Research Activities

Long-Term Monitoring
A strength of the HBES is the long-term monitoring program. The monitoring program at Hubbard Brook shows that short-term observations are often misleading and that decades may be required to detect real changes in complex ecosystems. The long-term record at the HBEF provides: 1) insight into ecosystem function, 2) empirical data for testing models and generating hypothesis,3) a record of extreme or unusual events, and 4) information that is relevant to regional, national and global issues. A summary of current long-term data sets developed through the HBES is provided in the table below.

TIn addition to the long-term monitoring program and the watershed manipulation studies, there are a number of shorter-term studies being conducted within the HBES.

Published Results
As would be expected in long-term ecosystem research, the publication rate at the beginning of the HBES was rather low (2 to 4 papers per year during 1962-1966). At least an annual period, and usually more than a single annual cycle, is required to evaluate metabolic or biogeochemical functions of an entire ecosystem. As long-term data accumulated, it became more attractive to potential cooperators and funding agencies to conduct research at Hubbard Brook. At the present time a large number of cooperating senior scientists, who have funds from a variety of sources (e.g., NSF, EPA, NOAA, DOE, Universities, Andrew W. Mellon Foundation), are actively involved in the current HBES. These trends in activity at Hubbard Brook are reflected by the large number of papers and books published throughout the period of study.

Over the duration of the HBES (1963-2001) there have been 6 books and some 1054 papers published. In addition, 535 abstracts were published, 124 graduate theses (49 M.S. theses and 75 Ph.D.) and 39 undergraduate honors theses completed.

Synthesis of the Hubbard Brook Ecosystem Study
Beginning in 1976, an effort was made to bring together some of the results of research that had been done at Hubbard Brook over the last 38 years. Currently, four synthesis volumes have been completed.

(1) Likens, G.E., F.H. Bormann, R.S. Pierce, J.S. Eaton and N.M. Johnson. 1977. Biogeochemistry of a Forested Ecosystem. Springer-Verlag, New York Inc. 146 pp. - Likens, G.E. and F.H. Bormann. 1995. Biogeochemistry of a Forested Ecosystem. Second Edition. Springer-Verlag, New York Inc. 159 pp.

(2) Bormann, F.H. and G.E. Likens. 1979. Pattern and Process in a Forested Ecosystem. Springer-Verlag, New York Inc. 253 pp.

(3) Likens, G.E. (ed.) 1985. An Ecosystem Approach to Aquatic Ecology: Mirror Lake and its Environment. Springer-Verlag, New York Inc. 516 pp.

(4) Likens, G.E. 1992. The Ecosystem Approach: Its Use and Abuse. Excellence in Ecology, Book 3. The Ecology Institute, Oldendorf-Luhe, Germany. 166 pp.

ph values 
Figure 12: Annual volume-weighted values of pH for precipitation at W6. Hubbard Brook has longest continuous record of precipitation chemistry in North America. pH values are low at Hubbard Brook due to inputs of strong acids associated with sulfur dioxide and nitrogen oxide emissions. Recent increases in pH are largely due to decreases in sulfur dioxide emissions in the eastern U.S. (updated from Likens 1989).

lead concentrations 
Figure 13: Trends in concentrations of Pb in precipitation and forest floor at the HBEF. The decline in concentrations of Pb since the mid-1970's is consistent with decreases in Pb emissions due to changes from leaded to unleaded gasoline (modified from Johnson et al. 1995).

Current long-term monitoring data sets developed through the HBES. The institution responsible for sample collection and funding source are indicated. Data management status includes: a) The Hubbard Brook web site, b) available from PI, and c) hardcopy. * Archived materials are maintained by the USDA FS.

Physical Hydrologic Monitoring
Institution Funding Source Status Year
Instantaneous streamflow
(8 stations)
  USFS USFS a,b 1956
Daily streamflow (8 stations) USFS USFS a,b 1956
Daily precipitation (22 stations) USFS USFS a,b 1956
Daily temperature: mean, min, max USFS USFS a,b 1952
Daily solar radiation USFS USFS a,b 1958
Weekly snow depth on snow courses USFS USFS a,b 1959
Weekly soil temperature and moisture USFS USFS a,b 1959
Hourly air temp., humidity, solar radiation, wind speed/direction, precipitation   USFS/IES USFS a,b --
Hourly canopy surface wetness IES IES b 1989
Air Chemistry
(SO2, HNO3, particulates, ozone)
IES EPA   1988
Solution Chemistry        
Weekly bulk precipitation
(6-10 stations)
IES This study a 1963
Event basis throughfall W5, W6 IES NSF-LTR b 1989
Monthly soil solution W5, W6 Syracuse NSF-LTER b 1984
Weekly stream at weirs of W1-6 IES This study a 1963
Monthly stream within W5, W6 Syracuse NSF-LTER a,b 1982
Mirror Lake        
Instantaneous streamflow
(3 inlets, outlet)
Daily precipitation (2 stations) USFS/IES USFS/NSF a 1956
Daily temperature, solar radiation, relative humidity, wind speed   USFS/USFS/IES USGS/USFS/NSF a 1979
Weekly chemistry (3 inlets, outlet) IES NSF a ~1965
Bi-monthly limnology (temp, chemistry, plankton) IES NSF/Mellon a 1965/
Bird populations Dartmouth NSF-LTER b 1969
Phytophagous insect populations Dartmouth NSF-LTER b 1969
W2 Vegetation, biomass, chemistry Wyoming NSF-LTER a 1970
W4 Vegetation, biomass USFS USFS a 1970
W5 Vegetation, biomass, chemistry Cornell/Yale NSF-LTER b 1985
W6 Vegetation, biomass, chemistry Yale NSF-LTER a 1965
Fine-root, biomass, chemistry Cornell NSF-LTER -- 1992
Litter-Fall Cornell NSF-LTER c 1988
Forest floor mass, chemistry
(W6, W5; 5-yr intervals)
  Yale NSF-LTER a 1968
Chemical and physical properties from soil pits (W5) Syracuse NSF-LTER b 1984
Chemical and physical properties from soil bags Syracuse NSF-LTER -- 1993
Archived Materials        
Herbarium specimens USFS * c  
Library USFS/IES/PVF * c  
Tree cores and cross sections Yale/USFS * c  
Forest floor Yale/Cornell/USFS * c  
Soils Syracuse/USFS * c  
Plant tissues Yale/USFS * c  
Plankton IES * c  
Water samples USFS * c  
Table 5: Summary of Current Long-Term Data Sets Developed Through the HBES

Hubbard Brook Experimental Forest Biosphere Reserve
Biosphere Reserves are part of an international program sponsored by UNESCO. The primary objectives of the Biosphere Reserve program are conservation of genetic diversity, environmental research and monitoring, and education. In 1976, the HBEF was designated a Biosphere Reserve as part of the Man And the Biosphere - Biosphere Reserve Program (MAN), representative of the northern hardwood-spruce forest (Cackler vegetation type). This area is currently the only Biosphere Reserve in the northeastern U.S.

Hubbard Brook Long-Term Ecological Research
n September 1987, the HBEF was awarded a Long-Term Ecological Research (LTER) grant through the NSF. The overall objective of the project "Long-Term Ecological Research at the Hubbard Brook Experimental Forest," is to develop a better understanding of the response of northern hardwood-ecosystems to large-scale disturbances. Particular emphasis is placed on the areas of (1) vegetation structure, composition and productivity; (2) dynamics of dead organic matter; (3) atmospheric-terrestrial-aquatic linkages; and (4) heterotroph population dynamics. The research is being conducted on sites within the HBEF with contrasting history of disturbance using experimental studies as well as analysis of long-term data. Specifically, research within the HBEF-LTER is examining the response of forest and aquatic ecosystems to disturbances that are common in the northeastern U.S. and southeastern Canada including: (1) silvicultural and land-use disturbance; (2) air pollution; (3) climatic disturbance or change; and (4) changes in populations of heterotrophs. This research is providing valuable information on long-term ecosystem responses to disturbance, knowledge needed by society to assess the effects of management and policy on the integrity of forest ecosystems in the this region.

Data Management
The long-term database is large, complex and increasingly difficult to manage, but it is the core of the HBES. Individual institutions collecting data develop their own data management programs. In collaboration with other HBES scientists, the USDA-FS has developed the HBES Database Management System. Long-term data on the chemistry of precipitation and streamwater for the HBEF and for Mirror Lake are managed by the IES. These data are also included in the HBES Database Management System, available on this site. Access to data and documentation is intended to foster increased exchange of information among cooperators as well as encourage scientists and students from outside the HBES to compare observations at Hubbard Brook to other sites worldwide.

The USDA-FS has also constructed a permanent archive facility at Hubbard Brook for long-term preservation of important material samples, such as soil, water, plant tissue, geological cores, etc.

In addition to routine data management activities, Ecological Data Exchange (EDEX) and Jointly Accessible Research Samples (JARS) programs have been implemented by Yale University. EDEX is an effort to save and make available forest plot data sets from the Northeast region. EDEX files are available through the USDA-FS bulletin board. JARS is a catalog of over 6,000 samples of plant and soil material that have been collected at Hubbard Brook and the Northeast. All JARS samples are stored in the USDA-FS storage building at Hubbard Brook. An archive of published materials, dissertations, correspondence, etc. is being established at IES. Questions concerning the Hubbard Brook data management may be made to: Hubbard Brook Data Manager, USDA Forest Service, P.O. Box 640, Durham, NH 03824.