HR: 1340h
AN: H13C-0445    [Abstracts]
TI: Estimating Leaf Area Index in Forests Using Airborne Laser Swath Mapping Data
AU: * Slatton, K C
EM: slatton@ece.ufl.edu
AF: University of Florida Dept. of Electrical and Computer Engineering, PO Box 116130, Gainesville, FL 32611 United States
AU: * Slatton, K C
EM: slatton@ece.ufl.edu
AF: University of Florida Dept. of Civil and Coastal Engineering, PO Box 116580, Gainesville, FL 32611 United States
AU: Kampa, K
EM: kittipat@ufl.edu
AF: University of Florida Dept. of Electrical and Computer Engineering, PO Box 116130, Gainesville, FL 32611 United States
AU: Lee, H
EM: fields@ecel.ufl.edu
AF: University of Florida Dept. of Electrical and Computer Engineering, PO Box 116130, Gainesville, FL 32611 United States
AB: In recent years airborne laser swath mapping (ALSM) has enabled topographic mapping at the several centimeter scale with meter scale horizontal sampling. ALSM has made it possible, for the first time, to study three-dimensional foliage structure on spatial scales extending from meters to tens of kilometers in a consistent geodetic frame of reference. A multiscale filter has been developed to separate ALSM returns from ground and vegetation over forests using statistical decision theory methods. As a result, it is possible to calculate probabilities of laser light interception by the canopy and by the ground, enabling a direct estimation of leaf area index (LAI) as a function of sample density. Most ALSM systems employ small laser footprints (less than 1 m diameter) to approximate point-to-point range measurements. As a result, individual tree canopies can often appear effectively opaque to a single laser shot. The ground is only detected when some fraction of the transmitted laser pulses pass through naturally occurring gaps in the canopy and intercept the surface (known as ground shots). LAI is an important parameter for understanding forest hydrologic processes because it impacts evaporation and transpiration rates, as well as the interception of precipitation. As with attempts to estimate LAI using microwave and multispectral data, ALSM-based estimates can suffer from saturation when extremely dense tree crowns occlude lower canopy layers. However, the high-resolution three-dimensional ALSM measurements allow for improved modeling of the discrete structure of the forest canopy, which makes it possible to characterize the saturation phenomenon. Simulated ALSM data and ground truthing are used to characterize the accuracy of LAI estimates from ALSM data acquired over mixed deciduous/coniferous forests of the Southeastern United States and to determine the estimation error caused by the saturation phenomenon as a function of canopy parameters.
DE: 1894 Instruments and techniques
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting