Resumen en inglés

In terrestrial ecosystems, nitrogen is an element of high demand for organisms, so the primary productivity of any ecosystem is limited by the availability of this element. Through the biological fixation of nitrogen, this element is contributed to the ecosystems defining the fertility of the soil, most of the nitrogen taken up by the plants is returned to the soil in an organic form through the litter that constitutes a deposit of matter and energy. for microorganisms. The litter that falls to the ground is decomposed by a great variety of microorganisms classified within functional groups that intervene in the degradation process, forming an organic substrate known as mulch. The objective of this study is to determine the diversity of bacteria with nitrogen-fixing capacity associated with leaf litter, in a fragment of tropical dry forest in Montería-Córdoba. For the development of the methodology, microorganisms were obtained from samples of litter and mulch from the interior and edge of the forest which were inoculated in a nitrogen-free medium (Burk's medium). A total of 77 morphotypes with nitrogen-fixing capacity were isolated from the litter under study, of which the mulch presented a greater diversity of isolates with respect to the litter (40 morphotypes with a total density of 115 x104 CFU / g of mulch) . Finally, it is shown that the litter at the edge of the forest presents a greater diversity of nitrogen fixers than the interior of the forest, with a total of 44 isolated morphotypes and a total density of 120 x104CFU / g of sample.