Metagenomic characterization of soil bacterial communities in young chestnut orchards in northern Portugal

Soil microorganisms play a crucial role in biogeochemical cycles and are key drivers of soil productivity. However, the soil bacterial community associated with the European chestnut (Castanea sativa Mill.) remains poorly characterized. In this sense, this study aimed to characterize the soil bacterial community in young chestnut orchards in northern Portugal and investigate its dynamics throughout the year. Soil samples were taken in three different periods of the year (spring, summer, and autumn) from two young chestnuts orchards located in Parada (41°38’12.53”N, 6°42’42.94”W) and Salgueiros (41°54’12.73”N, 7°01’40.95”W) with elevations of 740 and 1008 m, respectively. Soil DNA was extracted, and the 16S rRNA amplicons were sequenced using the Illumina MiSeq platform. Overall, the bacterial core of chestnut orchards predominantly consisted of four main phyla: Proteobacteria, Acidobacteriota, Actinobacteriota, and Chloroflexi, which were consistently present in both study sites and across all seasons. However, the phylum Chloroflexi, known for its metabolic and phenotypic diversity, exhibited the highest prominence at higher altitudes during autumn. Acidobacteriales and Acidobacteriaceae (Subgroup 1) of Acidobacteriota, as well as Rhizobiales, Sphingomonadaceae, Rickettsiale, and Micropespsaceae, Burkholderiales, and Xanthomonadales of Proteobacteria, as well as Thermoleophila and Acidimicrobia of Actinobacteriota were dominant across all seasons and in both study sites. This study provides valuable insights into the bacterial community associated with chestnut species and contributes to monitoring potential ecosystem changes resulting from climate change.