The management of mine tailings (MT) is commonly workload heavy, intrusive, and expensive. Phytostabilization offers a promising approach for MT management; however, it poses challenges due to the unfavorable physicochemical properties of these wastes. Nevertheless, native microorganisms capable of supporting plant growth and development could enhance the efficacy of phytostabilization. This study assesses the biological activity of microbial communities from the root zone of Baccharis linearis, which is naturally present in MT, in order to evaluate their biotechnological potential for phytostabilization. The root zone and bulk samples were collected from B. linearis plants located within a MT in the Mediterranean zone of Chile. Enzyme activities related to the cycling of C, N, and P were assessed. The community-level physiological profile was evaluated using the MicroRespTM system. Bacterial plant growth-promoting (PGP) traits and colony forming units (CFU) were evaluated through qualitative and microbiological methods, respectively. CFU, enzyme activities, and CLPP were higher in the root zone compared with the bulk samples. Five bacterial strains from the root zone exhibited PGP traits such as P solubilization and N acquisition, among others. The presence of microbial communities in the root zone of B. linearis with PGP traits suggests their potential to enhance the ecological management of MT through phytostabilization programs.

Phytoremediation, an environmentally friendly and sustainable approach for addressing Cu-contaminated environments, remains underutilized in mine tailings. Arbuscular mycorrhizal fungi (AMF) play a vital role in reducing Cu levels in plants through various mechanisms, including glomalin stabilization, immobilization within fungal structures, and enhancing plant tolerance to oxidative stress. Yeasts also contribute to plant growth and metal tolerance by producing phytohormones, solubilizing phosphates, generating exopolysaccharides, and facilitating AMF colonization. This study aimed to assess the impact of AMF and yeast inoculation on the growth and antioxidant response of Oenothera picensis plants growing in Cu mine tailings amended with compost. Plants were either non-inoculated (NY) or inoculated with Meyerozyma guilliermondii (MG), Rhodotorula mucilaginosa (RM), or a combination of both (MIX). Plants were also inoculated with Claroideoglomus claroideum (CC), while others remained non-AMF inoculated (NM). The results indicated significantly higher shoot biomass in the MG-NM treatment, showing a 3.4-fold increase compared to the NY-NM treatment. The MG-CC treatment exhibited the most substantial increase in root biomass, reaching 5-fold that in the NY-NM treatment. Co-inoculation of AMF and yeast influenced antioxidant activity, particularly catalase and ascorbate peroxidase. Furthermore, AMF and yeast inoculation individually led to a 2-fold decrease in total phenols in the roots. Yeast inoculation notably reduced non-enzymatic antioxidant activity in the ABTS and CUPRAC assays. Both AMF and yeast inoculation promoted the production of photosynthetic pigments, further emphasizing their importance in phytoremediation programs for mine tailings.

Despite the global expansion of forest plantations in Chile, their effect on biology properties of soil has still been only scarcely studied. Land use change in the Chilean Coastal Cordillera (36° to 40° S) is mainly attributed to the conversion of native forest to agriculture and forest plantations (Eucalyptus globulus and Pinus radiata de Don). The aim of this paper was to evaluate the changes in microbial composition (PCR-DGGE) and enzyme activity after the substitution of a native forest (e.g., Nothofagus spp.) by fast-growing exotic species and cropping. The most important factors that influence the abundance and diversity of bacteria and the fungi community were the soil organic matter (SOM) content, phosphorous (P-Olsen), calcium (Ca), boron (B), and water-holding capacity. These variables can better predict the microbial community composition and its enzymatic activity in the surface Ah horizon. Land use change also affected chemical soil properties of biogeochemical cycles. However, to deeply understand the connection between chemical and physical soil factors and microbial community composition, more research is needed. On the other hand, the expansion of forest plantations in Chile should be subject to legislation aimed to protect the biological legacy as a strategy for forest productivity as well as the soil microbial biodiversity.

Microplastics (MPs) are plastic particles that range in size from 0.1 μm to 5 mm. They have received widespread attention in the global environmental science community due to their potential effects on living organisms, ecosystem pollution, low recycling rate, and interaction with organic and inorganic contaminants. Although much research has been focused on MPs in aquatic ecosystems, terrestrial ecosystems have been largely overlooked. Consequently, there is still scarce knowledge on the sources and occurrence of MPs in soils. After being deposited in soil, MPs undergo an aging process that involves the breakdown of their polymeric chains, which promotes the interaction between MPs and organic and inorganic contaminants. This process further increases the toxicity of MPs when they sorb pollutants from the environment, which can be transported to water bodies and living organisms. However, research regarding the aging of MPs and their toxicity is needed since previous studies do not consider realistic soil conditions. Additionally, interactions between MPs and pollutants have been primarily studied for conventional MPs, with scarce research on such topics for degradable MPs, especially concerning interactions with metal(loid)s. In general, the interaction of degradable MPs with other contaminants and their further toxicity have been overlooked.

MPs have been shown to negatively affect some physical, chemical, and biological soil properties. However, results varied between studies, which have been associated with the type and shape of MPs, soil aggregate structure, porosity, water and oxygen availability, among others. More research is needed to confirm such relationships in soils. Previous studies have been mainly performed in Europe and Asia, with scarce research in Latin America. In Chile, only one study has been conducted on MPs in soils at field conditions, with other two studies regarding the effect of MPs and metals on soil biochemical properties under controlled environments. Therefore, considerable efforts should be taken to study MPs in Chilean soils. Thus, this study aims to address these gaps by considering some realistic approaches that are missing from current research on MPs. Specifically, this research will: 1) assess MPs in soils from different land uses and examine their association with soil properties; 2) evaluate degradable MPs; 3) study the ageing and adsorption capability of different MPs to metal(loid)s in soils; and 4) investigate the interactive effect of MPs and metal(loid)s under realistic conditions (including a real dose of MPs and metal(loid)s, temperature fluctuations, and soils from different land use types). By taking these steps, this study will provide novel insights into the occurrence of MPs in Chilean soils and shed light on the dynamics of soil microbial communities in the presence of MPs and metal(loid)s.

Based on the above, the proposed research aims to evaluate the effect of different types of MPs and their interaction with metal(loid)s on the soil community structure and functionality from different land use types under realistic conditions. The hypothesis is that MPs will negatively affect soil microbiome structure and functionality due to changes in soil physicochemical properties, which will be moderated by changes in the type, doses, ageing of MPs and their interactions with metal(loid)s in soil from different land type uses. This proposal will be conducted in the O’Higgins Region (VI) of Chile. Firstly, in Phase 1, six localities from different land use types will be selected: an urban wetland, agricultural field, and sclerophyll forest. Soil samples will be taken to quantify and characterize the types of MPs in soil. Secondly, in Phase 2, the evaluation of different types of aging of MPs (conventional and degradable) on chemical characteristics of such particles will be performed, which is based on the ability of MPs as carriers of metal(loid)s. With information and soils obtained from Phase 1, a realistic experimental approach will be performed in the Phase 3. These include the evaluation of aged MPs (degradable and non-degradable) on soil physicochemical and biochemical properties, and the study of degradable and non-degradable aged MPs with metal(loid)s on the functionality, structure, and co-occurrence patterns of soil microbial communities. These phases are designed to be performed over three years. This is the first study focused on the evaluation the effect of MPs and metal(loid)s on microbial communities of soils from different land use types in Chile.

Soil biological properties are sensitive indicators of soil quality changes due to perturbations occurred under agricultural management. The effects of contrasting tillage, increasing nitrogen fertilization doses, and crop rotations [e.g., bean, maize, bean (BMB) and bean, amaranth, bean (BAB)] on soil physicochemical and biological properties in an Andean soil from Ecuadorian highlands were evaluated in this study. Acid phosphatase, ?-Glucosidase, fluorescein diacetate hydrolysis, microbial biomass carbon (Cmic), soil basal respiration (BR), arbuscular mycorrhizal fungi (AMF) spore density, total glomalin content (TGRSP), and soil physicochemical properties were analyzed. Conventional tillage (CT) and crop rotation showed significant effects on soil physicochemical and biological properties. Towards the final crop rotations, no-tillage (NT) promoted BR, TGRSP, and higher AMF spore density in both crop rotations; the Cmic kept stable along time in BMB and BAB, while BR doubled its value when compared to CT. Results indicated that the AMF spore density increased by 308% at the end of the BMB, and 461% at the end of the BAB, while TGRSP increased by 18% and 32% at the end of BMB and BAB, respectively. Biological traits demonstrated to be strongly associated to the organic matter accumulation originated from crop residues under the NT post-harvest which improved soil moisture, biological activity, and AMF interaction. The conservative soil management system has definitively improved general soil properties when compared to soil conditions under the intensive soil management system in this research.

Los parámetros biológicos son usados como indicadores tempranos en la calidad de un suelo (ICS) agrícola, ya que responden rápidamente al manejo antrópico. El objetivo de esta investigación fue determinar el efecto del sistema de labranza: siembra directa (SD) y labranza convencional (LC), y de la fertilización nitrogenada después de los cultivos de fréjol y maíz, sobre ciertos indicadores biológicos de la calidad del suelo. El estudio se realizó sobre un molisol de la región andina del Ecuador. Se determinó la biomasa microbiana (BM), respiración microbiana (RM), y actividad enzimática (fosfatasa ácida, hidrólisis de la fluoresceína-diacetato [FDA], y ?-glucosidasa [?-G]). Los resultados mostraron que la fosfatasa presentó la mayor actividad bajo LC, la FDA respondió al efecto de los niveles altos de nitrógeno (N), la actividad de la enzima ?-G fue mayor en LC. Adicionalmente, el análisis de componentes principales seleccionó a los indicadores biológicos estudiados, como ICS. Se concluye que los indicadores biológicos del suelo fueron afectados por las prácticas de manejo estudiadas.