Exploring soil bacterial and fungal communities in Colombian terrestrial ecosystems modulated by altitude-influenced factors

A bacterial (16S rRNA) and fungal (ITS rRNA) taxonomic characterization was carried out using metabarcoding along an altitudinal gradient in the western range of the Valle del Cauca, Colombia. This study encompassed Tropical Dry Forests, Andean, and Páramo ecosystems in Laguna de Sonso (900 m.a.s.l), Yotoco (1,800 m.a.s.l), Bosque del Duende (2,400 m.a.s.l), and Páramo del Duende (3,200 m.a.s.l). The physicochemical analyses revealed soils with high organic matter (>10%), non-compacted, extremely acidic pH levels (4.4) at higher altitudes, and slightly to moderately acidic pH in lower areas (5.5-6.1). 59 plant families were identified, with Araceae, Lauraceae, and Fabaceae being the most abundant. The most abundant bacterial taxonomic assignments were Acidobacteriota and Proteobacteria phyla, while for fungi, it was Ascomycota and Basidiomycota. Alpha diversity analysis showed high community diversity, whereas beta diversity reflected composition differences among locations and their heterogeneity. The most abundant functional predictions for bacteria were chemoheterotrophic activity and nitrogen cycle involvement. At the same time, for fungi, it was ecological guilds related to pathogenic activity in both animals and plants, endophytes, and epiphytic saprotrophs. The PLS-PM analysis revealed an indirect influence of altitude on microbial abundance and diversity.