Differential diversity and structure of autotrophs in agricultural soils of Qinghai Province

The biodiversity of CO₂-assimilating bacterial communities is pivotal for carbon sequestration in agricultural systems. Changes in the diversity, structure, and activity of the soil chemolithoautotrophic bacteria were examined in four agricultural areas, Dulan (DL), Gonghe (GH), Huzhu (HZ), and Datong (DT) counties in Qinghai Province, where wheat, oilseed rape, and barley were planted. This process was performed using Illumina amplicon sequencing of the ribulose-1,5-bisphosphatecarboxylase/oxygenase (RubisCO) gene (cbbL Form I) and activity data. The diversity, community, and activity of soil autotrophic CO₂-fixing bacteria differed significantly across soil sites, whereas cbbL-bearing bacterial diversity and activity were similar across different crop types. RubisCO activity in the HZ region was significantly greater than in the other three regions (P < 0.001). The overall relative abundance trend of the bacterial taxa was similar among the three crop samples. Moreover, 31, 27, 10, and 8 significant linear discriminant analysis effect sizes were identified in the four regions collected from HZ, DL, DT, and GH, respectively. No significant biomarkers were detected in any of the crop groups. Some soil properties had significant relationships with the autotrophic bacterial community composition.

Importance: Agricultural soil plays important roles in carbon fixation during carbon capture and storage. Autotrophic bacteria that utilize inorganic compounds as electron donors for growth fix CO₂ photosynthetically or chemo-autotrophically in diverse ecosystems and affect soil organic carbon sequestration. Soil properties, agronomic management measures, and environmental factors can influence the community composition, abundance, and activity of CO₂-assimilating bacteria. This study aims at evaluating the effects of different regions and crop types on the abundance, composition, and activity of CO₂-fixing bacteria in agricultural soil.