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. Watershedconcept 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 Outputs Water: rain, snow, fog droplets Nutrients Wet deposition: dissolved in water Dry deposition: dust particles, gases Mineral weathering: chemicals from soil Water: streams Evapotranspiration Nutrients (water) (gases), CO2, N

Looking at inputs compared to outputsgives 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.

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 Recovery Hubbard Brook Acid Rain Story: Part 1

V. Ecosystem Recovery At the Hubbard Brook Experimental Forest and in much of the Northeast:chemical and biologicalrecovery 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 recoverybeen 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

Acid Rain Revisited, a Science Links publication by the Hubbard Brook Research Foundation www.hubbardbrookfoundtion.org For more information on acid rain, see…

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