Decrease of L-band SAR backscatter with biomass of dense forests
Synthetic aperture radar (SAR) is one of the most promising remote sensors to map forest carbon. The unique spaceborne and long-wavelength SAR data currently available are L-band data, but their relationship with forest biomass is still controversial, particularly for high biomass values. While many studies assume a complete loss of sensitivity above a saturation point, typically around 100 t.ha? 1, others assume a continuous positive correlation between SAR backscatter and biomass. The objective of this paper is to revisit the relationship between L-band SAR backscatter and dense tropical forest biomass for a large range of biomass values using both theoretical and experimental approaches. Both approaches revealed that after reaching a maximum value, SAR backscatter correlates negatively with forest biomass. This phenomenon is interpreted as a signal attenuation from the forest canopy as the canopy becomes denser with increasing biomass. This result has strong implications for L-band vegetation mapping because it can lead to a greater-than-expected under-estimation of biomass. The consequences for L-band biomass mapping are illustrated, and solutions are proposed.
| Main Authors: | , , , , , |
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| Format: | article biblioteca |
| Language: | eng |
| Subjects: | K01 - Foresterie - Considérations générales, U30 - Méthodes de recherche, F40 - Écologie végétale, télédétection, radar, forêt tropicale humide, biomasse, ressource forestière, cartographie, cycle du carbone, carbone, stockage, http://aims.fao.org/aos/agrovoc/c_6498, http://aims.fao.org/aos/agrovoc/c_24071, http://aims.fao.org/aos/agrovoc/c_7976, http://aims.fao.org/aos/agrovoc/c_926, http://aims.fao.org/aos/agrovoc/c_3050, http://aims.fao.org/aos/agrovoc/c_1344, http://aims.fao.org/aos/agrovoc/c_17299, http://aims.fao.org/aos/agrovoc/c_1301, http://aims.fao.org/aos/agrovoc/c_7427, http://aims.fao.org/aos/agrovoc/c_1432, http://aims.fao.org/aos/agrovoc/c_1229, |
| Online Access: | http://agritrop.cirad.fr/575920/ http://agritrop.cirad.fr/575920/1/document_575920.pdf |
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| Summary: | Synthetic aperture radar (SAR) is one of the most promising remote sensors to map forest carbon. The unique spaceborne and long-wavelength SAR data currently available are L-band data, but their relationship with forest biomass is still controversial, particularly for high biomass values. While many studies assume a complete loss of sensitivity above a saturation point, typically around 100 t.ha? 1, others assume a continuous positive correlation between SAR backscatter and biomass. The objective of this paper is to revisit the relationship between L-band SAR backscatter and dense tropical forest biomass for a large range of biomass values using both theoretical and experimental approaches. Both approaches revealed that after reaching a maximum value, SAR backscatter correlates negatively with forest biomass. This phenomenon is interpreted as a signal attenuation from the forest canopy as the canopy becomes denser with increasing biomass. This result has strong implications for L-band vegetation mapping because it can lead to a greater-than-expected under-estimation of biomass. The consequences for L-band biomass mapping are illustrated, and solutions are proposed. |
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