Pine Barrens & Grasslands in New England; Part II

In a previous post I briefly discussed two examples of fire-maintained vegetation in southern New England (http://ncplantcon.blogspot.com/2014/08/pine-barrens-grasslands-in-new-england.html). Ecologically similar sites, often referred to as "pine barrens" or "pitch pine barrens" are scattered around the region.  I visited examples of this unique vegetation in Maine, New Hampshire, and Massachusetts in late summer (2014).

Pitch Pine barren near Waterboro, Maine
understory of lowbush blueberry, sweetfern, and bear oak

Some examples were enchanting forests; gnarly & twisted pines with charred boles, multiple age classes, and patchy ground cover openings. All sites occurred on "sandplains" or glacial outwash plains. These deep sandy soils supported two consistent species across all sites visited; Pitch pine (Pinus rigida) & Bear Oak (Quercus ilicifolia). Bear Oak was often heavily dominant as a tall shrub or dense midstory layer.

Pinus rigida bole displaying epicormic shoots

Bear Oak (Quercus ilicifolia)

Many areas I visited were thickly stocked with dense Pitch Pine, while others were open woodlands. Fire history could partially explain those density differences, with more frequently burned sites supporting the woodlands.

Much of the region around the Waterboro Barrens, was burned over in Maine's largest series of forest fires in 1947. Since that time (and prior to restoration work), a 93% decline in open canopy pitch pine has been documented (2).


In addition to the loss of open woodlands, Patterson (1) found that stands unburned since 1947 had developed highly volatile, well aerated fuels conducive to high intensity, fast moving fires.

Waterboro Barrens thinning;
dense forest (left) unthinned, open woodland (right) mechanically thinned. 

Not surprisingly, a proactive management strategy of mechanically thinning trees and brush around exterior boundaries of the site has been implemented. This strategy serves a dual purpose of minimizing fire behavior while "restoring" some of the open canopy woodlands that have been lost. This management strategy was also being implemented at a New Hampshire site I visited. Hand crews were actively cutting, clearing, and piling brush in much the same way we have done on fire reintroduction projects in North Carolina (one of which involved pitch pine). Examples shown here (below) were presumably thinned to achieve this open structure.

Waterboro, Maine

Concord, New Hampshire

Pitch Pine Woodlands:

(contrast both to image at top of page)

While appearing structurally similar, understory composition varied considerably; Concord (right) was much richer floristically and perhaps has a longer and/or more recent history of prescribed fire; prescribed burns began there in 2003 and ~ 20 acres or so have been burned in most years since then (3). Managers at Concord have a compelling reason to reintroduce fire. In addition to restoring a rare and declining natural community type, and reducing wildfire risk, their site is the only location in New Hampshire and the world's easternmost location known to support the Karner Blue Butterfly (4).

Karner Blue (Lycaeides melissa samuelis), Concord, NH
Thanks to Harry LeGrand for ID confirmation!

This federally endangered species (also found in the midwestern US, and mentioned in an earlier blog regarding the connection with Sundial Lupine) has been reintroduced to the site, along with Lupines by biologists in New Hampshire.  One relatively small portion of the site was exceptional for its grassy character (see image below). I observed a number of plants there, but in no other "barrens", including Big Bluestem, DogBane, New Jersey Tea, Ground Cherry, and others.

Grassy open Pitch Pine Barren@Concord, New Hampshire

Karner Blue (?) perched on Dogbane (Apocynum cannabinum)@ Concord, New Hampshire

It will be interesting to see what management activities, especially prescribed fires, are conducted across these barrens and the results they achieve. Reducing dangerous fuel loads while restoring more natural structure seems like a logical way forward (see below), but the real proof comes with fire.

Brush piles from hand clearing around large Pitch Pine @ Concord, NH

References:
(1) http://www.umass.edu/nebarrensfuels/publications/pdfs/waterboro_pot_fire_bx.pdf
(2) http://www.umass.edu/nebarrensfuels/ne_barrens/waterboro_kennebunk_hollis/waterboro.html
(3) http://www.wildlife.state.nh.us/Wildlife/Nongame/projects/karner_project.html
(4) http://www.fws.gov/midwest/endangered/insects/kbb/pdf/kbb5YrReviewSept2012.pdf

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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

References:
(1) http://harvardforest.fas.harvard.edu/sites/harvardforest.fas.harvard.edu/files/publications/pdfs/Dwarf%20Pitch%20Pine_Motzkin%20and%20Orwig.pdf
(2) http://userwww.sfsu.edu/parker/bio821/papers/3-serotiny/Givnish1981.pdf

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