Acadian Forest, Maine

“The mission of the Penobscot Experimental Forest is to afford a setting for long-term research conducted cooperatively by USDA Forest Service scientists, university researchers, and professional forest managers in Maine; to enhance forestry education of students and the public; and to demonstrate how the timber needs of society are met from a working forest.” That statement was written in 1994 when the Penobscot was donated to the University of Maine. Land was purchased by nine pulp, paper, and land-holding companies in 1950 and leased to the Forest Service’s Northeastern Forest Experiment Station as a site for long-term forest management research in the northeastern spruce-fir forest. The Penobscot is now jointly managed by the university and the Northern Research Station at Durham, New Hampshire.

Located 15 km north of Bangor, Maine, the Penobscot is in the Acadian Forest, a region covering much of Atlantic Canada and adjacent Maine. An ecotone between boreal and broadleaf biomes, the region is dominated by mixed conifers. Red spruce is the signature species of the Acadian Forest, distinguishing it from similar forests around the Great Lakes where white spruce is common and red spruce is absent. Balsam fir, a boreal species, is at its southern limit, whereas other trees, including eastern hemlock and eastern white pine, are at their northern limits. Stand-replacing fires are less frequent than in the boreal forest or other temperate forests. Natural disturbances are insect epidemics (notably eastern spruce budworm) and windstorms, causing sporadic mortality. Most of the forest around Bangor has been cut periodically for high-value products since the 1790s. However, little of the 1,618-ha Penobscot was ever cleared or cut during the 20 to 40 years prior to its designation as an experimental forest.

Climate

The climate of the Penobscot is cool and humid. Average annual temperature is 6.6 °C, with February the coldest (7.1 °C) and July the warmest (20 °C). Normal precipitation is 106 cm, with 48 percent falling during the growing season, which averages 156 days.

Soils

The soils of the Penobscot are complex and variable because of glacial influences. Till derived from fine grained sedimentary rock is the principal parent material. Low till “ridges” are well-drained loams, stony loams, and sandy loams. Flat till areas between ridges are poorly and very poorly drained loams and silt loams. Low areas along watercourses and in depressions have lake and marine fine sediments that are poorly drained silt and silty clay loams.

Vegetation

The vegetation types on the Penobscot are typically more diverse than on the industrial spruce-fir forest farther north. The canopy is dominated by a mix of conifers, including hemlock, spruce (mostly red but some white and black), balsam fir, northern white-cedar, white pine, and occasional tamarack or red pine. Common hardwoods include red maple, paper and gray birch, and quaking and bigtooth aspen.

Research, Past and Present

Scientific studies on the Penobscot have been traditionally focused on management of mixed conifer stands for timber. Over the past 20 years, research was broadened to include fundamental studies of tree growth and maturation, spruce budworm predation, biodiversity, root structure and function, coarse woody material, economics, and growth-and-yield modeling. The longterm silvicultural experiment that is the basis for most of the research includes 10 replicated treatments representing a range of even-age and uneven-age prescriptions: clearcutting, three variants of shelterwood, selection with three cutting cycles, two forms of diameter-limit cutting, and an unmanaged control. Researchers with FERP are studying the effects of expanding gap shelterwood on several attributes of ecosystem structure and function.

Major Research Accomplishments and Effects on Management

The Penobscot is recognized internationally for its silvicultural research, including the only examples of uneven-age management of conifers in the Northeastern United States and Eastern Canada, where cutting cycles have been sustained over decades. Pioneering research on shelterwood removals, strip cutting, and precommercial thinning was conducted on the forest. Analyses of stand growth and development and economics of various silvicultural treatments have influenced management decisions throughout the region. The range of stand composition and structure in the long-term silvicultural study attracts cooperating scientists interested in the effects of forest management on hydrology, soils, plants, and animals. Technology transfer is a major undertaking, with numerous tours annually for students and professionals.

Collaborators

Because of ownership and proximity to the University of Maine, most cooperators are faculty and graduate students. A research unit at the Northeastern Research Station’s New Hampshire facility is responsible for Forest Service research. With the exception of FERP, other Penobscot research is guided jointly by a team of university faculty and Forest Service scientists. Collaborators also include researchers from other NE projects, Canadian Forest Service, University of Vermont, and University of New Hampshire, state forestry and wildlife agencies, and Small Woodland Owners Association of Maine.

Research Opportunities

There are nearly unlimited research opportunities in all aspects of ecology and management of conifer-dominated and mixed conifer-hardwood stands of the Acadian Forest. New research within the long-term silvicultural study is encouraged and facilitated by Forest Service scientists. Research in conjunction with FERP is approved by the director of that program. All other research proposed must be presented to the university and Forest Service team that manages the research program.

Facilities

At the Penobscot, there is an office, shop, and storage
space.
Lat. 44°51′ N, long. 68°37′ N

Contact Information

Penobscot Experimental Forest
USDA Forest Service
Northern Research Station
271 Mast Road
Durham, NH 03824
Tel: (603) 868-7632

Related Publications

Brissette, J.C. 1996. Effects of intensity and frequency of harvesting on abundance, stocking and composition of natural regeneration in the Acadian Forest of eastern North America. Silva Fennica 30(2):301-314.

Brissette, J.C., R.M. Frank, T.L. Stone, and T.A. Skratt. 1999. Precommercial thinning in a northern conifer stand: 18 year results. For. Chronicle 75(6): 967-972.

Frank, R.M. and J. C. Bjorkbom. 1973. A silvicultural guide for spruce-fir in the Northeast. Gen. Tech. Rep. NE-6. Broomall, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 29 p.

Frank, R.M.; T.L. Stone, H.S. Crawford. 1996. Tree/wildlife diversity responses to silvicultural practices in northern conifers. In: Proceedings of the 1995 Society of American Foresters Convention. Society of American Foresters, Bethesda, MD. p. 413-414.

Kenefic, Laura S.; Sendak, Paul E.; Brissette, John C. 2005. Digging Out the Data: USDA Forest Service Research on the Penobscot Experimental Forest

Kenefic, L.S.  2002.  Research on the Penobscot Experimental Forest.  SWOAM News. 27(2):9.

Safford, Lawrence O.; Frank, Robert M.; Little, Elbert L., Jr. 1969. Trees and Shrubs of the Penobscot Experimental Forest, Penobscot County, Maine. Research Paper NE-128. USDA Forest Service, Northeastern Forest Experiment Station, Upper Darby, PA 27 p.

Sendak, Paul E.; Brissette, John C.; Frank, Robert M. 2004. Managing Stands of Mixed Northern Conifers: 40-Year Results From the Penobscot Experimental Forest

Sendak, Paul E.; Brissette, John C.; Frank, Robert M. 2003. Silviculture affects composition, growth, and yield in mixed northern conifers: 40-year results from the Penobscot Experimental Forest. Can. J. For. Res. 33:2116-2128.

Seymour, R.S. and L.S. Kenefic. 1998. Balance and sustainability in multi-aged stands: a northern conifer case study. J. For. 98(7):12-17.

Seymour, R.S. 1995. The northeastern region. In: Barrett, J.W. (ed.). Regional silviculture of the United States, third edition. John Wiley & Sons, New York. p. 31-79.

Summary information presented here was originally published in:

Adams, Mary Beth; Loughry, Linda; Plaugher, Linda, comps. 2004. Experimental Forests and Ranges of the USDA Forest Service. Gen. Tech. Rep. NE-321. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 178 p.

Information may have been updated since original publication.