Quarry restoration treatments from recycled waste modify the physicochemical soil properties, composition and activity of bacterial communities and priming effect in semi-arid areas

The selection of a suitable organic amendment for recovery of semi-arid soils degraded by mining is key to the success of an ecological restoration. The aim of this research is to study the short-term responses of physicochemical, biochemical and biological properties, as well as the changes of a soil bacterial community at the genus level after application of five types of organic amendments in a limestone quarry in Almería (SE, Spain). The relationship among bacterial taxa with biochemical and physicochemical properties and priming effect from restored soils was also analysed. Six months after the application of organic amendments, the values of different soil status, such as total organic carbon, total nitrogen, assimilable phosphorus and labile organic matter forms (carbohydrates and polyphenols), basal respiration (BR) and enzymatic activities increased significantly with respect to unrestored soils. Similarly, a positive priming effect of soil organic matter mineralisation was produced by all organic amendments, being significantly higher (p < 0.05) in sewage sludge-treated soils. Bacterial diversity was higher in restored than in control soils. The restoration caused changes in soil bacterial communities' composition at the phylum and genus levels. It was observed that soil bacterial communities were significantly related to several physical, chemical and biochemical soil properties, establishing two different co-occurrence patterns between restored and unrestored soils. A first bacterial co-occurrence pattern showed significant positive correlations to pH and C/N ratio and negativity with the rest of the soil properties. The second bacterial pattern was positively correlated with carbohydrates, μg of C, priming effect, BR, β-glucosidase and phosphatase and negatively with pH and C/N ratio. It was concluded that soil bacterial communities are clearly influenced by the types of organic amendments applied. Bacterial taxa such as Taibaiella or Pseudomonas could perform key functions in the carbon cycle in restored soils.
This work was supported by the Spanish FEDER-Ministry of Science, Innovation and Universities Research Project BIORESOC (CGL2017-88734-R) and AGL2017-85755-R MINECO/AEI/FEDER, UE, and FEDER-Junta de Andalucía Research Projects RESTAGRO (UAL18-RNM-A021-B) and Restoration of Abandoned Agricultural Soils in Semiarid Zones to Improve Productivity and Soil Quality and Enhance Carbon Sequestration (P18-RT-4112). Natalia Rodríguez-Berbel acknowledges a Ph.D. research grant from Spanish Government (PRE2018-084964). Isabel Miralles is grateful for funding received from the Ramón y Cajal Research Grant (RYC-2016-21191) from Spanish Ministry of Economy, Industry and Competitiveness (MINECO) and Raúl Ortega thanks his postdoctoral contract HIPATIA at University of Almería Research Plan. The authors wish to emphasize that this work was made possible by the kindness of CEMEX ESPAÑA OPERACIONES, S.L.U. (“CEMEX”) owners of the land located in the cement factory in Gádor (Almería) on which the study was carried out and BIOMASAS DEL GUADALQUIVIR, S.A. and Servicios Ambientales las Chozas, S.L. companies, for giving their composting products to this research