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" 

"A shy-blooming thing" - Helonias bullata

Helonias bullata @ flowering peak, Atlantic coastal plain
April 08, 2016 Henrico Co, VA

"Few of our early spring flowers are more attractive or universally sought after by those who know it, than the "Swamp Pink"" said Stewardson Brown (Bartonia, 1910). Some seek them in the wet woods as I was lucky to do recently, but Brown indicated, "there are many people, however, who are familiar with and appreciative of its beauties, and equally keen to get it each spring, but who never saw and probably have no desire to see Helonias growing in its natural surroundings, but prefer to do their hunting along the curbs of Market Street" where plants .... were sold along the street each market day" (for a more thorough & colorful account, please read his original note which can be accessed online). 

Swamp Pink (Helonias bullata) was federally listed as a threatened species in 1988.  It is unclear whether or not over-collection was a factor in this listing decision. Brown's 1910 account certainly described both flower removals (thereby reducing seed production) and "clumps of roots offered also, a thing to be deplored in so rare a plant".  According to a recent assessment by the US Fish & Wildlife Service, "evidence of collection or trade of swamp pink as a garden plant remains patchy and anecdotal". However, several modern sources still encourage planting and trade in the threatened species. It seems clear such practices have done little to support permanent conservation and recovery of the species in its natural habitat. 

Remaining  natural Helonias populations are documented in widely separated regions from the New Jersey Pine Barrens, the Inner Coastal Plain of Virginia, the Valley & Ridge of Virginia, and the Southern Appalachians, including North Carolina. The map shown below illustrates the large territory lying in between these population centers and suggests the fact that the majority of the documented populations occur in the Atlantic Coastal Plain (New Jersey is considered to be the stronghold of the species (US Fish & Wildlife Service 5-Year Review: Summary and Evaluation, New Jersey Field Office).    

Helonias bullata range map

Courtesy of Kartesz, J.T.  2015.  Floristic Synthesis of North America. Version 1.0. Biota of North America Program (BONAP) (in press.)

Godt et al. (Conservation Biology, 1995) showed that Swamp Pink genetic diversity broadly corresponds with these regional population centers; Southern Appalachians being most diverse, Virginia intermediate, and New Jersey the most depauperate. As in many other species, such data suggest that the Southern Apps populations are more ancient, having persisted during glaciation, and more recently spread northward.  A logical conclusion follows that these "relictual" populations have particular conservation importance, due to their greater diversity.

Helonias bullata rosettes, suggestive of limited dispersal by ants
or slowly spreading rhizomes, although note former flower stalks
(Transylvania Co, NC)

Of course it is a mystery how Helonias could have "migrated" over such long distances post- glaciation. Its seeds have eliasomes (US Fish & Wildlife Service 5-year Review). These fleshy structures are believed to aid dispersal by ants (see my previous post on Sessile Trillium).
How long did it take those ants to carry seeds from North Carolina to New Jersey?





Most, but not all of the plants I have observed tend to appear highly concentrated, as expected from a species with localized seed dispersal. Another explanation is the plants are clonal, spreading rhizomatously; Sutter (Castanea 1984) believed seed production in the Southern Appalachians did little to maintain those populations. In part, this may be due to very low flower production. An 1872 note in the Bulletin of the Torrey Botanical Club (authorship unclear, at least to me) indicated, "the plant is a shy-blooming thing, only a few out of many sending up a scape, and those few being very far in between".

Swamp Pink maturing & elongating scape, amidst Spicebusg and Elderberry
Henderson Co., NC

After flowering scapes are produced, they rapidly elongate as they mature. The resulting scape may appear double or triple the length of the original inflorescence. Although few plants achieve this reproductive status, they apparently produce large numbers of seeds which drop shortly after maturing. Because seeds are short lived (US Fish & Wildlife Service Recovery Plan, 1991) localized conditions in the early spring strongly determine the likelihood of germination. Seeds falling into standing water and/or saturated condition germinate more rapidly than those dropping into dry conditions (Punsalan, unpublished thesis, 2013).

Helonias bullata flowering scape on hummock created by American Holly
Henrico Co, VA

Laidig et al. (Bulletin of Torrey Botanical Club, 2009) emphasized the "apparent limitation of Helonias to hummocks" in New Jersey.  The 1872 report (cited above) suggested, "the favorite situation for flowering seemed to be just on the edge of a swift stream or in rich moist earth.."  In my hazy recollections of sites visited, mucky wet soils were always present.  Only one population seemed to occur on obvious hummock and hollow topography (that being the one shown immediately above in the Atlantic Coastal Plain of Virginia).  One site, (shown below) crudely matched the first part of the 1872 habitat description.  A few other habitat examples are also shown below:

Helonias rosettes along headwater stream surrounded by Dog Hobble

The small population (right) was found directly on an elevated bank above a shallow and narrow headwater stream in the the Southern Appalachians of North Carolina. The rosettes present (yellow arrow) were found on the fairly steep bank above the normal water elevation; perhaps seeds washed in during higher water levels?

Helonias dense patch amidst Cinnamon & Royal Ferns 

A large, densely packed population (shown to the right) was found in a large, bowl shaped depression with no obvious flowing water and no surface out or inflow (Southern Appalachians of northern South Carolina). Note the shaded aspect with minimal dappling of light, and no flowering scapes present.

Helonias rosettes with fruiting scapes bordering Pitch Pine and Eastern Hemlock

A diffuse, widely scattered population occurred in an almost linear wetland basin or gentle valley (image right). The valley is wide enough and open enough to allow significant sunlight to the ground, where sphagnum appears to dominate. This is the only of the last 3 sites with flowering stems present.





Brown (Bartonia, 1910) pointed out that enthusiasts seeking Swamp Pink, "feel amply repaid by a few heads of its fragrant flowers, even if the getting entail some scratches, with wet feet thrown in".....I agree wholeheartedly! Seek them next spring, and take the "shy-blooming thing" the right way (see below).

Zach Bradford , Chesapeake Bay Region Steward with VA Natural Heritage Program
 "taking" Swamp Pink the right way

A species that matters - Cuphea viscosissima

Blue Waxweed or Clammy Cuphea (Cuphea viscosissima) is infrequently encountered in North Carolina. It has been reported from the northern mountains, southern mountains, and northern Piedmont - perhaps it is overlooked and unreported at stations in between?  The species is widely distributed in neighboring states to the north and west, but is apparently most common in Missouri and southern Illinois.

Clammy Cuphea (Cuphea viscosissima): perimeter of Mt. Vernon Prairie, MO (08/21/15)

One of the most interesting traits of Blue Waxweed is the abundance of sticky hairs (shown above) which are thought to serve as defense against insect pests. Several years ago I noticed this adaptation in action. A grasshopper had landed on a Cuphea stem presumably to feed but ended up stuck by its front and hind legs (see below). At the time, the grasshopper was alive and well. Perhaps it would have eaten its way free, or perhaps eventually succumbed? Either way, evolution was thwarted when I felt a bout of compassion and flicked the grasshopper free.

Grasshopper stuck on Blue Waxweed (Durham Co, NC - 9/27/11)

Plant conservationists are often expected to justify saving native plants, with the implication that each species must stand on merits that we can measure.  To many, an otherwise obscure and insignificant species (like Blue Waxweed) only really "matters" if it holds the cure for cancer, or provides some other potential human benefit. When the utilitarian argument is needed it comes in handy to have a couple local, supporting examples.

Blue Waxweed serves admirably. Unexpectedly, Cuphea viscosissima produces some of the highest concentrations of capric acid among herbaceous plants (1).  Also known as a medium chain triglyceride, this type of "goat smelling" fatty acid has several commercial and industrial uses whose demand is growing exponentially worldwide. However, current supply comes almost exclusively from oil palms and coconut, creating a virtual "tropical oilseed monopoly" (2). Consequently, Blue Waxweed has been under consideration for massive production. One estimate suggests that 2.7 million hectares of Cuphea fields could supply North America and Europe's demand. I can only imagine!

Cuphea viscosissima in natural habitat, bordering sandstone glade in Missouri (8-18-2015)

References
(1) http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1038&context=ncrpis_pubs
(2) https://hort.purdue.edu/newcrop/proceedings1993/V2-372.html

The fatal flowers of Tall Thistle (Cirsium altissimum)

Tall Thistle (Cirsium altissimum); Durham Co, NC (9/14/15)

I find Tall Thistle (Cirsium altissimum) to be one of our most interesting natives.  Perhaps this is because I often root for the underdog, and so many gardeners, farmers, and even "conservationists" despise thistles. Hopefully their aversion may change if they come to understand the wildlife uses of native thistles and more particularly the benefits for native bees and butterflies. A fairly impressive, preliminary list of these has been documented using Tall Thistle, including over 20 native bees and nearly as many butterflies (1)

Hummingbird Clearwing Moth (Hemaris thysbe) visiting Tall Thistle; Durham Co, NC (9/14/15)

Tall Thistle occurs widely across the eastern US, from the prairie regions eastward, but is largely absent from the southeastern coastal plain. In North Carolina it has been reported mainly from western Piedmont and mountain counties; Durham County appears to be the easternmost location in the state.

Predominately white flowering Cirsium altissimum with a scattering of pink flowers  (Durham Co, NC - 9/14/15)

The majority of plants I have seen in North Carolina flower white, with a lesser intermixing of pink flowers (elsewhere in the range flowers seem to be more typically pink or purple and less commonly white). Tall Thistle is "monocarpic" meaning individual plants die shortly after flowering and setting seed (the classic case of monocarpism is the Century Plant). Cirsium altissimum is sometimes listed as biennial, but one group of authors (2) documented individual plants taking up to 4 years to emerge from young rosettes (such as the one shown below) into flowering stems.

Densely pubescent leaves of C. altissimum

In comparison to most thistle species, Cirsium altissimum has relatively soft and prickle-free leaves. Lower leaf surfaces are covered with dense white pubescence and stems are obviously hairy to the naked eye. Large leaves, a foot or more long, may develop on heavily shaded plants (see below). Some flowering stems exceed 10' in height and most produce multiple blooms.

Large shade leaves of C. altissimum, almost free of thorns

The large natural range of Tall Thistle and frequent occurrence in many regions suggest this is not, generally, a species whose survival we would need to be overly concerned about. HOWEVER, in a strange twist of fate, Tall Thistle may now be threatened by efforts in Midwestern prairie regions to eliminate truly problematic and invasive thistle species. A "bio-control" agent (weevil) deliberately introduced to control non-native thistles actually uses Tall Thistle "as frequently and intensively as it uses the targeted, exotic host plant" (3).

Cirsium altissimum seems to thrive only in relatively open habitats.  Ironically, the site where Tall Thistle occurs in Durham Co, NC also happens to be both nutrient rich and moist, creating growing conditions very conducive to dense woody plant growth. This apparent conundrum seems to suggest, at least in our area, that Tall Thistle requires regular disturbance and is likely another in the growing list of fire benefiting species. In fact, the currently large Durham population only appeared after burning. Thus far, we have been able to keep a portion of the site open with a combination of prescribed fire, selective chainsaw removal of trees, and invasive plant control.

Tall Thistle (Cirsium altissimum) flowering in open, "savanna"; Durham Co, NC (9/25/15)

References:
(1) http://illinoiswildflowers.info/flower_insects/plants/tall_thistle.htm
(2) http://www.esajournals.org/doi/pdf/10.1890/ES11-00096.1
(3) http://www.researchgate.net/publication/26278359

Mountain Bog Recovery & Expansion

Bog edge, before thinning (June 2015)

Bog edge, after thinning (July 2015)

The above images were taken near the perimeter of a so-called "mountain bog" in western North Carolina.  The first image shows the conditions before active restoration, the second image shows the same locale after clearing dense rhododendron invasion.  The only evident trees in the initial image are red maple and a lone pitch pine (Pinus rigida). After clearing the dense brush, a number of previously hidden stems of Pitch Pine in the heart of the wetland become apparent. The images also document (especially the second one) a small tributary creek feeding into the site from a black plastic culvert. Hugging the margin of this tributary (just past the lone pitch pine) is a grove of pitcher plants (see image below). 

Numerous pitcher plants (Sarracenia jonesii) hiding in this dense herbaceous foliage

At one time other rare plants were apparently present here when the creek was able to fan out gradually across the area, and the site was more open. However, years ago a road was constructed through the edge of the wetland. Several feet of fill material buried portions of the wetland, and altered the hydrology in some subtle and not so subtle ways (plans are in the works to remove the offending road section and culvert in hopes of restoring more natural water flows and reopening original wetland surface area for bog plants, stay tuned!). The dense thicket of shrubs that developed along the altered stream course excluded nearly all ground layer plant diversity directly underneath. In addition, the thick wall of green created both a sun and rain shadow across the nearby pitcher plants (these pitchers thrive in open sun, in saturated soils).   

Bog edge, before Rhododendron removal (June 2015)

Bog edge, after Rhododendron removal (July 2015) 

Numerous studies have shown that canopy vegetation can intercept and effectively remove up to 50% of seasonal or annual rainfall (Carlyle-Moses and Gash 2011, Forest Hydrology and Biochemistry). In contrast to deciduous plants, the evergreen rhododendrons continue to intercept rainfall all year long. At this site, the result could be losses of as much as 30" of water recharge per year! By removing the wall of rhododendrons we hope to create more open, sunlit conditions and add water back into the wetland system.  

Pile of Rhododendron previously removed from interior and margins of bog

We have been working on this restoration for several years, having been slowed mainly by lack of funding and resources to complete the task; the Friends of Plant Conservation (www.ncplantfriends.org) has recently established a means by which people can support this effort. 

Mountain Bog interior conditions in 2011, before restoration, note forked pine tree

Mountain bog conditions in 2014 after interior brush removal, note forked pine

Elsewhere on this blog I have discussed a few of the rare plants whose populations have begun to rebound due, in part, to these restoration efforts.  Won't you help this progress continue?

Bluehearts

American Bluehearts (Buchnera americana) @ Taberville Prairie, Missouri (8-19-15)

I came across a few individuals of American Bluehearts (Buchnera americana) during recent explorations of the tallgrass prairie. According to Bruce Sorrie and Alan Weakley I was in the "heart of the range" for the species. Back home in North Carolina American Bluehearts is considered an endangered species and is believed to have been lost from nearly every location from which it has been documented. This made finding a few plants feel even more special even if they aren't so rare out in Missouri.  

Savanna Bluehearts (Buchnera floridana); Boiling Spring Lakes Plant Conservation Preserve, Brunswick Co, North Carolina (6-03-15)

Bluehearts was perhaps first documented in Carolina by Reverend Moses Ashley Curtis. In his "Catalogue of the Indigenous and Naturalized Plants of the State" (published in 1867 at the "N.C. Institution for the Deaf, and Dumb and the Blind"), Curtis provided no clues about the abundance of American Bluehearts but listed it only in the "Mid. and Up. Districts", regions most often referred to as the Piedmont and Mountains today. We now recognize an additional Buchnera species found in the coastal plain region as well, Savanna Bluehearts (Buchnera floridana) (see image above).  In contrast with American Bluehearts, Savanna Bluehearts characteristically has fewer and more compact flowers (although taxonomic treatments by Bruce Sorrie emphasize leaf characters to distinguish the two). There are some indications that Savanna Bluehearts may be pretty rare in North Carolina (although comprehensive data are lacking since it is not currently tracked by our Heritage Program). 

Buchnera sp. perhaps intermediate in some characters between B. americana and B. floridana?
St. Marks NWR, Northern Florida (7-05-14)

Savanna Bluehearts don't seem to occur further north than North Carolina, but rather extend southward across parts of the southeastern coastal plain, and may not extend beyond the coastal plain. American Bluehearts is primarily centered in Kansas, Oklahoma, and Missouri with spotty occurrences elsewhere, including into the northeast and to the edge of Lake Huron.  The ranges of the two species may overlap, but the extent to which this happens, especially the mid-south and parts of the southeast, remain unclear (at least to me) (see image above). Part of the reason the distribution and status of both species is uncertain is due to the fact that the two names are considered synonymous in many areas. For example, NatureServe lumps them together and therefore believes the combined entity is perhaps globally secure.  However, American Bluehearts have apparently been extirpated from several states and are considered quite rare or vulnerable in a significant number of others. If the populations consisting of Savanna Bluehearts were seperated from the tally, both species could turn out to be important elements of conservation concern.  

American Bluehearts amidst dense grass cover in tallgrass prairie remnant @ Taberville Prairie, Missouri

In the so-called heart of the American Bluehearts range, where I observed it, the species was found in "tallgrass prairie". Today, there are mere remnants of this once vast ecosystem that the US Fish & Wildlife Service (http://www.fws.gov/midwest/ecosystemconservation/tallgrass_prairie.html) believes has become "functionally non-existent over the last 150 years".   In my recent forays in Missouri prairies, I encountered American Bluehearts only in 2/20 + remnants visited and found < 5 individuals at each (although my observations were not systematic or comprehensive).  Savanna Bluehearts seems to have occupied longleaf pine savannas which could be considered ecologically analagous to tallgrass prairie, and has suffered a similar fate. Importantly both habitats were once subject to frequently recurring fires that likely benefit both Buchnera species.  A large part of the conservation challenge ahead will be to ensure that sufficient high-quality habitat remnants of both ecosystem are protected from ongoing threats and are adequately fire managed.   

Tallgrass Vignettes

Standing amidst this sward of tallgrass prairie in Southern Kansas one evening (08-22-15) brought this line from Willa Cather to mind: ".......I felt the grass was the country, as the water was the sea."

Sweet Coneflowers (Rudbeckia subtomentosa) @ Osage Prairie, Missouri (8-19-15)

Profusion of Flowering Spurge @ Linden's Prairie, Missouri (8-20-15)

A few stalks of flowering Big Bluestem (Andropogon gerardii) stand above patches of Flowering Spurge (Euphorbia corollata) and a few other species @ Paintbrush Prairie, MO (8-16-15)


Stiff Sunflower (Helianthus pauciflorus) patch @ Tallgrass Preserve, Kansas (8-16-15)

Big Bluestem flowering above Flowering Spurge, Rosinweed stem on the left @ Tallgrass Preserve, Kansas (8-16-15)

Ashy Sunflowers (Helianthus mollis) @ Paintbrush Prairie, Missouri (8-17-15)

Flowering assemblage with Blue Sage (Salvia azurea), Ironweed, and Goldenrods @ Taberville Prairie, Missouri (8-18-15)

Getting on to evening at Golden Prairie, Missouri (8-22-15)