STUDENT INSTRUCTIONS

For homework study the Hubbard Brook Experiment figure on your own*. In class you will work in pairs or small groups with other students to better understand the results and how/why the scientists did this research.

The Hubbard Brook clear-cut experiment is probably the most quoted ecosystem-scale study. Herb Bormann and Gene Likens chose this region of the White Mountains in New Hampshire because the Hubbard Brook Experimental Forest could be partitioned into reasonable sized, discrete watersheds drained by obvious streams. Impermeable bedrock beneath the site allowed the researchers to conduct input/output measurements by sampling precipitation and stream water at the base of the watersheds. For this study they monitored plant nutrient (calcium, potassium, nitrate) loss from the 6 watersheds by placing a V-notched weir across the stream exiting a watershed; the weir created a small dam and stream gauges continuously measured flow and water height. Water samples collected at the notch gave an integrated measure of nutrient loss from the watershed.

In the Watershed 2 study, all vegetation was cut during fall and winter of 1965; herbicide (Bromacil) applied for 3 years inhibited regrowth. They measured concentration of major ions in stream water before and after deforestation, including the years when herbicide was used. See the figure legend for more details about their methods.

*Use the step one-step two approach we have practiced in class. In step one you first figure out how the figure or table is set up (e.g. what the labels on the axes mean). You also need to have a pretty good idea of the experimental design — how the scientists set up the experiments — and the hypotheses they addressed. In step two you can continue on and interpret the data. For both steps write down any questions you have.