Time of Stablishment of Pastures and Their Relationship with Arbuscular Mycorrhiza in Hilly Terrain and Fertile Valley

The subject of this research was to evaluate the effect of the time of establishment (0-5 years, 5-10 years, and more than 10 years.) of pastures of Brachiaria sp. over theArbuscular Mycorrhizal Fungal populations (AMF): genus and spore distribution, length of extramatrical mycelia, root colonizations by AMF and septate fungi; the pastures resulting from fragmentation of the tropical rainforest with valley and hilly landscapes at Florencia, Caquetá, Colombia. Whichever the age of pasture, the genera Glomus and Acaulospora predominate; the change of coverage require more than ten years for different species of MAF to recolonize, adapt and diversify. In hilly terrain, the Brachiaria sp-MAF relationship decrease with time, specially after ten years of establishment; in valley landscapes the relationship is medium and homogeneous (21- 50%), while the root colonization by septate fungi increased, showing possibly a competitive mechanism by root space or a cooperative activity. Finally, the extramatrical mycelia and spores in any landscape had a variable behavior (increase, decrease or stability) with time.