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ANALYSIS OF YEAR 2002 SEASONAL FOREST DYNAMICS USING TIME SERIES IN SITU LAI MEASUREMENTS AND MODIS LAI SATELLITE PRODUCTS
Citation:
Pilant, A, J. Iiames, R S. Lunetta, T E. Lewis, AND J. Ediriwickrema. ANALYSIS OF YEAR 2002 SEASONAL FOREST DYNAMICS USING TIME SERIES IN SITU LAI MEASUREMENTS AND MODIS LAI SATELLITE PRODUCTS. Presented at Conference on Spectral Remote Sensing of Vegetation, Las Vegas, NV, December 3-5, 2002.
Impact/Purpose:
Our research objectives are to: (a) develop new methods using satellite remote sensor data for the rapid characterization of LC condition and change at regional to national scales; (b) evaluate the utility of the new NASA-EOS MODIS (Moderate Resolution Imaging Spectrometer) leaf area index (LAI) measurements for regional scale application with landscape process models (e.g., biogenic emissions and atmospheric deposition); (c) provide remote sensor derived measurement data to advance the development of the next generation of distributed landscape process-based models to provide a predictive modeling capability for important ecosystem processes (e.g., nutrients, sedimentation, pathogens, etc.); and (d) integrate in situ monitoring measurement networks with UAV and satellite based remote sensor data to provide a continuous environmental monitoring capability.
Description:
Multitemporal satellite images are the standard basis for regional-scale land-cover (LC) change detection. However, embedded in the data are the confounding effects of vegetation dynamics (phenology). As photosynthetic vegetation progresses through its annual cycle, the spectral signals of the landscape change. This research seeks to incorporate vegetation phenology as a tool for improving LC change detection. The Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Terra spacecraft provides two geophysical products used in this analysis: Normalized Difference Vegetation Index (NDVI: MOD I 3Q 1) and Leaf Area Index (LAI: MOD I 5A2). NDVI is related to ecosystem state, and LAI is an important input to ecosystem and landscape process models. LAI is of interest as an input to landscape process and biogenic volatile organic compounds emissions models. The U.S. Environmental Protection Agency (EPA) has established a number of long-term forest research sites in the Piedmont and Coastal Plain of the Albemarle-Pamlico Basin of North Carolina and Virginia (USA) to establish in situ reference data for validation of satellite geophysical products (e.g., NDVI and LAI). At each site, we conduct biophysical surveys of vegetation species composition and landscape characteristics, as well as time series optical surveys of LAI at various phenotogical stages. LAI is estimated indirectly using combined hemispherical photography and TRAC (Tracing Architecture and Radiation of Canopies) instrument optical surveys arranged in permanent grids and transacts. This report focuses on the architectural rather than spectral aspects of remote sensing of forest canopy. We present results of an analysis of in situ and MODIS LAI time series data for 2002.