URL http://dx.doi.org/10.1111/j.1365-2389.2009.01178.xSoil degradation processes have dramatically increased in their extent and intensity over the last decades. Progressively, actions have been taken in order to evaluate and reduce the major threats that have already wreaked havoc on soil conditions. Efficient and standardized monitoring of soil conditions is thus required but soil quality research is facing an important technological challenge because of the number of properties involved in soil quality. The objective of the present review is to examine critically the suitability of nearinfrared reflectance spectroscopy (NIRS) as a tool for soil quality assessment. We first detail the soil qualityrelated parameters (chemical, physical and biological) that can be predicted with NIRS through laboratory measurements. The ability of imaging NIRS (airborne or satellite) for mapping a minimum data set of soil quality is also discussed. Then we review the most recent research using soil reflectance spectra as an integrated measure of soil quality, from global site classification to the prediction of specific soil quality indices. We conclude that imaging NIRS enables the direct mapping of some soil properties and soil threats, but that further developments to solve several technological limitations identified are needed before it can be used for soil quality assessment. The robustness of laboratory NIRS for soil quality assessment allows its implementation in soil monitoring networks. However, its routine use requires the development of international soil spectral libraries that should become a priority for soil quality research.Les processus de dégradation des sols ont fortement augmenté au cours des dernières décennies. Des mesures sont progressivement mises en place afin d'évaluer et de limiter l'impact des principales menaces qui ont déjà provoqué une diminution préoccupante de la qualité des sols. Des méthodes efficaces et standardisées de suivi de la qualité des sols sont donc indispensables, mais les nombreuses propriétés impliquées dans la qualité des sols compliquent son évaluation rigoureuse. L'objectif de cette revue est d'examiner le potentiel de la spectroscopie proche infrarouge (SPIR) comme outil rapide de caractérisation de la qualité des sols. Nous dressons d'abord l'inventaire des propriétés du sol liées à sa qualité qui sont prédictibles par des mesures SPIR en laboratoire. Le potentiel de l'imagerie embarquée SPIR (satellite, avion) est également abordé. Nous réalisons ensuite une synthèse des applications utilisant la réflectance spectrale des sols comme mesure intégrée de leur qualité, depuis la classification de sites selon leur état de dégradation jusqu'à la prédiction d'indices spécifiques de qualité du sol. Nous concluons que l'imagerie SPIR permet de cartographier quelques propriétés et menaces pesant sur les sols, mais les limites technologiques relevées exigent d'importants développements pour en faire un outil robuste d'évaluation de la qualité des sols. La fiabilité de la technique SPIR ...

The absorbance of near-infrared (NIR) radiation by plants depends on the overtones of vibration, bending and stretching of the chemical bonds within their organic components. The wide variety of these bonds gives rise to characteristic NIR spectra, or ‘fingerprints', of plant materials. Do these fingerprints remain in the soil when the plants decompose and allow discrimination between soils that have supported different types of vegetation? We have compared the NIR spectra of grassland soil with those of soil under forest in the Vosges mountains in France. Near-infrared reflectances, R, from 370 samples of soil were recorded as A = log10(1/R) at wavelengths between 1100 and 2500 nm and averaged over 10-nm intervals to give spectra each with 140 values. A canonical variate analysis (CVA) of the raw spectra discriminated well, but not perfectly, between grassland and forest soil, with Mahalanobis distance, D, of 4.87. Standardization along the spectra to remove effects of varied mineral composition achieved complete separation between the two sources with D = 9.81. Canonical variate analysis of first and second derivatives of the spectra distinguished the two groups even better, with D = 12.27 and D = 16.65, respectively. The results show much promise for inferring past vegetative cover from NIR spectra deriving from the organic matter in the soil. The next step will be to extend these studies to see how well we can distinguish other types of vegetation from such spectra

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Determining sediment provenance allows a better understanding of fluvial palaeo-dynamics, and identifying involved watersheds, at broad spatio-temporal scales. Conventional approaches for source identification are usually based on the physical, mineralogical, geochemical, magnetic or isotopic properties of sediments. Rapid, non-destructive and, in well-established contexts, highly accurate, mid-infrared spectroscopy is an alternative method for investigating sediment sources. The present research objectives are: (i) to use the mid-infrared spectroscopy method to discriminate the provenance of fine sediments, by applying discriminant analysis on a large set of reference samples from three different watersheds in the Upper Rhine area (associated with the Rhine, Ill and Vosges tributaries); (ii) to clarify whether the provenance spectra signatures are influenced by riverine depositional contexts (bars versus banks) and, to some extent, by grain size and/or high organic matter content; and (iii) to apply the mid-infrared spectroscopydiscriminant analysis method to a study of fluvial palaeo-dynamics and determine the provenance of palaeo-channel infillings. Three main sedimentary sources, divided into eight sub-categories, have been characterized by 196 modern reference samples from 78 collecting sites. Discriminant analysis displayed a strong separating power by classifying correctly the origin of samples without any inter-group overlap, independently from the geomorphological context (bar or bank) and associated slight changes in organic matter contents or grain size. Mid-infrared spectroscopydiscriminant analysis investigations of the palaeo-channel infill, complemented by radiocarbon dates and mineralogical data, allowed reconstructing general trends for the local morpho-sedimentary dynamics over the last ca 12 millennia.

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