Forests
The Penobscot River watershed is over 90 percent forested (including forested wetlands). The upper catchment is predominantly spruce-fir forest and the lower watershed is a mix of spruce-fir, pine, and maple-beech-birch stands (Jackson et al., 2005). Much of the forest has been harvested since the dawn of the logging era in the 1700s, and logging continues throughout the watershed.

Wetlands
The great extent of wetland in the Penobscot watershed (almost one-third of the watershed; Jackson et al., 2005) soaks up water when it rains and slowly releases it to rivers and groundwater, with the ultimate effect of moderating fluctuations in the river's flow. The result is a highly predictable annual flood in the spring, gradually tapering to low water by summer's end. This flow is somewhat altered by the 116 licensed dams in the watershed (PNWRP, 2001). However, most of the dams are "run of the river" and they have allowed the river to retain a natural flow regime that supports numerous riparian swamps and wetlands (Jackson et al., 2005).

Within the river are aquatic plants like pondweed and wild celery. Riparian wetlands line the areas of the river with slower flows. Rare plants include Sagittaria calcyina , spongy arrowhead, and Carex oronensis, Orono sedge. Invasive plants include purple loosestrife.

All along the main tributaries of the lower Penobscot are extensive, flat areas where the ocean invaded the land after the glaciers retreated, forming a layer of marine silt and clay that became the bottom layers of today's bogs and fens (Davis and Anderson, 1999). Sunkhaze Meadows, Alton Bog, and Caribou Bog are good examples.

Sunkhaze Stream begins on the north slope of Bald Bluff Mountain , on the border of Amherst and T32 MD, near the divide between the Penobscot and Union river drainages. The stream flows westerly through freshwater meadows of the 9,337-acre Sunkhaze Meadows National Wildlife Refuge before discharging to the Penobscot in Milford . See Friends of Sunkhaze http://www.sunkhaze.org/ for more on the Sunkhaze watershed.

Caribou Bog, which runs north-south along the eastern side of Pushaw Lake in Bangor and Orono, is a bog dominated by Sphagnum moss. Historical ecological studies revealed that the bog began as a shallow lake (7,000 years ago) and transitioned into marsh and sedge meadow before becoming dominated by Sphagnum moss.

Alton Bog is a poor fen that drains to Birch Stream, which flows into the Stillwater branch of the Penobscot. The bog is bisected by Interstate 95, which is heavily salted during the winter. University of Maine studies have traced the movement of road salt into the bog, both via road runoff and from drifting dust, which eventually gets into the groundwater (Pugh et al., 1996; Schauffler et al., 1996).

Davis , R.B., and D.A. Anderson. 2001. Classification and distribution of freshwater peatlands in Maine. Northeastern Naturalist 8:1-50. PDF

Jackson , J.K., et al. 2005. Atlantic Coast Rivers of the Northeastern United States , pages 21-63 in Rivers of North America (A.C. Benke and C.E. Cushing, eds.) Boston : Elsevier Academic Press.

Penobscot Nation Water Resources Program. 2001. The Penobscot Nation and the Penobscot River basin : A watershed analysis and management project. Penobscot Nation Water Resources Program, Department of Natural Resources, Indian Island , Maine .

Pugh, A.L., IV, S.A. Norton, M. Schauffler, G.L. Jacobson, Jr., J.S. Kahl, W.F. Brutsaert, and C.F. Mason. 1996. Interactions between peat and salt-contaminated runoff in Alton Bog , Maine , USA . Journal of Hydrology 182:83-104.

Schauffler, M., G.L. Jacobson, A.L. Pugh, and S.A. Norton. 1996. Influence of Vegetational Structure on Capture of Salt and Nutrient Aerosols in a Maine Peatland. Ecological Applications 6:263-268.

CURRENT RESEARCH

Wetland surveys
Aram Calhoun from the University of Maine is advising the Maine student chapter of the Society for Conservation Biology in a survey of wetlands in the Penobscot River between Bangor and Old Town . The surveys (in 2006 and 2007) include field-checking NWI maps, documenting presence of in-stream and bordering wetlands, and inventorying vegetation species in each wetland. Support provided by Maine Sea Grant and The Nature Conservancy. Contact Aram at calhoun@maine.edu .

Wetland plant inventory
Meghan Whitney, a senior botany major at the University of Maine , is conducting a plant inventory of the banks of the Penobscot River between Ayer's Island and the Veazie Dam as part of her honors thesis (Fall 2007).

Wetland delineation
As part of permitting for the proposed dam removals, Woodlot Alternatives has been subcontracted by Kleinschmidt Associates and the Penobscot River Restoration Trust to conduct wetland inventories and delineations in the project area (Fall 2007). More information will be available in early 2008.

Wetland biomonitoring
The Maine DEP conducted wetland biomonitoring in the Penobscot River in 2006. Biological sampling included aquatic macroinvertebrates, epiphytic algae, and phytoplankton. Water samples were analyzed for nutrients, chlorophyll-a, etc. Final results are pending. Jeanne DiFranco , Maine DEP.

Periphyton Monitoring
Algal community data from streams in the Penobscot Basin, 2001-present, are currently being quality-assured. Tom Danielson , Maine DEP.