Estimating temporal changes in soil carbon stocks at ecoregional scale in Madagascar using remote-sensing |
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| Institution: | 1. IRD, UMR-Eco&Sols, 2 Place Viala, 34060 Montpellier cedex 2, France;2. Etc Terra, 127 rue d’Avron, Paris, France;3. CIRAD, UMR ECO&SOLS, F-34398 Montpellier, France;4. CIRAD, UPR BSEF, F-34398 Montpellier, France;5. Laboratoire des Radio-Isotopes, Route d''Andraisoro, 101 Antananarivo, Madagascar;1. Irstea, UR EMGR, Centre de Grenoble, F-38402 St-Martin-d’Hères, France;2. CIRAD, UPR BSEF, F-34398 Montpellier, France;3. Irstea, UR LISC, F-63172 Aubière, France;4. INRA, UMR AMAP, F-34000 Montpellier, France;1. CIRAD, UMR AMAP, TA A-51/PS1, Bd de la Lironde, 34398 Montpellier Cedex 5, France;2. CIRAD, UMR ECOFOG, BP 709, 97379 Kourou Cedex, French Guiana;3. CIRAD, UPR BSEF, 34398 Montpellier Cedex 5, France;4. IRD, UMR AMAP, TA A-51/PS1, Bd de la Lironde, 34398 Montpellier Cedex 5, France;1. Programa de Pós-graduação em Ecologia, Departamento de Zoologia e Ecologia, Universidade Federal de Santa Catarina, Florianópolis, Brazil;2. CIRAD, UMR AMAP, AMAP, Univ Montpellier, CIRAD, CNRS, INRAE, IRD, F-34398 Montpellier, France;3. Divisão de Sensoriamento Remoto, Coordenação de Observação da Terra, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, SP, Brazil;4. School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK;5. Universidade de São Paulo, Escola Superior de Agricultura “Luiz de Queiroz”, Laboratório de Ecologia, Manejo e Conservação de Fauna Silvestre (LEMaC), Piracicaba, São Paulo, Brazil;1. Laboratoire des Radioisotopes, Université d''Antananarivo, BP 3383, Route d''Andraisoro, 101 Antananarivo, Madagascar;2. Conservation International, 2011 Crystal Drive, Arlington, VA 22202, USA;3. Ecole Supérieure des Sciences Agronomiques, Département Eaux et Forêts, Université d''Antananarivo, BP 175, Antananarivo 101, Madagascar;4. Conservation International Madagascar, Villa Hajanirina, lot II W 27D, Rue Vittori Francois, Ankorahotra, 101 Antananarivo, Madagascar;5. Ecole Supérieure Polytechnique d''Antananarivo, Département Ingénierie pétrolière, Université d''Antananarivo, BP 1500, Antananarivo 101, Madagascar;1. UPR BSEF, CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement), Avenue Agropolis, 34398 Montpellier Cedex 5, France;2. AgroParisTech, Doctoral School ABIES, 19 Avenue du Maine, 75732 Paris Cedex 15, France;3. Center for International Forestry Research, Avenida La Molina, 15024 Lima, Peru;4. Center for International Forestry Research, Jalan CIFOR, Situ Gede, Sindang Barang, Bogor (Barat) 16115, Indonesia;5. Oregon State University, Fisheries and Wildlife Department, 2820 SW Campus Way, Corvallis, OR 97331, USA |
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| Abstract: | Soil organic carbon (SOC) plays an important role in climate change regulation notably through release of CO2 following land use change such a deforestation, but data on stock change levels are lacking. This study aims to empirically assess SOC stocks change between 1991 and 2011 at the landscape scale using easy-to-access spatially-explicit environmental factors. The study area was located in southeast Madagascar, in a region that exhibits very high rate of deforestation and which is characterized by both humid and dry climates. We estimated SOC stock on 0.1 ha plots for 95 different locations in a 43,000 ha reference area covering both dry and humid conditions and representing different land cover including natural forest, cropland, pasture and fallows. We used the Random Forest algorithm to find out the environmental factors explaining the spatial distribution of SOC. We then predicted SOC stocks for two soil layers at 30 cm and 100 cm over a wider area of 395,000 ha. By changing the soil and vegetation indices derived from remote sensing images we were able to produce SOC maps for 1991 and 2011. Those estimates and their related uncertainties where combined in a post-processing step to map estimates of significant SOC variations and we finally compared the SOC change map with published deforestation maps. Results show that the geologic variables, precipitation, temperature, and soil-vegetation status were strong predictors of SOC distribution at regional scale. We estimated an average net loss of 10.7% and 5.2% for the 30 cm and the 100 cm layers respectively for deforested areas in the humid area. Our results also suggest that these losses occur within the first five years following deforestation. No significant variations were observed for the dry region. This study provides new solutions and knowledge for a better integration of soil threats and opportunities in land management policies. |
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| Keywords: | Soil organic carbon Spectroscopy PLSR Random forest Soil-landscape factors Change detection Deforestation |
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