Here's Pyxie!

Pyxie (Pyxidanthera barbulata), near Zuni, Va (3/16/19)

I was able to shout that on a recent weekend in southeast Virginia, but was certainly not the first to do so. That "honor" goes to Bayard Long in 1936.  Long was a botanist most associated with the Philadelphia Botanical Club, collector of approximately 80,000 plant specimens, and long-time friend and associate of Dr. M.L. Fernald (an account of Long's career, and publications, as well as the following image of Long, can be found in Rhodora 72:130-136)

Bayard Long was part of an infamous botanical collecting excursion near Franklin, Virginia that resulted in nine "new to Virginia" or state record plants being found.  Long was later quoted as saying, "this is real botanizing!" in the fascinating recount of the trip (Fernald, M.L. 1937, Rhodora 39: nos 465-468) (Also reprinted by Fernald in; Contributions from the Gray Herbarium of Harvard University, 1937, and selected excerpts included in Frost & Musselman 1987: Castanea 52:16-46.)



One wonders if Pyxidanthera would have gone unnoticed had it not been for Long.  In an earlier paper on the "Plants from the Outer Coastal Plain of Virginia" (Rhodora 38: nos. 455-466), Fernald credited Long as follows, "...with his detailed knowledge of Coastal Plain plants and their proper habitats and his unequalled (sic) persistence and skill in finding them, no critical botanizing in eastern Virginia can be wholly successful without him". 

In terms of the overall significance of their botanical finds, Fernald said, "We had stumbled into what we had sought for four years, real unspoiled pine barren in Virginia".

View of "mature" longleaf pines at Blackwater Ecological Preserve, VA
perhaps not unlike what Fernald and Long would have seen if they looked up!

Today, Fernald & Long's collecting site is protected and being actively managed as Blackwater Ecologic Preserve.  Longleaf pine (Pinus palustris) is a prominent tree in parts of the Preserve, which for Virginia, is really significant. At the extreme northern edge of it's natural range, the Commonwealth is believed to support fewer than 200 INDIVIDUAL mature, native longleaf pines (Virginia Department of Forestry 2014, Status Report).

Pyxidanthera range map; 
Kartesz, J.T., The Biota of North America Program (BONAP). 2015
Taxonomic Data Center. (http://www.bonap.net/tdc). 

But back to Pyxie (Pyxidanthera barbulata). Sometimes known as Pyxie-Moss or other related and confusing common names, Pyxie is restricted to the Atlantic Coastal Plain of eastern North America.
Sorrie and Weakley 2001 (Castanea 66:5-82) recognized Pyxie as a coastal plain endemic with a bimodal phytogeographic pattern, as shown to the left.




Pyxie's distribution has a large spatial disjunction that was significantly larger until Fernald's team found it in Virginia, or as they stated, "the first station discovered between southern New Jersey and North Carolina".  According to Fernald, "Pyxidanthera barbulata literally carpeted the ground in many areas".  The best approximation of that pattern I could see today, is shown on the image below, although at this distance (and due to my lack of photographic skill) the Pyxie clumps appear almost as bare "sugar sand".

Pyxie as an abundant ground cover at Blackwater Ecologic Preserve, VA

Pyxie covered by pine needles

Frost & Musselman used Pyxidanthera as a nominal in one of the community types they recognized at Blackwater in 1987 (See citation above), while noting it only"at this one spot".  They referred to this community as "Pond Pine Flat" with both Pond Pine (Pinus serotina) and Turkey Oak (Quercus laevis) as dominants and nominals.  Interestingly, in my experience, these species usually occur in fairly different habitats and soil moisture regimes.  Fernald referred to the habitat as "thin woods of Pinus taeda and Quercus laevis".  He indicated (with a footnote) that they found this oak "to be the regular species of the area" at its northern range limit.  Much like longleaf pine, this range limit has not been significantly extended northward since then.  Turkey Oak is still found at the site but is, perhaps, not as abundant as suggested by Frost & Musselman. (I hope to address this in detail in the future).

Turkey Oak (Quercus laevis) buds (3/16/19)

Turkey Oak (Quercus laevis) stump sprouts (3/16/19), approximately 2 years after last fire; note main trunk
broken off and fallen to right of image

Pond Pine (Pinus serotina) stump sprout, same site as previous;
also approximately 2 years since last fire; note main stem still standing but dead

Since 1986, there have been approximately 16 prescribed fires here with undoubtedly significant effects. 

Structural and density differences at Blackwater Ecologic Preserve
Right: burned on ~ 2 year average return interval since 1986
Left: unburned during same interval

For now, Pyxie seems to be doing just fine! 

Longleaf Pine Sandhills - fire and wiregrass

The "sandhills region" of North Carolina supports some of the most extensive stands of longleaf pine remaining in the state. The preponderance of deep sandy soils not only gives the region its name, but helps explain why so much longleaf pine remains here given the even more substantial declines elsewhere in the state. The coarse, droughty sands are less conducive to most types of agriculture and, when forested, are not as easily overrun by other vegetation.  However, even when longleaf pine is present, regular burning is needed to maintain high quality stands.

Well-burned longleaf pine stand@Sandhills Gameland, NC
Note scorched boles, uneven spacing and diameters

Thankfully, certain land managers and owners are committed to the use of prescribed burning. They have maintained the best upland longleaf in the region through frequent and regular burning. These stands have open canopies, with minimal hardwoods, above dense swards of wiregrass (Aristida stricta).

Heavily fire-suppressed longleaf stand in Moore Co, NC
Note dense Turkey Oaks and absence of wiregrass

The vast majority of remaining stands are heavily altered due, in part to insufficient burning. On dry, sandy uplands these stands may become densely invaded by hardwoods like turkey oak (Quercus laevis), and wiregrass is sparse and barely evident. Such stands carry fire less readily and larger hardwoods become fire resistant and harder to control.

Moderately fire-suppressed longleaf stand in Moore Co., NC
Note patches of wiregrass, those in left foreground show greatly diminished vigor

Less severely fire suppressed stands retain patches of wiregrass and other herbaceous species. Hardwoods are less dominant, patchier, and often smaller. These smaller hardwood stems contribute less shade and litter, thus having less impact on fire dynamics and understory composition.

Wiregrass is a keystone species with a huge ecological impact. It flowers and seeds in the same season, primarily after being burned in the spring or summer, with upright flowering stalks emerging with the characteristic "three-awn" seeds. This happens only rarely in most stands where finds are either excluded or conducted only in the "dormant" season.

Wiregrass (Aristida stricta) flowering
@Pondberry Bay Plant Conservation Preserve, Sampson Co, NC

Wiregrass is a clump-forming bunchgrass whose narrow densely packed culms dry rapidly and carry fire even shortly after rain. In most relatively intact stands, wiregrass forms nearly continuous, dense ground cover. This density and continuity enhances the spread of low intensity fire which ultimately limits the establishment of woody stems.  Although we may imagine it take considerable time to convert an open, savanna-like stand to a dense, closed forest the changes occur surprisingly rapidly.

Dense swath of Wiregrass, note overlapping and draping culms
creating continuous fuel matrix for fire spread

Fire spreading across dense wiregrass layer

Longleaf pine - Turkey Oak Sandhill with suppressed and low density wiregrass,
stand has experienced infrequent, dormant season fire@Moore Co, NC

Longleaf pine - Turkey Oak Sandhill with dense wiregrass in good condition@Moore Co., NC
stand has experienced regular, somewhat frequent fire, but not recent growing season burning

Longleaf pine - with dense wiregrass after regular & frequent prescribed fire,
including growing season. Turkey Oak layer "burnt out"