Sunday, August 21, 2016

Longleaf pine restoration - bring on the fire, but first....

Elsewhere on this blog I have discussed the importance of fire for the maintenance and recovery of longleaf pine (Pinus palustris) habitats. I have not discussed the numerous challenges in being able to do so, and they can be considerable. This page will not be a full accounting of these challenges but is predicated on some of these. Namely, long-unburned stands may have extraordinary fuel loads that can be explosive and dangerous to reintroduce fire into.

Longleaf pine stand and prescribed burn near the coast of North Carolina;
flame lengths and intensity are greater than many managers would prefer 

   Longleaf "flattop"; these trees often represent remnants of
earlier forests skipped over by loggers
                                                            Bringing fire back into long-unburned stands places serious stress on the very trees fire management is intended to support. In stands where longleaf pines are sparse (image above) or where the individuals include older relicts, each tree is precious and valuable (image left). Longleaf remnants with "cat faces" (signs of previous naval stores harvest) are especially susceptible to fire damage (image below).                                                                 
Mechanically reducing the fuels in such stands can help protect high-value individual trees and lower overall fire intensity. However, doing so across large and heavily overgrown stands takes a concerted approach. Several years ago, we stepped up and took one (a concerted approach, that is).

The "concerted approach"!
Skid steer equipped with forestry cutter
We acquired a skid steer equipped with tracks to minimize ground disturbance, a special cab to protect the operator, and a "forestry cutter".  Examples of how we used it are shown below:       
  Disappearing mower and mowed swath
 through heavy "bay" fuels
Brunswick Co, NC

Mower headed straight toward remnant longleaf pine, barely evident from
a distance due to tall shrub and Pond Pine (Pinus serotina) encroachment

In these circumstances it was the perfect way to go "looking for longleaf".  

The images below show this stand before and after treatment. Note the lone Longleaf pine with the Y-shaped canopy near the center. Amazingly, a young longleaf pine was hiding in the dense brush immediately in front of this tree (click & enlarge image right). After clearing, the stand displayed the open structure typically associated with longleaf pine savannas and woodlands - a restoration success?.  Comment appreciated! 

Longleaf pine stand with relicts, after mulching treatment (same stand as above)
Note - turpentine faces on 2 of the trees.
Brunswick Co, N.C.

Tuesday, August 16, 2016

Shenandoah sinkhole ponds

Virginia Sneezeweed (Helenium virginicum) is a federally-listed "threatened" species associated with Shenandoah Valley sinkhole ponds in Virginia. A number of years ago, the species was also confirmed in Missouri in similar habitat, creating "one of the great phytogeographic mysteries of the Eastern North American flora" (1).

Virginia Sneezeweed (Helenium virginicum)

Large patch of Virginia Sneezeweed along margin of sinkhole pond, Augusta County, VA


This is a seed-banking species whose populations fluctuate widely at a given site. Flowering stems can become prolific and abundant under the right conditions (2) (image left)

Water levels in the sinks vary widely and fluctuate seasonally. The example shown below held over 12" of water while immediately adjacent ponds were completely dry.  Not surprisingly, the vegetation may also be quite variable both seasonally and between sites. For more detailed descriptions see (3) & (4) below.

Shenandoah sinkhole pond with standing water (July 12, 2016)
Note: Pin Oak (Quercus palustris) overhanging branch  

Shenandoah sinkhole pond, same site as above (August 04, 2016)
standing water still present, emergent Persicaria and Polygonum spp. superficially dominant
Shenandoah sinkhole pond with Buttonbush (Cephalanthus occidentalis) and emergent Eriocaulon

The sinkhole ponds are biologically important features of the Shenandoah Valley region and they support many other species in addition to Virginia Sneezeweed. These ponds are also extremely important for dragonflies (5) and reptiles and amphibians (4), in part, because the ephemeral water levels often restrict predatory fish populations.
Spotted Turtle (Clemmys guttata) - the only populations west
of the Blue Ridge are found in sinkhole ponds (4)
Image from coastal plain of VA
Amphibian egg masses in sinkhole pond (03-23-16)

Dragonfly exuvia on Lowland Loosestrife (Lysimachia hybrida)
in sinkhole pond, Augusta Co

Lowland Loosestrife (left) is considered significantly rare in Virginia, and known from a handful of sinkhole ponds.

A number of other rare plants may also be found:

Boltonia montana  - Augusta Co., VA (08-4-16)

Valley doll's daisy (Boltonia montana) is an extreme global rarity, known from 4 VA sites, all within a few miles of one another in Augusta County's sinkhole ponds. Described as new to science in 2006, this species also has an unusual phytogeographic pattern.

Northern St. John's Wort (Hypericum boreale)  -- Significantly rare in Virginia; known from Shendandoah sinkhole ponds and disjunct to interdunal ponds near the coast.

The ponds themselves are globally-rare and imperiled, In the two examples shown below, one has been artificially deepened and stocked with fish and the other used as a mini-landfill.

It's hard to image more important and special habitats. I hope to be able to play a small part in protecting them.

(1) Virginia Plant Atlas:
(2) Draft Recovery Plan:
(3) Descriptive Ecology:
(4) See Montane Depression Wetland types and links here (
(5) A new species of Boltonia....SIDA 22:873-886.

Sunday, July 10, 2016

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" 

Sunday, April 24, 2016

"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

Saturday, October 3, 2015

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)


Monday, September 28, 2015

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)