Friday, August 29, 2014

Pine Barrens & Grasslands in New England? Part 1

Leaving North Carolina for a casual visit to New England presents a bit of cultural and ecological shock. Its not just the accents but the vegetation!  While the southeastern US is known for some of the nations most fire-prone vegetation, New England's seems the polar opposite; dense, dark, forests heavy in Eastern Hemlock and White Pine, not the kind of places associated with frequent fire. While the majority of North Carolina may have experienced fires several times a decade (1) some authors have estimated fire return intervals in New England forests as infrequently as 230 to - 5,200 years (2)! Sort of boring stuff for a "normal" fire ecologist "down south".
Sandplain Grassland in southern Maine
with Northern Blazing Star

At least that's what I thought before I read the following prior to a recent visit to New England;
"It's a prairie, just like those out west," said Keith Fletcher, the Conservancy's Southern Maine Program Manager. "It has been maintained by (burning) for 5,000 years" (2).
Seriously,  I had to see that!

As the picture to the right illustrates, I was actually able to find a "prairie" in Maine. At least it was an open, mostly tree-less, herbaceous dominated site, on what appeared to be deep sandy soils. Experts at the Maine Natural Areas Program would likely call it a "Sandplain Grassland"(4).  I was lucky to be there just as the Northern Blazing Star (Liatris scariosa) was coming into bloom.  This plant is considered "Threatened" in Maine.  Flowering stems were beginning to poke up throughout the grassland, which seemed to be dominated by Poverty Oat Grass (Danthonia spicata).  The site was quite large and I was excited to explore, but the fact that the interior roads were closed for the season, coupled with the impatience of my travel partner to see the ocean (evidenced by some realistic looking tears) the visit was cut a bit short.

After a brief interlude at the coast, I was able (allowed?) to visit another jewel of southern Maine, the Wells Barren. My directions initially led me astray and caused me to nearly miss the site completely. Luckily that didn't happen because this place is great!

After an inauspicious start through "regular ole Maine Woods", the place opened up into an impressive "barren".

Unlike the "Prairie" or "sandplain grassland" at the previous site, the vegetation here was absolutely dominated by low-bush blueberry (Vaccinium angustifolium), often with an emergent layer of Pin Cherry (Prunus pensylvanica).

Fire Cherry over dense low-bush blueberry;
note Pitch Pines in background

Perhaps a better name for the Prunus is "fire cherry" in reference to its uncanny ability to recolonize burned areas. This appears to be the case at Wells Barren which is under fire management by The Nature Conservancy. There were a number of large Pitch Pine (Pinus rigida) around the perimeter but almost none in the interior where fire was presumably too frequent, or past land-uses had removed them.

Grassy, "sandplain-like" patch 
~ 10 meters in extent

Small openings stood out at a distance due to the tawny coloration of the Poverty Oat Grass, and the lack of Vacciniums or other shrubs. In one or two of these I noticed a few stems of Northern Blazing Star. These small areas looked like mini-sandplain grasslands. Not sure why these persisted or existed as islands in a sea of shrubs.  I could envision more frequent fire transitioning the whole site into a more grassy and less shrubby condition (perhaps explaining the first site?), but why these small islands in a matrix of blueberry with the same fire history?

Single Danthonia spicata clump
notice perimeter ring separation

One idea emerged after spotting a single grass clump (see image, lower right). This Poverty Oat Grass clump seemed to be surrounded by a small buffer separating it from the surrounding shrubs. It made me think of "allelopathy, a phenomenon where one species produces biochemicals that inhibits growth of others. A later bit of research turned up some evidence that, at least one Danthonia sp. is believed to exhibit alleloapthy (5).

Other than the extreme openness, or at least lack of well developed tree cover, the most notable aspect of the site was the density of Low bush blueberry (Vaccinium angustifolium). The image below gives some hint at this.

This site is a great reminder that fire has been used for many generations, and probably by native Americans, to enhance blueberry production.  Vaccinium angustifolium spreads primarily vegetatively, and this spread is encouraged by fire. It is well known in many regions that more vigourous blueberry growth often appears after fires.  It has been documented that heated or burned rhizomes produce more shoots (6).  At a site like this, it doesn't take long to pick your fill (See below) which may be reason enough to support more prescribed burning!

Next time we visit the Wells Barren we'll take a bucket

(1) Frost, C. Presettlement Fire Frequency Regimes of the UNited States: A First Approximation..
(2) Fahey & Reiners.  1981.  Fire in the Forests of Maine and New Hampshire. Bulletin of the Torrey Botanical Club 108.
(5) Slater, P.D., T.M. Cregan and P.D. Cregan. Allelopathic Effects of Danthona Richardsonii and Phalaris aquatica on Trifolium subterraneum. Australian Weeds Conference Proceedings.
(6) (Flinn, Marguerite A.; Pringle, Joan K. 1983. Heat tolerance of rhizomes of several understory species. Canadian Journal of Botany. 61: 452-457).

Sunday, August 24, 2014

Prairie Flora in North Carolina - All Hands on Dock (Silphium terebinthinaceum)

Prairie Dock (Silphium terebinthinaceum), a.k.a Prairie Rosinweed, is among the most conspicuous herbaceous perennials of tallgrass prairies of the midwestern United States (1).  The same is true for certain remnant, prairie-like habitats in parts of the NC Piedmont as well. Part of its conspicuousness, no doubt, comes from the distinctive & large basal leaves that may reach 12" in length (see image below).

Flowering stalks bolt upwards in late July & early August, topped by ball-like buds. Stalks may reach 6-10 feet in height before opening into bright yellow flowers around mid-August.

Silphium terebinthinaceum basal leaves in Durham Co, NC

The epithet, "terebinthinaceum" translates to "with turpentine" a reference to the presence of rosins which give many species in the genus their common name. I assume the rosin content would be toxic or inhibitory to grazing animals, but rumor has it that the "rosin" was once chewed by pioneers and that the plant is actually favored by some grazing animals. Curtis (2) apparently observed a "virgin prairie" when it was first put to use as a livestock pasture. He indicated that the horses and cattle sought out prairie docks and compass plants "like hidden candy at a child's birthday party."  There are suggestions that bison also feed upon Prairie Dock, but I have found no definitive references to this, possibly because their ranges no longer overlap.

Prairie dock develops a significant taproot (see image at Reference # 3), unlike Silphium astericus with which it commonly co-occurs on many Piedmont, North Carolina sites. Dhillion & Friese (4) found that Silphium terebinthinaceum had high levels of mychorrhizal activity (a symbiotic association between the roots and specialized fungi that often confer advantages to the plant in the form of drought resistance, nutrient uptake, etc.).

Very little seems to be known about seed dispersal or pollination, but there are strong suggestions that both are extremely distance limited. Coupled with habitat fragmentation, the result is extreme isolation between remaining populations.

A review of the S. terebinthinaceum range map (see also #5) indicates that North Carolina populations are the easternmost in the nation, significantly disjunct from the heart of the main population centers in Illinois and Missouri (2). What is it doing here in the Piedmont of North Carolina?

The NC Natural Heritage Program records Prairie Dock occurrences in Cabarrus, Davie, Durham, Granville, Mecklenburg, Stanly, Union, & Wake counties. Populations in Durham & Granville occur on rich clayey soils apparently weathered from diabase rocks, often with other species with prairie affinities. Until such sites are managed to maintain, or recreate, open conditions Prairie Dock appears to decline and persist only on road edges and powerlines.
Prairie Dock rosettes persisting along roadway in Durham (2006);
lack of mowing allowed dense saplings to encroach & suppress
 most individuals present
Same site as previous; mowed during growing season (May 2007)
Same site as previous; note numerous Prairie Dock rosettes (Sept 2007)
For long-term habitat improvement & maintenance prescribed fire is the most desirable technique and we have applied it with spectacular results at several Piedmont sites.  In most cases, our spring fires move relatively rapidly, exposing individual plants to direct heating for a short amount of time.  Hahn & Orock (6) found that Prairie Dock seeds are able to maintain viability even after 15 minutes of exposure to 150 degree C!

I concur with Schramm (6) "one would think that by now, fire would be universally accepted and vigorously applied in all restoration and management efforts, but fire is being used to conservatively." In addition, he says, "most remnants ... currently need regular burning to regain their original quality", a statement I also agree with in the Piedmont where prairie associated flora remains.

A grove of Prairie Dock flowering (Aug 2014) at site in Durham Co, NC
(same site as shown in preceding sequence)

(1) Gleason H.A. and Cronquist A. 1991. Manual of Vascular Plants of Northeastern United States and
Adjacent Canada. 2nd ed. The New York Botanical Garden, The Bronx, New York.
(2) Curtis, J.T. 1959. The Vegetation of Wisconsin. UW Press.
(3) Robertson, K. R. 2007 image.  see -
(4) Dhillion & Friese;
(6) Hahn P.G. & Orock, J.L. 2014. Effects of Temperature on Seed Viabaility of Six Ozark Glade Herb Species and Eastern Red Cedar (Juniperus virginiana). American MIdland Naturalist 171: 147-152
(7) Schramm, no date;

Thursday, August 21, 2014

Two Rare Botanists on a Witch (grass) Hunt


Dichanthelium is "perhaps the most complex and confusing genus in our region" (1). 

Sometimes a mere one tenth of a millimeter difference in a critical measurement can separate two taxa!
For obvious reasons, most folks avoid these smallish and difficult to identify grasses (do you have a micrometer handy?).

But Johnny Townsend of VA Natural Heritage Program (below right) and Richard LeBlond  (right) (formerly of NC Natural Heritage Program) are hardcore enough not to be afraid of the Witchgrasses!

I had the unexpected pleasure to show them around to a few sites in Durham County recently. 

Johnny rarely travels to NC; the Commonwealth keeps him quite busy. 

Richard told me he had never really botanized in the Piedmont before.  

But they came & hopefully will both return!

On this day it was a quest for rarities; mostly taxa that Richard had either named or is working on, and that had been showing up in VA recently. We all hoped they would turn up on one or more sites nearby as well!

After a brief orientation, including review of some pressed specimens Johnny had brought along, Herb & Pat Amyx, Thomas Blaine, and the rest of us headed off in search of live material.  I found it difficult to train my eye to seperate the Dichantheliums from the other vegetation. More difficult was rapidly distinguishing the common species at a mere glance, like Richard and Johnny were able to do.

After traipsing by 7 or 8 other taxa in the genus, innumerable other native species, and just as the sun and humidity seemed to be peaking, Johnny dropped to one knee in front of Ringed Witchgrass (D. annulum). One of our targets was found! Was it the humidity or the excitement that made my legs buckle slightly?

Dichanthelium annulum displaying "autumnal" growth

Ringed Witchgrass was given its currently accepted name in a publication by Richard LeBlond in 2001 (2), elevating it from its former genus Panicum (along with a host of others).

Dichanthelium annulum is considered "significantly rare" in NC. Records have been documented from 15 locations around the state, but only 2 are considered extant in the Natural Heritage Program database (the other locations are historic, meaning they have not been observed for decades).

The bulk of the historic reports are from Piedmont counties including Person, Orange, Wake, and Durham (no apparent coastal plain records but Richard has just informed me of a collection from Roanoke Island!). The habitat has been listed in Weakley's flora as "dry sandy or rocky soil of open woods, dry grasslands, and barrens and glades..." Our site was in a frequently burned, open oak-hickory woodland, on rich clayey soils, with a diverse native ground cover.

Several stems of D. annulum rising above
Partridge Pea (Chamaecrista fasciculata), Earle's Blazing Star (Liatris squarrulosa),
Maryland Senna (Senna marilandica), and others
Most stems of Ringed Witchgrass were relatively tall (over 12") and showed the remains of spring culms and panicles. Roughly 1/3 of the way up the stem were tufts of new leaves slightly hiding newly developing branches or panicles. We found plants in several locations in the first site visited, usually in places where taller plants seemed to be less frequent. With this find, we can once again consider D. annulum "extant" in Durham County. 

After continued traipsing and hunting we visited another site. It wasn't long before Johnny made the second significant find of the a relatively bare patch of rich soil, exposed by recent spring prescribed fire.

Given the local conditions, this taxon was easier to see but harder to explain taxonomically. Currently treated as Northern Witchgrass (Dichanthelium boreale), but also indicated as Panicum bicknelli (1) Richard is working toward a nomenclature change that will treat this as Dichanthelium bicknelli. Regardless of the taxonomy, the plants found are also considered "significantly rare" in North Carolina.  If all the existing records are assigned to the same taxon, this will constitute the 13th or so record in the state, most of which seem to be considerably west of Durham, mostly in the mountains.

Very similar habitat (although not co-occurring) to Ringed Witchgrass, but overall, a much different appearance. These plants were much more clumpy than D. annulum with abundant, sturdier, basally disposed leaves.  An obvious rosette was present (below, left): perhaps these will be the overwintering leaves present in many species? Numerous flowering culms were present (below, right).


(1) Weakley, A. S. 2012. Flora of the Southern and Mid-Atlantic States
(2) LeBlond, R.J. 2001. Sida 19: Taxonomy of the Dichotoma Group of Dichanthelium (Poaceae)


Richard LeBlond (right), "bowing down" before a rare specimen of (soon to be) Dichanthelium bicknelli. 

Saturday, August 16, 2014

Prairie Flora in North Carolina: Eastern Gamagrass

Tall culms of Eastern Gamagrass in a "Piedmont Prairie" in central NC
with Daniel Overcash & Louis Suther
Eastern Gamagrass (Tripsacum dactyloides) is one of North Carolina's tallest and most robust native grasses.  A clump forming, warm season, perennial, with flowering culms that can reach 7-8' in height, the species responds well to fire and thrives in open sunny, yet somewhat moist sites.

Flowering Tripsacum dactyloides with pistillate (below)
and staminate flowers (above)

Tripsacum is monoceious, producing both male (staminate) and female (pistillate) flowers on an individual inflorescence.

Tripsacum is perhaps one of the most ecologically and agriculturally important native genera from North America. Widespread throughout the eastern US, Mexico, & parts of S. America, Tripsacum was a key ancestor of modern day corn (1) and could eventually contribute to agricultural sustainability efforts focused on perennial rather than annual crops.  At least one cultivar has been developed between Gamagrass and Zea mays that may be a step in that direction (2)

Tripsacum patch expanding in old field at Manassas Battlefield, VA

It produces significant live, leafy biomass with high live - dead ratio and is highly palatable for many grazers. Because of this excellent forage quality, Gamagrass is a classic "decreaser" in range management terminology; when present, grazers actively and preferentially seek it out and cause it to decline under sustained pressure.

Tripsacum dactyloides cupule with persistent pistillate flowers

In mid-summer, large seeds develop and ripen progressively from the top, eventually disarticulating when ripe (see image, right). Due to their size, they have little chance of dispersing far from the mother plant. Under intense grazing pressure or declines due to other factors, it is easy to understand why Gamagrass would be slow to recolonize. Heavy seed predation by rodents may also be a limiting factor in spread (3).

Individual seeds are enclosed in a hardened case sometimes called a "cupule". When intact, this structure can inhibit germination of the enclosed seeds (3)

Tripsacum dactyloides cupules on mineral soil 

Large clumps of Gama tend to develop a characteristic "hollow" in the middle of an almost circular ring of leaves.  As the clump develops upright stems, a tent of sorts forms over the nearly bare middle, providing nesting habitat for a number of ground nesting birds associated with prairies (4). Many such birds are among the most declining in the Piedmont region.

Tripsacum clump developing concentric ring,
 beneficial to some ground nesting wildlife

Herb Amyx, Joan Schnier, John Thomas, Jon Stucky
observing a riverside patch of Tripsacum

As suggested by its relatively wide natural range, Gamagrass is adaptable to a host of conditions. In part, this is due to extensive aerenchyma  root tissue (essentially air passages) that allow it to thrive in wet or even infrequently flooded situations (see image, left).

In addition, the roots are able to penetrate restrictive soils (including claypans) and survive droughts and other limitations that other species can not (5).

Consequently, Eastern Gamagrass can be an important member of a number of natural community types. These include certain blackland prairies in Texas (5), and coastal prairies in Louisiana and Texas (6). I have also observed Gama as locally abundant or dominant in longleaf pine woodlands in eastern Texas and other remnant, prairie-like communities in southeast Texas. In North Carolina, Tripsacum is an important member of what may be North Carolina's only remaining prairie, and is becoming locally abundant in several frequently burned areas elsewhere in the Piedmont providing clues to other habitats it may have occurred in.

Gamagrass clumps in an open woodland in which prescribed fire has been used twice
Durham Co, NC

Although Tripsacum dactyloides appears to be indicative of prairie-like habitats across North Carolina, and perhaps through its natural range, I hesitate to suggest "introducing" it to natural areas without first applying regular prescribed fire (and having the means to continue to do so), obtaining open habitat structure, removing invasive plants, and having a pretty good indication it may have been present historically.  Having said that, not every "restoration" of such habitats needs Gamagrass or likely ever had it. I prefer allowing even like sites to have their own unique floristic assemblages.

(1) Eubanks, M. 2001.  The origin of maize: evidence of Tripsacum ancestory. Plant Breeders Reviews
(3) Anderson, R.C.  1985. Aspects of the germination ecology and biomass production of Eastern Gamagrass (Tripsacum dactyloides). Botanical Gazette 146.
(4) &newsletterid=1730)
(5) see
(7) Diamond, D. D. & F. E. Smeins. 1984. Remnant Grassland Vegetation and Ecological Affinities of the Upper Coastal Prairie of Texas. Southwestern Naturalist 29.

Saturday, August 9, 2014

Pitch Pine in Paradise

Although White Pine is the quintessential New England pine tree, Southern New England lies well within the natural range of Pitch Pine (Pinus rigida).   This tree is most often associated with relatively frequent fire and serotinous cones (covered in natural resins that must be melted by fire to release seeds). Therefore, I expect Pitch Pine to occur on sites or physical settings with the capability to experience periodic fires. I have visited a number of such places in the northeastern US, including NJ, Maine, New Hampshire, and Massachusetts.

Pitch Pine island view from across Paradise Pond

I recently noticed an unusual Pitch Pine forest on a tiny island completely surrounded by water. Known as Paradise Pond this small site in central Massachusetts was the last place I expected to see these trees. Obviously, the context and size would make it extremely unlikely this stand of trees would have ever experienced "natural" fire.

Aerial view of "pitch pine island" in the middle of Paradise Pond, MA
A field inspection and specialized transportation were clearly necessary; a fully restored, antique Morris canoe filled the bill perfectly (thanks Jane McFadden!).

Various size classes of pines were present, many with branches draping over the water. The understory vegetation, thickest around the lower edges, included northern bayberry, Sweet Gale, Sweet Pepperbush, maleberry, and the usual edible fruit bearing Ericaceuous shrubs. Cowwheat (Melampyrum lineare) may be the most common herbaceous plant.

Non-serotinous Pitch Pine cones on Paradise Pond

Due to an ongoing rainstorm and a hastier than planned departure, I didn't pay close enough attention to the majority of the pine cones, but many were clearly open and appeared to lack well developed serotiny.

Later, a cursory literature search revealed that other sites in Massachusetts (on rocky knobs) lack serotiny (1). In addition, fire frequency has been shown to be a local determinant of serotiny with less frequently burned sites tending toward less or even absent serotiny (2).  The near impossibility of fire on "Pitch Pine Island", could therefore help explain the non-serotinous cones I noted.

As noted earlier, the interior of the island was almost completely dominated by Pitch Pine of various sizes (see image below). With no signs of lightning or prescribed fire (I called the "managing agency" responsible for this stand to ask about the trees - they said they were probably spruce!) it is unclear why other species are not entering the midstory or canopy. I have seen many other sites where White Pine or hardwoods have become dense and begin to compete with Pinus rigida for growing space with inadequate fire regimes.

Interior view of "Pitch Pine Island"

A cursory look around the dense forests in the vicinity revealed only White Pines (and a lone, relict Pitch Pine on a nearby island).

How did these pines get to the island?? Perhaps a topic for future research!

Typical shoreline forest dominated by White Pine