Soil microbial communities from fertile islands under semi-arid conditions in La Guajira, Colombian Caribbean

Abstract

Abstract Fertile islands are key ecological arrangements for slowing desertification processes in arid and semi-arid environments. These islands harbor a great variety of microorganisms that play an important role in their establishment and dynamics. The taxonomic and functional diversity of bacteria on these islands is conditioned by the nurse tree and the characteristics of their environment. However, the microbial diversity associated with these vegetation patterns is not described in the semi-arid environments of northern South America. The present study analyzed the taxonomic and functional diversity of soil microbial communities of fertile islands belonging to three species of nurse trees in the Colombian Caribbean during a wet and a dry season. DNA extraction and massive sequencing were performed from soil surface samples under the nurse plant canopy and bare soil. The SILVA database was used for taxonomic analyses, DIAMOND and the KEGG database for functional analyses, and STAMP for statistical differences. Taxonomic and functional diversity was mainly determined by seasonality and the presence or absence of vegetation. No significant differences were found among nurse plant species. The highest taxonomic abundances were recorded in the dry season under the nurse tree for the phyla Proteobacteria and Actinobacteriota, and the genera Sphingomonas, Azospira, Solirubrobacter, Flavisolibacter, and Geodermatophilus. While the highest functional potential was detected in the wet season. The presence of several biogeochemical cycling modules and unique genera suggest the presence of microniches that could be differentiated by oxygen tension and nutrient availability due to seasonality and the presence or absence of vegetation.