© 2000 Heron Publishing—Victoria, Canada
Use of middle infrared radiation to estimate the leaf area index of a boreal forest
Doreen S. Boyd (1), Toby E. Wicks (2) and Paul J. Curran (2)
1. Centre for Earth and Environmental Science Research, School of Geography, Kingston University, Penryhn Road, Kingston-upon-Thames,
Surrey KT1 2EE, U.K. / 2. Department of Geography, University of Southampton, Highfield, Southampton, Hampshire SO17 1BJ, U.K. / Received June 3, 1999
Summary
The leaf area index (LAI) of boreal forest can be estimated using reflected radiation recorded by satellite sensors. Measurements
of visible and near infrared radiation are commonly used in the normalized difference vegetation index (NDVI) to estimate
LAI. However, research, mainly in tropical forest, has demonstrated that LAI is related more closely to radiation of middle
infrared wavelengths than of visible wavelengths. This paper derives a vegetation index, VI3, based on radiation from vegetation
recorded at near and middle infrared wavelengths. For a boreal forest canopy, the relationship between VI3 and LAI was observed
to be much stronger than that between NDVI and LAI. In addition, the LAI estimated using VI3 accounted for about 76% of the
variation in field estimates of LAI, compared with about 46% when using the NDVI. We conclude that information provided by
middle infrared radiation should be considered when estimating the leaf area index of boreal forest.
Keywords:
LAI, middle infrared radiation, NDVI, remote sensing, VI3.
