Soil microbial diversity and community are determined by anthropogenic
activities and environmental conditions, which greatly affect the
functioning of ecosystem. We investigated the soil bacterial diversity,
communities, and nitrogen (N) functional genes with different
disturbance intensity levels from crop, transition, to forest soils at
three locations in the coastal region of Georgia, USA. Illumina
high-throughput DNA sequencing based on bacterial 16S rRNA genes were
performed for bacterial diversity and community analyses. Nitrifying
(AOB amoA) and denitrifying (nirK) functional genes were further
detected using quantitative PCR (qPCR) and Denaturing Gradient Gel
Electrophoresis (DGGE). Soil bacterial community structure determined by
Illumina sequences were significantly different between crop and forest
soils (p < 0.01), as well as between crop and transition soils
(p = 0.01). However, there is no difference between transition and
forest soils. Compared to less disturbed forest, agricultural practice
significantly decreased soil bacterial richness and Shannon diversity.
Soil pH and nitrate contents together contributed highest for the
observed different bacterial communities (Correlations = 0.381). Two
OTUs (OTU5, OTU8) belonging to Acidobacteriales species decreased in
crop soils, however, agricultural practices significantly increased an
OTU (OTU4) of Nitrobacteraceae. The relative abundance of AOB amoA gene
was significantly higher in crop soils than in forest and transition
soils. Distinct grouping of soil denitrifying bacterial nirK communities
was observed and agricultural practices significantly decreased the
diversity of nirK gene compared to forest soils. Anthropogenic effects
through agricultural practices negatively affecting the soil bacterial
diversity, community structure, and N functional genes.
Vineyard soil bacterial diversity and composition revealed by 16S rRNA genes: Differentiation by vineyard management
