PARENT SESSION
Contributed Oral Session 19: Modeling: Movement and Population Dynamics
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 513 A, Level 5, Palais des congrès de Montréal
Modeling ecosystem carbon fluxes with optical remotely sensed data at leaf and ecosystem scales.
Cheng, Yufu*,1, Gamon, John1, Sims, Dan2, Claudio, Helen1, Luo, Hongyan3, Oechel, Walter3, 1 Department of Biological Sciences, Los Angeles, CA, USA2 Department of Geography, Muncie, IN, USA3 Global Change Research Group, San Diego, CA, USA
ABSTRACT- Monitoring carbon fluxes in different terrestrial environments is essential for understanding the contribution of these environments to the global carbon cycle. Using field based optical remotely sensed data, a light use efficiency model was applied to optical data from Sky Oaks, a Southern California chaparral ecosystem in the SpecNet and FluxNet networks. The study covered a five-year period (2000-2004), which included a severe drought in 2002 and a subsequent wildfire in July 2003. Two vegetation indices (Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI)) from field measurement were used to derive the fraction of photosynthetically active radiation absorbed by vegetation (fPAR) and light use efficiency. Meteorological data (e.g. photosynthetically active radiation (PAR) ) were acquired from the eddy tower (temporal rich, half-hourly) and tram measurement (spatial rich, every meter). Two modeling approaches were used to model carbon fluxes. One is that the ecosystem was treated as a big leaf. The vegetation indices from the tram were applied to the regression model from leaf level analysis to model the ecosystem carbon fluxes. The other approach treated the ecosystem as a two-layer systems (plant and soil). The land cover analysis was done by spectral mixture analysis to separate the land cover into plant and soil. The plant-atmosphere carbon fluxes were modeled using the same algorithm as the big leaf model and the soil fluxes were modeled using soil temperature and soil moisture. The modeled results were validated by the flux tower measurement. The modeled carbon flux showed that the big leaf approach model agreed with eddy fluxes before fire during the normal season, while the relationship broke down when the ecosystem experienced perturbation (severe drought and fire). The two-layered system modeling approach worked well at all the seasons, especially after fire.
Key words: Carbon flux, Remotely sensed data, Modeling, Scale