Estimation of vegetation clumping index using MODIS BRDF data

Abstract

The foliage clumping index quantifies the degree of the deviation of leaf spatial distribution in the canopy from the random case. It is of comparable importance for ecological models as the leaf area index for quantifying radiation interception and distribution in plant canopies. Previously, an improved angular index named normalized difference between hotspot and darkspot was proposed for retrieving the clumping index using multi-angle remote sensing data. Global maps of clumping index have been derived successfully from multi-angular Polarization and Directionality of Earth Reflectance (POLDER) data at ∼6 km resolution. In this article, we investigate whether it is feasible to derive the clumping index at 500 m resolution with the 16-day Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function model parameters product. The results are compared with an assembled set of field measurements from 63 different sites, covering five continents and diverse biomes.

Acknowledgements

This study was supported by the funding from FP7-REGPOT, No. 204727 EstSpacE. MODIS MCD43 BRDF product tiles were acquired from Land Processes Distributed Active Archive Center (LP DAAC). We thank Drs. Alemu Gonsamo, Lucie Homolova, Sylvain Leblanc, Kenlo Nishida Nasahara and Andrew Richardson for sharing their data. Dr. Crystal Schaaf provided constructive comments. The authors also thank two anonymous reviewers and the editor for their constructive feedback.