Ascending the Slippery Slope of Restoration

For several years now, I and the NC Plant Conservation Program have been working with the Eno River Association to restore their oldest Nature Preserve, the Blue Indigo Slopes.  The site is important, in part, due to the rare plants present as well as frontage on the Eno River . In addition, we view it as an important stepping stone in a landscape-level pollinator pathway in northern Durham (perhaps I will explain what that is in a future post).

During a routine visit this year, late in June, I noted general ecological conditions of the site and recorded mental notes on additional ecological restoration needs. A few observations follow:

Flowering Spurge (Euphorbia corollata)
widespread in eastern U.S.
often found in open sites or prairies
a few stems flowering here and there on the Slopes in esp. open areas

Piedmont Barbara's Buttons (Marshallia obovata)
locally abundant in some of our open, burned sites; this specimen
was flowering much later than typical for the species in our area
a small colony is present on the site

Post Oak (Quercus stellata) and Blackjack Oak (Quercus marilandica) sprouts and seedlings were apparent around the open edges of the site (see below). I think of these two oaks as likely historically important in many Piedmont open woodlands and savannas; both tolerate fire well. However, Blackjack is especially intolerant of shade and may be easily overwhelmed by faster growing, shade tolerant species - a major reason it is rarely seen today in the region.

Top: Blackjack Oak (Quercus marilandica) sapling amidst prairie flora
Bottom: Post Oak (Quercus stellata) sapling near clumps of Eastern Gamma Grass

Like many other rare plant sites in the Piedmont, this site was historically more open & prairie-like. A common attribute of these sites is the tendency to become heavily overgrown by dense trees and shrubs, presumably due to the absence of fire or grazing. One result of this change is the decline of  many understory species that are now of conservation concern and require special efforts to restore their populations.

We have begun an ecological restoration program supported by the Eno River Association Board, staff, and volunteers. Part of the restoration has involved slowly removing trees (mostly Loblolly Pine) and other invading brush from the site. As part of the broader effort we also conducted two consecutive spring-time prescribed burns on the Preserve. 

Results are becoming apparent!

The images above show a portion of the site before and after preliminary ecological restoration 

(November 2007 & February 2013); 

Note the large, limby eastern red cedar on the right side of both images

The green "clump" in the middle of the 2013 image is a shortleaf pine sprouting after fire

images complements of Kurt Schlimme of the Eno River Association.

The site's namesake, Wild Blue Indigo (Baptisia australis var. aberrans), suffered for years under the growing canopy. A decent number of individuals are still present but most are relatively small and still show diminished flowering. Consequently, very few of the individuals actually produce fruit. The individual shown below has only a single pod this season and appears to be affected by powdery mildew or some other pathogen. Although I don't know the identity of the white substance illustrated below we did document powdery mildew on these plants several years and a pathologist suggested heavy shade and associated moist conditions were contributing factors. We have purposely "gone slow" on the canopy re-opening, but the continued relatively poor vigor and possible mildew problems on the Wild Blue Indigo suggest we need to renew and expand our efforts. 

Newly developing Prairie Wild Blue Indigo Pod (Baptisia australis var. aberrans)
Typical "healthy" plants produce numerous pods, this is the lone pod on this individual

The site supports a scattered population of Starry Rosinweed (Silphium astericus) (left below) just coming into flower, as well as numerous Glade Wild Quinine (Parthenium auriculatum) (right below). As with the Blue Indigo, relatively few of the Glade Wild Quinine appear likely to flower this year.

An open prairie-like portion of the Eno River Association's Indigo Slopes Preserve (above). A Post Oak sapling can be seen near the back of the opening near the large pines, a Prairie Wild Blue Indigo individual occurs on the right, and scattered rosettes of Glade Wild Quinine (Parthenium auriculatum) can be seen throughout. The extent of the opening is less than 1/4 acre and surrounded by dense woods on at least 3 sides. We hope to significantly expand this opening, both up and downslope, in the near future.

Bearded Wonders - Xerophyllum asphodeloides

Turkey Beard (Xerophyllum asphodeloides) is a lily-like plant whose foliage superficially resembles a bunchgrass.  Weakley's Flora places it in the Xerophyllaceae (or Beargrass) Family.  Only 2 species occur in the family, and X. asphodeloides is the only eastern US native. In North Carolina, and elsewhere in the Southern Appalachians, Turkey Beard may be found on dry or even xeric ridges and slopes where periodic fire was an important ecological process. However, most of these areas are now fire suppressed and the Turkey Beard shows little flower production. Bourg & Gill (2000) conducted a series of experimental treatments and found that fire and canopy opening resulted in "an immense flowering response"; we produced a similar result after thinning and prescribed fire in Transylvania County, North Carolina. Like Bourg & Gill's study, the flowering results were dramatic 2 years after treatment.

Sunlight streams in after restoration & Turkey Beard responds

Over 100 flowering stalks appeared in 2014 after brush clearing in late 2011 and prescribed fire conducted in May 2012. This was especially surprising given the poor vigor of many of the vegetative tussocks prior to restoration (see below) and essentially no flowering.  

A highly suppressed tussock of Turkey Beard, prior to brush removal and prescribed fire; this individual was persisting under dense rhododendron shade. Most Turkey Beards I have seen in the region persist in similar condition

One unusual aspect of this population, is its occurrence in a wetland.  As mentioned above, the plant is usually associated with dry, rocky slopes or ridges. I haven't spoken to anyone who has seen Turkey Beard in a wetland such as seen below, although last week I observed a few plants growing on a wet flat stream bank under dense Dog Hobble (Leucothoe fontanesiana); the private landowner intends to follow our example and clear around their plants hoping for a similar flowering response.

Turkey Beard flowering amidst dense Cinnamon Ferns in a "mountain bog" habitat

A robust flowering scape of Turkey Beard growing adjacent to Purple Mountain Pitcher Plants (Sarracenia purpurea var. montana) 

The distribution of Turkey Beard and its western relative present an interesting puzzle for those interested in biogeography. The range maps presented below show the two Xerophyllum species and their natural ranges (from http://www.efloras.org). How did that happen??

           

Thanks to efloras.org

Shortleaf Pine (Pinus echinata) - Carolina Piedmont

Shortleaf Pine woodland with Post Oak (Quercus stellata) and Blackjack Oak (Quercus marilandica), Durham Co., NC

Increased attention is being focused on shortleaf pine by some foresters, ecologists, and restoration practitioners. An ongoing debate centers on how much shortleaf was present historically relative to the other native pines and hardwoods. We may never know the answer, however, it seems probable in our region (N.C. Piedmont) that mixed forest prevailed. According to Pinchot & Ashe 1897, "....no areas in the original forest...produce pure growth of either"

Range Map for Pinus echinata;
http://www.na.fs.fed.us/pubs/silvics_manual/Volume_1/pinus/echinata.htm

Although the preceeding map shows shortleaf ranging into the outer coastal plain there is general consensus that most of this area was historically dominated by other vegetation, especially longleaf pine woodlands and savannas. However, in the Piedmont there are intriguing "remnants" of shortleaf woodlands or savannas which share structural and compositional similarities with longleaf pine communities. 

Open Shortleaf Pine with herbaceous
understory including Indiangrass (Sorghastrum nutans)

Open Shortleaf "savanna"
 another view of well burned patch in Durham Co, NC

There is growing recognition that prescribed fire is an important management and ecological restoration tool in many shortleaf pine stands. To return long-suppressed stands to more open condition (such as the images above) frequent, regular fire is desirable. We try to burn these areas in the early spring on a 2-3 year rotation. 

  

Shortleaf Pine - Oak Forest; Spring 2014 prescribed fire

In the stand above, the nearly closed canopy from abundant oaks, especially Southern Red Oak (Quercus falcata), allows only patchy sunlight to reach the forest floor. Although fuel conditions were quite dry, the lack of sunlight penetration and wind movement underneath the trees and relative humidity in the high 30's fostered slow moving low flames and incomplete ground coverage.  

May 2014 Prescribed Fire in Shortleaf Pine - Oak Forest. Poverty Oat Grass (Danthonia spicata) is abundant and flowering in the left side of this view.  Patches of live green vegetation contributed to patchy coverage of this growing season burn.

Shortleaf Pine sapling on site burned ~ biennially for 10 years.
The small needles provide less surface for ice damage
than loblolly pine (Pinus taeda),
possibly explaining  its more northerly distribution.

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