From disturbance to resilience: early microbial community establishment in landslide soils of New Zealand.

Landslides strongly reshape mountain landscapes and initiate soil formation, yet microbial succession in newly formed soils remains poorly understood. We analysed bacterial and archaeal communities along a centennial landslide chronosequence in the Western Southern Alps of New Zealand using 16S rRNA gene amplicon sequencing and geochemical data. A core microbial community was established within ∼3 years and persisted for up to ∼100 years. Alpha diversity declined with soil age and was lowest in the oldest soils (Shannon: 4.8 ± 0.4 to 4.0 ± 0.2). Community composition showed strong and consistent turnover across the chronosequence, with age and soil geochemistry jointly explaining 19% of variation. Bacterial assemblages were dominated by Actinobacteriota, Chloroflexi, and Pseudomonadota, while archaea comprised 3.3%-9.5% of total abundance and were mainly dominated by Thermoproteota and Thermoplasmatota. Increasing soil age was associated with higher total organic carbon, greater abundance of oligotrophic taxa, and higher bacterial 16S rRNA gene copy numbers. Functional predictions indicated a transition from labile carbon turnover in young soils to enhanced potential for complex organic matter degradation in older soils. Overall, microbial communities assemble rapidly after disturbance and undergo gradual, predictable shifts toward more specialized and functionally differentiated assemblages during soil development.