Changes in conifer and deciduous forest foliar and forest floor chemistry and basal area tree growth across a nitrogen (N) deposition gradient in the northeastern US.
Authors:
Boggs, J.L. McNulty, S.G. Pardo, L.H. USDA, FS
Source:
Environmental pollution. 2007 Oct., v. 149, issue 3, p. 303-314.
NALT Subjects:
coniferous forests deciduous forests leaves bioaccumulation nitrogen atmospheric deposition air pollution forest litter forest trees tree growth basal area Picea rubens growing season air temperature nitrification dead wood biogeochemical cycles conifer needles climatic factors immobilization in soil temporal variation soil chemical properties mineralization montane forests forest ecology Northeastern United States
Issue Date:
Oct-2007
Abstract:
We evaluated foliar and forest floor chemistry across a gradient of N deposition in the Northeast at 11 red spruce (Picea rubens Sarg.) sites in 1987/1988 and foliar and forest floor chemistry and basal area growth at six paired spruce and deciduous sites in 1999. The six red spruce plots were a subset of the original 1987/1988 spruce sites. In 1999, we observed a significant correlation between mean growing season temperature and red spruce basal area growth. Red spruce and deciduous foliar %N correlated significantly with N deposition. Although N deposition has not changed significantly from 1987/1988 to 1999, net nitrification potential decreased significantly at Whiteface. This decrease in net potential nitrification is not consistent with the N saturation hypothesis and suggests that non-N deposition controls, such as climatic factors and immobilization of down dead wood, might have limited N cycling. Data from the 1999 remeasurement of the red spruce forests suggest that N deposition, to some extent, is continuing to influence red spruce across the northeastern US as illustrated by a significant correlation between N deposition and red spruce foliar %N. Our data also suggest that the decrease in forest floor %N and net nitrification potential across sites from 1987 to 1999 may be due to factors other than N deposition, such as climatic factors and N immobilization in fine woody material (<5 cm diameter).
