New Soil, Old Plants, and Ubiquitous Microbes: Evaluating the Potential of Incipient Basaltic Soil to Support Native Plant Growth and Influence Belowground Soil Microbial Community Composition

The scientific landscape of phytoremediation of tailings: a bibliometric and scientometric analysis

This article seeks to evaluate the scientific landscape of the phytoremediation of mine tailings through a series of bibliometric and scientometric techniques. Phytoremediation has emerged as a sustainable approach to remediate metal-contaminated mine waste areas. A scientometric analysis of 913 publications indexed in Web of Science from 1999 to 2023 was conducted using CiteSpace. The results reveal an expanding, interdisciplinary field with environmental sciences as the core category. Keyword analysis of 561 nodes and 2,825 links shows a focus on plant-metal interactions, microbial partnerships, bioavailability, and field validation. Co-citation analysis of 1,032 nodes and 2,944 links identifies seminal works on native species, plant-microbe interactions, and amendments. Temporal mapping of 15 co-citation clusters indicates a progression from early risk assessments and native plant inquiries to integrated biological systems, economic feasibility, and sustainability considerations. Recent trends emphasize multidimensional factors influencing adoption, such as plant-soil-microbe interactions, organic amendments, and field-scale performance evaluation. The findings demonstrate an intensifying translation of phytoremediation from scientific novelty to engineering practice. This quantitative and qualitative analysis of research trends aids in understanding the development of phytoremediation for mine tailings. The results provide valuable insights for researchers and practitioners in this evolving field.

Spatial Variation of Microbial Community Structure and Its Driving Environmental Factors in Two Forest Types in Permafrost Region of Greater Xing′an Mountains

Climate warming is accelerating permafrost degradation. Soil microorganisms play key roles in the maintenance of high-latitude permafrost regions and forest ecosystems’ functioning and regulation of biogeochemical cycles. In this study, we used Illumina MiSeq high-throughput sequencing to investigate soil bacterial community composition at a primeval Larix gmelinii forest and a secondary Betula platyphylla forest in a permafrost region of the Greater Xing’an Mountains. The Shannon diversity index tended to decrease and then increase with increasing soil depth, which was significantly higher in the L. gmelinii forest than in the B. platyphylla forest at 40–60 cm. Proteobacteria (19.86–29.68%), Acidobacteria (13.59–31.44%), Chloroflexi (11.04–27.19%), Actinobacteria (7.05–25.57%), Gemmatimonadetes (1.76–9.18%), and Verrucomicrobia (2.03–7.00%) were the predominant phyla of the bacterial community in two forest types. The relative abundance of Proteobacteria showed a decreasing trend in the B. platyphylla forest and an increasing trend in the L. gmelinii forest, whereas that of Chloroflexi increased and then decreased in the B. platyphylla forest and decreased in the L. gmelinii forest with increasing soil depth. The relative abundance of Acidobacteria was significantly higher in the B. platyphylla forest than in the L. gmelinii forest at 0–20 cm depth, whereas that of Actinobacteria was significantly higher in the L. gmelinii forest than in the B. platyphylla forest at 0–20 cm and 40–60 cm depth. Principal coordinate analysis (PCoA) and two-way analysis of variance (ANOVA) indicated that microbial community composition was more significantly influenced by forest type than soil depth. Redundancy analysis (RDA) showed that microbial community structure was strongly affected by soil physicochemical properties such as nitrate nitrogen (NO3−-N), pH, and total organic carbon (TOC). These results offer insights into the potential relationship between soil microbial community and forest conversion in high latitude permafrost ecosystems.

Can We Use Functional Annotation of Prokaryotic Taxa (FAPROTAX) to Assign the Ecological Functions of Soil Bacteria?

FAPROTAX is a promising tool for predicting ecological relevant functions of bacterial and archaeal taxa derived from 16S rRNA amplicon sequencing. The database was initially developed to predict the function of marine species using standard microbiological references. This study, however, has attempted to access the application of FAPROTAX in soil environments. We hypothesized that FAPROTAX was compatible with terrestrial ecosystems. The potential use of FAPROTAX to assign ecological functions of soil bacteria was investigated using meta-analysis and our newly designed experiments. Soil samples from two major terrestrial ecosystems, including agricultural land and forest, were collected. Bacterial taxonomy was analyzed using Illumina sequencing of the 16S rRNA gene and ecological functions of the soil bacteria were assigned by FAPROTAX. The presence of all functionally assigned OTUs (Operation Taxonomic Units) in soil were manually checked using peer-reviewed articles as well as standard microbiology books. Overall, we showed that sample source was not a predominant factor that limited the application of FAPROTAX, but poor taxonomic identification was. The proportion of assigned taxa between aquatic and non-aquatic ecosystems was not significantly different (p > 0.05). There were strong and significant correlations (σ = 0.90–0.95, p < 0.01) between the number of OTUs assigned to genus or order level and the number of functionally assigned OTUs. After manual verification, we found that more than 97% of the FAPROTAX assigned OTUs have previously been detected and potentially performed functions in agricultural and forest soils. We further provided information regarding taxa capable of N-fixation, P and K solubilization, which are three main important elements in soil systems and can be integrated with FAPROTAX to increase the proportion of functionally assigned OTUs. Consequently, we concluded that FAPROTAX can be used for a fast-functional screening or grouping of 16S derived bacterial data from terrestrial ecosystems and its performance could be enhanced through improving the taxonomic and functional reference databases.