In 1965, researchers deforested a New Hampshire basin, revealing dramatic increases in streamflow and nutrient levels, reshaping ecological understanding.
Deforestation experiment in New Hampshire
Between November 18 and December 31, 1965, researchers removed all vegetation from Basin 2 of Hubbard Brook in New Hampshire, which covers 15.6 hectares. The area was chosen for an ecological study to examine the effects of deforestation on streamflow and nutrient cycles.Streamflow increase observed
The deforestation led to a streamflow that exceeded expected levels by 39 percent in the first year, according to a study published in 1970 in Ecological Monographs. The study compared Basin 2 with Basin 6, a neighboring area left intact as a control.Experimental conditions
The experiment took place while the ground was covered with at least 30 cm of snow, and the cut trees were not removed from the basin. Stems and branches were reduced to a maximum height of 1 meter. Herbicides were applied during the growing seasons of 1966, 1967, and 1968 to prevent regrowth.Nutrient levels rise sharply
The study found that nitrate concentrations rose up to 56 times their original level in the second year, above the recommended health levels for drinking water almost constantly. Other elements showed significant increases, with average increases of 417 percent for calcium and 408 percent for magnesium.Long-term effects and repetition
The setup was not isolated. The Hubbard Brook teams repeated whole-basin deforestation experiments in 1974-1976 and again in 1983, and a later study notes significant increases in nitrate flux each time. This same study attributes these increases to reduced plant absorption, as well as increased mineralization and nitrification in the slope soils.
