Efecto del fuego sobre micorrizas y hongos endófitos radiculares en especies de campo natural

The Uruguayan territory is part of the Río de la Plata grasslands region, where extensive cattle ranching represents the most important agricultural activity. In some areas of the country, controlled burning is employed to improve forage availability by altering vegetation structure and promoting regrowth. The objective of this study was to understand how burning and grazing influence the presence of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in a group of native grassland plant species with varying responses to fire. An experiment examining the interaction of fire and grazing is underway in the Quebrada de los Cuervos y Sierras del Yerbal Protected Landscape, within an area dominated by Saccharum angustifolium ('paja estrelladora'). Plants from five species with varying responses to fire were collected: Stenachaenium megapotamicum and Hypoxis decumbens (favored), Saccharum angustifolium and Acanthostyles buniifolius (tolerant), and Solidago chilensis (sensitive). Samples were taken across three treatments: exclosure without burning (control), grazed and burned (one-year post-burn), and grazed and recently burned (two months post-burn). High colonization by AMF was observed across all treatments and species, with an occurrence rate exceeding 80%, while DSE had an occurrence rate above 72%. However, the presence of arbuscules was below 40%, and coils were observed in less than 5% of cases. Fire and grazing significantly influenced the presence of mycorrhizae, with varied effects depending on the plant species; some were favored while others were reduced by these factors. S. megapotamicum, which benefits from burning, exhibited the highest levels of mycorrhization, including the presence of arbuscules and vesicles. H. decumbens, another favored species, recorded the highest presence of coils. In favored or tolerant species, control treatments consistently displayed higher values than any burned treatments whenever differences were observed. Conversely, the sensitive species S. chilensis showed an opposite pattern, suggesting a promising direction for future research. This thesis provides novel data on plant-root fungi interactions in areas affected by fire and grazing. It highlights the need for further exploration of the effects of fire and its interaction with grazing on these interactions, as well as on potential impacts on plant populations.