Hubbard Brook Experimental Forest

The Hubbard Brook Experimental Forest is located in West Thornton, New Hampshire. It is an experimental area established in 1955 within the White Mountains National Forest in New Hamphire's central plateau and is administered by the U.S. Forest Service . Hubbard Brook was the site of many important ecological studies beginning in the 1960s which established the extent of nutrient losses when all the trees in a watershed are cut.

Hubbard Brook is a north temperate watershed covered with a mature forest, and it is still accumulating bio-mass . In one early study, vegetation cut in a section of Hubbard Brook was left to decay while nutrient losses were monitored in the runoff . Total nitrogen losses in the first year were twice the amount cycled in the system during a normal year. With the rise of nitrate in the runoff, concentrations of calcium, magnesium, sodium, and potassium rose. These increases caused eutrophication and pollution of the streams fed by this watershed. Once the higher plants had been destroyed, the soil was unable to retain nutrients.

Early evidence from the studies indicated that total losses in the ecosystem due to the clear-cutting were a large number of the total inventory of species . The site's ability to support complex living systems was reduced. The lost nutrients could accumulate again, but erosion of primary minerals would limit the number of plants and animals sustained in the area.

Another study at the Hubbard Brook site investigated the effects of forest cutting and herbicide treatment on nutrients in the forest. All of the vegetation in one of Hubbard Brook's seven watersheds was cut and then the area was treated with the herbicides. At the time the conclusions were startling: deforestation resulted in much larger runoffs into the streams. The pH of the drainage stream went from 5.1 to 4.3, along with a change in temperature and electrical conductivity of the stream water. A combination of higher nutrient concentration, higher water temperature, and greater solar radiation due to the loss of forest cover produced an algal bloom , the first sign of eutrophication. This signaled that a change in the ecosystem of the watershed had occurred. It was ultimately demonstrated at Hubbard Brook that the use of herbicides on a cut area resulted in their transfer to the outgoing water.

Hubbard Brook Experimental Forest continues to be an active research facility for foresters and biologists. Most current research focuses on water quality and nutrient exchange. The Forest Service also maintians an acid rain monitoring station, and conducts research on old-growth forests. The results from various studies done at Hubbard Brook have shown that mature forest ecosystems have a greater ability to trap and store nutrients for recycling within the ecosystem. In addition, mature forests offer a higher degrees of biodiversity than do forests that are clear-cut.

See also Aquatic chemistry; Cultural eutrophication; Decline spiral; Experimental Lakes Area; Nitrogen cyle

[Linda Rehkopf ]

RESOURCES

BOOKS

Bormann, F. H. Pattern and Process in a Forested Ecosystem: Disturbance Development and the Steady State Based on the Hubbard Brook Ecosystem Study. New York: Springer-Verlag, 1991.

Botkin, D. B. Forest Dynamics: An Ecological Model. New York: Oxford University Press, 1993.

PERIODICALS

Miller, G. "Window Into a Water Shed." American Forests 95 (May-June 1989): 58–61.