The Gran Sabana (GS, Northern South America) is a humid savanna region (treeless savanna intermingled with forest patches) with a long history of vegetation changes under fire disturbances. A number of hypotheses seek to explain the importance of environmental factors (e.g., climate, fire) in the origin and maintenance of the GS savannas. In order to fully comprehend the ontogeny of the GS, this thesis was aimed at conducting a detailed palaeoecological evaluation of vegetation dynamics and ecological processes (e.g. feedbacks, resilience) from the Late Glacial to the present, analysing two sedimentary archives (Lacustrine: Lake Encantada, peat bog: Fidencio). Currently, the GS savannas are being highly threatened due to excessively frequent fires. In addition, forest patches are being replaced by grassland. Therefore, in order to achieve ecosystem sustainability, this investigation was also aimed at forecasting potential vegetation responses and suggesting some guidelines for the savannas management. To accomplish the objectives, the palaeoecological assessment was based on palynological analysis and multiproxy approach (e.g., geochemical proxies, ecological indices) where possible. Lake Encantada's basin is currently dominated by grassland with morichales (Mauritia flexuosa palm stands). The results suggest that the multifactorial interplay between fire regime, diversity, grasses availability, moisture and rates of recovery (RR) could have caused the vegetation changes during the Holocene and also contributed to the degree of resilience of plant communities. Forest patches were resilient to fire during specific time intervals. The vegetation changes suggest the following general trend: expansion of forest patches between -8700 and 6400 cal yr BP, probably driven by the interplay between fires, high RRs and diversity. Despite wetter climate from 5400 cal yr BP, the savanna expanded under higher fire occurrence, which was potentially related to human land-use practices. The modern grassland with morichales ...