C. M. Brasier, F. Robredo, and J. F. Ferraz, Evidence for Phytophthora cinnamomi involvement in Iberian oak decline, Plant Pathology, vol.42, issue.1, pp.140-145, 1993.

D. Bronaugh and A. Werner, zyp: Zhang + Yue-Pilon trends package. Pacific Climate Impacts Consortium. R package version 0, pp.10-11, 2013.

A. Caritat, E. Gutiérrez, and M. Molinas, Influence of weather on cork-ring width, Tree physiology, vol.20, issue.13, pp.893-900, 2000.

S. Cerasoli, F. C. Silva, and J. M. Silva, Temporal dynamics of spectral bioindicators evidence biological and ecological differences among functional types in a cork oak open woodland, International journal of biometeorology, vol.60, issue.6, pp.813-825, 2016.

O. A. Correia, G. M. Oliveira, M. A. Martins-loução, and F. M. Catarino, Effects of bark-stripping on the water relations of Quercus suber L. Scientia gerundensis, vol.18, pp.195-204, 1992.

A. Costa, H. Pereira, and A. Oliveira, Variability of radial growth in cork oak adult trees under cork production. Forest ecology and management, vol.175, pp.239-246, 2003.

A. Costa, H. Pereira, and M. Madeira, Landscape dynamics in endangered cork oak woodlands in Southwestern Portugal, Agroforestry Systems, vol.77, p.83, 1958.

A. Costa, H. Pereira, and M. Madeira, Analysis of spatial patterns of oak decline in cork oak woodlands in Mediterranean conditions, Annals of Forest Science, vol.67, issue.2, p.204, 2010.
URL : https://hal.archives-ouvertes.fr/hal-00883534

F. Costa-e-silva, A. C. Correia, A. Piayda, M. Dubbert, C. Rebmann et al., Effects of an extremely dry winter on net ecosystem carbon exchange and tree phenology at a cork oak woodland. Agricultural and forest meteorology, vol.204, pp.48-57, 2015.

D. Silva, P. M. Aguiar, C. A. Niemelä, J. Sousa, J. P. Serrano et al., Cork-oak woodlands as key-habitats for biodiversity conservation in Mediterranean landscapes: a case study using rove and ground beetles (Coleoptera: Staphylinidae, Carabidae), Biodiversity and conservation, vol.18, issue.3, pp.605-619, 2009.

T. S. David, M. O. Henriques, C. Kurz-besson, J. Nunes, F. Valente et al., Water-use strategies in two co-occurring Mediterranean evergreen oaks: surviving the summer drought, Tree physiology, vol.27, issue.6, pp.793-803, 2007.

S. P. Faias, J. A. Paulo, J. H. Palma, and M. Tomé, Understory effect on tree and cork growth in cork oak woodlands, 2018.

J. P. Ferreira, Models to predict the impact of the climate changes on aquifer recharge, p.103, 2007.

S. Godinho, N. Guiomar, R. Machado, P. Santos, P. Sá-sousa et al., Assessment of environment, land management, and spatial variables on recent changes in montado land cover in southern Portugal, Agroforestry systems, vol.90, issue.1, pp.177-192, 2016.

A. C. Gouveia and H. Freitas, Intraspecific competition and water use efficiency in Quercus suber: evidence of an optimum tree density?, Trees, vol.22, issue.4, p.521, 2008.

M. Häusler, J. M. Silva, S. Cerasoli, G. López-saldaña, and J. M. Pereira, Modelling spectral reflectance of open cork oak woodland: a simulation analysis of the effects of vegetation structure and background, International Journal of Remote Sensing, vol.37, issue.3, pp.492-515, 2016.

. Icnf, IFN6-Áreas dos usos do solo e das espécies florestais de Portugal continental, Resultados preliminares. Instituto da Conservação da Natureza e das Florestas, Lisboa, 34. IUSS working group WRB, p.132, 2006.

R. Joffre and S. Rambal, How tree cover influences the water balance of Mediterranean rangelands, Ecology, vol.74, issue.2, pp.570-582, 1993.

J. Ju and J. G. Masek, The vegetation greenness trend in Canada and US Alaska from 1984-2012 Landsat data. Remote Sensing of Environment, vol.176, pp.1-16, 2016.

Y. Ke, J. Im, J. Lee, H. Gong, and Y. Ryu, Characteristics of Landsat 8 OLI-derived NDVI by comparison with multiple satellite sensors and in-situ observations, Remote Sensing of Environment, vol.164, pp.298-313, 2015.

M. G. Kendall, Rank Correlation Methods, 1975.

H. N. Kim, H. Y. Jin, M. J. Kwak, I. Khaine, H. N. You et al., Why does Quercus suber species decline in Mediterranean areas?, Journal of Asia-Pacific Biodiversity, vol.10, issue.3, pp.337-341, 2017.

H. B. Mann, Nonparametric tests against trend, Econometrica: Journal of the Econometric Society, pp.245-259, 1945.

M. P. Mendes, L. Ribeiro, T. S. David, and A. Costa, How dependent are cork oak (Quercus suber L.) woodlands on groundwater? A case study in southwestern Portugal, Forest Ecology and Management, vol.378, pp.122-130, 2016.

G. Moreno, S. Aviron, S. Berg, J. Crous-duran, A. Franca et al., Agroforestry systems of high nature and cultural value in Europe: provision of commercial goods and other ecosystem services, Agroforestry Systems, pp.1-15, 2017.

J. V. Natividade, . Lisbon, R. Ogaya, A. Barbeta, C. Ba?nou et al., Satellite data as indicators of tree biomass growth and forest dieback in a Mediterranean holm oak forest, Subericultura. Direcção Geral dos Serviços Florestais e Aquicolas, vol.72, pp.135-144, 1950.

J. A. Paulo and M. Tomé, Predicting mature cork biomass with t years of growth from one measurement taken at any other age. Forest ecology and management, vol.259, pp.1993-2005, 2010.

J. A. Paulo, S. Faias, C. Ventura-giroux, and M. Tomé, Estimation of stand crown cover using a generalized crown diameter model: application for the analysis of Portuguese cork oak stands stocking evolution, IForest. Biogeosciences and Forestry, 2015.

J. A. Paulo, J. H. Palma, A. A. Gomes, S. P. Faias, J. Tomé et al., Predicting site index from climate and soil variables for cork oak (Quercus suber L.) stands in Portugal, New forests, vol.46, issue.2, pp.293-307, 2015.

J. A. Paulo, H. Pereira, and M. Tomé, Analysis of variables influencing tree cork caliper in two consecutive cork extractions using cork growth index modelling, Agroforestry systems, vol.91, pp.221-237, 2017.

H. Pereira, Cork: biology, production and uses, p.336, 2007.

A. N. Pettitt, A non-parametric approach to the change-point problem, Applied statistics, pp.126-135, 1979.

. R-core-team, R: A language and environment for statistical computing. R Foundation for Statistical Computing, 2017.

A. Rigueiro-rodríguez, J. Mcadam, and . Mosquera-losada, Agroforestry in Europe: current status and future prospects, vol.6, 2008.

M. A. Romero, J. E. Sánchez, J. J. Jiménez, L. Belbahri, A. Trapero et al., New Pythium taxa causing root rot on Mediterranean Quercus species in South-west Spain and Portugal, Journal of Phytopathology, vol.155, issue.5, pp.289-295, 2007.

J. Rouse, R. H. Haas, J. A. Schell, and D. W. Deering, Monitoring vegetation systems in the Great Plains with ERTS, 1974.

D. P. Roy, V. Kovalskyy, H. K. Zhang, E. F. Vermote, L. Yan et al., Characterization of Landsat-7 to Landsat-8 reflective wavelength and normalized difference vegetation index continuity, Remote Sensing of Environment, vol.185, pp.57-70, 2016.

P. K. Sen, Estimates of the regression coefficient based on Kendall's tau, Journal of the American Statistical Association, vol.63, pp.1379-1389, 1968.

X. She, L. Zhang, Y. Cen, T. Wu, C. Huang et al., Comparison of the continuity of vegetation indices derived from Landsat 8 OLI and Landsat 7 ETM+ data among different vegetation types, Remote Sensing, vol.7, issue.10, pp.13485-13506, 2015.

J. S. Silva, Os montados. Fundação Luso-Americana, 2007.

M. D. Steven, T. J. Malthus, F. Baret, H. Xu, and M. J. Chopping, Intercalibration of vegetation indices from different sensor systems, Remote Sensing of Environment, vol.88, issue.4, pp.412-422, 2003.

P. M. Teillet, J. L. Barker, B. L. Markham, R. R. Irish, G. Fedosejevs et al., Radiometric cross-calibration of the Landsat-7 ETM+ and Landsat-5 TM sensors based on tandem data sets. Remote sensing of Environment, vol.78, pp.39-54, 2001.

H. Theil, A rank-invariant method of linear and polynomial regression analysis, Nederlandse Akademie Wetenchappen Series, A, vol.53, pp.386-392, 1950.

T. Pohlert, trend: Non-Parametric Trend Tests and Change-Point Detection, 2018.

M. Vaz, J. S. Pereira, L. C. Gazarini, T. S. David, J. S. David et al., Drought-induced photosynthetic inhibition and autumn recovery in two Mediterranean oak species (Quercus ilex and Quercus suber), Tree Physiology, vol.30, issue.8, pp.946-956, 2010.

J. Wang, P. M. Rich, K. P. Price, and W. D. Kettle, Relations between NDVI and tree productivity in the central Great Plains, International Journal of Remote Sensing, vol.25, issue.16, pp.3127-3138, 2004.

C. Werner and O. Correia, Photoinhibition in cork-oak leaves under stress: influence of the barkstripping on the chlorophyll fluorescence emission in Quercus suber L, Trees, vol.10, pp.288-292, 1996.

Z. Zhu and C. E. Woodcock, SAF de sobreiro com culturas permanentes 3.1.1.00.1 Florestas de sobreiro 1 3.1.1.01.1 Florestas de sobreiro 3.1.1.01.1 Florestas de sobreiro 3.1.1.00.1 Florestas de sobreiro 1 3.1.1.01.1 Florestas de sobreiro 3.1.1.02.1 Florestas de sobreiro com folhosas 3.1.1.00.1 Florestas de sobreiro 1 3.1.1.01.1 Florestas de sobreiro 3, vol.118, pp.83-94, 2012.

, from annual burned areas maps of the Nature and Forests Conservation Portuguese Institute (Instituto da Conservação da Natureza e das Florestas, ICNF), Diplôme : Ingénieur agronome, agroalimentaire et territorial Spécialité : Agronomie Spécialisation / option : Télédétection et Environnement (TELENVI) Enseignant référent : Hervé Nicolas Auteur : Valentine AUBARD Date, 1984.

, Lisboa Maîtres de stage : João Manual Das Neves Silva et Joana Amaral Paulo Nb pages : 30 Annexe(s, p.16

. Année-de-soutenance, , 2018.

, Titre français : Suivi des bois de chênes lièges et chênes verts avec Google Earth Engine Titre anglais : Monitoring cork and holm oak woodlands with Google Earth Engine

, Afin de quantifier ce phénomène, les tendances sur 34 ans de l'indice de végétation par différence normalisé (NDVI) ont été cartographiées à une précision de 30 mètres, pour l'ensemble des forêts de chênes lièges (Quercus suber) et de chênes verts (Q. ilex) du Portugal continental. L'indice NDVI est un bon proxy pour suivre la santé et la productivité des arbres au cours du temps. Les images de Landsat 5, 7 et 8 ont été utilisées pour obtenir une série temporelle de 1984 à 2017. Les NDVI de MODIS servirent de comparaison après l'an 2000. Google Earth Engine permet d'utiliser librement ces images. Les valeurs de NDVI de Landsat 5 et 8 furent ajustées à celles de Landsat 7. Pour minimiser l'impact spectral de la végétation de sous étage, seuls les NDVI de Juillet et Août furent utilisés. Les tests de Mann-Kendall (MK) et contextuel de MK ont permis d'estimer la significativité et le signe des tendances, et l'estimateur de Theil-Sen (TS) les pentes. Cette méthodologie a d'abord été testée sur six parcelles de chênes lièges. Des modèles linéaires ont montré l'effet significatif des précipitations et de l'extraction du liège sur les variations de NDVI. Un test de Pettitt révéla des ruptures de tendance significatives autour de l'an, 2000.

, All imagery were freely available and treatable on Google Earth Engine. NDVI values of Landsat 5 and 8 were adjusted to Landsat 7 values. Only July and August NDVI were used to minimize the spectral contribution of understorey vegetation and its phenological variability, thus focusing on the tree layer. Signs and significance of trends were calculated by Mann-Kendall (MK) and contextual MK tests, and their slopes using Theil-Sen (TS) estimator. The methodological approach was first tested on six cork oaks stands. Linear models revealed the effect of annual cumulated precipitation and debarking on NDVI variations. All trends were found significant. A Pettitt test showed significant change-points around the year 2000, Oak woodlands are being documented to be declining in southern Europe. In order to verify and quantify this phenomenon, 2000.