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Télédétection appliquée à l’étude de l’effet de la variabilité climatique et de la gestion pastorale sur la productivité et la phénologie végétale des prairies supra-forestières

Abstract : Mountain grasslands are wide distributed ecosystems which are particularly vulnerable to climate and land use changes. In this context, the main objective of this thesis was to assess the effect of climate and pastoral drivers on mountain grasslands vegetation at different spatiotemporal scales. In particular, we wanted to understand plant responses to annual variations of climate (temperature and precipitation), long term warming and extreme events (heat waves and droughts); as well as the land management impact (grazing intensity and calendars). Hence, we performed several analyses using phenological, meteorological and pastoral metrics. First, we derived phenological metrics mainly from the Normalized Difference Vegetation Index (NDVI) extracted from two sources: satellite remote sensing images at moderate (MODIS) and high (Landsat and SPOT) resolution and field remote sensing measures acquired with portable and fixed sensors over five mountain grasslands. Second, we estimated meteorological metrics from reanalysis of the climatic model SAFRAN provided by Météo France. Third, we estimated pastoral metrics from two regional pastoral surveys (1996-1997 and 2012-2014) and several local documents (“cahiers d’alpage”) produced within the project “Alpages Sentinelles”. Regarding mountain grasslands vegetation, our results showed: (i) widely distributed greening trends, (ii) higher tolerance to heat waves than to droughts, (iii) higher sensibility to climate factors than to grazing pressures, (iv) weak but positive responses to grazing, and (v) a regrowth potential at the end of the season. The originality of our results was to exhibit the stronger relationships between climate factors and vegetation phenology, than between the latter and grazing pressures. Moreover, we highlighted the important contributions of remote sensing data to study mountain ecosystems.
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Submitted on : Tuesday, March 12, 2019 - 4:17:06 PM
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Monica Cecilia Corona Lozada. Télédétection appliquée à l’étude de l’effet de la variabilité climatique et de la gestion pastorale sur la productivité et la phénologie végétale des prairies supra-forestières. Biodiversité et Ecologie. Université Grenoble Alpes, 2018. Français. ⟨NNT : 2018GREAV049⟩. ⟨tel-02065391⟩

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