Hubbard Brook sandbox experiment

Ecology 74(2), March 1993, 583-598 reports on the 5-year sandbox experiment at the Hubbard Brook Experimental Forest in New Hampshire. Sandboxes, or lined pits filled with homogenized soil, sand, and topsoil, were planted with a variety of tree species, primarily in order to assess nitrogen fixation. One sandbox was kept unvegetated, and it lost 4 tons per ha per yr of soil organic matter, or 2 T C if we assume that soil organic matter is 50% carbon by weight. Sandboxes planted with red or pitch pine seedlings lost half that, or 1 T C per ha per yr.

The study concluded that nitrogen deposition or leaching was unimportant compared to biological nitrogen fixation.