Résumé
Tropical grasslands face two major challenges: maintaining food security in the face of growing needs and coping with global change. In French Guyana, pastures are not very profitable for farmers in a constrained climatic context and are criticized for their potential contribution to Amazon deforestation. This work aims to study the sustainability of pasture cover in French Guiana and to characterize the weed flora. On the other hand, this work seeks to determine the relationship between agronomic practices and pasture degradation, mainly with the evolution of pasture flora 4 years after the implementation of dynamic rotational grazing. Flora surveys of 83 stations in 21 exploitations, distributed from Regina to Saint-Laurent-du-Maroni, have been done. 132 species were referenced as weeds. 27% of the stations are characterized by a degradation index greater than or equal to 25%, and 23% by a degradation index greater than or equal to 50%. The weed flora mainly is mainly composed of Cyperaceae, Mimosa pudica and Spermacoce verticillata are the two most frequent and abundant weeds. Cyperus aromaticus, a recently recorded alien species, is of concern. No environmental factors seem to be linked to the level of degradation, but agronomic practices are the most likely to explaining it. This work contributed to the collaborative portal on weeds in tropical agrosystems, WIKTROP, on Guianese pastures.