@inproceedings{fdi:010008438,
  title = {{B}iogenic soil crust affecting satellite spectral response : abstract},
  author = {{K}arnieli, {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{F}or the last 20 years, a large number of scientific and technical efforts have been conducted in studying the vegetation patterns and dynamics in the desert transition zone, especially in {N}orth {A}frica. {T}his study suggests a new interpretation for the vegetation remote sensing signal in arid and semi-arid zones. {T}he study is dealing with the effect of biogenic soil crust, which consist of mosses, lichens, algae and cyanobacteria, on satellite spectral reflectance. {I}t was found that : under arid and semi-arid conditions where natural higher vegetation is sparse and covers less than 30% of the surface, the photosynthetic signal in the satellite images is caused mainly by non-vascular plants ; a slight photosynthetic signal exists when the microphytic crusts are dry but a notable signal occurs when they are wet. {W}hen wet, the {NDVI} value can rise up to 30%, although no photosynthetic activity of higher plants is observes ; although the new vegetation indices, such as {SAVI} and {MVI}, are supposed to overcome {NDVI}'s limitations, and especially the soil brightness background effect, it was found that all the vegetation indices will be affected similarly by the microphytic crust ; the microphytes are active mainly after rain and flood events. {T}hey are observed at the beginning of the rainy season when the annuals are still dy and the perennials have not yet budded. {F}urthermore, they are also active in the dry seasons after dew nights. {C}onsequently, microphytes activity can affect the interpretation of the {VI}s during both wet and dry season. {T}he current cloud screening procedures may lead to a misinterpretation of the {NDVI} since they are base on the highest {NDVI} value during the entire compositing period ; the higher spectral signal from microphytes crusts occurs across the desert transition zone. ({R}{\'e}sum{\'e} d'auteur)},
  keywords = {{TELEDETECTION} {SPATIALE} ; {DONNEES} {SATELLITE} ; {ANALYSE} {SPECTRALE} ; {REFLECTANCE} ; {COUVERT} {VEGETAL}},
  numero = {},
  pages = {597},
  booktitle = {{S}urveillance des sols dans l'environnement par t{\'e}l{\'e}d{\'e}tection et syst{\`e}mes d'information g{\'e}ographiques = {M}onitoring soils in the environment with remote sensing and {GIS}},
  year = {1996},
  ISBN = {2-7099-1331-3},
  ISSN = {0767-2896},
  URL = {https://www.documentation.ird.fr/hor/fdi:010008438},
}