Predicting leaf and canopy 15N compositions from reflectance spectra

Abstract

We explored whether 15N concentration could be predicted from reflectance spectra of fresh leaves, and, if so, whether the spectral features were related to the 15N concentration on a canopy scale. Leaf scale reflectance (R) measurements were conducted in Ghanzi, Botswana using a spectrophotometer in March 2005 and canopy scale leaf R was measured in a series of successional fields in Northern Virginia, USA using the same instrument in September 2005. Results showed that there was a strong correlation between foliar 15N concentration and spectral data in both visible and near-infrared wavelength regions. Stepwise regressions showed that the first-difference of the log1/R [(log 1/R)'] could explain 76 to 92% of the variation in foliar δ 15N, providing the most reliable correlations with foliar 15N at bands near 600 and 700 nm. The present study indicates the possibility of estimating fresh leaf 15N abundance from high-resolution reflectance at leaf and canopy levels. Copyright 2007 by the American Geophysical Union.