The term "grassland" is broadly used to refer to natural communities where the ground layer of vegetation is dominated by grasses, graminoids (grass-like plants), and forbs, though shrubs, tree saplings, scattered trees, mosses, lichens, and even bare rock or soil may be present to varying degrees. Everyone is familiar with the nearly treeless tallgrass prairies of the Midwestern U.S. but the southeastern U.S. is home to many atypical grasslands that many, if not most, people would walk by and dismiss as grasslands. Although many atypical grasslands may not look "prairie-like" or "savanna-like" one thing that connects them is the presence of sun-loving herbaceous species, many of which often grow in typical grasslands. In the Ridge and Valley ecoregion of southwestern Virginia, east Tennessee, northwestern Georgia, and northeast and central Alabama, dolomite and limestone seep communities represent one of these atypical grasslands.
These tiny open wetlands occur on steep to moderately sloping seepage slopes in hilly, dissected landscapes. Springs bubble out of the sides of hill slopes through cracks in the underlying dolomite bedrock and flow over shallow gravelly or rocky slopes. Sometimes deeper sediments accumulate toward the bottom of seeps. Due to the shallow soils and constant seepage, trees are prevented from growing too large because these slopes are subjected to slumping or slope creep. However, just outside the seepage zone, where slope creep is not as prevalent, sediments may be moist or dry, but tend to accumulate to deeper depths. These deeper-soiled areas support forests or woodlands.
Trees can't grow to large sizes in these seeps, but a variety of small- to medium-sized shrubs, herbs, graminoids (=grasses, sedges, and rushes), and mosses are able to endure the shallow, saturated soils.
The term "fen" is often used for a wide variety of open, groundwater-fed wetlands. Traditionally it has been applied to wetlands underlain by calcareous/mafic bedrock with alkaline or circumneutral pH and mucky sediments. In recent decades there has been a growing realization that such communities are not always easy to separate from wetlands with acidic soils, some of which are called acid seeps or bogs. Due to this lack of a clear-cut difference based on soil/groundwater chemistry, some ecologists advocate calling the wide variety of groundwater-fed seepage wetlands fens. Those that are more on the alkaline end of the spectrum are called "rich fens" and tend to have a greater dominance by broadleaf herbs and grasses and usually lack Sphagnum (peat) moss. Those that are more acidic are often called "poor fens" and tend to have more coverage by sedges and ferns, and Sphagnum is often abundant or dominant. These wetlands of the Southern Ridge and Valley would tend to fit into the "rich fen" type.
Rich fens themselves vary tremendously across the eastern U.S. depending on such variables as topography, slope, depth to bedrock, substrate (muck soils, gravel), etc. Sometimes the term "fen" is reserved for those wetlands in level to gently sloping sites where sediments may become fairly deep. In these situations, sediments are rich in organic matter and become dark, often blackish, and are smooth (not gritty or fibrous) when rubbed between the fingers. Many 20th century ecologists describe fens such as this as occurring mostly in the northeastern U.S. in regions formerly covered by glaciers during the last ice age.
These deep-soiled rich fens do occur in unglaciated regions south of the glacial boundary, in parts of the Southeast and lower Midwest. Two exceptional examples include Grasshopper Hollow Fen in the Missouri Ozarks and Bluff Mountain Fen in the Blue Ridge Mountains of northwestern North Carolina. These deep-soiled calcareous or mafic fens will be described in more detail in future blog posts...stay tuned.
Above: Fens are considered by many ecologists to be groundwater-fed wetlands in basins, flats, and other topographic lows, that tend to have alkaline pH (due to calcareous or mafic bedrock), organic mucky soils, and dominated by graminoids, forbs and shrubs. The best known classic fens are in the glaciated regions of the northeastern U.S. and eastern Canada, but some large classic fens occur in the Southeastern Grasslands Initiative focal area such as Bluff Mountain Fen, Ashe Co., North Carolina (above left, credit, Alan Weakley) and Grasshopper Hollow Fen, Reynolds Co., Missouri (above right, credit, Jim Rathert, Missouri Dept. of Conservation).
In the meantime, the terms seep, seepage wetland, seepage glade, or seepage fen are used for similar wetlands that lack substantial organic soils due to shallow depth to bedrock or abundant bedrock exposures that tend to occur on slopes. These seeps when developed over limestone or dolomite, or mafic or ultramafic metamorphic rocks tend to be alkaline. Those over granite, gneiss, sandstone, and chert tend to be acidic. The Southern Ridge and Valley Dolomite Seep community described here would fit the alkaline type and is developed on shallower soils. Therefore, I advocate referring to these natural openings as seeps and reserve the term fen for the deeper soiled examples. Again, more on these later....
Calcareous hillslope seep communities are found at just a few areas within the Southeastern Grasslands Initiative focal area, including parts of the Missouri and Arkansas Ozarks, the Outer Bluegrass of southern Ohio, the Interior Plateaus of central Tennessee, and the Ridge and Valley from western Virginia south to central Alabama.
No matter where they occur, they all tend to provide refuge for numerous rare plants (including a few that are endemic to these open seeps), rare insects (e.g. dragonflies) and a wide diversity of aquatic macroinvertebrates, salamanders, and aquatic snails.
Aaron "Golden-Boy" Floden Discovers a Botanical Goldmine
In my last year of graduate school at the University of Tennessee-Knoxville in 2007, I received a phone call from Mark Mayfield, botanist at Kansas State University. Mark explained how one of his undergraduate students, Aaron Floden, was about to move to Knoxville and described him as one of the most talented botanists he had ever seen. I told Mark we would make room for him in the herbarium and looked forward to Aaron being a part of our Tennessee botany family.
When Aaron moved to Knoxville he made an immediate impact on Tennessee botany. It was about that same time that Google had just introduced Google's "Street View." In fact, it was Aaron who first showed Street View to me. While playing around with it, he began using Street View to explore Tennessee's backroads from the comfort of his office.
One of the first projects Aaron embarked upon after moving to Knoxville was attempting to rediscover the rare Needleleaf Beaksedge (Rhynchospora capillacea). This sedge had not been seen in Tennessee since the early 1930s when it was last collected about 40 miles north of Knoxville in an area that now mostly lies beneath Norris Lake, a large lake dammed as part of Franklin Roosevelt's New Deal projects.
While "virtually-cruising" the backroads of Campbell County, Tennessee, Aaron was intrigued by one open area along the side of a rural backroad. Thinking about it now, it's kind of surprising to me that one of Google's cars would have even been on that dead-end road. He saw an area with an open canopy just a few feet off the road that looked like a seepage wetland.
Not long after, Aaron jumped in the car and drove up to the site. What he found was incredible. Stepping about 20 feet off the roadside, he found an open dolomite seep. The seep was quite large and originated upslope about 100-200 feet and was about 30 feet wide. The portion higher on the slope was surrounded by forest but no trees were rooted in the seep itself. The lower half of the seep was beneath a small utility-line right-of-way.
Around the margins of the open seep, the dominant shrub was an exceptionally narrow-leaved form of what most people previously had called Bushy St. Johnswort (Hypericum densiflorum), but he realized it was likely a forgotten species long ago recognized by J.K. Small as Hypericum interior.
In the middle of the seep, the vegetation was quite short and throughout were little hummocks. And there on the little mossy mats was the Needleleaf Beaksedge (Rhynchospora capillacea) that initially had inspired his search. And, it was there in abundance. Just like that, he rediscovered a lost species that no Tennessee botanist really thought would be rediscovered. Most of us had assumed the population last observed in the 1930s was submerged beneath Norris Lake.
But, Aaron's big day was just beginning. Growing there among the tussocks of the Needleleaf Beaksedge was a small white-flowered "lily" with narrow strap-like leaves and a sticky stem. He instantly recognized it as Sticky False Asphodel (Triantha glutinosa), a species not previously known from Tennessee. This find is what botanists call a "state record." Interestingly, both the Sticky False Asphodel and the Needleleaf Beaksedge, are northern species that are near their southern range limit in North America in Tennessee. They are more common in the fens of the northeastern U.S. and eastern Canada.
It takes a sharp botanist to be able to notice what Aaron observed next. Across the open seep are numerous graminoids. The term "graminoid" is just a catch-all term for a "grass-like" plant and includes grasses, sedges, and rushes. In Tennessee alone, there are more than 150 species of sedge in the genus Carex and it takes a honed eye to be able to identify many of them to species. But Aaron noticed that this seep was home to two really significant sedges that turned out to be new state records. These included the Interior Sedge (Carex interior) and Rigid Sedge (Carex tetanica).
No doubt, Aaron must have been on a botanical high as he slowly worked his way upslope through the magnificent seep. I, myself, have been in similar situations and you have to almost catch your breath because cool stuff and new discoveries are coming at you from all sides. It can be hard to slow down and process it all. Throughout the seep one of the dominant plants was the Large-leaved Grass-of-Parnassus (Parnassia grandifolia). This gorgeous fall-blooming plant is stunning with its green-veined petals. It is rare in Tennessee and throughout most of the South, but was doing great at this seep.
Reaching the top of the seep, Aaron found a small straggling shrub that seemed unusual. After studying it for a bit he concluded that it was the rare Alderleaf Buckthorn (Rhamnus alnifolia), which had only been found in Tennessee a couple of other times at just a couple of other sites.
Having been to this seep myself later with Aaron, I remember vividly the view looking down from the top of the seep and being amazed at the incredible diversity and assortment of rare and disjunct plants. Looking back downslope, Aaron observed that the most dominant plant in the entire seep was actually the most significant find of all.
Throughout the seep was a fairly robust herb with broad, stiff, tri-lobed leaves and a lean stem topped by rounded clusters of white flowers. He instantly recognized the plants to belong to a genus known as Trautvetteria (Tassel-Rue or Bugbane). In the eastern U.S. the Carolina Tassel-Rue (Trautvetteria caroliniensis) is occasional along streambanks, in seeps, and other wet habitats. Aaron realized these plants differed in having fewer leaf lobes and in their coarse texture and leaves held in a different position. He realized that he had just discovered a totally new species.
The most significant discovery Aaron made was the discovery of a completely new species to science (the leafy plant pictured above) that is known only from 4 counties in Tennessee north of Knoxville and nowhere else worldwide. Aaron Floden formally named this species in November 2017 and it is called Trautvetteria fonticalcarea. Left and center photos by Aaron Floden; right photo by Edward E. Schilling.
I remember being a little envious of Aaron's remarkable discovery. Certainly I was proud for him but I couldn't help but fantasize about being there myself. Aaron made such a big impact at the University of Tennessee Herbarium and in Tennessee botany in general that he easily won the favor of the herbarium director, Dr. Eugene Wofford. In fact, Dr. Wofford referred to him as "The Second Coming." A few years before Aaron got to UT, my fellow PhD lab-mate, Joey Shaw, had enjoyed being the favorite of Dr. Wofford. Then, when I arrived in 2003, Joey kidded that I had replaced him as Dr. Wofford's favorite. But, when Aaron came in with a bang, he became the new favorite. Joey and I began to refer to him as the "Golden Boy." To those of us lucky enough to call Aaron a good friend, we like to refer to him as Aaron "Golden" Floden, or simple "Goldie."
After that discovery, Goldie went on to find dozens of other seeps across a four-county area (Anderson, Campbell, Claiborne, Union) of upper east Tennessee, including nearly two-dozen populations of the new Tassel-Rue. In fact, just about a month ago, Aaron and Dr. Ed E. Schilling (his PhD advisor at UT) formally named this new species after several years of research. It was named Trautvetteria fonticalcarea, reflecting the calcareous seeps to which it is endemic. This cool new species is only found in Tennessee and nowhere else worldwide. Prior to its discovery, it was part of a special club of about of 100 species of plants that botanists know about that are restricted to grasslands and grassland-related habitats.
Recently, Aaron has been working with Tennessee Valley Authority botanist, Adam Dattilo, to search for and study more of these seeps within the Powell River watershed. They have found many populations of rare plants never before documented and have determined that this particular dolomite seep community represents a new community type, not previously described or recognized by community ecologists. Some of these seeps have prairie species, like Prairie Dock (Silphium terebinthinaceum), and other unexpected species. They have even found new populations of the extremely rare Showy Lady's Slipper Orchid (Cypripedium reginae).
While looking for new seeps, they've had to explore a lot of non-seep habitat such as dry to moist calcareous forests and woodlands, which is the matrix habitat in which these seeps are found. In these woods they've found new populations of Northern White Cedar (Thuja occidentalis) and discovered three additional new state record species for Tennessee, White Rattlesnake Root (Nabalus albus), Wood's Sedge (Carex woodii), and Mountain Ricegrass (Patis racemosa).
Three new state record species found by Aaron Floden during his survey of dolomite seeps in the Powell River Watershed. These are species found in adjacent rocky woods outside of the seeps. Left: White Rattlesnake Root (Nabalus albus); Center: Mountain Ricegrass (Patis racemosa);Right: Wood's Sedge (Carex woodii). Credit: Aaron Floden.
Aaron continues to work on studying this rare community, in spite of the fact that he has gone on to St. Louis to work for the Missouri Botanical Garden as Flora of Missouri Curator. But his work takes him well outside Missouri to most parts of the Southeast and he even frequently goes on expeditions to east Asia (China, north Vietnam) where has discovered several species, including a new genus. His incredible work highlights just how much continued baseline surveys are needed to better understand our natural world.
These open wetlands are mostly in private ownership. Their small size makes them very susceptible to invasion by invasive species or to degradation by any number of factors. Unfortunately, we will never know just how much of this community we have lost because there were certainly seeps that now are beneath Norris Lake and we may have lost populations of species that no longer occur in the state that are known from similar seep communities farther northeast in Virginia--we will never know.
Thanks to Aaron for making such a great contribution to conservation! I hope I have captured the essence of his discovery and I hope our readers are as inspired by his work as I am.
Contributed by: Dwayne Estes