Contents
I.
II.
III.
IV.
V.
History of Hubbard Brook
Watershed Concept
Discovery of Acid Rain
Long-term Monitoring
Ecosystem Recovery
I. History of Hubbard Brook
I. 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
II. Watershed concept
This analyzes
the relationship
between the
amount and
timing of
inputs
&
outputs
from forested
watersheds.
Hubbard Brook Acid Rain Story: Part 1
The northern forest can be
viewed as
a network of watersheds,
which all have
input-output relationships.
II. Watershed concept
Inputs
Water: rain, snow,
fog droplets
Nutrients
Wet deposition:
dissolved in water
Dry deposition: dust
particles, gases
Mineral weathering:
chemicals from soil
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.
II. Watershed concept
HBES researchers began looking at
the chemistry of
rain and snow
(inputs)
compared to
the chemistry of
streams.
(outputs)
III. Discovery of Acid Rain
HBEF researchers measured pH
(the measure of acidity and alkalinity)
From Acid Rain Revisited, pg. 5
Hubbard Brook Acid Rain Story: Part 1
III. Discovery of Acid Rain
In 1963, Drs. Likens, Bormann and Johnson noticed
something strange about the pH of the rain at Hubbard
Brook Experimental Forest.
Normal rain has a pH of about 5.2, but rain at HBEF had
pH levels of 4.0 to 4.2 - very acidic.
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
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
This led to the question:
Where was the acid rain
coming from?
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,
And
The Clean Air Interstate Rule of 2005
include reductions in sulfur emissions.
IV. Long-term Monitoring
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 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.
V. Ecosystem Recovery
• Chemical recovery
– Occurs first
– Defined by chemical
characteristics of
streams and soils
Hubbard Brook Acid Rain Story: Part 1
• 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 Recovery
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.
For more information on the role of the Hubbard
Brook Ecosystem Study in acid rain research,
please view the next slideshow.
The Hubbard Brook Acid Rain Story
Part II: The Calcium Experiment
For more information on acid rain, see…
Acid Rain
Revisited,
a Science Links
publication by
the Hubbard Brook
Research
Foundation
www.hubbardbrookfoundtion.org