Introduction Page 9


Watershed Experiments

  • How do you think a forest responds to a type of logging in which all its trees were cut down and removed?
  • How is this response different from that of a forest in which trees were removed in wide strips - but the whole watershed was not cut at one time?
  • At the HBEF, acid rain has washed many nutrients out of forest soils. What would happen if these nutrients were added back to the soil?

    Using the "Small Watershed Approach," scientists at the HBEF have been trying to answer these and other questions by conducting experiments on the "experimental watersheds". On this page and the next, you will learn a little about each of these watersheds, the research conducted on them, and what it all means.


    First, take a look at this map and the photo. The photo shows Watershed 101 in the center with Watersheds 2 and 4 to the right. As you can see on the map, there are 10 marked watersheds, 9 of which have weirs (Watershed 101 does not have a weir).

    Seven of the watersheds are on one side of the Valley and face south; the other 3 are on the side that faces north. These watersheds were marked out so scientists could study forests and conduct experiments to see how entire watersheds respond to different types of disturbances and treatments.

    The Hubbard Brook Experimental Forest

    The watershed experiments:

    1. In the WS2 experiment, all trees in the watershed were cut down (but not removed), and a herbicide was applied for 3 years to inhibit vegetation regrowth. Scientists wanted to study how trees affect the biogeochemistry of northern hardwood forests, how ecosystems respond to deforestation and how plants affected water yield (i.e., if trees were cut down, would more water come out of the forest?).

    2. Watershed 4 (1970)

      In this watershed experiment, scientists cut down and removed all the trees in three different series of 25 meter-wide strips. Herbicide was not applied, because in this experiment scientists were interested in doing research on a certain type of logging technique.

    3. Watershed 5 (1983)

      All the trees in WS5 were cut and removed in a logging experiment designed to mimic real logging conditions. As with the other experiments, scientists were interested in learning how a disturbance like this would affect the forest in the watershed.

    4. Watershed 1 (1999)

      Over the past several decades, acid rain has been falling on HB and leaching calcium out of forest soils. Because it is important to plants, scientists are concerned that the decrease in available calcium may be negatively affecting plant growth. In an experiment designed to examine how lower soil calcium levels have affected northern hardwood forests, we added over 50 tons of calcium to an entire watershed.

         


    • To learn more about each of the watershed experiments, click here for a short tour of hypotheses, methods, and results.

    • Click on one of the links below to take a tour of one of the watersheds. These tours were designed for a college or college-educated audience, and are not part of this Introduction (they are part of the HB website). Use your browser's "Back" button to return to this page.
    • On the next page of this Introduction you will learn more about how scientists actually gather the data for these experiments.

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