PARENT SESSION
Contributed Oral Session 75: Biogeochemistry: Soil Chemical Flux
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 513 E, Level 5, Palais des congrès de Montréal
Scaling biogenic trace gas emissions from plots to regions: Effects of Morella faya (Fire tree) stand size on soil N2O and NOx fluxes in Hawaii Volcanoes National Park.
Hall, Sharon*,1, Asner, Gregory2, 1 Colorado College, Colorado Springs, CO2 Department of Global Ecology, Stanford, CA
ABSTRACT- Soils are estimated to be the largest natural source of nitrous oxide (N2O) and nitric oxide (NO) globally, but annual and regional budgets for these gases are limited by large variability in fluxes over space and time. We measured N-oxide emissions and soil N cycling in a range of tropical, montane ecosystems in Hawai'i Volcanoes National Park, including forests supporting native Ohia trees and the exotic N-fixer, Morella faya (Fire tree). In order estimate the effect of M. faya invasion on regional N-oxide fluxes, we sampled gases and soils in both in wet and dry forests that differed substantially in M. faya canopy area, and we used novel, airborne spectroscopic techniques and photon transport modeling to extrapolate emissions to the landscape scale. In wet forest sites, soil N transformations and fluxes of N-oxides were significantly higher under large, contiguous M. faya stands (2.2 ng N2O -N cm-2 h-1) compared to isolated M. faya trees (0.1 ng N2O cm-2 h-1). Fluxes from under isolated M. faya trees in wet forests did not differ from native Ohia stands (0.2 ng N2O -N cm-2 h-1). In contrast, presence but not size of M. faya patches significantly increased NO fluxes in dry forests, but neither had any effect on soil N2O emissions compared to Ohia. Our results suggest that the combined use of ground-based measurements, modeling, and remote sensing techniques will help to refine regional estimates of N-oxide emissions from soils.
Key words: Morella faya, Nitrous oxide, tropical, scaling