Enrichment Experiments Research Articles

Increasing photosynthetic benefit with decreasing irrigation frequency in an Australian temperate pasture exposed to elevated carbon dioxide.

Elevated atmospheric CO2 (e[CO2]) often enhances plant photosynthesis and improves water status. However, the effects of e[CO2] vary significantly and are believed to be influenced by water availability. With the future warmer climate expected to increase the frequency and severity of extreme rainfall, the response of plants to e[CO2] under changing precipitation patterns remains uncertain. We examined the effects of e[CO2] and different irrigation regimes on perennial ryegrass in a Free-Air CO2 Enrichment (FACE) experiment. Immediately after irrigation, the mean net photosynthetic rate was 21.2% higher under e[CO2] compared to ambient conditions. This benefit increased over time, reaching 31.3% higher as days since watering increased, indicating a substantial increase in photosynthetic benefit with longer intervals between watering. Mean stomatal conductance was 21% lower in ryegrass under e[CO2] immediately after irrigation compared to ambient plots. However, the reduction in stomatal conductance under e[CO2] decreased as the interval between irrigation events increased, showing no difference 7-10 days after an irrigation event. These results imply that plants benefit most from carbon fertilisation, assimilating relatively more carbon and losing less water, during periods with less frequent rainfall. These findings have significant implications for understanding leaf-level responses to climate change.

Combined effects of climate stressors and soil arsenic contamination on metabolic profiles and productivity of rice (Oryza sativa L.).

Rice productivity and quality are increasingly at risk in arsenic (As) affected areas, challenge that is expected to worsen under changing climatic conditions. Free-Air Concentration Enrichment experiments revealed that eCO2, eO3, and eTemp, whether acting individually or in combination with low and high As irrigation, significantly impact rice yield and grain quality. Elevated CO₂ significantly increased shoot biomass, with minimal impact on root biomass, except under low As irrigation conditions. In contrast, eTemp alone reduced both shoot and root biomass, though the effect was not significant; eO₃ alone had little to no effect. Combined climatic stressors showed slight positive effects on growth. Under low As irrigation, eCO2 and eO3 promoted root growth but reduced shoot growth, while eTemp significantly suppressed both. High As irrigation exacerbated yield reductions, with the most severe decline observed under eTemp (66%), followed by eCO2 (48%), eO3 (36%), and their combination (35%). Arsenic irrigation, whether low or high, reduced macro and micronutrient concentrations in rice grains, with calcium being sole exception, remaining stable or even increasing. Sugar metabolites decreased under eCO2, eO3, and eTemp, but increased with As irrigation. Interestingly, climatic variables generally reduced grain As levels, high As irrigation combined with eCO2 exposure resulted in elevated grain As. This poses a dual concern: increased cancer risk due to As but potential benefit for individuals with diabetes, as the higher amylose content contributes to lower glycemic index. However, rice grown under high As irrigation exhibited significant nutritional imbalances, being rich in maltose and amylose but deficient in organic acids, phytosterols, fatty acids, organosilicons, and carboxylic acids. These findings underscore the dual threat of climate change and As contamination to rice productivity and quality. Developing resilient rice varieties with low grain As content is essential to ensure sustainable agricultural production and nutritional security in As affected regions.

Stream bryophytes promote “cryptic” productivity in highly oligotrophic headwaters

AbstractRecent observations document increased abundance of algae in the headwater streams of Hubbard Brook Experimental Forest (HBEF). It is possible that this “greening up” of HBEF streams may be due to climate change, with rising temperatures, altering terrestrial phenology, and shifting hydrologic regimes. Alternatively, stream “greening” could be from the slow recovery of stream chemistry after decades of acid rain, which has led to rising pH, declining concentrations of toxic Al3+, and low solute concentrations. Four years of weekly algal measurements on artificial moss and ceramic tiles, along with six nutrient enrichment experiments, revealed new insights about the interactions between these two autotrophs. We found that in protected weir ponds and in stream channels, algal biomass was higher on artificial moss substrates than on tiles—with this effect amplified in the stream channels. These results suggest that bryophytes can provide physical protection from flood scour or may trap nutrients to support algal growth. In stream channels, algal biomass was higher in well‐lit habitats and time periods indicating strong light limitation. We only measured nitrogen and phosphorus limitation of algal biomass in nutrient enrichment experiments conducted within weir ponds, with higher light availability and lower flow. By comparison, results from the remaining four instream experiments provided little evidence for nutrient limitation, with only one trial showing increased algal growth in response to nutrient addition. The most striking implication of our study is the role of bryophytes in providing refugia, and potentially nutrients, to algae in shaded and oligotrophic headwater streams.

Elevated CO2 Increased Antibiotic Resistomes in Seed Endophytes: Evidence from a Free-Air CO2 Enrichment (FACE) Experiment.

Climate warming affects antibiotic resistance genes (ARGs) in soil and the plant microbiome, including seed endophytes. Seeds act as vectors for ARG dissemination in the soil-plant system, but the impact of elevated CO2 on seed resistomes remains poorly understood. Here, a free-air CO2 enrichment system was used to examine the impact of elevated CO2 on seed-associated ARGs and seed endophytic bacteria and fungi. Results indicated that elevated CO2 levels significantly increased the relative abundance of seed ARGs and mobile genetic elements (MGEs), especially those related to beta-lactam resistance and MGEs. Increased CO2 levels also influenced the composition of seed bacterial and fungal communities and the complexity of bacteria-fungi interactions. Fungi were more sensitive to changes in the CO2 level than bacteria, with deterministic processes playing a greater role in fungal community assembly. Co-occurrence network analysis revealed a stronger correlation between fungi and ARGs compared to bacteria. The structure equation model (SEM) showed that elevated CO2 directly influenced seed resistomes by altering bacterial composition and indirectly through bacteria-fungi interactions. Together, our work offers new insights into the effects of elevated CO2 on antibiotic resistomes in the seed endosphere, highlighting their increased dissemination potential within soil-plant systems and the associated health risks in a changing environment.

Glycopolymer-Mediated Selective Separation of Middle Rare Earth Elements.

The selective separation of rare earth elements (REEs) remains a formidable challenge due to limitations of current methodologies, which struggle to achieve the separation efficiency required for their critical industrial applications. Middle REEs (MREEs), characterized by their intermediate ionic radii, are particularly challenging to separate without size-specific trapping mechanisms. In this study, we report a novel approach that synergistically combines heavy metal sequestration with size-selective separation, utilizing negatively charged glycopolymers to achieve the targeted separation of MREEs. We systematically investigated the binding affinities of these glycopolymers for various REEs, focusing on the selective isolation of MREEs through a controlled variation of glycopolymer properties, including degree of polymerization (DP) and charge density. Our findings reveal a distinctive U-shaped selectivity profile, with a marked preference for Samarium (Sm) and Europium (Eu) over other REEs such as Cerium (Ce), Gadolinium (Gd), and Holmium (Ho). This selectivity underscores the potential for designing tailored separation processes optimized for specific MREEs. Moreover, enrichment experiments demonstrated the practical viability of our methodology, achieving over 10 % selectivity for Sm in a Ce/Sm mixture with a 10 : 1 Ce/Sm ratio, a trend that held for Sm in a Ho/Sm Mixture with a 10 : 1 Ho/Sm ratio, indicating significant selectivity over both light and heavy REEs. A subsequent separation experiment using a 1 : 1 Ce/Sm mixture yielded a 15 % enrichment after only five passes through a filter containing minimal amounts of glycopolymer, highlighting the promise of further refinement for enhanced separation efficiency.

Glycopolymer‐Mediated Selective Separation of Middle Rare Earth Elements

AbstractThe selective separation of rare earth elements (REEs) remains a formidable challenge due to limitations of current methodologies, which struggle to achieve the separation efficiency required for their critical industrial applications. Middle REEs (MREEs), characterized by their intermediate ionic radii, are particularly challenging to separate without size‐specific trapping mechanisms. In this study, we report a novel approach that synergistically combines heavy metal sequestration with size‐selective separation, utilizing negatively charged glycopolymers to achieve the targeted separation of MREEs. We systematically investigated the binding affinities of these glycopolymers for various REEs, focusing on the selective isolation of MREEs through a controlled variation of glycopolymer properties, including degree of polymerization (DP) and charge density. Our findings reveal a distinctive U‐shaped selectivity profile, with a marked preference for Samarium (Sm) and Europium (Eu) over other REEs such as Cerium (Ce), Gadolinium (Gd), and Holmium (Ho). This selectivity underscores the potential for designing tailored separation processes optimized for specific MREEs. Moreover, enrichment experiments demonstrated the practical viability of our methodology, achieving over 10 % selectivity for Sm in a Ce/Sm mixture with a 10 : 1 Ce/Sm ratio, a trend that held for Sm in a Ho/Sm Mixture with a 10 : 1 Ho/Sm ratio, indicating significant selectivity over both light and heavy REEs. A subsequent separation experiment using a 1 : 1 Ce/Sm mixture yielded a 15 % enrichment after only five passes through a filter containing minimal amounts of glycopolymer, highlighting the promise of further refinement for enhanced separation efficiency.

A Proof-of-Principle Study for δ15N Measurements of Aqueous Dissolved Nitrate With a Modified LC-IRMS Interface.

The analysis of nitrogen isotopes in aqueous dissolved nitrate is an effective method for identifying pollution sources and offers the potential to study the nitrogen cycle. However, the measurement of nitrogen isotope ratios of nitrate still requires extensive sample preparation or derivatization. In this study, a modified commercially available liquid chromatography-isotope ratio mass spectrometer (LC-IRMS) interface is presented that enables automated measurement of δ15N signatures from nitrate by online reduction of nitrate in two consecutive steps. First, vanadium(III) chloride is used as a reducing agent to convert NO3 - to NxOy under acidic conditions. The mix of nitrogen oxides is then transferred into a stream of helium and reduced to nitrogen (N2) analysis gas via a hot copper reactor. Prior to the online conversion of aqueous nitrate into elemental nitrogen, the sample was chromatographically separated from potential matrix effects on a PGC column. Precision was achieved at a level below 1.4‰ by injecting 10 μL of 50 mg L-1 N, using five different nitrate standards and reference materials. These materials spanned a range of more than 180‰ in δ15N. To demonstrate the applicability of the method, we measured water samples from an enrichment experiment, where isotopically enriched ammonium chloride was administered into a small river over the course of 2 weeks. In contrary to our expectation, the δ15N values of river nitrate showed values between +0.4 ± 0.4‰ and +4.1 ± 0.3‰, varying over a small range of 3.7‰. Our study showed that the measurement of nitrate nitrogen isotope ratios with a modified LC-IRMS system is possible but that further modifications and improvements would be necessary for a robust and user-friendly instrument.

Impacts of elevated CO2 and partial defoliation on mineral element composition in rice.

This study explores how elevated CO2 concentration may alter the source-sink dynamics in rice by providing additional carbon for photosynthesis, thereby affecting nutrient absorption and distribution. A free-air CO2 enrichment experiment was conducted on a japonica cultivar Wuyunjing 27 in 2017 and 2018 growing seasons. The plants were exposed to ambient and elevated CO2 level (increased by 200 μmol·mol-1) and two source-sink manipulation treatments (control with no leaf cutting and cutting off the top three leaves at heading). The elevated CO2 significantly increased the above-ground biomass and the straw non-structural carbohydrate concentration by an average of 19.3% and 12.5%, respectively. Significant changes in the concentrations of N, S, Fe, and Zn in straw were noted under elevated CO2, with average decreases by 7.1, 7.2, 11.6, and 10.1%, respectively. The exposure to elevated CO2 significantly enhanced the elements accumulation, yet it had minimal impact on their distribution across different organs. When compared to intact rice, removing the top three leaves at heading reduced the above-ground biomass by 36.8% and the straw non-structural carbohydrate content by 44.8%. Leaf-cutting generally increased the concentration of elements in stem, leaf, and grain, likely due to a concentration effect from reduced biomass and carbohydrate accumulation. Leaf-cutting reduced element accumulation and shifted element allocation in rice organs. It increased the proportion of elements in stems while reduced their presence in leaves and grains. Our study suggests that a dilution effect may cause a decrease in mineral elements concentrations under elevated CO2 because of the increase in biomass and carbohydrates.

Coexposure to ambient air pollution and temperature and its associations with birth outcomes in women undergoing assisted reproductive technology in Fujian, China: A retrospective cohort study

BackgroundThe interactions between pollutants and temperature coexposure, the mixing effects and their potential mechanisms remain uncertain. MethodsThis retrospective cohort study included 11,766 women with infertility who received treatment at Fujian Hospital between 2015 and 2024. The daily mean concentrations of the six pollutants and the relative humidity and temperature data were acquired from the Fujian region. Data on genes were obtained from the Comparative Toxicogenomics Database. ResultsO3 (aOR=0.80, 95 % CI=0.725-−0.891) and temperature (aOR=0.936, 95 % CI=0.916-−0.957) were negatively correlated with live birth rates. Moreover, PM10 (aOR=1.135, 95 % CI=1.028-−1.252) and PM2.5 (aOR=1.146, 95 % CI=1.03-−1.274) were positively associated with preterm birth. Among the effects on live births, PM2.5, PM10, NO2, CO, and SO2 had significant synergistic effects with temperature; in addition, O3 had significant antagonistic effects with temperature. A notable trend toward declining live birth rates with elevated concentrations of mixed pollutants was observed. Different infertility patients have different sensitivities to coexposure. Gene enrichment and cell experiments are associated mainly with cellular life activities. ConclusionsIndividual effects, interactions, and mixed effects between temperature and air pollutants and birth outcomes persist when air pollutant levels are relatively low. AAP may trigger miscarriage through cytotoxic effects.

Nutrients limiting the growth of planktonic and benthic-littoral primary producers in Patagonian Andean Lakes

In this work, we assess differences in nutrient limitation (nitrogen and phosphorus) between benthic-littoral (in the littoral habitat) and planktonic (in the epi-pelagic habitat) primary producers of seven Patagonian Andean lakes in southern South America. We conducted nutrient enrichment experiments using nitrate, ammonium, and phosphate to identify which nutrient(s) restrict primary producers’ growth in each lake habitat. Also, we determined the concentration of dissolved inorganic nitrogen (DIN), soluble reactive phosphorous (SRP), and the nitrogen to phosphorous ratio (DIN:SRP) at the littoral and epi-pelagic habitats of each lake. For all the lakes, benthic-littoral primary producers were limited by nitrogen, while planktonic primary producers in the epi-pelagic habitat were colimited by nitrogen and phosphorus. Our study is the first to show that different nutrients limit the growth of benthic-littoral and planktonic primary producers in Patagonian Andean lakes. This contributes to our understanding of lake ecology in a region where there is limited information on benthic-littoral habitats. This is important because globally, there is an increase in periphyton blooms in the benthic-littoral habitats of oligotrophic lakes, while the pelagic habitats remain unchanged. Additionally, we found nutrient concentrations in the lakes are up to 7.4 times higher than those described in previous studies, which may be related to anthropogenic impact and natural events. If nutrient levels continue to increase, algal blooms in Patagonian Andean lakes may become a regional issue, especially in the benthic-littoral habitats.

Influences of Cr(VI) on SOD Activity, MDA, and MT Content in the Hepatopancreas and Gill of Portunus trituberculatus

The toxic effect and differences of Cr(VI) on superoxide dismutase (SOD) activity, MDA, and metallothionein (MT) content in the hepatopancreas and gill of Portunus trituberculatus were investigated during Cr(VI) enrichment (15 days) and release experiments (15 days). Results showed that the 1.50 and 0.30 mg/L test groups significantly exhibited higher SOD, MDA, and MT content in the hepatopancreas and gill compared with the control group after 15 days of enrichment (p < 0.05). After 15 days of Cr release, the SOD, MDA, and MT content in the hepatopancreas and gill of both test groups recovered to the normal level of the control group (p > 0.05). The gill of P. trituberculatus achieved the highest SOD activity, MDA, and MT content earlier than the hepatopancreas, but the highest values were lower. The gill showed a shorter recovery time than the hepatopancreas. We concluded that the gill of P. trituberculatus exhibited a more rapid response to, and recovery from, Cr(VI) exposure compared to the hepatopancreas, making it a more sensitive tissue for assessing Cr(VI) toxicity, though both tissues showed a capacity for recovery after the removal of the contaminant.

Castanet: a pipeline for rapid analysis of targeted multi-pathogen genomic data.

Target enrichment strategies generate genomic data from multiple pathogens in a single process, greatly improving sensitivity over metagenomic sequencing and enabling cost-effective, high-throughput surveillance and clinical applications. However, uptake by research and clinical laboratories is constrained by an absence of computational tools that are specifically designed for the analysis of multi-pathogen enrichment sequence data. Here we present an analysis pipeline, Castanet, for use with multi-pathogen enrichment sequencing data. Castanet is designed to work with short-read data produced by existing targeted enrichment strategies, but can be readily deployed on any BAM file generated by another methodology. Also included are an optional graphical interface and installer script. In addition to genome reconstruction, Castanet reports method-specific metrics that enable quantification of capture efficiency, estimation of pathogen load, differentiation of low-level positives from contamination, and assessment of sequencing quality. Castanet can be used as a traditional end-to-end pipeline for consensus generation, but its strength lies in the ability to process a flexible, pre-defined set of pathogens of interest directly from multi-pathogen enrichment experiments. In our tests, Castanet consensus sequences were accurate reconstructions of reference sequences, including in instances where multiple strains of the same pathogen were present. Castanet performs effectively on standard computers and can process the entire output of a 96-sample enrichment sequencing run (50M reads) using a single batch process command, in $<$2 h. Source code freely available under GPL-3 license at https://github.com/MultipathogenGenomics/castanet, implemented in Python 3.10 and supported in Ubuntu Linux 22.04. The data underlying this article are available in Europe Nucleotide Archives, at https://www.ebi.ac.uk/ena/browser/view/PRJEB77004.

Assessing forest biomass and diversity of tree populations in Tekam Forest Reserve, Pahang, Malaysia

Abstract. Ruziman HH, Mohti A, Nik Ali NNBNA, Ismail A, Pardi F. 2024. Assessing forest biomass and diversity of tree populations in Tekam Forest Reserve, Pahang, Malaysia. Biodiversitas 25: 2821-2827. Free Air CO2 Enrichment (FACE) experiments are long-term monitoring projects to comprehend the response of forest ecosystems to future atmospheres with CO2 enriched. Therefore, the research aims to determine the forest biomass and species diversity in the FACE system of Tekam Forest Reserve (TFR), Pahang, Malaysia. The sampling plots of 25 m × 20 m were established in TekamFACE as experimental plot and control plot in TFR. Allometric equation, Shannon-Wiener, and Evenness indices were used to estimate the standing biomass, carbon stock and species diversity, respectively. Tekam FACE system recorded total forest biomass of 54.38 ton/ha, contributed by 42.82 tons/ha of Above-Ground Biomass (AGB) and 11.56 tons/ha of Below-Ground Biomass (BGB). High carbon stock was also estimated at both forest plots with 27.19 tons/ha in TekamFACE and 17.35 tons/ha in control plot. These values indicated that the forest has high biomass, which can contribute to carbon sequestration that help mitigate the impacts of climate change. Further, this forest recorded high Species Diversity (H’) and Species Evenness (E) at TekamFACE (H’ = 4.04; E = 0.93) and control plot (H’ = 3.53; E = 0.83). Overall, this research emphasized that forests with rich biodiversity have substantial carbon sequestration capacity for the adaptation of forest ecosystems to future atmospheric changes.

Effects of increased temperature and altered POC composition on a bathyal macrofaunal community in Cabo Verde, NE Atlantic

Deep-sea ecosystems are particularly important to the cycling of matter and energy in the oceans and therefore in regulating Earth’s climate. The Atlantic Ocean is already experiencing significant abiotic changes, with expected warmer temperatures coupled with decreased particulate organic carbon (POC) export flux. However, there is yet a large gap in our understanding of warming impacts on deep benthic ecosystems and in the organic matter processing by benthic organisms in the seafloor. This study employed an experimental approach to assess the single and cumulative effects of two climate change stressors, temperature and POC quality, on macrofaunal benthic assemblages in the Cabo Verde Basin (CVB, Equatorial Atlantic) bathyal continental slope. Incubation enrichment experiments with 13C and 15N labelled diatoms Phaeodactylum tricornutum simulated climate projections for the next century with a balanced design, studying the effect of either increased temperature (+2°C), reduced POC quality (dialysed labile fraction), or both, against a control treatment. We found that echinoderms and polychaetes rapidly ingested labelled algae at rates between 0.02 and 21.9 µg C m−2 d-1. Given a strong spatial variability in macrofaunal biomass, the carbon and nitrogen incorporation by macrofauna was not affected by a + 2 °C warming, by a decreased organic matter quality, or the combination of both factors. Our study provides valuable insights into the biodiversity, biomass, and ecosystem functioning (C and N uptake rates) of deep-sea benthic ecosystems in the N Atlantic, and stress that potential effects of warmer temperatures and POC quality on carbon and nitrogen incorporation by macrofauna remain uncertain. We highlight the value of these experiments to better understand the effects of climate change on deep-sea ecosystems.

Getting allometry right at the Oak Ridge free‐air CO2 enrichment experiment: Old problems and new opportunities for global change experiments

Societal Impact StatementFree‐air CO2 enrichment (FACE) experiments provide essential data on forest responses to increasing atmospheric CO2 for evaluations of climate change impacts on humanity. Understanding and reducing the uncertainty in the experimental results is critical to ensure scientific and public confidence in the models and policy initiatives that derive therefrom. One source of uncertainty is the estimation of tree biomass using mathematical relationships between biomass and easily obtained and non‐destructive measurements (allometry). We evaluated the robustness of the allometric relationships established at the beginning of a FACE experiment and discuss the challenges and opportunities for the new generation of FACE experiments.Summary Long‐term field experiments to elucidate forest responses to rising atmospheric CO2 concentration require allometric equations to estimate tree biomass from non‐destructive measurements of tree size. We analyzed whether the allometric equations established at the beginning of a free‐air CO2 enrichment (FACE) experiment in a Liquidambar styraciflua plantation were still valid at the end of the 12 year experiment. Aboveground woody biomass was initially predicted by an equation that included bole diameter, taper, and height, assuming that including taper and height as predictors would accommodate changes in tree structure that might occur over time and in response to elevated CO2. At the conclusion of the FACE experiment, we harvested 23 trees, measured dimensions and dry mass of boles and branches, and extracted and measured the woody root mass of 10 trees. Although 10 of the harvested trees were larger than the trees used to establish the allometric relationship, measured aboveground woody biomass was well predicted by the original allometry. The initial linear equation between bole basal area and woody root biomass underestimated final root biomass by 28%, but root biomass was just 21% of total wood mass, and errors in aboveground and belowground estimates were offsetting. The allometry established at the beginning of the experiment provided valid predictions of tree biomass throughout the experiment. New allometric approaches using terrestrial laser scanning should reduce an important source of uncertainty in decade‐long forest experiments and in assessments of centuries‐long forest biomass accretion used in evaluating carbon offsets and climate mitigation.

Getting to the root of the problem: Soil carbon and microbial responses to root inputs within a buried paleosol along an eroding hillslope in southwestern Nebraska, USA

Large quantities of soil carbon (C) can persist within paleosols for millennia due to burial and subsequent isolation from plant-derived inputs, atmospheric conditions, and microbial activity at the modern surface. Erosion exposes buried soils to modern root-derived C influx via root exudation and root turnover, thus stimulating microbial activity leading to SOC decomposition and accumulation through organo-mineral stabilization of modern C. With this study we aim to quantify how modern root-derived C inputs impact paleosol C decomposition and stabilization across varying degrees of isolation from modern surface conditions in southwestern Nebraska, USA, where hillslope erosion is bringing a buried Late-Pleistocene-early Holocene paleosol (the “Brady Soil”) closer to the modern surface. We collected Brady Soil samples from 0.2 m, 0.4 m, and 1.2 m below the modern surface and conducted two lab-based incubations. Soils were amended with either (1) a lab-synthesized mixture of low molecular weight compounds (12 atom% 13C), or (2) 13C enriched root residues (92 atom% 13C), in 30-day and 240-day incubation experiments, respectively. We determined microbial responses to synthetic root exudates and residues by partitioning the 13C label from Brady Soil C, including measurements of total, root, and primed C respiration, microbial biomass C (MBC), microbial C use efficiency (CUE). To assess the capacity of isolated paleosols to accrue modern plant C, we used Nano-scale Secondary Ion Mass Spectrometry imaging. We found that: (1) adding root-derived C inputs primed Brady Soil C across all depths, and was mediated by depth and composition of root additions; (2) root-derived C inputs stimulated microbial biomass C (MBC) growth similarly across depths, but the magnitude of CUE and MBC varied by chemistry of root-derived additions; (3) new particulate organic matter was incorporated into mineral-associated pools over time; (4) material from the added root residues was found in association with bacterial cells and fungal hyphae as well as with soil aggregate and mineral surfaces. Our study shows that paleosols defy expectations of C content and reactivity with depth, and changes in land cover and climate will expose buried paleosols to modern surface conditions, increasing respired C. This work highlights the importance of evaluating the role resurfacing buried soils through landscape change plays in C cycle feedbacks to the climate system.

Ultrasound-assisted deep eutectic solvents extraction of podophyllotoxins from Juniperus sabina L: Optimization, enrichment, and anti-drug resistant bacteria activity

Podophyllotoxin, along with its congeners and derivatives exhibit strong biological activity mainly as antitumor drugs and antiviral agents. Here, the ultrasound-assisted extraction of podophyllotoxins including α-peltatin, podophyllotoxin, podophyllotoxinone and deoxypodophyllotoxin from Juniperus sabina L. leaves using deep eutectic solvents (DESs) were developed first time. To simultaneously and effectively extract four target podophyllotoxins, 19 DESs were screened to determine the best solvent to extract podophyllotoxins. Choline chloride-lactic acid (1:1) with 30 % water content was proved to have the best extraction effect. The optimal extraction process with DES were DES/solid ratio 30 mL/g, reaction temperature 44℃, time 53 min and ultrasound power 495 W. Under optimized extraction conditions, the total podophyllotoxins extraction yield was 27.520 mg/g, 196.84 % higher than that using traditional methanol solvent. The yield of α-peltatin, podophyllotoxin, deoxypodophyllotoxin and podophyllotoxinone were 13.567, 9.548, 2.021, 2.204 mg/g, respectively. Subsequently, the podophyllotoxins were effectively isolated from the deep eutectic solvent using D101 macroporous resin. The optimal process for enriching target podophyllotoxins by D101 macroporous resin were as follows: 30 mg/mL of crude extract solution, five bed volumes feed volume for adsorption; six bed volumes of 80 % ethanol for desorption. Moreover, a scale-up enrichment experiment of podophyllotoxins was performed under optimum procedure, and the results showed that the target podophyllotoxins yield was increased by 8.92 times, with recoveries in the range of 75.86–85.69 %. Additionally, the enriched podophyllotoxins effectively restored the antibacterial efficacy of cefazolin against methicillin-resistant Staphylococcus aureus and colistin-resistant Escherichia coli, resulting in 16–64-fold reduction in MIC. Therefore, the method developed in this study could be an eco-friendly, efficient and sustainable alternative for the selective extraction and enrichment of active compounds from plant material.

Global diversity and ecological functions of viruses inhabiting oil reservoirs

Oil reservoirs, being one of the significant subsurface repositories of energy and carbon, host diverse microbial communities affecting energy production and carbon emissions. Viruses play crucial roles in the ecology of microbiomes, however, their distribution and ecological significance in oil reservoirs remain undetermined. Here, we assemble a catalogue encompassing viral and prokaryotic genomes sourced from oil reservoirs. The catalogue comprises 7229 prokaryotic genomes and 3,886 viral Operational Taxonomic Units (vOTUs) from 182 oil reservoir metagenomes. The results show that viruses are widely distributed in oil reservoirs, and 85% vOTUs in oil reservoir are detected in less than 10% of the samples, highlighting the heterogeneous nature of viral communities within oil reservoirs. Through combined microcosm enrichment experiments and bioinformatics analysis, we validate the ecological roles of viruses in regulating the community structure of sulfate reducing microorganisms, primarily through a virulent lifestyle. Taken together, this study uncovers a rich diversity of viruses and their ecological functions within oil reservoirs, offering a comprehensive understanding of the role of viral communities in the biogeochemical cycles of the deep biosphere.

Soil organic carbon under decadal elevated CO2: Pool size unchanged but stability reduced

Soil organic carbon (SOC) dynamics under elevated atmospheric CO2 concentration has been widely reported, however, in which the behaviors of active and passive fractions remain inadequately explored. Here we studied this issue using three pairs of active and passive fractions of SOC under a 10-year free-air CO2 enrichment experiment (550 ​± ​17 ​ppm) in a cropland in the North China Plain. We found that decadal elevated CO2 increased the root biomass, root exudation rate and microbial biomass, but had little effects on SOC pool size. Elevated CO2 increased the readily oxidizable organic carbon (ROOC) and particulate organic carbon (POC) due to the increments of root C input, but decreased their paired passive fractions possibly because of the carbon input-induced positive priming effect. Our results indicate the reduced stability of SOC pool under elevated CO2. This is significant for better predicting SOC feedback to future climate change.

Carbon-phosphorus cycle models overestimate CO2 enrichment response in a mature Eucalyptus forest.

The importance of phosphorus (P) in regulating ecosystem responses to climate change has fostered P-cycle implementation in land surface models, but their CO2 effects predictions have not been evaluated against measurements. Here, we perform a data-driven model evaluation where simulations of eight widely used P-enabled models were confronted with observations from a long-term free-air CO2 enrichment experiment in a mature, P-limited Eucalyptus forest. We show that most models predicted the correct sign and magnitude of the CO2 effect on ecosystem carbon (C) sequestration, but they generally overestimated the effects on plant C uptake and growth. We identify leaf-to-canopy scaling of photosynthesis, plant tissue stoichiometry, plant belowground C allocation, and the subsequent consequences for plant-microbial interaction as key areas in which models of ecosystem C-P interaction can be improved. Together, this data-model intercomparison reveals data-driven insights into the performance and functionality of P-enabled models and adds to the existing evidence that the global CO2-driven carbon sink is overestimated by models.