Document: MIR-3-89-8

Characterizing stand age of California chaparral using multi-scale remote sensing.

SCHMIDTS, M.J.*, D.KOHN, D.A.SIMS, H.QIU and J.A.GAMON

California State University, Los Angeles, CA 90032-8524 USA ¹

Abstract:
A full understanding of the carbon cycle would benefit from simple methods to determine stand age from remote sensing. Using reflectance at 3 scales (leaf, stand, and landscape), we explored the ability of several spectral indices to distinguish physiological differences associated with stand age of chaparral vegetation of Southern California. These indices included NDVI (a "greenness" index), WBI (a measure of water content), and PRI (a measure of xanthophyll cycle activity and relative photosynthetic rate). Landscape images were obtained from NASA's AVIRIS sensor and leaf and stand scale measurements were made with a field spectrometer. Preliminary results show that WBI and NDVI increase with stand age at the canopy scale but not at the leaf scale, revealing the effect of canopy structure on spectral reflectance. When correlating the NDVI and WBI across stand ages we found a good correlation (R²=0.8) with an increasing slope between three and twenty year old sites indicating that combinations of these indices can detect different stand ages. At the leaf scale both PRI and photosynthesis decreased with stand age supporting the hypothesis that optical sampling can detect physiological differences associated with stand age. Further work will include a more thorough analysis of seasonal and scaling effects.

Keywords: remote sensing, stand age, spectral indices, photosynthesis

This abstract is being presented at: 10:30 AM in session:
REMOTE SENSING