Soil carbon estimation from eucalyptus grandis using canopy spectra
Mapping soil fertility parameters, such as soil carbon (C), is fundamentally important for forest management and research related to forest growth and climate change. This study seeks to establish the link between Eucalyptus grandis canopy spectra and soil carbon using raw and continuum-removed spectra. Canopy-level spectra were collected using a hand-held 350-2500nm spectroradiometer and soil samples obtained at depths from 0-1.2m and analysed for carbon content. Partial least squares (PLS) selection was used to selected optimal bands for soil carbon assessment and further bootstrapped to select 35 Variable Importance in Projection (VIP) parameters, based on correlation (r) and standard error (SE). Results indicated that continuum-removed spectra and soil C yielded stronger significant correlations, when compared to soil C and raw spectra. The predictive models developed for future soil C estimation showed that continuum-removed spectra exhibited improved adjusted R2 values in both instances, i.e., when using all significant bands and the most significant 35 VIP bands. The results indicate a distinct potential for forest managers to monitor the status of soil C in commercial forestry compartments using canopy-level spectra and determine how much fertilizer is required to optimize tree growth.
Keywords: Soil carbon, Canopy spectra