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Accueil du site → Doctorat → Brésil → Dinâmica temporal de índices de vegetação no Pampa do Rio Grande do Sul e Uruguai e suas relações com os elementos meteorológicos regionais

Universidade Federal do Rio Grande do Sul (2013)

Dinâmica temporal de índices de vegetação no Pampa do Rio Grande do Sul e Uruguai e suas relações com os elementos meteorológicos regionais

Wagner, Ana Paula Luz

Titre : Dinâmica temporal de índices de vegetação no Pampa do Rio Grande do Sul e Uruguai e suas relações com os elementos meteorológicos regionais

Temporal dynamics of vegetation indices in the pampa of Rio Grande do Sul and Uruguai and their relations with regional meteorological elements

Auteur : Wagner, Ana Paula Luz

Université de soutenance : Universidade Federal do Rio Grande do Sul

Grade : Doctorat 2013

Résumé
The objectives of the present research are to describe the patterns of the time/space dynamics of vegetation indices in the Pampa of Rio Grande do Sul and identify the relations established between these indices and the inter-annual climate variability. This study was performed over pasture regions that were partitioned in thirteen grassland over the research area. We used image data from different time series of NDVI (Normalized Difference Vegetation Index), EVI (Enhanced Vegetation Index) from the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, and surface metrics collected from 20 different weather stations, time series from MEI (Multivariate ENSO Index) data, and results from estimated indices of drought ARID (Agricultural Reference Index for Drought), from February 2000 to August 2011. The NDVI and EVI indices have presented similar average time patterns, with highest peaks in the summer season and minimal values in the winter. However, the EVI presented a higher potential for the detection of annual variations. In the relations between the responses of grassland vegetation coverage to the climatic conditions, we observed that the annual season was the growth-limiting variable for the pasture growth and this was related to the bioclimatic requirements of vegetation. The oscillations in the seasonal climatic conditions had different effects on the response of vegetation indices towards the region and annual season. The high inter-annual variability observed in the meteorological variables responsible for these oscillations was partially associated to the El Niño South Oscillation (ENSO) phenomenon. We observed seasonality in the relationship patterns between the hybrid condition and the vegetative development of the regional pastures, whereas the drought index ARID was efficient for describing special-time effects of hydric stress in the Pampa grasslands. We verified inverse relationships with the response of vegetation, whereas highest correlations occurred in the summer. The spatial variation observed in the grasslands vegetation, in response to soil variations, altitude, and management, did not change the patterns of the relations observed, although they have changed their intensity. The present results show that the local climatic conditions are the critical feature that determines the temporal pattern of the vegetation vigor of pastures in the Pampa of RS and Uruguay. The floristic composition and the type of soil modulated this pattern, whereas the meteorological conditions were responsible their inter-annual variability. The vegetation indices were revealed as potential representatives for describing the relations between the spacetime variations in the patterns of grassland vegetation and climate in Pampa of Rio Grande do Sul and Uruguay.

Sujets : Sensoriamento remoto Vegetação Rio Grande do Sul Uruguai Meteorologia

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