Thesis Structure
CHAPTER 3. Vegetation changes in the Neotropical Gran Sabana (Venezuela) around the Younger Dryas Chron. Paleoecological analysis of the oldest time interval found to date in
1.4. Main objectives
vegetation, i.e., the expansion of treeless savannas, the decline of forests, and the appearance and establishment of morichales. According to Rull (1998), the morichales would have been expanding their range since the Last Glacial Maximum, favored by both climate and fire. The decrease or disappearance of forests in all sequences studied reveals that these are probably not favored by present‐day conditions (climatic and fire incidence). Indeed, this evidence, which mainly comes from the Urué record, also highlights the importance of fire in shaping the current GS landscape. The landscape shift recorded at Urué also agrees with a potential impoverishment of GS soils after fire disturbance, which could influence plant succession processes (Fölster et al., 2001; Dezzeo et al., 2004a; Dezzeo and Chacón, 2005).
1.4. Main objectives
The general objective of this study was to achieve an understanding the Gran Sabana landscape dynamics from the Late Glacial period to the present, as well as the origin and main drivers of modern GS landscapes. The data obtained will hopefully provide insights regarding the resilience of the Gran Sabana ecosystems to perturbations. To this end, multi‐proxy palynological analyses of three sequences were carried out based mainly on pollen, NPP and pteridophyte spore identification, and charcoal analysis.
The specific objectives of the present work are summarized as follows:
- To enhance the number of proxies that can be useful for paleoecological research in the Neotropics, as well as to adjust the laboratory protocol for neotropical sediments.
- To reconstruct past plant communities and their changes since the Late Glacial period at a sub‐millennial scale. Within this objective, emphasis will be placed on attempting to infer the major drivers involved, as well as possible synergies between these and dating the origin of the present GS ecosystems.
- To compile an overview of the paleoecological research that has been carried out to date in the Gran Sabana aimed at (i) clarifying whether the different sequences studied are subject to local or regional forcing factors; (ii) making comparisons with other sub‐
continental records (from northern South American low‐ and midlands); and (iii) attempting to establish regional trends.
- To study the real fire regime in GS, including its origin in the study area, its relationships with past and modern indigenous practices, and its effects upon vegetation. A derived aspect of this topic is a focus on improving our knowledge about the time of arrival human settlements in the region through paleoecological data.
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