Hubbard Brook Experimental Forest (HBEF) was established in 1955 as a major
center for hydrologic research in New England. The site is
located within the boundaries of the White Mountain National Forest in central
New Hampshire. The 3,138-ha, bowl-shaped Valley has hilly terrain, ranging
from 222 to 1,015 m altitude. During the first eight years following establishment
a network of precipitation and stream-gauging stations, weather instrumentation,
as well as soil and vegetation monitoring sites on small experimental watersheds
were developed. Data from these installations combined with several initial
studies formed the hydrometeorologic foundation for much of the future research
at the HBEF. The major emphasis in these early studies was to determine the
impact of forest land management on water yield and quality, and flood flow.
The Hubbard
Brook Ecosystem Study (HBES) originated in 1960 with the idea of the small
watershed approach to study element flux and cycling. A joint research program
between the USDA Forest Service and Dartmouth College was established by a
cooperative agreement in 1963. Also that year, funds from a grant from the
National Science Foundation (NSF) provided the start of the HBES research
program. Support from the USDA Forest Service and the NSF has been continuous
since that time. In 1988 the HBEF was designated as a Long Term Ecological
Research (LTER) site by the National Science Foundation. On-going cooperative
efforts among diverse educational institutions, private institutions, government
agencies, foundations and corporations have resulted in one of the most extensive
and longest continuous data bases on the hydrology, biology, geology and chemistry
of natural ecosystems.
Annual
precipitation averages about 1,400 mm, with one-third to one-quarter as snow.
Approximately 111 separate storms occur each year. A snowpack usually persists
from mid-December until mid-April, with a peak depth in March of about 1,020
to 1,270 mm, having about 250 to 300 mm of water content. January averages
about –9oC, and long periods of low temperatures from –12oC to
–180C are common. The average July temperature is 18oC. The average
number of days without killing frost is 145; however, the growing season for
trees is considered to be from 15 May to 15 September. The estimated annual
evapotranspiration is about 500 mm.
Soils at
Hubbard Brook are predominantly well-drained Spodosols, more specifically,
Typic Haplorthods, derived from glacial till, with sandy loam textures. There
are no residual soils. These soils are acidic (pH about 4.5 or less) and relatively
infertile (base saturation of mineral soil ~ 10%). A 20- to 200-mm thick forest
floor layer is present, except where the soil surface has been disturbed by
fallen trees. Soil depths, including unweathered till, average about 2.0 m
surface to bedrock, although this is highly variable. Soil on the ridgetops
may consist of a thin accumulation of organic matter, resting directly on
bedrock. The separation between the pedogenic zone and the virtually unweathered
till and bedrock below is distinct. Depth to the C horizon averages about
0.6 m. At various places in HBEF, the C horizon exists as an impermeable pan.
Rocks of all sizes are scattered throughout the soil profile. In many locations
boulder fields are prominent features.
The area is entirely forested, mainly with deciduous northern hardwoods: sugar maple (Acer saccharum), beech (Fagus grandifolia), and yellow birch (Betula allegheniensis), and some white ash (Fraxinus americana) on the lower and middle slopes. Other less abundant species include mountain maple (Acer spicatum), striped maple (Acer pensylvanicum), and trembling aspen (Populus tremuloides). Red spruce (Picea rubens), balsam fir (Abies balsamea), and mountain paper birch (Betula papyrifera var. cordifolia) are abundant at higher elevations and on rock outcrops. Hemlock (Tsuga canadensis) is found along the main Hubbard Brook. Pin cherry (Prunus pensylvanica), a shade intolerant species, dominates all sites for the first decade following a major forest disturbance. Logging operations ending around 1915-1917 removed large portions of the conifers and better quality, accessible hardwoods. The present second-growth forest is even-aged and composed of about 80 to 90% hardwoods and 10 to 20% conifers.
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.
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![]() Watershed 2 |
![]() Watershed 4 |
![]() Watershed 5 |
Experimental manipulation is a research approach that has been used extensively at Hubbard Brook. A number of whole watershed, stream and lake manipulations have been conducted to test research hypotheses, obtain quantitative information on pertinent environmental issues and to validate process-related formulations used in simulation models. Whole ecosystem manipulations conducted at Hubbard Brook include:
Watershed | Size (ha) | Year Gauged | Treatment |
1 | 11.8 | 1956 | Calcium manipulation in 1999. About 1.2 metric tones/ha of calcium (as wollastonite CaSiO3) applied. |
2 | 15.6 | 1957 | Clear felled in winter 1965-66; no products removed; treated with herbicides summers of 1966, 1967, 1968. Left to regrow from 1969. |
4 | 36.1 | 1961 | Clear-cut to a 2 cm minimum diameter, by strips in three phases, 1970, 1972, 1974. Timber products removed. |
5 | 21.9 | 1962 | Whole-tree clear-cut to 5 cm diameter, 1983-1984. Timber products removed. |
6 | 13.2 | 1963 | None; biogeochemical reference watershed. |
101 | 12.1 | 1970 | Clear-cut to a 5 cm minimum diameter, as a block in 1970. Timber products removed. Note: streamflow quantity is not monitored, only water quality. |
The
Robert S. Pierce Ecosystem Laboratory provides 835 m2 of space, including
six offices, four laboratories, one conference room, six dormitory rooms,
a kitchen, baths and showers. A sample archive building was constructed in
1990 to house and archive samples of soil, water, plant tissue, and other
materials. In addition, there are 280 m2 of maintenance, storage, garage and
shop facilities. There are 16 km of gravel roads within the Experimental Forest.
A trail system allows access to major research installations such as precipitation
stations.