found a home in roadside clearings and powerline cuts where regular removal of trees has created an opening for them to grow and sometimes thrive.

This summer the Virginia Tech Restoration Ecology Lab team has been hard at work doing plant and soil surveys in several counties of northern Virginia. We are partnering with the Clifton Institute and Virginia Working Landscapes to find out where these rare grassland plants can be found and what are the greatest threats these populations face.

American bluehearts (Buchnera americana) – a charismatic hemiparasite and rare denizen of high-quality Virginia grasslands. Photo by JL Reid.

Many of the native vegetation surveys have taken us to the locations people might expect to find high-quality grassland plants, such as parts of Manassas Battlefield National Park where the soil and ecosystem have remained relatively undisturbed for almost 80 years. Other areas are much less expected. Rare plants also show up in power line right of ways and strips of roadside with tire tracks crisscrossing them in every direction and markers stuck in the ground indicating the soil was completely displaced to bury utility lines.

A flourishing native grassland at Manassas National Battlefield Park. In July, it was bedazzled with the hot pink inflorescences of scaly blazing star (Liatris squarrosa). Photo by JL Reid.
A hidden gem – high diversity native grassland along a back road in Culpeper County. The two lines show our 50 × 2 m sampling transect. Photo by JL Reid.

During June, we collected samples from 29 sites to compare plant species diversity with the amount of carbon stored in the soil. We also sampled soils from grassland restoration plantings and pastures “improved” with tall fescue (Schedonorus arundinaceus) to compare the effect of different management practices and ecological restoration on soil carbon sequestration. The soil work is my part of the project. My prediction is that soil carbon storage will be greatest in diverse, native grasslands and lowest in degraded fescue fields. I expect that restored grasslands will be intermediate.

A “blackjack” soil sample from a power line right of way in Culpeper County. This soil had so much clay you could pull it out of the probe and tie it in an overhand knot. Photo by JL Reid.

Power line right of ways are an interesting focus of this study because they present both opportunities and challenges for plant conservation. Power companies keep these areas open by cutting out trees and spraying young sprouts with herbicide. This management is the only reason that grasslands exist in these places today, but the rare plants that live there are at constant risk of collateral damage. At least two of the areas that we sampled in June were sprayed in July, harming populations of rare plants like Torrey’s mountain mint (Pycnanthemum torreyi) and stiff goldenrod (Solidago rigida).

Rose-pink (Sabatia angularis) next to a power line right of way in Prince William County. This plant can give away a good grassland even at 60 miles per hour. Photo by JL Reid.

The vegetation surveying team has already observed over 450 species across the 29 sites sampled. Not all of these species are a welcome presence though. Invasive species appear to pose one of the largest threats to Virginia grassland ecosystems we have observed in the field. A newly emerging and particularly aggressive invader is joint-head grass (Arthraxon hispidis) which we have found in many of the sites we are sampling. This annual grass is similar to Japenese stiltgrass (Microstegium vimineum) but there is very little information about its effects on grassland ecosystems or methods for controlling it.

Joint-head grass (tan-colored thatch) smothering one of the most diverse grasslands in northern Virginia. Photo by JL Reid.

The plant survey team is now doing a second round of sampling to identify later-blooming species, and they are collating information about the land use history at each of our study sites. The soil samples we collected are currently being analyzed (by me) in a lab at Virginia Tech. We will start analyzing data in the fall and hope this summer’s fieldwork will help inform future research projects and the conversation around land management in Virginia grasslands.

The author collects a panic grass (Dichanthelium sp.) for further observation. Photo by JL Reid.

To find out how ecological restoration affects grassland soil carbon storage in northern Virginia, follow the author on Twitter @KathlynnLewis.

A ten-year woodland restoration trajectory

Leighton Reid describes a long-term ecological research project at Shaw Nature Reserve (Franklin County, Missouri, USA). To learn more, read the new research paper (email the author for a pdf copy – jlreid@vt.edu) or tune in for a webinar from the Natural Areas Association on April 21 (register here).

In 2000, the Dana Brown Woods were dark and dense. Brown oak leaves and juniper needles covered the sparsely vegetated ground, and invasive honeysuckle was creeping in around the edges. Biologically, the woodland was getting dormant.

In contrast, the woods today are lit by sunlight everywhere except the lowest-lying streambanks, and the ground is hardly visible beneath a green layer of diverse, ground-level foliage. These changes were most likely caused by two actions: burning the woods, and cutting out invasive trees and shrubs.

Many practitioners have seen woodlands recover to some extent when they are burned, but few have documented the recovery as thoroughly and over so long a period of time as Nels Holmberg and James Trager.

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Nels Holmberg (left) discussing the finer points of Rubus identification with Quinn Long in the Dana Brown Woods.

Nels is an ecologist and sheep farmer in Washington, Missouri. He has inventoried the plants at several state parks and natural areas. In 2000, Nels teamed up with Shaw Nature Reserve’s resident natural historian, James Trager, and together they designed a study to describe how ecological restoration was changing the woodland flora at the reserve. They picked the Dana Brown Woods as their study area.

In a nutshell, Nels and James chose 30 random points on a map. They divided the points evenly across three ecological communities. They placed 10 points in mesic woodlands – the gently sloping parts of the property where white oak and shagbark hickory were most prevalent. Ten points were in areas dominated by eastern red cedar – mostly thin-soiled ridgetops that faced the south, and ten points were in forest – the lower, thicker-soiled toe slopes where northern red oak and Shumard oak were dominant in the canopy with paw paws and spicebush down below.

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Three ecological communities in the Dana Brown Woods: (A) red cedar dominated areas which, after removing red cedar, looked more like dolomite glades in some parts; (B) mesic woodlands with lots of oak and hickory in the canopy; and (C) forest – which had a much darker understory.

At each point, Nels hammered in a t-post, then walked 50 m in the steepest direction and hammered in another t-post. This was his transect. Every year for more than a decade (2000-2012), Nels walked the transects and recorded every stem of every species that was inside of 10 0.5-m2 study plots. Actually, he did this twice per year – once in the spring to capture the ephemeral plants, and once in early summer. Over the course of the study he spent more than 200 days in the field.

Canopy Cover

Dana Brown Woods before (left) and after (right) red cedar removal, with Nels’s 30 transects. The horizontal axis of the image is about 0.9 km. Imagery is from Google Earth.

During this time the stewards at Shaw Nature Reserve were busy restoring the woods. From 2001-2012, they burned the woods five times. This amounted to about one fire every three years. In 2005-2006, they brought in a logging crew to remove all of the eastern red cedars.

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James Trager lights a fire in a woodland at Shaw Nature Reserve.

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One of several thousand red cedar stumps from trees that were harvested from the Dana Brown Woods in 2005-2006.

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One of Nels’s sampling quadrats in the Dana Brown Woods. Photo: Nels Holmberg.

I met Nels and James in 2014. I had just joined Missouri Botanical Garden’s Center for Conservation and Sustainable Development as a postdoc, and I was looking for a local research project. I heard that Nels Holmberg had a giant dataset about woodland restoration, so I called him and asked if I could look at it. Nels said “Sure!”. I imagined he would send me an Excel file. Instead he brought in a giant cardboard box full of yellow legal pads where he had recorded his data.

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One of hundreds of datasheets where Nels recorded his detailed observations.

It took a long time to digitize all of the data. There were more than 50,000 data points. But once we had it all together, this is what we learned:

After eleven years of restoration, the number of native plant species in Dana Brown Woods increased by 35%, from 155 species in 2001 to 210 species in 2012. This increase was linear. That is, the number of native species was still increasing at the end of the study. If we repeated the study today, we expect the number of native species would be even greater than in 2012.

The number of native species increased at different speeds and to different degrees in different ecological communities. In the lower and wetter forest areas, the numbers didn’t really shift very much. They jumped around but not in one direction. In the woodland areas, the number of native species increased by about 23% in the first three years and then leveled out. But in the higher and drier areas where red cedars had been dominant, the number of plants increased linearly by 36%.

Native Species Richness

Changes in the number of native plant species recorded over time in the Dana Brown Woods. On the left are overall changes for the whole management unit. On the right are changes for different ecological communities within the management unit. The management interventions are shown in gray.

The plant species that benefited from the restoration were mostly forbs and grasses. A couple of the biggest “winners” were black snakeroot (Sanicula odorata) and nodding fescue (Festuca subverticillata). There were also some “losers”: Virginia creeper (Parthenocissus quenquefolia) and spring beauty (Claytonia virginica) both declined over time. Relatively few of the species that became more common were “conservative” – i.e., dependent on intact habitat. Mostly they were more widespread and tolerant species.

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Co-author Olivia Hajek demonstrates a hog peanut (Amphicarpaea bracteata) – a good representative of the type of species that benefited most from the restoration. Hog peanut is an herbaceous legume that is common in many woodlands, including disturbed ones.

Our study did not include a control treatment, but counterfactuals exist at Shaw Nature Reserve (although they are becoming fewer and fewer with the excellent stewardship of Mike Saxton and many others). There are still thick patches of eastern red cedar covering remnant glades on parts of the property. Woodlands that have not been regularly burned are now filled with bush honeysuckle (Lonicera maackii), wintercreeper (Euonymus fortunei), and other invaders. And low-lying forest that has not been restored is very dark with fire-intolerant sugar maple (Acer saccharum) casting much of the shade. If we had included a control treatment in our experiment, these are probably the trends we would have found – definitely not a spontaneous resurgence of diverse native plants.

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Fragrant sumac (Rhus aromatica) was present at the outset of restoration and remained relatively stable.

Why does this work matter? The biggest value of this study is that it shows a relatively long-term restoration trajectory, and it does so in fine botanical detail. Many managers and scientists already have data to show that fire and tree thinning increase woodland plant diversity. This study adds another dimension. It shows how quickly plant diversity recovered. It also shows how the speed and shape of the recovery varied across the landscape. We hope that other scientists and practitioners will compare the recovery trajectories in the Dana Brown Woods to their own natural areas. To facilitate that, we have made all of the underlying data freely available online.

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Buffalo clover (Trifolium reflexum) is a conservative species that is present in Dana Brown Woods but was not detected in any of the survey plots.

One of the next steps for this research is to figure out how and when to re-introduce some more conservative plants. Although the Dana Brown Woods became much more diverse as it was being restored, most of the plants were early successional or generalist species. We found very few habitat specialists that cannot tolerate disturbance, which suggested to us that some of these species may have been lost from the site at some time in the past. To learn how conservative plants might be re-introduced, we have started a new experiment testing the effects of soil microbes, competition, and time since the start of restoration on the success of introduced seedlings from seven conservative plant species. In the next year or two, we hope to have new information and recommendations for restorationists looking to add more specialized biodiversity to their woodlands.

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Freemont’s leather flower (Clematis fremontii) is a restricted species occurring on dolomite glades in southeastern Missouri. Although it is present at Shaw Nature Reserve less than one kilometer from Dana Brown Woods, it has not colonized the restored glade habitats there. This photo is from Valley View Glade near Hillsboro, Missouri.

To learn more about this research, you can read the original research paper in Natural Areas Journal. Email me for a pdf copy (jlreid@vt.edu). You can also tune in on April 21 for a webinar on this work. Register here.

Tale of two Highlands Part I: Horton Plains, Sri Lanka

This post is contributed by Dr. James Aronson, a restoration ecologist at MBG’s Center for Conservation and Sustainable Development, and his son Thibaud Aronson. James is also a researcher with the CNRS (National Center for Scientific Research) in Montpellier, France.

In Sinhalese Sri Lanka means “Resplendent Isle”, a fine name indeed for this tear-shaped island off the coast of southeastern India, just north of the equator. Last month I travelled with my son on a self-guided Natural History + Ecological Restoration visit, we are finding and photographing cloud forests and birds galore, like the endangered endemic Sri Lanka whistling thrush, Myophonus blighi, and the Kashmir flycatcher, Ficedula subrubra, which over-winters exclusively in the Sri Lanka highlands, from its very restricted breeding grounds in Kashmir, northern India.

We were also looking at the mosaic of grasslands, cloud forests, and lowland forests we find here from a restoration ecology perspective.  That means we’re trying to “read” the landscapes we see in terms of known transformations carried out during the British colonial era (1815 and 1948, when Sri Lanka was known as Ceylon), and since independence. The remarkable Horton Plains National Park is a mosaic of montane grassland (ca. 35%) and cloud forest (ca. 65%), encompassing the headwaters of three major rivers. It was declared a sanctuary in 1969 and elevated to national park status in 1988; it became part of a large UNESCO World Heritage site in 2010. In the central highlands of Madagascar, grasslands appear to occupy about 99% and most people assume they are anthropogenic…. This month, I’m travelling with Leighton Reid in the Central Highlands of Madagascar, and we will be blogging about this soon.

But, the history of preservation in the highlands here goes back a lot further, to the days when the Isle was part of the British empire, along with all of India. According to information we gathered at the extraordinary, and poorly known Hakgala Botanic Gardens, the great English botanist and explorer Joseph Dalton Hooker had advised the British government to leave all montane forests above 5000 ft. (ca. 1300 m) above sea level “undisturbed” and after 1873 the administration prohibited clearing and felling of forests throughout the central highlands. What a great idea that was! It is too bad there were not enlightened laws on hunting of wild animals as well. One Scottish officer in colonial service in Sri Lanka bragged he had shot and killed over 1400 elephants in Horton Plains and nearby. Today, there are none left there and, so far as we could determine, no plans to reintroduce them from the other remarkable parks, including Yalla and Uda Walawe….

So, what is the significance of the absence of elephants in this park? And, what else can we learn from past regimes and historic periods in Sri Lanka? For starters, we discover that conservation, and respect for other organisms goes back much further than the 19th century. Consider the sign at the entrance to Udawattakele Forest Reserve, near Kandy, one of the historic capitals from the long period of successive kingdoms the island had known prior to the European colonial chapter in Sri Lanka’s history:

O Great King, the birds of the air and the beasts have an equal right to live and move about in any part of this land as thou. The land belongs to the peoples and the other beings and thou are only the guardian of it.”

-Arahath Mahinda (a son of the emperor Asoka the Great, who brought Buddhism to Sri Lanka)

How would it be if we could revive that approach to the Web of Life in our own day and age?

So, what has Horton Plains National Park, with its grassland-forest mosaic, its tourists, and its absent elephants got to do with the Central highlands of Madagascar? For one thing, we can see that fire is a big ecological driver in both areas. The abundant arborescent Rhododendrons in Horton Plains tell a vivid tale in this regard.

Rhododendron arboreum subsp. zeylanicum at Horton Plains National Park. It appears to be fire-resistant and is the only tree species present in large areas of grasslands subject to fire.

Rhododendron arboreum subsp. zeylanicum at Horton Plains National Park. It appears to be fire-resistant and is the only tree species present in large areas of grasslands subject to fire.

On the grand scale of things, Sri Lanka’s Central highlands also resemble those of Madagascar’s since both are the crowns of a poor, emerging tropical island with small and very similar human population size (21 million vs. 24 million), despite being much nearly ten times smaller, and with over 30,000 years of human history, as compared to merely two millennia for Madagascar.

Horton Plains also has remarkable conservation value both for its biodiversity and the ecosystem services it provides to people. Also, as I said, it’s a mosaic of grasslands and cloud forest, that in the past was certainly much affected by both elephants and fire.

Finally, both Sri Lanka (along with the Western Ghats of southern India) and Madagascar count among the world’s biodiversity hotspots, easily visible in their fauna and flora, which is one of the main reasons why MBG researchers, and many others travel and work in Madagascar.

Now, let’s turn back to fires. A big fire hit Horton Plains in 1998, and there are serious invasions of two noxious, cosmopolitan weeds, namely Gorse and Bracken fern. Some control work is underway on the Gorse, but the Bracken fern is apparently not seen as being a problem. Rainbow trout were introduced in the 19th c. and apparently have displaced all native fish, and are taking a toll on native shrimp and no doubt other fauna.