Site Description

The Howland Forest research site is located about 35 miles north of Bangor at 45° 12' N, 68° 44' W at an elevation of 60 m within a spruce-hemlock-fir stand approximately 19.5 m in height. The site lies within the Northern Experimental Forest of International Paper. The natural stands in this boreal-northern hardwood transitional forest consist of spruce-hemlock-fir, aspen-birch, and hemlock-hardwood mixtures. The topography of the region varies from flat to gently rolling, with a maximum elevation change of less than 68 m within 10 km. Due to the region's glacial history, soil drainage classes within a small area may vary widely, from well drained to poorly drained.

Consequently, an elaborate patchwork of forest communities has developed, supporting exceptional local species diversity. Additionally, almost 450 ha of the surrounding area consists of bogs and other wetlands. Generally, the soils throughout the forest are glacial tills, acid in reaction, with low fertility and high organic composition. These soils primarily lie within three suborders: orthods, orchrepts, and aquepts. The climate is chiefly cold, humid, and continental and the region exhibits a snowpack of up to 2 m from December through March.

This site was established by the University of Maine, with the cooperation and collaboration of International Paper in 1986 during the EPA MCCP program and the NAPAP program, and is currently supported by the USDA Forest Service through its Global Change Program, the Department of Energy (DOE) through theNIGEC Program and the DOE Office of Science, and the National Science Foundation (NSF).The site is well documented in terms of historical characterization of forest species types and age, other species types in the canopy and at the ground, and structural density vertically within the canopy.  Atmospheric and environmental parameters from below the soil, through the forest canopy and above the treetops have been monitored continuously since 1987.

Aerial View of the Main Tower and Surrounding Forest

Originally as part of the MCCP and NAPAP programs and continuously since 1987, in collaboration with NOAA's Atmospheric Turbulence and Diffusion Division [ATDD] at Oak Ridge, TN we have been monitoring and evaluating wet and dry deposition of important air pollutants to landscapes using simple instrumentation and inferential modeling.

Since 1990 The Woods Hole Research Center [WHRC] has been an active collaborator with University of Maine personnel at the Howland site. Together we have jointly installed and maintained a CO2profile measurement system collecting continuous data at four elevations within and above the canopy. In addition, we currently collaborate in assessing soil and coarse woody debris CO2 fluxes.

Since 1988, NASA Goddard's Biospheric Sciences Branch has played an active role in collaborating with the University of Maine in remote sensing research at Howland and the modeling of forest ecosystem response to global change issues (Forest Ecosystems Dynamics [FED] Project). This work has emphasized the detection of features and patterns at local to regional spatial scales and the exploration of mechanisms that cover temporal scales ranging from seconds to centuries. This Maine-NASA collaboration continues as the FED program assesses ecosystem patterns in a linked modeling framework involving models of forest succession, soil processes, and energy exchange.  Our ongoing measurements of ecosystem function complement the existing structural databases and allow much more rigorous tests of the modeling framework. In addition, the models are expected to help pose further key questions relating to ecosystem function and carbon storage.

Measuring Below-Canopy Radiation.

The University maintains an electrically-connected meteorological station at a 25 m walk-up meteorological tower and an adjacent field laboratory building located within a large spruce stand. Two new remote 30 m towers were erected in the late 1990's to increase spatial coverage of the forest system measurements.  These remote towers also provide site specific core measurements for specific carbon sequestration experiment projects.

Faculty and staff of the University's Department of Plant,Soil, and Environmental Sciences maintain the infrastructure providing continuous collection of atmospheric and soil parameters. Some of the most important and useful data sets include diurnal surface energy and mass budgets (net radiation, sensible heat flux, latent heat flux, CO2 flux, and heat storage), standard micrometeorological data, wet and dry chemistry, soil moisture, salinity and temperature, soil carbon stocks and soil chemical, microbiological and physical properties, stand biomass estimates from both ground-based inventories and radar images, allometric relationships for stand biomass components, a stem map by species, litter production, needle water potential and stomatal conductance, needle chemistry, and a continuous monitoring of CO2 and ozone concentrations within and above the forest canopy.

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