Soil properties influence bacterial abundance and diversity under different land-use regimes in semi-arid environments

Abstract

Bacterial diversity is known to be a driver of soil ecosystem services and it is influenced by the natural integrity of the environments. Samples from garden soil, saline soil and sludge-impacted soil were studied to evaluate the influence of soil properties on bacterial abundance and diversity for improved management. Soil samples were collected from 0 to 15 cm depth and analyzed for selected physico-chemical properties using routine labo- ratory procedures. 16S rRNA gene-based metagenomics analysis was used to identify and quantify bacteria from the samples. Garden soil had pH (H 2 O) of 5.8, electrical conduc- tivity (EC) of 0.3 dS m −1 , organic matter (OM) content of 0.66%, total phosphorus (P) and cation exchange capacity (CEC) of 132 ppm and 2.40 Cmol kg −1 , respectively, and 8.39% clay; sludge impacted soil had a pH (H 2 O) of 5.8, EC of 5.7 dS m −1 , OM content of 57.5%, 2641 ppm P, CEC content of 8.62 Cmol kg −1 and 18.23% clay; while salt affected (saline) soil had a pH (H 2 O) of 7.6, EC of 4.4 dS m −1 , OM of 0.5%, P content of 24.9 ppm, CEC of 4.05 Cmol kg −1 and 13.07% of clay contents. The distribution of bacteria phyla identified in the soils is as follows: sludge-impacted soil (15), garden (13) and bare saline (10). Next generation sequencing shows that five of the phyla in the order Proteobacteria > Actinobac- teria > Firmicutes > Bacteroidetes > Acidobacteria were present and dominant in all the soils. Soils under the different land uses significantly varied in their properties. It is con- cluded that bacterial diversity was influenced by the degree of habitat disturbance caused by variation in land-use management practices which affected properties of the soils. This study opens up new frontiers in expanding metagenomics studies in the semi-arid en- vironments of Botswana and contributes to the identification of soil bacteria which are useful to ecosystem functions.