Abstract
Poplars, known for their diversity, are trees that can develop symbiotic relationships with several groups of microorganisms. The genetic diversity of poplars and different abiotic factors influence the properties of the soil and may shape microbial communities. Our study aimed to analyse the impact of poplar genotype on the biomass and community composition of the microbiome of four poplar genotypes grown under different soil conditions and soil depths. Of the three study sites, established in the mid-1990s, one was near a copper smelter, whereas the two others were situated in unpolluted regions, but were differentiated according to the physicochemical traits of the soil. The whole-cell fatty acid analysis was used to determine the biomass and proportions of gram-positive, gram-negative and actinobacteria, arbuscular fungi (AMF), other soil fungi, and protozoa in the whole microbial community in the soil. The results showed that the biomass of microorganisms and their contributions to the community of organisms in the soil close to poplar roots were determined by both factors: the tree-host genotype and the soil environment. However, each group of microorganisms was influenced by these factors to a different degree. In general, the site effect played the main role in shaping the microbial biomass (excluding actinobacteria), whereas tree genotype determined the proportions of the fungal and bacterial groups in the microbial communities and the proportion of AMF in the fungal community. Bacterial biomass was influenced more by site factors, whereas fungal biomass more by tree genotype. With increasing soil depth, a decrease in the biomass of all microorganisms was observed; however, the proportions of the different microorganisms within the soil profile were the result of interactions between the host genotype and soil conditions. Despite the predominant impact of soil conditions, our results showed the important role of poplar genotype in shaping microorganism communities in the soil.
Highlights
The soil microbiome plays a key role in water and nutrient uptake, pathogen protection, pollutant immobilization and other processes observed in terrestrial ecosystems [1,2,3,4,5]
We showed that F:B ratio may be differentiated by poplar genotype which suggests that the biomass of soil microorganisms is mainly determined by site and soil depth, but fungi and bacteria that settle near poplar roots are significantly impacted by tree genotype
Our study revealed a significant impact of soil conditions, soil depth and poplar genotype, and their interactions on the biomass of microorganisms and their contribution to the soil community, with the site being the dominant factor
Summary
The soil microbiome plays a key role in water and nutrient uptake, pathogen protection, pollutant immobilization and other processes observed in terrestrial ecosystems [1,2,3,4,5]. The community composition and biomass of the soil microbiome have been shown as sensitive indicators of changes in the nutrient status of soil [6], plant species composition [7], soil pollutant deposition [8] and climate changes [9]. The role of plant genotypes in shaping soil microbial communities has less been studied, and most studies have focused on short-lived crop plants, e.g., barley, tomato, cucumber, sweet pepper and chickpea [10,13,14], or on Forests 2020, 11, 262; doi:10.3390/f11030262 www.mdpi.com/journal/forests. The host genotype was found to shape endophytic microbial communities present in different plant tissues (roots, stem, leaves) [1,17,18]
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