A comparative evaluation of spectral vegetation indices for the estimation of biophysical characteristics of Mediterranean semi-deciduous shrub communities

Abstract

Human civilizations have made intensive use of the Mediterranean Basin for millennia, resulting in a profound impact on the natural ecosystems. Nowadays, the drier zones with degraded soils are covered with drought semi-deciduous plant communities. The aim of this study was to compare the ability of various spectral vegetation indices (VIs) computed from a Landsat Thematic Mapper (TM) image to discriminate different vegetation biophysical parameters of these communities and thus to assess their capability to monitor long-term vegetation changes. It was found that although semi-deciduous plants display a spectral behaviour similar to that of semi-arid vegetation, VIs can estimate not only vegetation abundance but also changes in vegetation structure. Normalized difference VIs are highly correlated to vegetation amount-related parameters while soil-related VIs respond basically to canopy structural parameters. Our results indicate that satellite imagery can be used to map biomass in Mediterranean scrubland regions, and show that it has the potential to discriminate types of semi-deciduous shrub communities with different crown architectures.

Acknowledgements

This project was funded by the Portuguese Ministry for Science and Technology/JNICT (Grant no. PEAM/C/RNT/57/91). We are grateful to Carlos Santos, Cláudia Franco, Evelina Moura, Serafim Pinto and Sérgio Rodrigues for field assistance, and to the City Council of Mértola for logistic support during the field campaigns.