PROCEEDINGS: Index of Abstracts
BIOGEOCHEMICAL CYCLING OF CARBON, NITROGEN, AND
SULFUR AT THE HOWLAND INTEGRATED FOREST STUDY SITE, HOWLAND, MAINE
Assistant Research Professor, Professor of Forest
Soils, Research Associate Professor Emeritus of Climatology, Faculty
Associate, and Associate Professor of Soil Microbiology, respectively,
Department of Applied Ecology and Environmental Sciences, 5722 Deering
Hall, University of Maine, Orono, ME 04469-5722.
The biogeochemistry of C, N, and S was studied for six years at
the Howland Integrated Forest Study (HIFS) site by measuring those
constituents in major above- and below-ground pools and fluxes.
Leaching losses of C from the solum were much less than CO2
efflux, with a mean annual leaching rate of 31.2 kg ha-1
yr-1. Carbon return to the forest floor via litterfall
and outputs via CO2 efflux were relatively equal. Mean annual total
(wet+plus) atmospheric deposition inputs were 5.51 kg ha-1
yr-1 for NO3-N, 2.64 kg ha-1 yr-1
for NH4+N, and 8.09 kg ha-1 yr-1 for SO42-S;
wet deposition inputs for C were 6.67 kg ha-1 yr-1.
Sulfur-deposition, in the form of SO2 dry deposition, and SO42-
in wet deposition showed significant decreasing temporal trends
during the six year study period. There were no significant temporal
trends for NO3- in neither dry nor wet deposition. Wet deposition
of NH4+, however, showed a significant decreasing pattern through
the study period. Decreases in precipitation chemical flux was likely
the result of decreases in precipitation volume through the study
period because no significant decreases in concentration of SO42-
or NH4+ occurred. There was a net ecosystem retention of NO3- and
NH4+, attributable to the N-deficiency of this forest. Mean annual
input-output for SO42-, however, was near zero for the study period,
indicating the conservative behavior of that ion in this ecosystem.
Ongoing research is attempting to further define the temporal trends
in C, N, and S cycling, and to determine the mechanisms controlling
these characteristics including the effects of temperature and moisture.