PARENT SESSION
Poster Session #32: Plant Ecology I.
Wednesday, August 8, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Tests of soil calcium effects on forest dynamics in northeastern USA.

BIGELOW, SETH¹, CANHAM, CHARLES¹, ¹

ABSTRACT- Availability of surface soil calcium (Ca) may help determine species dynamics of forests. We fertilized individual saplings to test if Ca is limiting in oak-northern hardwood forest in NW Connecticut, USA. The trees studied were Acer saccharum, A. rubrum, Fagus grandifolia, Fraxinus americana, Quercus rubra, and Tsuga canadensis. Base-cation deficiency was tested for by adding salts of Ca, magnesium, or potassium; quantities equal to half the amount on the exchange complex were added over a two-year period. Aluminum toxicity was tested for by titrating sodium carbonate additions to elevate soil pH by one-half unit. Nitrogen (N) deficiency was tested for by adding Ca nitrate or salts of ammonium or nitrate at rates that provided half as much N as is mineralized over two years. Each fertilizer was applied to ~20 saplings of each species, and light availability was assessed with fish-eye photography. After two years there were two instances of increased radial growth: Ca increased growth of A. saccharum, and nitrate increased growth of F. americana. It was concluded that Ca availability helps determine recruitment success of an ecologically important species--A. saccharum--and that N availability, as commonly assumed, helps to determine recruitment success of other species.

KEY WORDS: nutrient limitation, recruitment, forest dynamics, base-cation deficiency