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Zinc oxide (ZnO) nanoparticles (NPs) coated with 1‐butyl‐3‐methylimidazolium tetrafluoroborate ionic liquid (IL) (ZnO‐[BMIM][BF4] NPs) and ZnO NPs without IL coating were both synthesized by co‐precipitation. Various analytical methods were used to characterize the synthesized NPs. X‐ray diffraction (XRD) analysis revealed that ZnO NPs had a mean crystallite size of 32 nm and that of ZnO‐[BMIM][BF4] NPs was 22 nm. IL alters the Fourier transform infrared spectroscopy (FTIR) peaks of the as‐prepared ZnO NPs. A blueshift was seen in the absorption peak of ZnO‐[BMIM][BF4] NPs as compared to bare ZnO NPs. An examination of the UV–visible (UV–Vis) spectra revealed that the optical bandgap decreases with the addition of IL to ZnO NPs. Scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HR‐TEM) investigation revealed the morphology and size of the nanostructured particles. The chemically prepared ZnO‐[BMIM][BF4] NPs displayed the irregular spherical‐shaped morphologies in the range of nanoscale. Transmission electron microscopy (TEM) showed the conventional hexagonal wurtzite structure of ZnO‐[BMIM][BF4] NPs. Synthesized ZnO‐NPs in water have a zeta potential of −13.1 mV, showing that they are stable solutions. Thermal behaviour of ZnO NPs was studied using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The agar‐well diffusion technique was used to investigate and compare the antimicrobial activity of synthesized ZnO‐[BMIM][BF4] NPs against the following bacteria and fungi: Streptococcus aureus, Pseudomonas aeruginosa and Candida albicans. The MCF7 breast cancer cells were used to assess the anticancer capabilities of ZnO‐[BMIM][BF4] NPs at various doses (100 μg/mL, 10 μg/mL, 1 μg/mL, 100 ng/mL, 10 ng/mL and 1 ng/mL) using MTT assays. The range of cell inhibition was determined to be from 19.14% to 70.52%. The percentage of cytotoxicity increases was observed when the concentration of synthesized ZnO‐[BMIM][BF4] NPs ranges from 1 ng/mL to 100 μg/mL. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) in temperate forests is a crucial part of the global C cycle. The C and nitrogen (N) inputs may greatly increase in forest ecosystems affected by atmospheric CO2 concentration, N deposition, and other climate change, which may further affect SOC dynamics in temperate forests. Nevertheless, how C and N inputs interact to influence the soil priming effect (PE) in the organic and mineral layers of temperate forests remains unclear. Here, we used easily available C and N sources, such as 13C‐glucose with 2% SOC contents and ammonium nitrate (input C:N ratio = 10), to examine the effects and mechanisms of exogenous C and N inputs on soil CO2 production and PE in both soil layers of a temperate forest. Our research revealed that exogenous C input caused a positive PE in both soil layers, with the mineral layer showing a larger PE per unit of SOC than the organic layer (OL). Although C input increased C loss from native SOC, soil net C accumulation still increased. The C and N inputs decreased the soil PE in both soil layers, suggesting that N input alleviates substrate N limitation and weakens microbial N mining in both soil layers. Meanwhile, the C and N inputs increased the exogenous C remaining in the organic layer, which was beneficial for soil C sequestration. Compared to the organic layer, the response of the mineral layer to C and N inputs was weaker. This study suggests that C and N interact to affect PE on SOC decomposition and this interaction should be considered in modeling and prediction of soil C cycling. [ABSTRACT FROM AUTHOR]

Despite the importance of South Africa's Afromontane grasslands for ecosystem services (water supply and biodiversity), soil organic carbon (SOC) research remains limited. These grasslands evolved with fire, and fire exclusion leads to native plant afforestation. This study investigated SOC fractions and origin to understand the impact of fire‐exclusion‐driven afforestation and aspect on SOC storage in Afromontane grasslands. This study in Cathedral Peak Research Catchments, initiated in the 1940s, compared an afforested fire‐excluded site (AF) to a periodically burnt (accidental fires, 2–5 years interval) grassland (PB) within the same catchment (Catchment‐IX). Additionally, it compared a south‐facing periodically burnt grassland (Catchment‐IX) to a north‐facing biennially burnt grassland (Catchment‐VI). Soil samples collected at soil‐depth increments (0–5, 5–10, 10–15, 15–20, 20–30, 30–60 and 60–100 cm) revealed that, within Catchment IX, PB had more topsoil SOC stocks and microbial activity than AF but similar active carbon (C) concentrations. As expected, δ13C values revealed that SOC in PB originates from C4 grasses, whilst it mostly originates from C3 plants in AF. The south‐facing slope (Catchment‐IX) had more SOC stocks, microbial activity and active C compared to the north‐facing slope (Catchment‐VI). Fire‐exclusion‐driven afforestation changed SOC input from roots to litter, thus reducing SOC storage. Cooler south‐facing slopes are better C reservoirs. Afromontane grasslands show greater potential for C sequestration than afforested systems. [ABSTRACT FROM AUTHOR]

Background: Soils under organic farming systems exhibit better quality and higher biological activity than conventional systems. Manure addition, especially coupled with reduced or no tillage, significantly enhances microbial biomass and activity by improving soil physical properties and providing carbon (C) and nitrogen (N) sources. While several studies have examined the effects of transitioning from conventional to organic farming on soil chemistry and biochemistry, limited research has explored the influence of land use variations on soil fertility within long‐term organic farming systems. Aims: Therefore, the aim of this study was to assess how three different land uses—pasture, vegetable crops, and orchard—affected soil fertility under a long‐term organic farming system. Methods: Soil samples were collected from the 0 to 15 cm layer of plots used for pasture, vegetable crops and orchard, being the latter cover cropped with legumes, and analyzed to determine chemical and biochemical soil parameters. Results: Contrary to expectations, high land use intensity (vegetable crops and orchard soils) resulted in increased soil organic C and total N, compared to low intensity (pasture). Such an increase was ascribed to farmyard manure addition that counteracted the negative impact of tillage. Consequently, microbial biomass C and activity also increased. The greatest availability of organic substrates favored bacteria, particularly gram‐positive strains, shaping the microbial community. However, despite changes of microbial biomass and of the main microbial groups, microbial activity was only slightly affected, suggesting high functional redundancy of microorganisms in long‐term organic farming soil. Conclusions: Results suggested that if land use intensification provides for organic supply, its negative impact on soil fertility may be mitigated. [ABSTRACT FROM AUTHOR]

Novel metal complexes were synthesized by mixing N1,N3‐bis(4‐phenylthiazol‐2‐yl)malonamide with Cr (III), Fe (III), Cu (II), and Zn (II) nitrates in a 1:2 (L: metal) ratio. Through the use of several analytical and spectral methods, the structures of all compounds were determined. It was determined that the novel ligand functions through O2N2 sites as a neutral tetradentate. The thermal stability and the thermodynamic parameters were evaluated using thermal gravimetric analysis and the Coats‐Redfern equations. Powder X‐ray diffraction investigation revealed the type of unit cell and the degree of crystallinity. The complexes were further tested for their antibacterial efficacy, with molecular simulation using several proteins demonstrating the strongest action against a range of pathogens. Optimization for all compounds were made through the basis set DFT/B3LYP/LANL2DZ to find the theoretical stability, FMO orbitals, energy gaps, molecular electrostatic potentials (MEPs), and evaluate physical parameter. Here, the electrochemical properties of the metal complexes were investigated using cyclic voltammetry and electrochemical impedance spectroscopy methods. Additionally, [Cr2(L)(NO3)4(H2O)4](NO3)2 complex has been authorized that has high electrocatalytic characteristics, making it attractive for use in supercapacitor applications. [ABSTRACT FROM AUTHOR]

In addition to standard laboratory testing of soil samples, on-farm soil health monitoring methods are needed to help farmers assess progress in adopting new management practices. However, there is currently a lack of studies evaluating the suitability of semi-quantitative on-farm indicators to accurately rank target soil properties according to laboratory results. Therefore, this study assessed methods with potential for field use compared to common laboratory approaches for the determination of (i) soil organic carbon (SOC), (ii) carbon (C) fractions and (iii) microbial activity. The comparison allowed the evaluation of the validity, practicality and cost-effectiveness of the approaches. For this purpose, three sites in north-eastern Austria with contrasting soil textures (light, medium, heavy) and two different management systems (namely 'pioneer' and 'standard') were selected. Pioneer soils are managed long-term according to principles of soil health using conservation agricultural practices while neighbouring fields under standard management represent conventional practices. Beyond texture and site differences, both laboratory and field-adapted approaches revealed differences between the pioneer and standard systems. Overall, management-specific differences were most pronounced in the light and heavy textured soil. Although the laboratory methods provided more accurate results with less variability, the fieldbased approaches still identified trends in soil health parameters in the pioneer system. Our study can thus serve as a guide for the selection of suitable parameters and methods for assessing soil health in different areas of research and practical application. [ABSTRACT FROM AUTHOR]

Summary: Bacteria colonize plant roots and engage in reciprocal interactions with their hosts. However, the contribution of individual taxa or groups of bacteria to plant nutrition and fitness is not well characterized due to a lack of in situ evidence of bacterial activity.To address this knowledge gap, we developed an analytical approach that combines the identification and localization of individual bacteria on root surfaces via gold‐based in situ hybridization with correlative NanoSIMS imaging of incorporated stable isotopes, indicative of metabolic activity.We incubated Kosakonia strain DS‐1‐associated, gnotobiotically grown rice plants with 15N–N2 gas to detect in situ N2 fixation activity. Bacterial cells along the rhizoplane showed heterogeneous patterns of 15N enrichment, ranging from the natural isotope abundance levels up to 12.07 at% 15N (average and median of 3.36 and 2.85 at% 15N, respectively, n = 697 cells).The presented correlative optical and chemical imaging analysis is applicable to a broad range of studies investigating plant–microbe interactions. For example, it enables verification of the in situ metabolic activity of host‐associated commercialized strains or plant growth‐promoting bacteria, thereby disentangling their role in plant nutrition. Such data facilitate the design of plant–microbe combinations for improvement of crop management. [ABSTRACT FROM AUTHOR]

Numerous studies have investigated the spatiotemporal variability in water microbial communities, yet the effects of relic DNA on microbial community profiles, especially microeukaryotes, remain far from fully understood. Here, total and active bacterial and microeukaryotic community compositions were characterized using propidium monoazide (PMA) treatment coupled with high‐throughput sequencing in a river‐reservoir ecosystem. Beta diversity analysis showed a significant difference in community composition between both the PMA untreated and treated bacteria and microeukaryotes; however, the differentiating effect was much stronger for microeukaryotes. Relic DNA only resulted in underestimation of the relative abundances of Bacteroidota and Nitrospirota, while other bacterial taxa exhibited no significant changes. As for microeukaryotes, the relative abundances of some phytoplankton (e.g. Chlorophyta, Dinoflagellata and Ochrophyta) and fungi were greater after relic DNA removal, whereas Cercozoa and Ciliophora showed the opposite trend. Moreover, relic DNA removal weakened the size and complexity of cross‐trophic microbial networks and significantly changed the relationships between environmental factors and microeukaryotic community composition. However, there was no significant difference in the rates of temporal community turnover between the PMA untreated and treated samples for either bacteria or microeukaryotes. Overall, our results imply that the presence of relic DNA in waters can give misleading information of the active microbial community composition, co‐occurrence networks and their relationships with environmental conditions. More studies of the abundance, decay rate and functioning of nonviable DNA in freshwater ecosystems are highly recommended in the future. [ABSTRACT FROM AUTHOR]

Shrub cover in semiarid rangelands may induce changes in soil resources and ecosystem functioning. However, it is unknown the real influence that shrub vegetation has on soil quality in rangelands used for livestock purposes. We evaluated the shrub cover effect on 12 chemical and biochemical parameters of soil quality. In a semiarid Monte rangeland of Argentina, 6 paddocks were selected and 10 m transects were placed in a patch with (Sh) and without shrubs (WSh). Then, sites with grasses (Sh‐G and WSh‐G), bare ground‐litter (Sh‐BL and WSh‐BL), and under shrub cover (Sh‐S) were selected. In spring 2017 and 2018, a composite soil sample (0–10 cm in depth) was taken at each site (n = 6). Sh‐G and Sh‐S sites presented high values of soil organic matter, soil organic nitrogen, particulate organic matter (POM), and cellulase activity (CA); WSh‐BL and Sh‐BL sites were associated with the lowest contents of these variables. For the rest of the soil quality parameters, the soil sampling sites showed similar values. These results show that woody presence should not be directly linked to soil quality loss. Although we did not detect a shrub effect in all parameters studied, in the context of appropriate grazing management, the presence of plant species of different functional groups has a positive effect on organic matter and N content of soil close to them. Moreover, in these sites, high POM values represent an important reservoir of potentially available nutrients, and promote CA necessary for fresh litter decomposition improving the soil quality of semiarid rangelands. [ABSTRACT FROM AUTHOR]

Mowing, as a common grassland utilization strategy, affects nutrient status in soil by plant biomass removal. Phosphorus (P) cycle plays an important role in determining grassland productivity. However, few studies have addressed the impacts of mowing on P cycling in grassland ecosystems. Here, we investigated the effects of various mowing regimes on soil P fractions and P accumulation in plants and litters. We specifically explored the mechanisms by which mowing regulates ecosystem P cycling by linking aboveground community with soil properties. Our results showed that mowing increased soil dissolvable P concentrations, which probably met the demand for P absorption and utilization by plants, thus contributing to an increased P accumulation by plants. Mowing promoted grassland P cycling by a reciprocal relationship between plants and microbes. Short‐term mowing enhanced P cycling mainly through increased root exudation‐evoked the extracellular enzyme activity of microbes rather than the alternations in microbial biomass and community composition. Long‐term mowing increased P cycling mainly by promoting carbon allocation to roots, thereby leading to greater microbial metabolic activity. Although mowing‐stimulation of organic P mineralization lasted for 15 consecutive years, mowing did not result in soil P depletion. These results demonstrate that P removal by mowing will not necessarily lead to soil P limitation. Our findings would advance the knowledge on soil P dynamic under mowing and contribute to resource‐efficient grassland management. [ABSTRACT FROM AUTHOR]

Since 2008, European and German legislative initiatives for climate protection and reduced dependency on fossil resources led to the introduction of biofuels as CO2‐reduced alternatives in the heating oil sector. In the case of biodiesel, customers were confronted with accelerated microbial contaminations during storage. Since then, other fuel alternatives, like hydrogenated vegetable oils (HVOs), gas‐to‐liquid (GtL) products, or oxymethylene ether (OME) have been developed. In this study, we use online monitoring of microbial CO2 production and the simulation of onset of microbial contamination to investigate the contamination potential of fuel alternatives during storage. As references, fossil heating oil of German refineries are used. Biodiesel blends with fossil heating oils confirmed the promotion of microbial activity. In stark contrast, OMEs have an antimicrobial effect. The paraffinic Fischer–Tropsch products and biogenic hydrogenation products demonstrate to be at least as resistant to microbial contamination as fossil heating oils despite allowing a diversity of representative microbes. Through mass spectrometry, elemental analysis, and microbial sequencing, we can discuss fuel properties that affect microbial contaminations. In summary, novel, non‐fossil heating oils show clear differences in microbial resistance during long‐term storage. Designing blends with an intrinsic resistance against microbial contamination and hence reduced activity might be an option. [ABSTRACT FROM AUTHOR]

Over the last few years, in the literature on the incorporation of crop residues in agricultural fields to mitigate climate change, there has been a growing tendency to no longer distinguish between the storage and the sequestration of organic carbon in soils. Applying, apparently for the first time, a simple "back‐of‐the‐envelope" calculation to available mineralization kinetics data, we show graphically that there are fundamental differences, both quantitatively and qualitatively, between the two concepts of storage and sequestration. To avoid confusion, they should therefore never be used interchangeably, especially when addressing farmers and policymakers. Several simplifying assumptions made in the calculations, and about which a considerable lack of understanding persists, mean that at this stage, the graphical visualization we obtained is likely to still be optimistic in terms of the already low (10%) efficacy of sequestering carbon in soils. Several research avenues are outlined to deepen our grasp of the processes involved. [ABSTRACT FROM AUTHOR]

Wildfire impacts on soil microbial community structure and functional activity have attracted a growing attention because of the higher sensitivity of soil microbes to wildfire. Soil extracellular enzymes play pivotal roles in biogeochemical processes, such as mediating carbon (C) and nutrient cycling. However, little is known about how post‐fire changes in soil biogeochemical properties and microbial community composition affect soil extracellular enzyme activities. This study explored the responses and regulating factors of C‐, nitrogen‐(N), and phosphorus‐(P) acquiring extracellular enzyme activities across a wildfire chronosequence (i.e., 1, 6, 13, and 50 years after fire) in subtropical–temperate ecotonal forests in Central China. The activities of C‐(β‐glucosidase), N‐(N‐acetylglucosaminidase), and P‐(acid phosphatase) acquiring enzymes declined with time post‐fire, with the highest values one‐year post‐fire. The response of C‐acquiring enzyme activity to fire was positively correlated with bacterial biomass, suggesting that microbial compositions were related to post‐fire changes in extracellular enzyme decomposition. The response of N‐acquiring enzyme activity to fire was positively correlated with soil P availability, while P‐acquiring enzyme activity was positively correlated with soil N availability. Overall, soil extracellular enzyme activity declined with time post‐fire, suggesting wildfire may reduce microbial demand for nutrients over time. Future research is needed to elucidate fire impacts on microbial processes for nutrient‐microbial‐enzyme linkages. [ABSTRACT FROM AUTHOR]

Plants live in association with a diversity of soil microorganisms, which are extremely important in affecting plant growth and soil biogeochemical cycling.By adopting plant trait‐based approaches, we explored the linkages between rhizosphere soil microbial activity and plant resource acquisition strategy of above‐ and below‐ground across a range of tree species in a subtropical evergreen mixed forest. The microbial activities were represented by diverse extracellular enzymes relevant to carbon, nitrogen and phosphorus cycling and soil organic carbon (SOC) mineralization.At the species level, leaf and root traits were mainly represented by two leading dimensions, that is, the 'fast‐slow' economics spectrum on which leaf and root traits were well aligned and the orthogonal collaboration gradient in the root.Both extracellular enzymes and SOC mineralization in the rhizosphere varied greatly across plant species. We found that diverse rhizosphere soil microbial activities positively correlated with the classical 'fast‐slow' conservation gradient of plant resource acquisition (especially above‐ground), that is, the rhizosphere soil microbes associated with fast‐growing plant species feature higher metabolism than that of slow‐growing plant species. In comparison, rhizosphere soil microbial activities were independent of the plant collaboration gradient in the root, and it might be an alternative exploitative strategy in foraging soil nutrients for plants.Synthesis. Our study strengthens the multivariate nature of plant resource acquisition in adapting to above‐ and below‐ground stresses. The findings on the linkages between rhizosphere soil microbial activity and plant resource acquisition strategy have the potential to improve our understanding and prediction of plant species turnover impacts on soil biogeochemical cycles. [ABSTRACT FROM AUTHOR]

Soil health is one of the key factors in determining the sustainability of global agricultural systems and the stability of natural ecosystems. Microbial decomposition activity plays an important role in soil health; and gaining spatiotemporal insights into this attribute is critical for understanding soil function as well as for managing soils to ensure agricultural supply, stem biodiversity loss, and mitigate climate change. Here, a novel in situ electronic soil decomposition sensor that relies on the degradation of a printed conductive composite trace utilizing the biopolymer poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) as a binder is presented. This material responds selectively to microbially active environments with a continuously varying resistive signal that can be readily instrumented with low‐cost electronics to enable wide spatial distribution. In soil, a correlation between sensor response and intensity of microbial decomposition activity is observed and quantified by comparison with respiration rates over 14 days, showing that devices respond predictably to both static conditions and perturbations in general decomposition activity. [ABSTRACT FROM AUTHOR]

Spectral Induced Polarization (SIP) has been suggested as a non‐invasive monitoring proxy for microbial processes. Under natural conditions, however, multiple and often coupled polarization processes co‐occur, impeding the interpretation of SIP signals. In this study, we analyze the sensitivity of SIP to microbially‐driven reactions under quasi‐natural conditions. We conducted flow‐through experiments in columns equipped with SIP electrodes and filled with natural calcareous, organic‐carbon‐rich aquifer sediment, in which heterotrophic denitrification was bio‐stimulated. Our results show that, even in the presence of parallel polarization processes in a natural sediment under field‐relevant geochemical conditions, SIP is sufficiently sensitive to microbially‐driven changes in electrical charge storage. Denitrification yielded an increase in imaginary conductivity of up to 3.1 μScm−1 ${\upmu }\mathrm{S}\,{\mathrm{c}\mathrm{m}}^{-1}$ (+140%) and the formation of a distinct peak between 1 and 10 Hz, that matched the timing of expected microbial activity predicted by a reactive transport model fitted to solute concentrations. A Cole‐Cole decomposition allowed separating the polarization contribution of microbial activity from that of cation exchange, thereby helping to locate microbial hotspots without the need for (bio)geochemical data to constrain the Cole‐Cole parameters. Our approach opens new avenues for the application of SIP as a rapid method to monitor a system's reactivity in situ. While in preceding studies the SIP signals of microbial activity in natural sediments were influenced by mineral precipitation/dissolution reactions, the imaginary conductivity changes measured in the biostimulation experiments presented here were dominated by changes in the polarization of the bacterial cells rather than a reaction‐induced alteration of the abiotic matrix. Plain Language Summary: To better predict the contribution of microbes to groundwater clean‐up it is important to locate microbes in the ground that are actively removing contaminants and measure how fast they are doing so. Our ability to do so, however, is limited by the difficulty in visualizing underground processes. Electrical methods such as spectral induced polarization (SIP) have been applied to monitor microbes and provide an alternative to visualize them underground. SIP, however, has so far only been shown to work in controlled environments and its sensitivity in natural systems remains a question. In this study, we conducted experiments with sediment collected from an underground aquifer, in which we stimulated microbial activity through the addition of nitrate, a widespread groundwater contaminant. Our results show that microbial consumption of nitrate causes a distinct SIP signal that is similar to SIP signals of bacteria in previously studied well‐controlled systems. Furthermore, we propose an approach to separate the SIP signal of microbes from that of other processes that occur in natural groundwater. This enables us to quickly asses where the microbes are active and can potentially improve future experiments through the localization of microbial hot‐spots and SIP‐guided sampling for more detailed microbiological analysis. Key Points: Microbial denitrification in natural sediments can be tracked using spectral induced polarization (SIP)σ″ ${\sigma }^{{\prime\prime}}$ spectra of a natural microbial community match reported spectra from single strains and the level of microbial activity affects σ″ ${\sigma }^{{\prime\prime}}$Superimposing Cole‐Cole terms provides a framework for separating microbial and abiotic contributions from SIP signals [ABSTRACT FROM AUTHOR]

Subterranean estuaries are biogeochemically active coastal sites resulting from the underground mixing of fresh aquifer groundwater and seawater. In these systems, microbial activity can largely transform the chemical elements that may reach the sea through submarine groundwater discharge (SGD), but little is known about the microorganisms thriving in these land‐sea transition zones. We present the first spatially‐resolved characterization of the bacterial assemblages along a coastal aquifer in the NW Mediterranean, considering the entire subsurface salinity gradient. Combining bulk heterotrophic activity measurements, flow cytometry, microscopy and 16S rRNA gene sequencing we find large variations in prokaryotic abundances, cell size, activity and diversity at both the horizontal and vertical scales that reflect the pronounced physicochemical gradients. The parts of the transect most influenced by freshwater were characterized by smaller cells and lower prokaryotic abundances and heterotrophic production, but some activity hotspots were found at deep low‐oxygen saline groundwater sites enriched in nitrite and ammonium. Diverse, heterogeneous and highly endemic communities dominated by Proteobacteria, Patescibacteria, Desulfobacterota and Bacteroidota were observed throughout the aquifer, pointing to clearly differentiated prokaryotic niches across these transition zones and little microbial connectivity between groundwater and Mediterranean seawater habitats. Finally, experimental manipulations unveiled large increases in community heterotrophic activity driven by fast growth of some rare and site‐specific groundwater Proteobacteria. Our results indicate that prokaryotic communities within subterranean estuaries are highly heterogeneous in terms of biomass, activity and diversity, suggesting that their role in transforming nutrients will also vary spatially within these terrestrial–marine transition zones. [ABSTRACT FROM AUTHOR]

Given that global change is predicted to increase the frequency and severity of drought in temperate forests, it is critical to understand the degree to which plant belowground responses cascade through the soil system to drive ecosystem responses to water stress. While most research has focused on plant and microbial responses independently of each other, a gap in our understanding lies in the integrated response of plant‐microbial interactions to water stress. We investigated the extent to which divergent belowground responses to reduced precipitation between sugar maple trees (Acer saccharum) versus oak trees (Oak spp.) may influence microbial activity via throughfall exclusion in the field. Evidence that oak trees send carbon belowground to prime microbial activity more than maples under ambient conditions and in response to water stress suggests there is the potential for corresponding impacts of reduced precipitation on microbial activity. As such, we tested the hypothesis that differences in belowground C allocation between oaks and maples would stimulate microbial activity in the oak treatment soils and reduce microbial activity in in the sugar maple treatment soils compared to their respective controls. We found that the treatment led to declines in N mineralization, soil respiration, and oxidative enzyme activity in the sugar maple treatment plot. These declines may be due to sugar maple trees reducing root C transfers to the soil. By contrast, the reduced precipitation treatment enhanced soil respiration, as well as rates of N mineralization and peroxidase activity in the oak rhizosphere. This enhanced activity suggests that oak roots provided optimal rhizosphere conditions during water stress to prime microbial activity to support net primary production. With future changes in precipitation predicted for forests in the Eastern US, we show that the strength of plant‐microbial interactions drives the degree to which reduced precipitation impacts soil C and nutrient cycling. [ABSTRACT FROM AUTHOR]

Microbial activity is the driving force of the carbon cycle, including the digestion of biomass in the soil, oceans, and oil deposits. This natural diversity of microbial carbon sources poses challenges for humans. Contamination monitoring can be difficult in oil tanks and similar settings. To assess microbial activity in such industrial settings, off‐gas analysis can be employed by considering growth and non‐growth‐associated metabolic activity. In this work, we describe the monitoring of CO2 as a method for measuring microbial activity. We revealed that the CO2 signal corresponds to classical growth curves, exemplified by Pseudomonas fluorescens, Yarrowia lipolytica, and Penicillium chrysogenum. Deviations of the CO2 signal from the growth curves occurred when the yield of biomass on the substrate changed (i.e., the non‐growth‐associated metabolic activities). We monitored CO2 to track the onset of microbial contamination in an oil tank. This experimental setup was applied to determine the susceptibility of heating oil and biodiesel to microbial contamination long before the formation of problematic biofilms. In summary, the measurement of CO2 production by bacteria, yeasts, and molds allowed the permanent monitoring of microbial activity under oil storage conditions without invasive sampling. [ABSTRACT FROM AUTHOR]

Scale formation in water drainage systems occurs in diverse forms. In tunnel drainage systems in particular, calcium carbonate deposition can significantly impair water discharge, resulting in costly maintenance work and tunnel closures. This review paper presents and discusses the state of knowledge as well as the current challenges regarding scale formation in tunnel drainage systems in terms of typification, parameters controlling formation, such as hydrochemistry, interfacial phenomena, microbial activity, and countermeasures, such as appropriate adaptation of construction materials, drainage design, inhibitor use and cleaning. Detailed knowledge of the case‐specific scale formation environment and the scaling capacities of the waters provides the basis for the tailored development and evaluation of suitable strategies for successfully reducing maintenance efforts and tunnel closure. For this purpose, time‐ and site‐resolved monitoring of the composition of the solid phases, waters and the tunnel atmosphere during the implementation of the construction project and during the operation of the tunnel is paramount. [ABSTRACT FROM AUTHOR]

It is well established that application of biochar to soils can promote soil fertility, which ultimately may enhance plant growth. While many mechanisms have been proposed to explain this, one specific mechanism, the "microbial refugia hypothesis," suggests that biochar may provide physical protection for soil microbe from soil microfauna that otherwise exert top‐down control on microbial biomass and activity. We tested the microbial refugia hypothesis by incubating two boreal soils with and without biochar derived from a wood mixture of boreal tree species (Picea abies and Pinus sylvestris), and with and without soil nematodes. We measured phospholipid fatty acids (PLFA) as a relative measure of microbial biomass, and several variables indicative of microbial activity, including extractable nutrient concentrations (NH4+, NO3−, and PO4−), heterotrophic N2‐fixation, and soil respiration. Contrary to our expectations, we found that biochar by itself did not stimulate microbial biomass or activity. Furthermore, we found that nematode addition to soil stimulated rather than depressed the biomass of several bacterial PLFA groups. Finally, interactive effects between the nematode treatment and biochar never worked in a way that supported the microbial refugia hypothesis. Our findings suggest that a typical boreal biochar applied to boreal soils may not have the same stimulatory effect on microbial biomass and activity that has been shown in some other ecosystems, and that enhanced plant growth in response to biochar addition sometimes observed in boreal environments is likely due to other mechanisms, such as direct nutrient supply from biochar or amelioration of soil pH. [ABSTRACT FROM AUTHOR]

Biochar application is attracting attention to be an effective soil organic carbon (SOC) management to prevent land degradation, though quantitative information of its effect on carbon dioxide (CO2) flux and associated microbial responses is still scarce, especially in degraded tropical agroecosystems. We conducted a 27‐month field experiment with periodically measuring environmental factors, CO2 efflux rate, microbial biomass C (MBC), and SOC stock, and evaluated the impact of land management (control (C), biochar (B; 8.2 Mg C ha−1), farmyard manure (FYM) (M; 1.1 Mg C ha−1 yr−1), and a mixture of both (BM) on CO2 flux, microbial responses (MBC and qCO2 as microbial activity) and C budget, in tropical alkaline cropland of southern India. Based on the relationship between the CO2 efflux rate and environmental factors, cumulative CO2 flux was estimated at 2.4, 2.7, 4.0, and 3.7 Mg C ha−1 in the C, B, M, and BM treatments, respectively. Biochar application increased soil moisture though did not affect CO2 flux, causing a positive C budget (6.7 Mg C ha−1), because of the limited response of microbes to increased soil moisture due to the small amount of SOC. Biochar and FYM combined application did not increase CO2 flux compared with FYM alone, contributing to the largest SOC increment (8.9 Mg C ha−1) with a positive C budget (9.1 Mg C ha−1), due to little difference of microbial responses between the two treatments. Hence, biochar application combined with FYM could be an effective SOC management in the degraded cropland of southern India. [ABSTRACT FROM AUTHOR]

Afforestation projects are a growing focus of urban restoration efforts to rehabilitate degraded landscapes and develop new forests. Urban forests provide myriad valuable ecosystem services essential for urban sustainability and resilience. These essential services are supported by natural soil microbial processes that transform organic matter to critical nutrients for plant community establishment and development. Nitrogen (N) is the most limiting nutrient in forest ecosystems, yet little information is known about N cycling in urban afforestation efforts. This study examined microbially mediated processes of carbon (C) and N cycling in 10 experimental afforested sites established across New York City parklands under the MillionTreesNYC initiative. Long‐term research plots were established between 2009 and 2011 at each site with low and high diversity (two vs. six tree species) treatments. In 2018, 1‐m soil cores were collected from plots at each site and analyzed for microbial biomass and respiration, potential net N mineralization, and nitrification, denitrification potential, soil inorganic N, and total soil N. Field observations revealed markedly different trajectories between sites that exhibited a closed canopy and leaf litter layer derived from trees that were planted and those that did not fit this description. These two metrics served to group sites into two categories (high vs. low) of afforestation success. We hypothesized that: (1) afforestation success would be correlated with rates of C and N cycling, (2) high diversity restoration techniques would affect these processes, and (3) inherent soil properties interact with plants and environmental conditions to affect the development of these processes over time. We found that high success sites had significantly higher rates of C and N cycling processes, but low and high diversity treatments showed no differences. Low success sites were more likely to have disturbed soil profiles with human‐derived debris. Afforestation success appears to be driven by interactions between initial site conditions that facilitate plant community establishment and development that in turn enable N accumulation and cycling, creating positive feedbacks for success. [ABSTRACT FROM AUTHOR]

Dryland soils consistently exhibit a low capacity for the long‐term accumulation and storage of organic matter, which has been primarily attributed to low plant biomass inputs under drought suppression. Whether, and how, soil organic matter (SOM) compositions contribute to the consistently low SOM storage have been puzzling. A fundamental understanding of this mechanism is particularly essential to achieve the aspiration of '4 per mille Soils for Food Security and Climate'.By screening the molecular composition of dissolved organic matter (DOM), the gatekeeper of SOM decomposition, we explored the transformation processes among the pools of SOM, DOM and microbial biomass carbon (MBC) in soils along a precipitation gradient on dryland grasslands of the Tibetan Plateau.The results revealed that the number and mean weight of DOM molecules significantly decreased, and the soil DOM composition gradually shifted to be more labile along the transition from meadow, steppe, to desert with decreasing precipitation, coinciding with the substantial reduction in SOM. Compared with meadow soils, DOM degradability increased by 8.7% in steppe soils and by 23.4% in desert soils. The ratio of soil MBC to total organic carbon was threefold higher in desert than in meadow, and positively correlated with DOM degradability, indicating that labile DOM accelerated microbial growth and SOM decomposition in desert soils. Structural equation model and correlation analyses demonstrated that the DOM degradability was primarily controlled by soil dissolved nitrogen and soil organic C and soil DOC/DN ratio.Synthesis and application. This study at a molecular level provides a novel insight into the important role of the degradability of dissolved organic matter in carbon accumulation in dryland soils with consistently low organic matter storage. The findings will inform better global managements of soil organic matter under consideration of both food security and climate change. [ABSTRACT FROM AUTHOR]

Mechanisms of soil organic carbon (SOC) stabilization have been widely studied due to their relevance in the global carbon cycle. No‐till (NT) has been frequently adopted to sequester SOC; however, limited information is available regarding whether sequestered SOC will be stabilized for long term. Thus, we reviewed the mechanisms affecting SOC stability in NT systems, including the priming effects (PE), molecular structure of SOC, aggregate protection, association with soil minerals, microbial properties, and environmental effects. Although a more steady‐state molecular structure of SOC is observed in NT compared with conventional tillage (CT), SOC stability may depend more on physical and chemical protection. On average, NT improves macro‐aggregation by 32.7%, and lowers SOC mineralization in macro‐aggregates compared with CT. Chemical protection is also important due to the direct adsorption of organic molecules and the enhancement of aggregation by soil minerals. Higher microbial activity in NT could also produce binding agents to promote aggregation and the formation of metal‐oxidant organic complexes. Thus, microbial residues could be stabilized in soils over the long term through their attachment to mineral surfaces and entrapment of aggregates under NT. On average, NT reduces SOC mineralization by 18.8% and PE intensities after fresh carbon inputs by 21.0% compared with CT (p <.05). Although higher temperature sensitivity (Q10) is observed in NT due to greater Q10 in macro‐aggregates, an increase of soil moisture regime in NT could potentially constrain the improvement of Q10. This review improves process‐based understanding of the physical and chemical mechanism of protection that can act, independently or interactively, to enhance SOC preservation. It is concluded that SOC sequestered in NT systems is likely to be stabilized over the long term. [ABSTRACT FROM AUTHOR]

Over the last few years, the question of whether soil carbon sequestration could contribute significantly to climate change mitigation has been the object of numerous debates. All of these debates so far appear to have entirely overlooked a crucial aspect of the question. It concerns the short‐term mineralization kinetics of fresh organic matter added to soils, which is occasionally alluded to in the literature, but is almost always subsumed in a broader modelling context. In the present article, we first summarise what is currently known about the kinetics of mineralization of plant residues added to soils, and about its modelling in the long run. We then argue that in the short run, this microbially‐mediated process has important practical consequences that cannot be ignored. Specifically, since at least 90% of plant residues added to soils to increase their carbon content over the long term are mineralized relatively rapidly and are released as CO2 to the atmosphere, farmers would have to apply to their fields 10 times more organic carbon annually than what they would eventually expect to sequester. Over time, because of a well‐known sink saturation effect, the multiplier may even rise significantly above 10, up to a point when no net carbon sequestration takes place any longer. The requirement to add many times more carbon than what one aims to sequester makes it practically impossible to add sufficient amounts of crop residues to soils to have a lasting, non‐negligible effect on climate change. Nevertheless, there is no doubt that raising the organic matter content of soils is desirable for other reasons, in particular guaranteeing that soils will be able to keep fulfilling essential functions and services in spite of fast‐changing environmental conditions. Highlights: Attempts to promote soil carbon sequestration to mitigate climate change have so far ignored the short‐term effects of the mineralization of plant residues added to soils.Only about 10%, at most, of added plan residues remain in soils after mineralization by soil organisms.To have a significant effect on climate change, farmers would need to add impractically large amounts of plant residues, requiring unrealistic nitrogen inputs.Therefore, rather than as a mitigation strategy, farmers should aim to increase the carbon content of soils to make them resilient to climate change. [ABSTRACT FROM AUTHOR]

Climate change is associated with more intense phases of heat, drought or precipitation that can have a negative impact on soil properties. Our goal was to understand if elevated CO2 (eCO2) and temperature (eT), and a multicomponent (eCO2eT) climate effect will influence soil properties from cereal‐legume intercrops differently compared to sole crops. We hypothesized that cereal‐legume intercrops can regulate climate effects, causing soil properties and greenhouse gas fluxes to be similar to ambient climate conditions. eT and eCO2eT decreased soil organic carbon (C) (p =.001) and nitrogen (N) (p =.003) but increased (p =.011) soil nitrate in all crop systems, compared to ambient conditions. For crop systems, soil ammonium was lower (p =.001) with all climate effects, but nitrate was greater (p =.011) with eCO2 and eCO2eT compared to ambient conditions. The microbial community had a preferential (p =.024) consumption of C3 sources in the sole crops. Climate effects also influenced how C and N were accessed by microbes in all crop systems, shifting (p =.001) species richness and microbial community structure. CO2 fluxes were greater (p =.001) with eT and eCO2, whereas N2O fluxes were greater (p =.005) with eCO2 and eCO2eT. However, greenhouse gas fluxes from the intercrop were similar between eT or eCO2eT and ambient conditions. For soil properties, we rejected our hypothesis since cereal‐legume intercrops did not have an advantage over sole crops to cope with single‐ and multicomponent climate effects, but we partially accepted our hypothesis since greenhouse gas fluxes were similar between AMB and eT or eCO2eT. [ABSTRACT FROM AUTHOR]

Ants are widely regarded as ecosystem engineers because of their effect on soil structure and on the flow of energy. However, little is known about their influence on the carbon flux in tropical humid savannah. Recent investigations in a humid savannah ecosystem in Lamto showed that ant nests' association with perennial grasses enhances their growth and productivity. This study aimed at understanding the influence of ant nests on soil micro‐organism's activity beneath grass tufts. The kinetic of mineralisation was tested in laboratory conditions at various times (days 1, 2, 4 and 7) beneath three grass species associated and not associated with ant nests, following the CO2 amount released at 30℃ during soil respiration. The amount of CO2 released from the soil is higher beneath grass tufts associated with ant nests compared with those not associated with ant nest. The highest amount of CO2 released from the soil was found beneath Hyparrhenia diplandra tufts followed by Andropogon schirensis tufts and the lowest under Loudetiasimplex tufts. This study has shown that ant nests' association with grass tufts enhances microbial activity in this savannah ecosystem. [ABSTRACT FROM AUTHOR]

BACKGROUND: Untreated high‐strength salinity wastewaters pose a serious threat to the environment. Anaerobic treatment is an effective process with double advantages of waste stabilization and energy production. However, high organic compound and sodium toxicity in high‐salinity wastewaters adversely affect the performance of anaerobic treatment. In this study, anaerobic hybrid (AH) and upflow anaerobic sludge blanket (UASB) reactors were investigated for their efficiencies to alleviate the negative effects of high‐salinity wastewater. RESULTS: Double increases in the NaCl concentration drastically deteriorated the performances of both reactors. The activities of acetoclastic methanogens (ACM) and hydrogenotrophic methanogens (HTM) in both reactors decreased to 22–28% and 36–40% compared to the previous period, respectively. However, the methanogen population (Methanosarcinales and Methanobacteriales) was not affected negatively. The AH reactor exhibited excellent performance during the recovery and restart periods, which only required 7 days to complete the recovery period. Furthermore, during the restart period, the AH reactor showed high chemical oxygen demand (COD) removal efficiency, methane (CH4) production and yield as ≈90%, 2600 mL day−1 and 0.30 m3 CH4 kg−1 CODremoved, respectively. The rate of biomass washout from the AH reactor also was lower compared to the UASB reactor. The concentration of attached biomass in the packed zone of the AH reactor gradually increased indicating the growth of an active microbial biofilm. CONCLUSION: The excellent performance of the AH reactor was presumably a result of its packed zone configuration which provided the supporting media to entrap smaller microbial aggregates, reduce biomass washout and support the growth of active biofilm. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Understanding changes in soil functions in response to land‐use change is important for guiding agricultural practices towards sustainable soil management. We evaluated the differences in soil properties (soil organic matter, water extractable carbon (C) and nitrogen (N), microbial biomass, pHKCL and exchangeable cations) and microbial processes (respiration potential, net N mineralization, net nitrification and metabolic potential of soil bacteria), as well as the relative importance of soil properties in explaining changes in processes under three land uses (potato crops, fallow fields and eucalyptus plantations) in the agricultural highlands of the Central Andes. Soils under potato crops were characterized by the highest net N mineralization and net nitrification rates, and extractable phophorus (P), and the lowest microbial biomass P. Conversion to eucalyptus plantations led to an increase in soil organic matter, water extractable C and microbial biomass, and a decrease in extractable P and metabolic diversity of soil bacteria. Higher exchangeable aluminium (Al) indicated soil acidification under eucalyptus. Fallow practices did not lead to major changes in soil properties and microbial processes, indicating that fallow practices for up to 6 years were too short to substantially contribute to soil fertility restoration. Hot water extractable carbon (HWC) showed the best relationship with soil processes (respiration potential, net N mineralization and net nitrification). Our results highlight the necessity of alternative management practices for maintaining soil fertility under potato crops, the drastic modification of soil properties and processes under eucalyptus plantations, and the potential of HWC as a proxy for monitoring land‐use‐induced changes in soil functions related to C and N cycling. Highlights: Effects of conversion from potato crops to eucalyptus and fallow on soil properties and processes were assessed.Under eucalyptus, soil respiration increased; metabolic diversity and N transformations decreased.Short fallow periods did not result in soil fertility restoration.Hot water extractable C was the best indicator of changes in soil processes. [ABSTRACT FROM AUTHOR]

When using mechanical harvesting, the sugarcane trash can be partially recovered for use as feedstock for bioenergy. However, the amount of trash that can be removed without prejudicing the sustainability of the sugarcane production system has still been little studied. The aim of this study was to evaluate the short‐term impact of removing part of the sugarcane trash using enzymatic and microbiological soil quality indicators. We tested three rates of trash removal: 0% (T0), 50% (T50) and 100% (T100). The microbial biomass C (Cmic) and N (Nmic), β‐glucosidase activity (GA) and the ratios Cmic as a per cent of Ctot and Nmic as a per cent of Ntot were highest for T100. The urease activity decreased with an increase in trash removal. The specific activity of β‐glucosidase did not differ between the treatments, while the specific activity of urease showed the same pattern as the absolute activity. The metabolic quotients (qCO2) were higher for T50 and T100 with no significant difference between them. The principal component analysis showed that the first component, which explained 77.66% of the total variance, was significantly correlated with Nmic, basal respiration and GA and discriminated the three treatments. The results showed that the removal of part of the trash adversely affected some of the soil quality attributes. This suggests the need for monitoring over a period of years in sugarcane areas where part of the trash is removed for industrial purposes, in order to better understand the cumulative impact on soil quality and to ensure the sustainability of bioenergy production. [ABSTRACT FROM AUTHOR]

BACKGROUND: Three lab‐scale sequencing batch reactors were used to investigate the effects of Fe3+ on aerobic granular sludge (AGS) formation, nutrient removal, and microbial community. RESULTS: The addition of 6 and 12 mg Fe3+ L−1 could not shorten the granulation time. However, compared to the reactor without Fe3+ addition (average sludge volume index at 30 min (SVI30) 70.8 mL g−1; stable average particle size 548 μm), the addition of 12 mg Fe3+ L−1 helped improve the physical properties of AGS (average SVI30 57.0 mL g−1; stable average particle size 1067 μm). Furthermore, with 12 mg Fe3+ L−1 addition (Fe3+ to PO43−‐P molar ratio = 1.33), effective removal of NH4+‐N (≤0.5 mg L−1) and PO43−‐P (<1 mg L−1) was achieved. The addition of Fe3+ reduced the microbial diversity and specific activity of heterotrophic bacteria, but promoted the growth of nitrite‐oxidizing bacteria. The growth of particle size not only increased the active biomass ratio and microbial diversity, but alleviated the inhibition effect of Fe3+ on the specific heterotrophic bacteria activity. CONCLUSION: The addition of Fe3+ had both negative and positive effects on the formation and stability of AGS. The results will help enrich the understanding of AGS application in nutrient removal and especially that of phosphorus. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Soil management systems cause many changes in the microenvironment that directly affect activity and diversity of microorganisms. In lowlands, there is a gap in relation to the adoption of no‐tillage (zero‐tillage) and the impact it has on soil under cultivation of irrigated rice. This study, an in‐field experiment, evaluated the microbial enzymatic activity and diversity in an Entisol cultivated with rice under different managements for 22 years. The experiment started in the 1994/95 growing season, and the treatments were no‐tillage, conventional, and pregerminated management systems. After 22 years, the data obtained on most of the evaluation dates indicated that no‐tillage increased microbial biomass carbon (+45%), microbial biomass nitrogen (+54%), and basal respiration (+54%). No‐tillage compared to management under soil tillage (pregerminated and conventional tillage) increased the activity of β‐glucosidase (+43%), acid phosphatase (+68%), diacetate fluorescein (+34%), and urease (+96%). The enzyme activity was correlated with the soil organic carbon content and particulate fraction. Despite the relatively high enzyme activity with no‐tillage, bacterial richness was maintained in this soil management system. The Proteobacteria phylum has a greater abundance in the NT (43.2%) in relation to the CT (32.3%). Bacteroidetes phylum has a lower abundance in the NT (10.0%) in relation to the CT (15.2%). The Verrucomicrobia phylum has a greater abundance in NT (8.9%) in relation to CT (4.9%). The results suggest that no‐tillage is an important management tool in the recovery of irrigated rice areas whose soil has undergone microbiological degradation. [ABSTRACT FROM AUTHOR]

Tropical and subtropical ecosystems are widely affected by the expansion of agriculture over pristine lands. Despite research efforts, knowledge of the impact of land‐use change on soil is still limited by intrinsic variability, inconsistent results and inadequate replication. This study aimed to better understand the consequences of land‐use change by focusing on long‐term effects on both soil biotic and abiotic parameters. For this purpose, we selected three productive farms under similar management, each of them with pristine forest sites and agricultural sites that had been deforested for ~15 and ~30 years. In each site, we analysed soil microbiological (phospholipid fatty acids [PLFAs], biomass and activity) and physicochemical parameters. Long‐term land‐use change caused a detriment in soil microbial biomass, activity and fungal abundance, but only small changes in PLFA composition. In fact, PLFA composition was more affected by soil physicochemical properties such as carbon‐to‐nutrient ratios and labile carbon than by land use. Some physicochemical parameters (e.g., organic carbon and nutrients) were also negatively affected by land‐use change and were more sensitive to time under agricultural use than microbiological parameters. The lower sensitivity of microbiological parameters could be the result of severe drought conditions at sampling, which may have affected soil microbial communities in both land uses. We were also able to detect associations between specific microbiological and physicochemical parameters. Among these, we identified some that seemed to result from their co‐variation in response to land‐use change and others that seemed to be independent of land use. Overall, our results show that soils can suffer further deterioration several years after deforestation. In order to restore soil health in these degraded lands, we need to keep on investigating the physical, chemical and biological mechanisms responsible for this deterioration. Highlights: Land‐use change affected soil microbiological and physicochemical parameters.Microbiological parameters seemed to stabilize after continuous agriculture.Soil organic C, total N and fine particles were still reduced after long‐term cultivation.Microbiological parameters were mostly associated with C‐to‐nutrient ratios and labile C.Drought conditions may have affected microbial response to land‐use change. [ABSTRACT FROM AUTHOR]

Plant roots release various organic materials that may modify soil structure and affect heat and mass transfer processes. The objective of this study was to determine the effects of a synthetic root exudate (SRE) on penetrometer resistance (PR), thermal conductivity (λ), hydraulic conductivity (k) and evaporation of water in a sandy soil. Soil samples, mixed with either distilled water or the SRE, were packed into columns at a designated bulk density and water content, and incubated for 7 days at 18°C. Soil PR, λ, k and evaporation rate were monitored during drying processes. Compared with those incubated with water, samples incubated with SRE had visible hyphae, greater PR (0.7–5.5 MPa in the water content range of 0.11 to 0.22 m3 m−3) and λ (0.2–0.7 W m−1 K−1 from 0.05 to 0.22 m3 m−3), and increased k in the wet region but decreased k in the dry region. SRE treatment also reduced the overall soil water evaporation rate and cumulative water loss. Analysis of X‐ray computed tomography (CT) scanning showed that the SRE‐treated samples had a greater proportion of small pores (<60 μm). These changes were attributed mainly to SRE‐stimulated microbial activities. Highlights: The effects of incubating a sandy soil with a synthetic root exudate (SRE) on soil physical properties and evaporation are examined.SRE incubation increased the fraction of small pores.SRE incubation increased soil penetrometer resistance and thermal conductivity.Soil hydraulic conductivity was increased in the wet region but was reduced in the dry region.SRE incubation reduced the overall evaporation rate and cumulative water loss. [ABSTRACT FROM AUTHOR]

The amount of reactive nitrogen has more than doubled in terrestrial ecosystems due to human activities such fertiliser application that is predicted to increase dramatically in coming decades. We conducted a 3‐year experiment in a Neotropical savanna in which we determined the effects of increased N deposition on litter decomposition in plots subjected to different levels of N addition (50 kg N ha−1 year−2, 20 kg N ha−1 year−2, or no N addition). For this, we compared the litter decomposition from the bunchgrass Tristachya leiostachya using litter collected from plots with different N addition treatments. Five randomly selected bags of litter from each N addition treatment (origin) were distributed to each plot (destination). We also compared litter nitrogen (N) concentration and indicators of microbial activity (basal respiration, carbon of microbial biomass, metabolic quotient, enzyme activity) in all plots. We found that nitrogen addition influences litter decay, but in idiosyncratic ways that differ between years. In year 1, litter decomposed faster in high‐N addition plots than in low‐N and control plots, regardless of its origin. In contrast, litter from high‐N addition plots decomposing fastest in year 2, regardless of its destination. Finally, there was no effect of either litter origin or destination on the rate of decomposition in year 3. Litter collected in high‐N addition plots had a concentration of N 12–17% higher than litter collected in other plots and higher in 2009 than in other years. Four years after the beginning of the fertilisation experiment, NH4+ concentration and the microbial activity in the soil did not differ between the treatments. Our findings suggest that the levels of N addition predicted for Neotropical savannas can alter litter N concentrations and the process of litter decomposition, but that the direction and magnitude of these changes may be challenging to predict since that precipitation can influence the mechanisms regulating decomposition in the Cerrado. [ABSTRACT FROM AUTHOR]

The distribution, fate, and effects of antibiotics and heavy metal residues in agricultural soil caused by long‐term application of organic fertilizers are of increasing concern. However, the ecotoxic effects of the interaction between antibiotics and heavy metals vary with the physicochemical properties of the soil, and it is still unclear how these substances interact with soil microbial functions. A short‐term microcosm experiment was conducted to investigate effects of the typical antibiotic oxytetracycline (OTC) with heavy metals (zinc [Zn] and copper [Cu]) alone or in combination on nitrification process and soil microbial activity in two different types of soil (FQ: sandy loam soil and NB: clay loamy soil). Results indicated that soil types influenced the toxic effects of antibiotics and heavy metals. Zn and Cu alone and when combined with OTC inhibited and retarded nitrification processes and reduced nitrous oxide emissions, which were mainly attributed to the inhibitory effects on ammonia‐oxidizing microorganisms. Moreover, Zn and Cu alone or combined with OTC increased soil respiration, but decreased the abundances of bacteria and fungi. In contrast, OTC alone had no significant effect on soil respiration but increased the abundance of fungi in both soils. Together, our results suggest that the widespread occurrence of antibiotics and heavy metals in agriculture soils may pose significant eco‐environmental risks by altering nitrification process and soil microbial activity. [ABSTRACT FROM AUTHOR]

Piper betle L., belonging to Piperaceae family, known as a traditional herbal medicinal plant and used for several health benefits in Asian countries. Currently, demand for its products such as herbal drugs, medicines, and natural herbal formulations has increased. The beneficial effects of betel leaves and its products have traditionally exploited for the treatment of several diseases like bad breath, cuts, injuries, inflammations, cold cough, indigestion, etc. Till now, a broad range of bioactive compounds including polyphenols, terpenes, etc., has been identified from the extracts and essential oil (EO) of betel leaves. The structural and functional characterization of the extract and EO bio-actives has been derived by various advanced standard methods. Most of the health-related benefits of betel leaves have been associated with their bioactive phenolic compounds. The extract of this highly perishable product can be used in organic synthesis, food, and beverage industry, pharmaceuticals, etc., to the environmental issues. The present review provides information on extraction techniques, identification of bioactive compounds, and their biological activities. That apart, information on processing, preservation, and health benefits along with their mechanisms has also been added. [ABSTRACT FROM AUTHOR]

Microbial processing of aggregate‐unprotected organic matter inputs is key for soil fertility, long‐term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro‐ and micro‐nutrients) on decomposition and biochemical transformation of standard plant materials buried in 21 grasslands from four continents. Addition of multiple nutrients weakly but consistently increased decomposition and biochemical transformation of plant remains during the peak‐season, concurrent with changes in microbial exoenzymatic activity. Higher mean annual precipitation and lower mean annual temperature were the main climatic drivers of higher decomposition rates, while biochemical transformation of plant remains was negatively related to temperature of the wettest quarter. Nutrients enhanced decomposition most at cool, high rainfall sites, indicating that in a warmer and drier future fertilized grassland soils will have an even more limited potential for microbial processing of plant remains. [ABSTRACT FROM AUTHOR]

CO2 efflux from the litter layer, litter heterotrophic respiration, is an important component of the forest carbon cycle. Litter heterotrophic respiration mediated by microorganisms varies in response to seasonal environmental changes, such as temperature and moisture. Here, we aimed to quantify seasonal variation in litter heterotrophic respiration and determine how the microbial biomass influences microbial activity and hence litter heterotrophic respiration in a warm temperate forest. We performed in situ high‐frequency measurements of litter heterotrophic respiration per unit area (R_area), which are able to capture CO2 pulses during rainfall, for over 2 years. Microbial activity, which is the CO2 efflux per unit weight (R_mass) considering the change in the amount of substrate, was calculated based on R_area. In parallel, we measured substrate‐induced respiration (SIR) each month, as an index of microbial biomass. We identified seasonal hysteresis in R_area, which was higher in spring (January to July) than in fall (August to December), despite the temperature being similar in both periods. Of interest, R_mass and SIR also showed similar seasonal hysteresis in relation to temperature. Additionally, potential microbial activity without the effect of temperature and moisture was positively related to SIR. This result indicates that seasonal hysteresis with temperature in microbial activity was driven by microbial biomass seasonality, and thus, it leads to seasonal hysteresis in litter heterotrophic respiration in relation to temperature. Our findings highlight the importance of not only the environmental factors and substrate depletion but also biotic factors for estimating heterotrophic respiration. Key Points: Litter heterotrophic respiration measured by an automated chamber system showed seasonal hysteresis in relation to temperatureMicrobial activity also showed similar seasonal hysteresis with temperature, which was driven by microbial biomass seasonalityIt highlights the important role of microbial biomass seasonality in determining litter heterotrophic respiration [ABSTRACT FROM AUTHOR]

Species‐rich plant communities have been shown to be more productive and to exhibit increased long‐term soil organic carbon (SOC) storage. Soil microorganisms are central to the conversion of plant organic matter into SOC, yet the relationship between plant diversity, soil microbial growth, turnover as well as carbon use efficiency (CUE) and SOC accumulation is unknown. As heterotrophic soil microbes are primarily carbon limited, it is important to understand how they respond to increased plant‐derived carbon inputs at higher plant species richness (PSR). We used the long‐term grassland biodiversity experiment in Jena, Germany, to examine how microbial physiology responds to changes in plant diversity and how this affects SOC content. The Jena Experiment considers different numbers of species (1–60), functional groups (1–4) as well as functional identity (small herbs, tall herbs, grasses, and legumes). We found that PSR accelerated microbial growth and turnover and increased microbial biomass and necromass. PSR also accelerated microbial respiration, but this effect was less strong than for microbial growth. In contrast, PSR did not affect microbial CUE or biomass‐specific respiration. Structural equation models revealed that PSR had direct positive effects on root biomass, and thereby on microbial growth and microbial biomass carbon. Finally, PSR increased SOC content via its positive influence on microbial biomass carbon. We suggest that PSR favors faster rates of microbial growth and turnover, likely due to greater plant productivity, resulting in higher amounts of microbial biomass and necromass that translate into the observed increase in SOC. We thus identify the microbial mechanism linking species‐rich plant communities to a carbon cycle process of importance to Earth's climate system. [ABSTRACT FROM AUTHOR]

Composts are effective to promote rehabilitation after drastic disturbance. The eruption of Puyehue–Cordón Caulle complex in 2011 deposited 25–30 cm of tephra in the Argentinean area known as "De los Siete Lagos," where soil and vegetation had been removed from many sites for the construction of National Route 40 between 2005 and 2015. Roadside revegetation is limited by the drastic disturbance, but also by depth and low nutrient content of the tephra. Our objective was to study substrate and plant rehabilitation after the application of different composts (biosolids compost, BC, and municipal waste compost, MC) and seeding (Trifolium repens and Poa domingensis). Eighteen months after the eruption the following treatments were installed: control, BC and MC, nonseeded and seeded (n = 3). Composts were applied at 60 Mg/ha and seeds were sowed at 2 g/m2. Physicochemical substrate properties (moisture, pH, electrical conductivity [EC]), nutrient content (organic C, available P, total N), and microbial activity (respiration, N mineralization, enzymatic activities) were assessed 15 months after the start of the experiment. Plant cover and biomass were estimated three times during summer–early autumn. Seeding had no effect on roadside revegetation. Composts significantly promoted substrate rehabilitation, as BC had a positive effect on moisture, nutrient content (total N, available P, N mineralization), and microbial activity (leucine‐aminopeptidase and acid phosphomonoesterase activities), while MC significantly increased EC and pH. Finally, composts significantly increased plant cover and biomass, but the community was dominated by exotics favored by harsh environmental conditions and absence of a native seed bank. [ABSTRACT FROM AUTHOR]

Increasing soil organic carbon (SOC) in agroecosystems is necessary to mitigate climate change and soil degradation. Management practices designed to reach this goal call for a deeper understanding of the processes and drivers of soil carbon input stabilization. We identified main drivers of SOC stabilization in oil palm plantations using the well‐defined spatial patterns of nutrients and litter application resulting from the usual management scheme. The stabilization of oil palm‐derived SOC (OP‐SOC) was quantified by δ13C from a shift of C4 (savanna) to C3 (oil palm) vegetations. Soil organic carbon stocks under frond piles were 20% and 22% higher compared with harvest paths and interzones, respectively. Fertilization and frond stacking did not influence the decomposition of savanna‐derived SOC. Depending on management zones, net OP‐SOC stabilization equalled 16–27% of the fine root biomass accumulated for 9 years. This fraction was similar between frond piles and litter‐free interzones, where mineral NPK fertilization is identical, indicating that carbon inputs from dead fronds did not stabilize in SOC. A path analysis confirmed that the OP‐SOC distribution was largely explained by the distribution of oil palm fine roots, which itself depended on management practices. SOC mineralization was proportional to SOC content and was independent on phosphorus availability. We conclude that SOC stabilization was driven by C inputs from fine roots and was independent of alteration of SOC mineralization due to management. Practices favouring root growth of oil palms would increase carbon sequestration in soils without necessarily relying on the limited supply of organic residues. [ABSTRACT FROM AUTHOR]

Biogenic volatile organic compounds (BVOCs) can be released from soils to the atmosphere through microbial decomposition of plant residues or soil organic carbon, root emission, evaporation of litter‐stored BVOCs, and other physical processes. Soils can also act as a sink of BVOCs through biotic and abiotic uptake. Currently, the source and sink capabilities of soils have not been explicitly accounted for in global BVOC estimates from the terrestrial biosphere. In this review, we summarize the current knowledge of soil BVOC processes and aim to propose a generic framework for modelling soil BVOCs based on current understanding and data availability. To achieve this target, we start by reviewing measured sources and sinks of soil BVOCs and summarize commonly reported compounds. Next, we strive to disentangle the drivers for the underlying biotic and abiotic processes. We have ranked the list of compounds, known to be emitted from soils, based on our current understanding of how each process controls emission and uptake. We then present a modelling framework to describe soil BVOC emissions. The proposed framework is an important step toward initializing modelling exercises related to soil BVOC fluxes. Finally, we also provide suggestions for measurements needed to separate individual processes, as well as explore long‐term and large‐scale patterns in soil BVOC fluxes. Plain Language Summary: Living plants emit biogenic volatile organic compounds (BVOCs), which have impacts on regional and global climate. However, BVOCs can also be released from fallen leaf litter, plant roots, and soil organic matter, and some compounds are also consumed by soil microbes. In this article, we begin by sorting out the processes that govern soil emissions and uptakes of BVOCs and summarize the current understanding and available data for each process. Furthermore, we propose a generic modelling framework to add soil BVOC‐related processes into the typical structure existing in many ecosystem models. We also provide suggestions for future measurements that would help with model‐data integration. Key Points: We present biotic and abiotic drivers for soil BVOC emissions and sinksWe summarize the often‐reported compounds and key processes regulating their fluxesWe propose a generic framework for including soil BVOCs in ecosystem models [ABSTRACT FROM AUTHOR]

After abandonment of agricultural lands (ongoing on 220 million hectares worldwide), degraded arable soils undergo self‐restoration and development towards natural ecosystems. We studied the linkage between microbial properties and density fractions of soil organic matter (SOM) during post‐agricultural restoration of former arable Phaeozems and Chernozems. The chronosequence study was conducted in two contrasting bioclimatic zones of European Russia: deciduous forest (Luvic Phaeozem) and dry steppe (Calcic Chernozem). Each chronosequence included an arable soil, 3–4 soils with increasing periods after abandonment (from 7 to 35 years), and reference sites with native soils. The basal respiration (BR) and microbial biomass (Cmic) were closely correlated with the soil organic carbon (Corg) content as well as SOM density fractions: free particulate organic matter (fPOM), occluded particulate organic matter (oPOM), and mineral–SOM. The greatest increase in most properties was common in the top 0–5 cm and was maximal for fPOM and oPOM fractions (by 1.5–2.5‐times), Cmic (1.9‐times), and BR (1.5–2.5‐times). For the first time, the duration of full recovery of soil properties depending on climate were estimated. Generally, ~40–120 and 20–30 years in the forest and steppe, respectively, are required to restore Corg, total nitrogen (TN), and Cmic contents in the 0‐ to 5‐cm layer after the abandonment of agricultural lands. The maximal restoration rates of all properties are common in the first 15–20 years after abandonment. [ABSTRACT FROM AUTHOR]

BACKGROUND The rumen microbiota has been used as inoculum for in vitro studies and as a probiotic to improve productivity in young animals. However, great variability across studies has been noted depending on the inoculum considered. The present study aims to assess the relevance of different factors (microbial fraction, collection time, donor animal diet, fermentation substrate and inoculum preservation method) to maximize the rumen inoculum activity and set the standards for further in vitro and in vivo applications. RESULTS: Rumen inoculum sampled at 3 h after feeding led to greater microbial growth and activity [+12% volatile fatty acid (VFA), +17% ammonia] compared to before feeding. Similar results were noted when rumen liquid or rumen content were used as inocula. Rumen inoculum adapted to concentrate diets increased microbial activity (+19% VFA) independently of the substrate used in vitro. Freezing‐thawing the inoculum, in comparison to fresh inoculum, decreased microbial activity (−14% VFA, −96% ammonia), anaerobic fungi and protozoa, with holotrichs protozoa being particularly vulnerable. Inoculum lyophilization had a stronger negative effect on microbial activity (−51% VFA) and delayed re‐activation of the microbes, leading to lower levels of methanogens and anaerobic fungi, as well as almost complete wipe out of rumen protozoa. CONCLUSIONS: Fresh rumen fluid sampled at 3 h after feeding from donor animals that were fed concentrate diets should be chosen when the aim is to provide the most diverse and active rumen microbial inoculum. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: The streams and rivers are considered hotspots of CO2 exchange; and representative direct CO2 emission measurements are essential for a correct regional estimate. We measured CO2 emission flux at 15 sites at land–water interface downstream of a point source during low flow for three consecutive months for the year 2017. The general range of CO2 efflux observed here was close to the results of regional studies, although values near the point source were disproportionately high (>350 mg/m2/h). CO2 emission flux showed strong dependence on total organic carbon (TOC; R2 = 0.96; P < 0.001), NH 4 + (R2 = 0.88; P < 0.001), soluble reactive‐P (SRP; R2 = 0.91; P < 0.001) and microbial activity measured in terms of fluorescein diacetate activity (FDAase; R2 = 0.92; P < 0.001) and substrate induced respiration (SIR; R2 = 0.96; P < 0.001). Because point source‐associated interfaces provide heterogeneous habitats, our study suggests the need for large scale monitoring of CO2 emission at land–water interface of major rivers for more correctly presenting the regional scale CO2 budget. [ABSTRACT FROM AUTHOR]

Summary: Biochar can enhance plant growth and reduce diseases, but frequently the optimal doses for these two benefits do not coincide. An approach is needed that will extend the range of biochar doses resulting in a concurrence of maximum benefits for both plant productivity and disease suppression. A biochar‐amended growth medium was pre‐conditioned by pre‐planting fertigation in order to enhance the indigenous microbial community structure and activity. Cucumber plant performance and resistance against damping‐off caused by Pythium aphanidermatum were monitored. Soil microbial activity, as well as bacterial and fungal community structure, were assessed by high‐throughput 16S rRNA and ITS1 gene amplicon sequencing. Pre‐conditioning enhanced the efficacy of biochar for improving plant performance and suppressing soilborne disease through enriching the medium in beneficial soil microorganisms, increasing microbial and fungal diversity and activity, and eliminating biochar phytotoxic compounds. The pre‐conditioning process brought dose–response curves for both growth and disease resistance into sync, resulting in maximum benefits for both. These findings suggest that pre‐conditioning should be incorporated as an important stage during biochar application in soil and soilless media. [ABSTRACT FROM AUTHOR]

We investigated the effects of compost (CM), made from poultry and cattle manure with spent mushroom substrate, plus chemical fertilizers (CFs) on soil organic carbon (C) and nitrogen (N) fractions in silty loam soil of the Loess Plateau. Eight fertilizer practices were applied in a 7-year-old 'Red Fuji' apple (Malus domestica Borkh.) orchard for 360 days. Compared to CM alone, CM-CFs decreased slightly soil total organic C but increased total N by 4.3-11.6%. Notably, CM-CFs increased soil microbial biomass C (MBC) by 2.7-26.5% and microbial biomass N (MBN) by 7-13.7%. Soil water-soluble carbon (WSC) was increased by 20.7% and 19.2% when 2% CM plus N and phosphorus (P) (2%M-NP) and 4% CM plus N and P (4%M-NP) were applied, respectively. Whereas 0.5% CM plus N and P (0.5%M-NP) increased WSC by 9.3% on day 30 but decreased it by 7.2% from 30-360 days. Hot water-soluble C increased by 13.1-14.6% from 0-180 day, but thereafter, the effect disappeared. Compared to CFs, CM-CFs increased MBN by 35.1-115.6%, and increased alkali-hydrolyzable-N by 3.5-55.8% over 180-360 days of incubation. Additionally, CM-CFs promoted N mineralization, increasing NH4-N and NO3-N contents. Based on the changes in C and N fractions and available nutrients, 2%M-NP (45 t/ha of CM plus 450 kg/ha of N and 157.5 kg/ha of P) may be the optimal fertilizer strategy for stimulating soil microbial growth and activity, and enhancing nutrient cycling for apple growth. [ABSTRACT FROM AUTHOR]

Abstract: Decomposition of organic matter in semi‐arid ecosystems is a key component of the terrestrial carbon (C) cycle. The well‐known inaccuracies in predicting litter decay in water‐limited regions were lessened by considering solar radiation as an abiotic decay driver of photodegradation. Moreover, exposure to high solar irradiance in dry periods often led to massive facilitation of litter decay in subsequent wet periods (“photoacceleration”), though in many studies this effect was absent. Recently, water vapour and dew were identified as modulators enabling substantial microbial degradation during rainless periods. Here, we investigated, (1) whether the activity of micro‐organisms modifies litter traits, such as litter quality and microbial community in dry periods, consequently altering the loss of litter mass and nitrogen (N) in wet periods, and (2) whether it can co‐occur with photoacceleration. By successively introducing litter to the field at the beginning and the end of the dry season, we found that microbial activity during the dry season affected litter mass and N loss during the wet season. Low microbial activity in the dry season led to inhibition of mass loss in the wet season, while high microbial activity led to facilitation of mass loss. Microbial activity during the dry season also caused strong inhibition of N loss from litter during the wet season, likely by enhancing the dry‐season N loss. A microclimate manipulation experiment using radiation filters showed that microbial activity and exposure to solar radiation jointly modified the litter during the dry season and affected subsequent decay in the wet season. Knowledge of biotic and abiotic modifications of litter during dry periods and their implication for wet periods enhances our understanding of litter decay in semi‐arid regions. Furthermore, it can improve biogeochemical model predictions of C and N cycling in drylands and in the many regions that are projected to experience a drier climate during the coming decades. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]