PARENT SESSION
Poster Session #18: Remote Sensing and GIS.
Tuesday, August 7, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
91
Detecting age of Southern California chaparral stands with spectral reflectance.
Schmidts, Miriam1, Sims, Daniel1, Zutta, Brian1, Qiu, Hong1, Gamon, John1, 1
ABSTRACT- Frequent fires in Southern California chaparral vegetation lead to a mosaic of differently aged stands, which vary in species composition, biomass and photosynthetic activity. This study explored the ability of remote sensing to detect the age of chaparral vegetation at the canopy scale. Using a field spectrometer the spectral reflectance of stands aged 0, 3, 20 and more than 40 years was measured at 1-meter intervals along 100-meter transects over a full year. Since we found that existing spectral reflectance indices are limited in their ability to distinguish stand ages, we explored alternative indices that represent the structural and physiological differences between stand ages. Principal component and discriminant analyses were used to determine the wavelengths that account for most of the variability between ages in a given season. The results of both analyses agree that the green (500-600 nm) and the red/near-infrared (650-800 nm) spectral regions best distinguish stand ages. The variability of the spectral signature across seasons provides an additional distinguishing factor between stand ages. An index combining those spectral regions as well as the annual variability within ages efficiently separates stand ages and is an improvement over the use of conventional spectral reflectance indices. This index can be used to map stand age from airborne imagery.
KEY WORDS: stand age, reflectance index, green & red/near-infrared spectral regions, annual variability