PARENT SESSION
Contributed Oral Session 32: Soil Nutrient Dynamics and Acid Deposition
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal
Atmospheric deposition, soil nutrient availability and the composition of northeastern U.S. forests.
Finzi, Adrien*,1, Zaccherio, Meredith1, 1 Boston University, Boston, MA
ABSTRACT- The input of nitrogen (N) via atmospheric deposition to northeastern US forests has increased rapidly since the onset of the industrial revolution. During the same period of time, inputs of acids in precipitation leached substantial quantities of base cations (i.e. calcium, magnesium) from soil. With the enactment of the clean air act, acid-precipitation inputs to northeastern forests declined as did the deposition of base cations. From a historical perspective, these processes have left northeastern forests rich in N but poor in calcium (Ca). We studied the potential consequences of these changes in nutrient availability for forest composition by transplanting seedlings of four species into replicate plots in the understory and in canopy gaps amended with N and Ca in factorial combination. The growth and survivorship of seedlings was followed over four years from 2000 through 2004. Increasing N availability increased the growth rate and survivorship of red maple and sugar maple seedlings, had no effect on the growth or survivorship of red oak and significantly decreased the survivorship of white pine. Increasing calcium availability increased survivorship in all species but only the growth rate of sugar maple. Changes in soil nutrient availability caused by changes in atmospheric chemistry are therefore likely to alter forest composition. Increasing N deposition is likely to reduce the abundance of white pine through its negative effects on the survivorship of this species. The loss of calcium from soils is likely to reduce the abundance of red oak in forest communities as suggested by significantly higher rates of seedling mortality in unfertilized plots (i.e. Ca poor forest soils). Red maple and sugar maple may increase in abundance because the negative effects of Ca loss on growth and survivorship were offset by enhanced seedling performance with increasing in N availability.
Key words: Global Change, Forest Ecology, Nitrogen, Calcium