Abstract
PurposeMining activities have negative effects on soil characteristics and can result in low pH, high heavy metal content, and limited levels of essential nutrients. A tailings storage area located in northwestern Québec showed natural colonization by plants from the adjacent natural environment. The objective of the study was to determine the main edaphic parameters that structured microbial populations associated with the indigenous woody plants that had naturally colonized the site.MethodsMicrobial populations were studied in the bulk soil, the rhizosphere, and inside plant roots using Illumina sequencing, ordination analysis (i.e., redundancy analysis (RDA) and principal coordinates analysis (PCoA)), ternary plotting, and statistical analysis (MANOVA).ResultsThe main variables that drove the microbial community patterns were plant species and the tailings pH. Indeed, the main bacterial classes were Gammaproteobacteria and Deltaproteobacteria in both the rhizosphere and root endosphere. Analysis revealed that some dominant operational taxonomic units (e.g., Pseudomonas sp., Acinetobacter sp., and Delftia sp.) were present in increased proportions in roots for each plant species under study. This study also revealed that many of the most abundant fungal genera (e.g., Claussenomyces, Eupenicillium, and Trichoderma) were more abundant in the rhizosphere than in the root endosphere.ConclusionsThis comprehensive study of the microbial community dynamics in the bulk soil, rhizosphere, and root endosphere of boreal trees and shrubs could be beneficial in facilitating the rehabilitation of disturbed ecosystems.
Highlights
In Québec, more than 100 years of mining activities have etched into the province
It is essential for the plants to associate with soil microorganisms that can promote the growth of the plant, such as PGPR, which provide several benefits to plants (Van Der Heijen et al 2008; Ma et al 2011)
Canonical Redundancy analysis (RDA) showed that the key environmental parameters driving the presence of the 30 most abundant bacterial and fungal taxa in the three environments are plant species (p_s) and pH, which partly confirms our first hypothesis stating that plant species, pH, and water content would be the key drivers of the microbial community structure (Fig. 2 and Table 1)
Summary
In Québec, more than 100 years of mining activities have etched into the province. Since 1890, many metals have been mined in this province, most notably iron, nickel, zinc, copper, and gold, leaving hundreds of abandonedGagnon et al Annals of Microbiology (2020) 70:41 and little or no organic content make it difficult for the establishment of primary successional plants (Sheoran et al 2010). Microbial communities (e.g., bacteria, ectomycorrhizal (ECM) fungi, arbuscular fungi (AM), and dark septate endophytes (DSEs)) living in the plant rhizosphere can alleviate the phytotoxicity of metals through various mechanisms. They can exclude some metals via restricted membrane permeability or by actively transporting metals outside the cell. These microbial communities may enhance the mobilization and uptake of nutrients by plants (Courty et al 2010) For their part, plants are able to recruit specific microorganisms to populate the rhizosphere and roots by modulating the secretion of molecules in their root exudates (i.e., sugars, hormones, amino acids, organic acids, etc.). In the context of mine site reclamation, PGPR microorganisms associated with pioneer plants could improve phytoremediation success (Zhuang et al 2007; Hrynkiewicz and Baum 2011)
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