HR: 1340h
AN: B43C-1457    [Abstracts]
TI: Integrating eddy covariance estimates of GPP, LUE, and airborne lidar estimates of fPAR for local to regional scaling and assessment of GPP from MODIS
AU: * Chasmer, L
EM: lechasme@yahoo.ca
AF: Dept. of Geography, Queen's University, McIntosh-Corry Hall, Kingston, ON K7L 3N6, Canada
AU: McCaughey, H
EM: mccaughe@post.queensu.ca
AF: Dept. of Geography, Queen's University, McIntosh-Corry Hall, Kingston, ON K7L 3N6, Canada
AU: Treitz, P
EM: paul.treitz@queensu.ca
AF: Dept. of Geography, Queen's University, McIntosh-Corry Hall, Kingston, ON K7L 3N6, Canada
AU: Barr, A
EM: alan.barr@ec.gc.ca
AF: Climate Research Branch, Meteorological Service of Canada, 11 Innovation Blvd, Saskatoon, SK S7N 3H5, Canada
AU: Black, A
EM: andrew.black@ubc.ca
AF: Faculty of Land and Food Systems, University of British Columbia, 135-2357 Main Mall, Vancouver, BC V6T 1Z4, Canada
AU: Hopkinson, C
EM: chris.hopkinson@nscc.ca
AF: Applied Geomatics Research Group, Centre of Geographic Sciences, 50 Elliott Rd, Lawrencetown, NS B0S 1M0, Canada
AU: Shashkov, A
EM: alexander.shashkov@ec.gc.ca
AF: Meteorological Service of Canada, Environment Canada, 4905 Dufferin St., Downsview, ON M3H 5T4, Canada
AB: The adequate representation of within-pixel heterogeneity is essential for the extrapolation of CO2 and water fluxes from the canopy to regional and global scales. In this study, we use small-footprint, discrete-pulse-return airborne light detection and ranging (lidar) data to estimate spatial and temporal variation of gross primary productivity (GPP) across a post-harvest jack pine chronosequence in Saskatchewan, Canada. GPP is estimated from lidar-derived fraction of photosynthetically active radiation absorbed by the canopy (fPAR), measured incoming PAR radiation, and two light use efficiency (LUE) terms. The first GPP model uses maximum LUE based on species type and age and the second is based on the relationship between vegetation fractional cover from lidar and decreasing LUE. Both are controlled using meteorological driving mechanisms. The results are compared with eight-day products from the Moderate Resolution Imaging Spectroradiometer (MODIS) at the flux tower MODIS pixel level. In order to understand better some of the biases associated with scaling, we use GPP estimates from lidar to scale from pixel resolutions of 1 m to 25 m, 250 m, 500 m, and 1000 m, within both homogeneous and heterogeneous areas. Species and age-based LUE models are an improvement over biome-based LUE models used within the MODIS GPP algorithm. Differentiation between cloudy periods with diffuse shortwave radiation and sunny days with direct shortwave radiation also improve GPP estimates using species and age-based maximum LUE. Where maximum LUE models are not available per species and age class, increasing fractional cover of vegetation can be used to reduce LUE. When compared with measured GPP from EC for pixels containing towers, MODIS tends to over-estimate GPP by less than 30% at the mature jack pine site, but becomes more biased with decreasing age and increasing site heterogeneity. Increasing site heterogeneity creates biases when scaling GPP from 1 m to 1 km resolutions, especially as a result of land cover patch edges and differences (e.g. patches of forest and patches of cleared land within a single MODIS pixel).
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: 2007 Fall Meeting