Spectral and botanical classification of grasslands: Auxois example

Abstract

Botanical observations were made in the field, and in situ reflectance measurements were made over a French test-site in Auxois (Burgundy). Reflectance measurements were made with a multi-channel radiometer (ISCO SR 140) and a two band, hand-held Biometer, at four different periods during the growing season. Principal components analysis of the reflectance data show that the most important wavelengths for spectral classification of grasslands are: 550, 675, 850, 1400 nm, while the important period is mid-April, at the begining of plant growth. Factorial analysis of botanical relevés leads to grasslands associations definition. Once the associations defined, they are transformed into agro-ecological units, and may be spectrally characterized. A model of spectral behaviour through time could be drawn for the different agro-ecologiacl units. The knowledge of such a spectral behaviour is fundamental before any attempt of grassland mapping, and green aerial phytomass productivity evaluation through remote-sensing data.