Integrated Forest Study (IFS): Atmospheric Deposition and Forest Nutrient Cycling: Oak Ridge Loblolly Site

The Integrated Forest Study (IFS) was a project to evaluate the
effects of atmospheric deposition on nutrient cycling in forest
ecosystems. Deposition and nutrient cycling were monitored at 17
forested sites in the northwestern, northeastern, and southeastern
United States and in Canada and Norway. The IFS was primarily funded
by the Electric Power Research Institute (EPRI).

The Oak Ridge Loblolly Pine site was located on the U.S. Department of
Energy Reservation, National Environmental Research Park, near Oak
Ridge, Tennessee. The site consisted of loblolly pine with an
understory of red maple, yellow poplar, black cherry, and dogwood. The
ground cover consisted of extensive grass with patches of blackberry
and honeysuckle. The site was located on an alluvial soil derived from
shale on one of the upper terraces of the Clinch River.

Data collected included biomass and nutrient content of the overstory,
understory, floor, and soils; atmospheric deposition, throughfall,
stemflow, and soil solution fluxes for major ions; organic matter and
nutrient fluxes; and atmospheric concentrations of ions from wet and
dry deposition.

Data on atmospheric chemistry and wet deposition were collected on an
event basis throughout the year. Nutrient cycling data were collected
at or adjacent to the study area. Wet deposition of all major ions was
collected with automatic collectors. Atmospheric chemistry
measurements were made on an event basis using samplers situated on
5-10 m towers above the forest canopy. These measurements included:
(1) major ions in aerosols collected on teflon filters and in coarse
particles dry-deposited on inert plates; (2) sulfur dioxide (SO2) and
nitric acid (HNO3); and (3) ozone (O3) sampled continuously with UV
absorption detectors. Meteorological data were also collected
continuously from the towers including mean temperature, solar
radiation, relative humidity, wind direction and wind speed, and
precipitation amount.

The seasonal and annual input of ions in rain, throughfall, and
stemflow were calculated from the product of precipitation-weighted
mean ion concentrations in each solution and the hydrologic flux. Dry
deposition was calculated from the product of event mean air
concentrations and appropriate deposition velocities. Organic matter,
nitrogen (N), phosphorous (P), sulfur (S), potassium (K), calcium
(Ca), and magnesium (Mg) contents of vegetation, forest, and floor,
and soils and nutrient fluxes via litterfall, throughfall, and soil
solution were estimated. Aboveground vegetation biomass was estimated
from regression equations. Forest floor mass was determined by random
destructive sampling and soil nutrient content was estimated.
Litterfall was collected in traps and analyzed for nutrient content.
Bulk throughfall was collected and analyzed and stemflow was collected
using collar methods. Soil solutions were collected by means of
tension lysimeters.

At the LP Site, deposition of H2O, and ions of SO4, NO3, Cl, H2PO4, H,
NH4, K, Na, Ca, Mg, Al in solution, organic nitrogen, weak acidity,
and alkalinity were measured from vapors, and fine and coarse
particles (dry deposition) and from precipitation and fog/cloud (wet
deposition). Below canopy fluxes (throughfall flux, spatial
variability of throughfall fluxes, stemflow flux,
throughfall+stemflow, and net canopy exchange) were measured for each
element. Forest floor and soil solution fluxes were also measured for
each element.