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Mapping the effects of water stress on sphagnum: preliminary observations using airborne remote sensing / A. Harris in Remote sensing of environment, vol 100 n° 3 (15 february 2006)  

Public [article]  inRemote sensing of environment > vol 100 n° 3 (15 february 2006) . - pp 363 - 378 Titre : Mapping the effects of water stress on sphagnum: preliminary observations using airborne remote sensing Type de document : Article/Communication Auteurs : A. Harris, Auteur ; R.G. Bryant, Auteur ; A.J. Baird, Auteur Année de publication : 2006 Article en page(s) : pp 363 - 378 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] analyse spectrale [Termes IGN] canopée [Termes IGN] eau de surface [Termes IGN] humidité du sol [Termes IGN] image aérienne [Termes IGN] indice d'humidité [Termes IGN] plante aquatique d'eau salée [Termes IGN] réflectance spectrale [Termes IGN] réflectance végétale [Termes IGN] Royaume-Uni [Termes IGN] Sphagnum (genre) [Termes IGN] stress hydrique [Termes IGN] tourbe [Termes IGN] zone humide Résumé : (Auteur) Remote sensing of near-surface hydrological conditions within northern peatlands has the potential to provide important large-scale hydrological information regarding ecological and carbon-balance processes occuring within such systems. This article details how field knowledge of the spectral properties of Sphagnum spp., airborne remote sensing data and a range of image analysis approaches may be combined to provide a suitable proxy for near-surface wetness. Co-incident field and airborne remote sensing data were acquired in May and September 2002 over an important UK raised bog (Cors Fochno). A combination of laboratory-tested NIR and SWIR water-based and biophysical spectral reflectance indices were applied to field and airborne reflectance spectra of Sphagnum pulchrum to elucidate changes in near-surface moisture conditions. Field results showed significant correlations between water-based indices (moisture stress index (MSI) and floating water band indices (fWBI980 and fWB1200) and measures of both near-surface volumetric moisture content (VMC) and water-table position. Spectral indices formulated from the NIR (fWBI980 and fWBI1200) proved to be the most useful for indicating near-surface wetness across the widest range of moisture conditions because of their ability to penetrate deeper into the Sphagnum canopy. Correlations between a biophysical index based upon chlorophyll content and both hydrological measures were not significant, possibly due to relatively high levels of surface wetness at the field site in both May and September. S. pulchrum lawns were successfully located and mapped from airborne imagery using the mixed tuned match filtering (MTMF) algorithm. Importantly, MSI derived from airborne data was significantly correlated with both field moisture and the water-table position. Relationships between measures of near-surface wetness and the MSI for naturally heterogeneous canopies were, however, found to be weaker for airborne imagery than for associated field data. This is likely to be a result of the formulation of the MSI itself and the possible preferential detection of "wetter" pixels within the imagery. This effectively reduced the ability of MSI to detect subtle changes in near-surface wetness under high moisture conditions, but would not impede the use of the index under drier conditions. Results from the field data suggest that indices formulated from the NIR may be more suitable for detailed estimations of near-surface and surface wetness at the landscape-scale although reliable hyperspectral data are required to test fully the performance of such indices. The relative merits of using such an approach to determine near-surface hydrological conditions across entire peatland complexes are also discussed. Numéro de notice : A2006-036 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2005.10.024 En ligne : https://doi.org/10.1016/j.rse.2005.10.024 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=27763 [article]