Enzyme activities (EAs) respond to contamination in several ways depending on the chemical form and content of heavy metals and metalloids (HMs) and their interactions with various soil properties. A ...systematic and mechanistic understanding of EA responses to HM contamination in soil is necessary for predicting the consequences for nutrient availability and the cycling of carbon (C), nitrogen (N), phosphorus (P) and sulphur (S). In this study, a meta-analysis based on 671 observations found the activities of seven enzymes to decrease in response to soil contamination with Pb, Zn, Cd, Cu and As. HM contamination linearly reduced the activities of all enzymes in the following order: arylsulfatase > dehydrogenase > β-glucosidase > urease > acid phosphatase > alkaline phosphatase > catalase. The activities of two endoenzymes: arylsulfatase (partly as exoenzyme) and dehydrogenase were reduced by 72% and 64%, respectively. These reductions were two times greater than of exoenzymes: β-glucosidase, urease, acid phosphatase, alkaline phosphatase and catalase (partly endoenzyme). This reflects the much stronger impact of HMs on living microorganisms and their endoenzymes than on extracellular enzymes stabilized on clay minerals and organic matter. Increasing clay content weakened the negative effects of HM contamination on EAs. All negative effects of HMs on EAs decreased with soil depth because HMs remain mainly in the topsoil. EAs involved in the cycling of C and S were more affected by HMs than the enzymes associated with the cycling of N and P. Consequently, HM contamination may alter the stoichiometry of C, N, P and S released by enzymatic decomposition of organic compounds that consequently affect microbial community structure and activity.
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•The effect of heavy metals on enzyme activities (EAs) was studied by meta-analysis.•EAs were reduced in heavy metal (HM) contaminated soils.•The reductions in EAs by HMs were two times greater in endoenzymes than exoenzymes.•Higher clay content and soil depth decreased the effect of HM contamination on EAs.•EAs involved in C and S cycling were more affected than enzymes related to P and N.
Copper (Cu) mining has to address a critical environmental issue related to the disposal of heavy metals and metalloids (HMs). Due to their deleterious effects on living organisms, Cu and arsenic ...(As) have gained global attention, and thus their monitoring in the environment is an important task. The aims of this study were: 1) to evaluate the alteration of soil enzyme activities (EAs) and soil microbial functional diversity with Cu/As contamination, and 2) to select the most reliable biochemical indicators of Cu/As contamination. A twelve-week soil experiment was performed with four increasing levels of Cu, As, and Cu/As from 150/15 to 1000/100 mg Cu/As kg−1. Soil enzyme activities and soil community-level physiological profile (CLPP) using MicroResp™ were measured during the experiment. Results showed reduced EAs over time with increasing Cu and Cu/As levels. The most Cu-sensitive EAs were dehydrogenase, acid phosphatase, and arylsulfatase, while arginine ammonification might be related to the resilience of soil microbial communities due to its increased activity in the last experimental times. There was no consistent response to As contamination with reduced individual EAs at specific sampling times, being urease the only EA negatively affected by As. MicroResp™ showed reduced carbon (C) substrate utilization with increasing Cu levels indicating a community shift in C acquisition. These results support the use of specific EAs to assess the environmental impact of specific HMs, being also the first assessment of EAs and the use of CLPP (MicroResp™) to study the environmental impact in Cu/As contaminated soils.
•Soil enzyme activities (EAs) were studied in a Cu/As contaminated soil over time.•Microbial community level physiological profile (CLPP) was studied with MicroResp™.•Dehydrogenase, arylsulfatase, and acid phosphatase were suitable indicators.•Carbon substrate utilization decreased with increasing Cu soil contents.•Arsenic did not consistently affect to EAs and CLPP.
Different techniques have been developed for the remediation of Cu contaminated soils, being the phytoremediation a sustainable and environmentally friendly strategy, but its use in mine tailings is ...scarce. Arbuscular mycorrhizal fungi (AMF) can decrease the Cu concentration in plants by favouring the stabilization of this metal through different mechanisms such as the production of glomalin, immobilization in the fungal wall of hyphae and spores, and the storage of Cu in vacuoles. Additionally, the use of organic amendments promotes the beneficial effects produced by AMF and improves plant growth. Based on the above, the aim of this study was to determine the effect of AMF inoculation and compost application at different doses on the growth of Oenothera picensis in a Cu mine tailing. One group of plants were inoculated with Claroideoglomus claroideum (CC) and other was non-inoculated (NM). Both CC and NM were grown for two month under greenhouse conditions in pots with the Cu mine tailing, which also had increasing compost doses (0%, 2.5%, 5%, and 10%). Results showed greater biomass production of O. picensis by CC up to 2-fold compared with NM. This effect was improved by the compost addition, especially at doses of 5% and 10%. Therefore, the increase of mycorrhizal and nutritional parameters in O. picensis, and the decreasing of Cu availability in the mine tailing, promoted the production of photosynthetic pigments together with the plant growth, which is of importance to accomplish phytoremediation programs in Cu mine tailings.
•We used C. claroideum and compost to establish O. picensis directly in Cu mine tailings.•Compost rates of 5–10% greatly increased the intra- and extraradical fungal growth.•C. claroideum strongly reduced the Cu availability in mine tailing in compost treatments.•Joint use of AMF and compost reduced the plant toxicity and increased photosynthetic pigments.•Our study supports the joint use of AMF and compost for remediation of mine tailings.
Forest fires alter soil microbial communities that are essential to support ecosystem recovery following land burning. These alterations have different responses according to soil abiotic pre- and ...post-fire conditions and fire severity, among others, and tend to decrease along vegetation recovery over time. Thus, understanding the effects of fires on microbial soil communities is critical to evaluate ecosystem resilience and restoration strategies in fire-prone ecosystems. We studied the state of community-level physiological profiles (CLPPs) and the prokaryotic community structure of rhizosphere and bulk soils from two fire-affected sclerophyll forests (one surveyed 17 months and the other 33 months after fire occurrence) in the Mediterranean climate zone of central Chile. Increases in catabolic activity (by average well color development of CLPPs), especially in the rhizosphere as compared with the bulk soil, were observed in the most recently affected site only. Legacy of land burning was still clearly shaping soil prokaryote community structure, as shown by quantitative PCR (qPCR) and Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene, particularly in the most recent fire-affected site. The qPCR copy numbers and alpha diversity indexes (Shannon and Pielou's evenness) of sequencing data decreased in burned soils at both locations. Beta diversity analyses showed dissimilarity of prokaryote communities at both study sites according to fire occurrence, and NO
was the common variable explaining community changes for both of them. Acidobacteria and Rokubacteria phyla significantly decreased in burned soils at both locations, while Firmicutes and Actinobacteria increased. These findings provide a better understanding of the resilience of soil prokaryote communities and their physiological conditions in Mediterranean forests of central Chile following different time periods after fire, conditions that likely influence the ecological processes taking place during recovery of fire-affected ecosystems.
The phosphorus (P) addition can be helpful in the mitigation of the adverse effects of water deficit stress. However, the efficiency of wheat in utilizing both components has not been assessed in ...field conditions. This research aims to assess the effects of P and water addition on phosphorus use efficiency (PUE) and water productivity (WP) in field conditions for select wheat cultivars co-adapted to climate-induced agronomic challenges. Three wheat cultivars were selected based on their PUE and water WP from a previous experiment. The trials were conducted in field conditions over two consecutive years, from 2020 to 2021 (Season 1) and 2021–2022 (Season 2). The plants were grown on an andisol with a soil P concentration of 10 mg P kg−1 and 30 mg P kg−1. Two irrigation treatments were imposed: Well-watered (+W) and dryland (-W). The plants were sampled at three stages: tillering (Z25), anthesis (Z65), and ripening (Z95). At the end of the phenological cycle, grain yield components, grain yield, grain quality, PUE, and WP were evaluated. Phosphorus addition promotes plant growth, especially in the early vegetative stages, by enhancing tiller development and nutrient and water uptake. These effects were critical during the anthesis and ripening stages, enhancing yield components and higher grain production. Differential responses were observed across cultivars, underscoring the genotype-specificity in PUE and WP. Seasonal water deficit stress modulated these effects, highlighting a more complex genotype-environment-nutrient interaction. The water addition promoted PUE and WP, suggesting a synergy between the two components. Among the cultivars, Chevignon outperformed in grain yield, PUE, and WP. However, while phosphorus, water, and environmental factors influenced grain quality, the genetic background of the cultivar was the primary determinant of these components. This study advocates for implementing individual nutrient management strategies tailored to the specific cultivar and adaptable to environmental conditions under climate change.
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•Phosphorus boosts wheat growth by 30% under dryland conditions.•Phosphorus enhances gluten and protein content in wheat under dryland conditions.•Phosphorus use efficiency (PUE) varies across phenological stages and wheat cultivars.•The genetic background of cultivars predominantly determines wheat grain protein and gluten composition.
The main organic input for the elaboration of growing media is peat (Sphagnum spp.), due to its physical and chemical characteristics. However, the mining of this material creates a considerable ...impact in the local ecosystems from which this is obtained, along with a global impact because of the emission of greenhouse gasses. Thus, sustainable materials that can replace, or reduce the use of peat, while maintaining or improving attributes in the growing media and plant growth, are greatly needed. Therefore, this work aims to evaluate the effects of the use of different proportions of compost and biochar on the biological characteristics of growing media and (Lactuca sativa L.) seedling growth prior to transplanting. Out of the biological variables evaluated, the β-glucosidase activity showed the greatest results in growing media based on 80% peat and based on 70% peat, 5% compost and 5% biochar. Moreover, growing media based on the combination of compost, biochar and peat maintained most of the Lactuca sativa L. (Oak Leaf variety) seedling traits obtained in the growing media based on only peat. These findings emphasize the need to further investigate further biological conditions for alternative materials to peat, and the need to pay attention to feedstock initial characteristics and processing in order to obtain high quality organic inputs for optimum growing media.
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.
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.
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