30
Contents
I. History of Hubbard Brook
II. Watershed Concept
III. Discovery of Acid Rain
IV. Long-term Monitoring
V. Ecosystem Recovery
I. History of Hubbard BrookI. History of Hubbard Brook
The Hubbard Brook Experimental Forest was established by the U.S.D.A. Forest Service in 1955 to study how water flows through forests (hydrology).
I. History of Hubbard Brook
The Hubbard Brook Ecosystem Study was founded by in 1963 by Dr. Robert S. Pierce of the USDA Forest Service and Drs. Gene E. Likens, F. Herbert Bormann, and Noye M. Johnson, of Dartmouth College.
Dr. G.E. Likens and Dr. F.H. Bormann, 2003 Not pictured: Dr. R.S. Pierce, Dr. N.M. Johnson
I. History of Hubbard Brook
Likens, Bormann, Johnson and Pierce pioneered cooperative research to study nutrient cycling, which is how elements and nutrients move through forests.
This is called biogeochemistry (the integration of biology, geology and
chemistry).
In 1967 the keystone scientific paper of the Hubbard Brook Ecosystem Study was published in the journal Science by
Drs. Bormann and Likens:
Bormann, F. H. and G. E. Likens. 1967. Nutrient cycling. Science 155(3761):424-429
I. History of Hubbard Brook
This analyzes the relationship
between the amount and
timing of
inputs&
outputs
from forested watersheds.
II. Watershed conceptII. Watershed concept
Hubbard Brook Acid Rain Story: Part 1
The northern forest can be viewed as
a network of watersheds, which all have
input-output relationships.
Water: rain, snow, fog droplets
Nutrients
Wet deposition: dissolved in water
Dry deposition: dust particles, gases
Mineral weathering: chemicals from soil
II. Watershed concept
Inputs Outputs
Water: streams
Evapotranspiration
Nutrients
(water)
(gases), CO2, N
Looking at
inputs compared to outputs
gives you a sense of what’s happening chemically
inside the forest.
HBES researchers began looking at
the chemistry of rain and snow
(inputs)
compared to
the chemistry of streams.
(outputs)
II. Watershed concept
HBEF researchers measured pH (the measure of acidity and alkalinity)
From Acid Rain Revisited, pg. 5
III. Discovery of Acid RainIII. Discovery of Acid Rain
Hubbard Brook Acid Rain Story: Part 1
In 1963, Drs. Likens, Bormann and Johnson noticed something strange about the pH of the rain at Hubbard Brook Experimental Forest.
One rain sample had a pH of 2.85, less than that of orange juice!
These findings were published in the journal Environment in 1972: Likens, G.E., F.H. Bormann, and N.M. Johnson. 1972.
Acid Rain. Environment 14: 33-40.
III. Discovery of Acid Rain
Normal rain has a pH of about 5.2, but rain at HBEF had pH levels of 4.0 to 4.2 - very acidic.
Scientists had known for a while that industrial pollution
could result in rain that was acidic…
but the Hubbard Brook Experimental Forest is in the White Mountains of New Hampshire,
which is far from most pollution sources.
III. Discovery of Acid Rain
Where was the acid rain coming from?
This led to the question:
III. Discovery of Acid Rain
They realized that emissions from power plants and heavy industry in the mid-western U.S travelled to NH and
dropped with the rain and snow.
Hubbard Brook Research Foundation: Acid Rain Revisited
III. Discovery of Acid Rain
HBES scientists hypothesized that:
If industries reduced sulfur dioxide emissions from these plants, the pH of rain at the Hubbard Brook Experimental Forest (and the entire northeastern U.S.) would increase, or become less acidic.
III. Discovery of Acid Rain
Research done by HBES scientists helped inform the decision by
the U.S. Congress to cut back on sulfur emissions from power plants.
The Clean Air Act of 1970, The CAA Amendments of 1990,
AndThe Clean Air Interstate Rule of 2005
include reductions in sulfur emissions.
III. Discovery of Acid Rain
Long-term monitoring of precipitation and stream water chemistry was essential for
evaluating these laws.
To understand the effect of the legislation, we had to know:
• how the ecosystems behaved before the laws.
• how they behaved after the laws began to take effect.
IV. Long-term MonitoringIV. Long-term Monitoring
Long-term monitoring has shown that:
• Rain and snow pH are increasing gradually.– Precipitation is becoming less
acidic.
• Chemical and biological characteristics of the forest are responding more slowly.– Ecosystem recovery is delayed.
IV. Long-term Monitoring
• Chemical recovery– Occurs first– Defined by chemical
characteristics of streams and soils
• Biological recovery– Occurs after
chemical recovery– Most short-lived
organisms respond relatively quickly (like insects)
– Long-lived organisms may take decades to respond (like trees)
V. Ecosystem RecoveryV. Ecosystem Recovery
Hubbard Brook Acid Rain Story: Part 1
At the Hubbard Brook Experimental Forest and in much of the Northeast:
chemical and biological recovery thresholds have not been met,
so….acid rain is still a problem.
V. Ecosystem Recovery
Acid rain has changed the chemistry of soils at the HBEF
• Made soils more acidic.
• Accelerated the leaching of base cations (such as calcium and magnesium) from soils that help to buffer acidity.
• Increased inorganic aluminum in soil, which can be toxic to organisms.
• Caused sulfur and nitrogen to accumulate in soil.
V. Ecosystem Recovery
Acid rain has weakened trees’ ability to respond to stress.
V. Ecosystem Recovery
It has impacted lakes
and streams.
V. Ecosystem Recovery
Why has ecosystem recovery
been delayed?
More experimentation
and long-term monitoring
were needed
to find the answers.
V. Ecosystem Recovery
The Hubbard Brook Acid Rain StoryPart II: The Calcium Experiment
For more information on the role of the Hubbard Brook Ecosystem Study in acid rain research,
please view the next slideshow.
For more information on acid rain, see…
Acid Rain Revisited,
a Science Links publication by
the Hubbard Brook Research
Foundation
www.hubbardbrookfoundtion.org
