Abstract
Soil bacterial communities change from year to year, but whether changes are coordinated across distant ecosystems has not been investigated. We analyzed 1,212 soil cores collected from 2020 to 2024, at 20 National Ecological Observatory Network (NEON) sites spanning arctic tundra, tropical forest, grassland, and desert ecosystems. Bacterial composition, profiled by 16S rRNA data amplicon sequencing, varied significantly among years in 15 of 21 site by horizon strata (PERMANOVA, pooled p = 0.001, mean R² = 0.12). Genus level temporal trajectories were positively correlated among strata (mean Spearman ρ = 0.167-0.218, p = 0.001, 999 permutations for year labels), indicating coordinated changes of interannual communities across geographically separated sites. Geographic distance was not associated with community synchrony (Spearman ρ = −0.035, one-sided p = 0.333), and similarity in preseason temperature anomalies did not predict synchrony in the primary analysis (ρ = 0.056, p = 0.289). Soil pH similarity showed a weak association with synchrony of bacterial communities (Spearman ρ = −0.181, one-sided p = 0.043), which should be interpreted with caution. Overall, these results provide evidence for coordinated interannual dynamics of soil bacterial communities across continental-scale ecosystems, while the environmental drivers and mechanisms underlying this coordination should be the focus of future studies.