HR: 1340h
AN: B43D-1593    [Abstracts]
TI: Using narrowband vegetation indices to estimate ecosystem-atmosphere CO2 flux for a mixed hardwood forest
AU: * Garrity, S R
EM: sgarrity@uidaho.edu
AF: Geospatial Laboratory for Environmental Dynamics, College of Natural Resources, University of Idaho, Moscow, ID 83844-1135, United States
AU: Vierling, L A
EM: leev@uidaho.edu
AF: Geospatial Laboratory for Environmental Dynamics, College of Natural Resources, University of Idaho, Moscow, ID 83844-1135, United States
AB: The productivity of terrestrial ecosystems is a fundamental component in the global carbon cycle. While satellite data are increasingly relied upon to derive information on earth surface characteristics that affect biosphere- atmosphere interactions, such as carbon cycling, there remain substantial uncertainties in the estimates of vegetation productivity and related processes derived from these sensors. In order to reduce these uncertainties data are needed to better understand the relationship between narrowband reflectance of shortwave radiation by vegetation canopies and carbon exchange between these canopies and the atmosphere. We mounted a narrowband spectroradiometer approximately 26 m above a mixed forest canopy to quantify midday canopy reflectance while simultaneously measuring CO2 and radiation fluxes at the University of Michigan Biological Station Ameriflux site throughout the 2006 and 2007 growing seasons. Narrowband spectral vegetation indices (SVIs) were used as proxies for canopy structure and physiological function and regressed against flux measurements to assess their efficacy for predicting CO2 fluxes. We found that certain narrowband SVIs were well correlated with factors such as canopy light absorption (r2 = 0.97, p<0.0001) and light use efficiency (r2 = 0.73, p<0.0001). Furthermore, when these SVIs were combined in a simple model to predict gross carbon uptake, they explained much of the variability in midday Net Ecosystem Exchange (r2 = 0.87, p<0.0001). These results show that optical signals from remote platforms may be useful for scaling carbon exchange of mixed temperate forests to scales beyond that of an individual tower flux footprint.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: 2007 Fall Meeting