L archéologie et l archéobotanique des complexes de champs suréle-vés dans les savanes littorales de la Guyane et sur l écologie des écosystèmes créés par ces anciens remaniements du paysage

Landscapes of seasonally flooded savannas of the Guianan coast appear to have been co-constructed by complementary actions of human and natural ecosystem engineers. Pre-Columbian farmers transformed savannas by making raised fields, producing a marked and organized topographic heterogeneity. We will answer major open questions about the history of these systems: what was the period of occupation, the identity of plants cultivated, and the economic and social organization of the moundbuilders? Why were these sites abandoned? We postulate that once these mounds were formed, manmade heterogeneity set in motion resource concentration mechanisms driven by natural ecosystem engineers that have maintained heterogeneity by self-organizing processes ever since raised fields were abandoned by farmers. We will test two hypotheses: (1) The degree of conservation of these ancient structures depends on environmental variables that influence the population dynamics of ecosystem engineers. (2) Manmade heterogeneity conditions the functioning and diversity of soil and plant communities. Combining methods from a wide range of disciplines from human, physical and biological sciences, we will document how processes set in motion by ancient human transformation of landscapes affect the current and future functioning of ecosystems.