Partial Least Squares Path Modeling Research Articles

Effects of warming on soil organic carbon pools mediated by mycorrhizae and hyphae on the Eastern Tibetan Plateau, China

Mycorrhizae and their hyphae play critical roles in soil organic carbon (SOC) accumulation. However, their individual contributions to SOC components and stability under climate warming conditions remain unclear. This study investigated the effects of warming on the SOC pools of Picea asperata (an ectomycorrhizal plant) and Fargesia nitida (an arbuscular mycorrhizal plant) mycorrhizae/hyphae on the eastern Tibetan Plateau. The results indicated that mycorrhizae made greater contributions to SOC accumulation than hyphae did by increasing labile organic carbon (LOC) components, such as particle organic carbon (POC), easily oxidizable organic carbon, and microbial biomass carbon, especially under warming conditions. Plant species also had different effects on SOC composition, resulting in higher mineral-associated organic carbon (MAOC) contents in F. nitida plots than in P. asperata plots; consequently, the former favored SOC stability more than the latter, with a lower POC/MAOC. Partial least-squares path modelling further indicated that mycorrhizae/hyphae indirectly affected LOC pools, mainly by changing soil pH and enzyme activities. Warming had no significant effect on SOC content but did change SOC composition by reducing LOC through affecting soil pH and iron oxides and ultimately increasing SOC stability in the presence of mycorrhizae for both plants. Therefore, the mycorrhizae of both plants are major contributors to the variation of SOC components and stability under warming conditions.

Nitrogen Addition Decreased Respiration and Heterotrophic Respiration but Increased Autotrophic Respiration in a Cabbage (Brassica pekinensis Rupr) Experiment in the Northeast Plains

Farmland soil respiration (Rs) significantly impacts the global carbon (C) cycle. Although nitrogen (N) can promote crop growth and increase yields, its relationship with Rs and its constituents, including autotrophic respiration (Ra) and heterotrophic respiration (Rh), remains unclear. Therefore, a field study was carried out in a cabbage (Brassica pekinensis Rupr) system to probe the impact of N addition on Rs, Ra, and Rh. Five levels of N addition, including 0 kg N hm−2·yr−1 (N0), 50 kg N hm−2·yr−1 (N50), 100 kg N hm−2·yr−1 (N100), 150 kg N hm−2·yr−1 (N150), and 200 kg N hm−2·yr−1 (N200), started in March 2022. The Rs (Ra and Rh) and soil samples were measured and collected twice a month. The findings revealed the following: (1) N fertilizer enhanced Ra while reducing Rs and Rh; (2) soil temperature (ST), belowground net primary productivity (BNPP), soil inorganic N (SIN), and soil total C/total N (C/N) were the significant elements influencing Ra, and microbial biomass carbon (MBC), SIN, and microbial diversity (MD) were the primary factors influencing Rh; (3) partial least squares-path models (PLS-PM) showed that ST and SIN directly impacted Rh, while ST and BNPP tangentially influenced Ra; (4) 150 kg N hm−2·yr−1 was the ideal N addition rate for the cabbage in the region. In summary, the reactions of Ra and Rh to N fertilizer in the Northeast Plains are distinct. To comprehend the underlying processes of Rs, Ra, and Rh, further long-term trials involving various amounts of N addition are required, particularly concerning worsening N deposition.

Differences in dissolved organic matter and analysis of influencing factors between plantations pure and mixed forest soils in the loess plateau

The dissolved organic matter (DOM) in forest ecosystems significantly impacts soil carbon cycling due to its active turnover characteristics. However, whether different plantation forest soil profiles exhibit distinct DOM characteristics remains unclear. Hence, utilizing fluorescence spectroscopy and the parallel factor analysis (PARAFAC) method, a 1-meter soil profile analysis was carried out on three distinct artificial forests (Pinus tabuliformis (PT), Quercus crispula (QC), and a mixed forest of PT and QC (MF)), concurrently assessing the impact of soil chemical properties and enzyme activity on dissolved organic matter (DOM). The findings indicated that the mean concentration of dissolved organic carbon (DOC) was greatest in the MF and lowest in PT, exhibiting considerable variation with soil depth, suggesting that mixed tree species may promote the discharge of organic matter. The fluorescence spectra revealed two distinct peaks: humic-like fluorescence peaks (Peaks A and C) and a protein-like fluorescence peak (Peak T), with the most intense fluorescence observed in MF soil. As the soil depth increased, the fluorescence intensity of Peaks A and C steadily declined, while the intensity of Peak T rose. Four DOM components were identified in three types of plantations forests: surface soil was dominated by humic acid-like fluorescent components (C1 and C2), while the deep soil was primarily characterized by protein-like fluorescence components (C3 and C4). Different soil profile fluorescence parameter indices indicated that the source of DOM in the surface soil (i.e., 0–20 cm) was mainly allochthonous inputs, whereas, in the deep soil (i.e., 60–100 cm), it was mainly autochthonous, such as microbial activity. The findings from the partial least squares path modeling (PLS-PM) revealed that TP, aP, NH4+-N, and the combined impact of soil enzymes were influential in shaping the diversity of DOM attributes. Put differently, alterations in DOM concentration were concomitantly influenced by forest classification, soil characteristics, and depth. It has been demonstrated that, in contrast to monoculture forests, the establishment of mixed forest models has been more advantageous in enhancing the soil dissolved organic matter (DOM). These discoveries offer innovative perspectives on the dynamic characteristics of DOM in soil profiles and its influencing factors under different plantations forest planting patterns.

Insights into growth stages and genotypes in airborne Pb accumulation in Oryza sativa L. grains: Utilizing isotope fingerprinting alongside a model study

Atmospheric exposure is an important pathway of accumulation of lead (Pb) in Oryza sativa L. grains. In this study, source contributions of soil, early atmospheric exposure, and late atmospheric exposure, along with their bioaccumulation ratios were examined both in the pot and field experiments using stable Pb isotope fingerprinting technology combined with a three-compartment accumulation model. Furthermore, genotype differences in airborne Pb accumulation among four field-grown rice cultivars were investigated using the partial least squares path model (PLS-PM) linking rice Pb accumulation to agronomic traits. The findings revealed that during the late growth period, the air-foliar-grain transfer of Pb was crucial for rice Pb accumulation. Approximately 69–82% of the Pb found in polished rice was contributed by atmospheric source, with more than 80% accumulating during the late growth stage. The air accumulation ratios of rice grains were genotype-specific and estimated to be 0.364–1.062 m3/g during the late growth. Notably, grain size exhibited the highest standardized total effects on the airborne Pb concentrations in the polished rice, followed by leaf Pb and the upward translocation efficiency of Pb. The present study indicates that mitigating the health risks associated with Pb in rice can be achieved by controlling atmospheric Pb levels during the late growth stage and choosing Japonica inbred varieties characterized by large grain size.

Anthropogenic dissolved organic matter accumulation fuels greenhouse gas diffusive emissions in urban lakes along trophic state levels

Lakes are an important reservoir of dissolved organic matter (DOM) and also emit large amounts of greenhouse gases (GHGs), such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Yet, the linkages between quantity and quality of DOM and GHGs emissions are still not well understood. Hence, we investigated how DOM optical properties mediated dissolved GHGs levels and diffusive fluxes along a trophic state level in subtropical urban lakes, China. Our study showed that anthropogenic protein-like DOM (tryptophan- and tyrosine-like components) dominated the DOM pools, comprising 62% of total fluorescence DOM (FDOM). Partial least squares path modeling (PLS-PM) showed that the direct contribution of relative abundance of DOM to CO2 and CH4 diffusion in the highly-eutrophic state was higher than in the mesotrophic and lightly/moderately-eutrophic states. In particular, protein-like DOM primarily accounted for CO2 variations (44%-49%), while humic- and protein-like DOM contributed comparably to CH4 variations (38%-40% vs. 36%-40%). Furthermore, in the lightly/moderately- and highly-eutrophic states, nutrients contributed to DOM, CO2 and CH4 in both direct and indirect ways, while phytoplankton (chlorophyll a, Chl-a) negatively and directly affected carbon emissions. However, only nitrogen content directly contributed to N2O production and diffusion in the mesotrophic and lightly/moderately-eutrophic states. We concluded that protein-like DOM enrichment has the potential to trigger CO2 and CH4 diffusion and this process is largely mediated by nutrient levels. N2O diffusion is found to be mainly influenced by nitrogen loadings and forms. Our findings highlight the urgency for effective strategies to reduce anthropogenic DOM inputs and control nutrient levels to reduce GHGs diffusion in highly human-impacted aquatic systems.

Impact of Scientific Activity and Innovation on Economic Competitiveness: An Analysis of Kazakhstan

This study is aimed to evaluate the influence of scientific activity and innovation on the economic performance of a country, measured by Gross Domestic Product (GDP), using Kazakhstan as a case study. Employing Partial Least Squares Path Modeling (PLS-PM), a variance-based Structural Equation Modeling (SEM) approach, the research analyzed secondary data to explore the structural relationships between scientific investment, activity, and their subsequent impact on GDP and innovative organizational activity. The methodology was centered on assessing the measurement model for reliability and validity, and the structural model for the strength and significance of the relationships using path coefficients and R-squared values. Hypotheses were formulated to test the expected positive influences of scientific activity and internal R&D costs on GDP, and the role of scientific activity in driving innovative activity within organizations. The results indicated a positive relationship between scientific activity and GDP, confirming the hypothesis that science contributes significantly to economic development. Internal R&D costs were found to have a strong positive impact on scientific activity, highlighting the importance of R&D investment. However, innovative activity within organizations showed a negative association with GDP, suggesting a more complex relationship that may not lead to immediate economic gains. Scientific activity was also seen to positively influence organizational innovation. The study’s findings emphasize the need for strategic planning and investment in scientific research and education to bolster economic development.

Chemical Recalcitrance Rather Than Soil Microbial Community Determined Short-Term Biochar Stability in a Poplar Plantation Soil

The stability of biochar is fundamental to its soil carbon (C) sequestration potential. The relative importance of chemical recalcitrance and the soil microbial community on biochar stability is still unclear. To unveil the question, we conducted a 60-day incubation to explore the stability of two rice-straw-derived biochars pyrolyzed at 300 and 500 °C (denoted as BS300 and BS500), as well as the relative contribution of the soil microbial community and biochar chemical recalcitrance to biochar stability in a poplar plantation soil. Biochar-derived cumulative carbon dioxide (CO2) emission was estimated to be 41.3 and 6.80 mg C kg−1, accounting for 0.73 and 0.11% of the amended biochar-derived organic C (OC) in BS300 and BS500 treatments, respectively. The mean retention time (MRT) estimated by double-exponential model fitting was 49.4 years for BS300 and 231 years for BS500. Compared to control, BS300 and BS500 decreased β-D-glucosidase activity by 20.9 and 18.0%, while they decreased phenol oxidase activity by 31.8 and 18.9%, respectively. Furthermore, BS300 increased the soil microbial metabolic quotient (qCO2) by 155%, but BS500 decreased it by 13.4%. In addition, BS300 resulted in a 520% higher biochar-derived hot-water-extractable OC than BS500. Partial least-squares path modeling (PLSPM) showed that the path efficients of biochar’s chemical recalcitrance and microbial qCO2 were 0.52 and 0.25, respectively, and that of the soil microbial activity is neglected. We conclude from this short-term study that chemical recalcitrance imposed a greater effect than soil microbial community on biochar stability.

Yield, Quality, and Nitrogen Leaching of Open-Field Tomato in Response to Different Nitrogen Application Measures in Northwestern China.

The overuse of fertilizers in open-field tomato leads to soil deterioration through nutrient leaching and increases the risk of agricultural non-point source contamination. Currently, the combined effects of different fertilization methods on soil nitrogen leaching and tomato production are still unclear. Therefore, the most effective fertilization method for open-field tomato should be discovered by examining how different fertilization methods affected tomato yield and quality, nitrogen use efficiency (NUE), and soil nitrogen leaching. Compared with CK (no fertilization), fertilization significantly increased the yield, total sugar (TS), total soluble solids (TSS), and vitamin C (vC) contents of fruits (p < 0.05), and OPT (optimal fertilization, controlled release nitrogen application, 240 kg ha-1) had the largest effect on increasing yield, quality, and net profit. However, when the fertilizer application rate reached 375 kg ha-1, these indices decreased. Nitrogen leaching concentrations, leaching amount, and titratable acids (TAs) increased with increased nitrogen application rates. Compared with other treatments, OPT reduced the total leaching amounts of total nitrogen (TN), nitrate nitrogen (NO3--N), and ammonia nitrogen (NH4+-N) by 30.09-51.79%, 24.89-50.03%, and 30-65%, respectively. Principal component analysis (PCA) showed that OPT achieved the highest overall score in terms of yield, quality, and nitrogen leaching conditions. The partial least squares path modeling (PLS-PM) further reveals that applications of high amounts of nitorigen have a positive effect on soil nitrogen leaching. The amount of nitrogen leaching vegetatively affects tomato yield and quality, while plant uptake of nitrogen positively affects tomato production. These findings confirm the importance of using controlled-release fertilizers and reducing nitrogen inputs to control nitrogen leaching and enhance open-field tomato yields.

Effects of land use patterns on soil properties and nitrous oxide flux on a semi-arid environmental conditions of Loess Plateau China

Ecosystems and agroecosystems strongly influences the global warming by nitrogen oxide (N2O) emission. In a recent climate change scenario, nitrogen and carbon sequestration is obligatory under different land-use patterns. However, soil nitrogen elements and carbon content in the recover process of degraded environmental conditions on the Dingxi Loess Plateau has not been clearly understood. Thus, in this current study, we selected four representative land use patterns, including picea asperata (PA), which is based on forest land; Medicago sativa (MS), which is based on grassland; abandoned bare land (AL), which is based on abandoned land; and wheat field (WF), which is based on farmland, to study soil quality indicators and N2O greenhouse gas and relationships amongst environmental factors and N2O flux. Our results depicted that PA and MS significantly increased organic carbon (SOC), total phosphorous (TP), gravimetric water content (SWC), soil bulk density (BD), total nitrogen (TN), ammonium nitrogen (NH4+-N), and microbial biomass nitrogen (MBN) whist decreased soil nitrate nitrogen (NO3--N) content and soil pH value over AL land-use pattern. However, WF land-use pattern showed reduced trend of above mention studied parameters than AL. Additionally, compared to AL, PA and MS significantly reduced the total soil N2O emissions, with reductions of 24.91% and 14.77% in 2021 and 29.08% and 17.53% in 2022, respectively. The WF significantly increased the total N2O emissions, increasing by 53.18% and 40.37% in 2021 and 2022, respectively. Moreover, environmental variables for instance aerial temperature, precipitation had significant correlation with soil N2O based on linear regression analysis, soil NO3--N and soil temperature had significant positive correlation with soil N2O flux while NH4+-N, BD, and SWC were negatively correlated with N2O flux. The Partial Least Squares Path Model (PLS-PM) indicates that soil temperature and soil moisture was the dominant factor for controlling soil N2O emissions followed by soil nutrients and land use patterns. Accordingly, in the context of vegetation restoration process of the study area, the proportion of forest land and grassland should be increase to cope with future climate change scenario. This research result can provide theoretical basis and technical support for scientific understanding and evaluation of soil N2O emission mechanisms and nitrogen sink functions under different land-use patterns in semi-arid region of China.

Impact of coconut-fiber biochar on lead translocation, accumulation, and detoxification mechanisms in a soil–rice system under elevated lead stress

Biochar, an environmentally friendly material, was found to passivate lead (Pb) in contaminated soil effectively. This study utilized spectroscopic investigations and partial least squares path modeling (PLS-PM) analysis to examine the impact of coconut-fiber biochar (CFB) on the translocation, accumulation, and detoxification mechanisms of Pb in soil-rice systems. The results demonstrated a significant decrease (p < 0.05) in bioavailable Pb concentration in paddy soils with CFB amendment, as well as reduced Pb concentrations in rice roots, shoots, and brown rice. Synchrotron-based micro X-ray fluorescence analyses revealed that CFB application inhibited the migration of Pb to the rhizospheric soil region, leading to reduced Pb uptake by rice roots. Additionally, the CFB treatment decreased Pb concentrations in the cellular protoplasm of both roots and shoots, and enhanced the activity of antioxidant enzymes in rice plants, improving their Pb stress tolerance. PLS-PM analyses quantified the effects of CFB on the accumulation and detoxification pathways of Pb in the soil–rice system. Understanding how biochar influences the immobilization and detoxification of Pb in soil–rice systems could provide valuable insights for strategically using biochar to address hazardous elements in complex agricultural settings.

Evaluating Pseudomonas monteilii JK-1 as an in-feed probiotic: Enhancing growth, immune-antioxidant, disease resistance and modulating gut microflora composition in grass carp (Ctenopharyngodon idella)

Host-derived probiotics are microorganisms sourced from the host's gut environment, aimed at enhancing growth and overall health. Given the increasing stringency in the regulation of antibiotics within animal production, the adoption of in-feed probiotics has emerged as a compelling antibiotic alternative in aquaculture. Here, we investigate the impact of Pseudomonas monteilii JK-1 on the growth performance and disease resistance of grass carp (Ctenopharyngodon idella). The results indicate that P. monteilii JK-1 leads to a significant increase in weight gain (WG), specific growth rate (SGR), and survival rate, along with a substantial reduction in pathogen load (Aeromonas) (P < 0.05). Furthermore, we observed a noteworthy improvement in the expression of key immune-related genes, including interleukin 1β (IL-1β), interleukin 10 (IL10), tumor necrosis factor alpha (TNF-α), and transforming growth factor beta (TGF-β) in both the head kidney and gut (P < 0.05). This effect extends to the augmentation of the activities of crucial antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in both liver and gut tissues (P < 0.05). Notably, P. monteilii JK-1 exerts a positive influence on the complexity of the gut microbiome ecological network. In this context, Cetobacterium emerges as a keystone microbiota responsible for maintaining interspecies interactions and enhancing gut network stability. Moreover, our study establishes a positive connection between Cetobacterium and growth performance and between Akkemansia and immune response, respectively. In addition, the result of partial least squares path model (PLS-PM) showed that P. monteilii JK-1 does not directly enhance growth performance and pathogen resistance but does so by regulating keystone taxa and promoting gut network stability. Collectively, this study offers a nuanced comprehension of how probiotics enhance growth and boost disease resistance, focusing on the gut microbial ecological network. These findings showed that P. monteilii JK-1 has potential application as a probiotic in grass carp, which may provide a new strategy of preventing and controlling bacterial diseases in this species.

An Earthworm Peptide Alters Soil Nematode, Microbial, and Nutrient Dynamics: A Novel Mechanism of Soil Food Web Feedbacks

Earthworms are soil macrofauna that control soil ecosystems by strongly influencing soil nematodes, microorganisms, and nutrient cycling, as well as soil environmental factors. We have discovered an earthworm cyclic peptide that disrupts nematode DNA, affecting its lifespan, reproduction, and feeding preferences. To investigate the effects of this peptide on soil, it was added to soil, and changes in soil nematode, bacterial and fungal communities, soil nutrient contents, and basal respiration were measured on days 5 and 21. The results showed that the peptide reduced soil basal respiration on day 5 and soil NO3-N on day 21, decreased soil fungivores nematodes on day 5 and soil nematode abundance on day 21, and increased soil fungal community richness and diversity. It also altered the soil bacterial community structure between day 5 and the soil fungal community structure on days 5 and 21. The peptide regulates the soil environment by influencing the structure of soil bacterial and fungal communities through the soil nematode community, as demonstrated by partial least squares path modelling (PLS-PM) analyses. Earthworm cyclic peptides mediates tri-trophic interactions between earthworms, nematodes, microbes, and environmental factors, providing new insights into soil biota interactions and feedback in dynamic soil food webs.

Spatial, Geographical, Climatic, and Edaphic Influences on Moss Community Structure: A Case Study from Qinhuangdao, China

In the realms of ecology and biogeography, the interaction between biodiversity and environmental factors is a critical area of research. This intersection highlights how biological communities, especially among groups like bryophytes, are influenced and shaped by their surrounding environmental conditions. This study presents a pioneering investigation into the diversity and community structure of mosses in Qinhuangdao, Hubei Province, China, a region marked by its diverse topography and climate. Employing extensive field surveys across 30 plots, we gathered and analyzed the relationship between moss species distribution and environmental variables, including topographical, climatic, and soil factors. Utilizing a range of analytical techniques, such as cluster analysis, canonical correspondence analysis (CCA), and partial least squares path modeling (PLS-PM), we characterized the intricate relationships between moss biodiversity and environmental gradients. The research has documented 84 species distributed among 36 genera and 13 families. Solar radiation has a great impact on moss diversity. There were significant differences between Form. Entodon compressus and Form. Plagiobryum demissum. Climate has a great impact on the community structure of mosses. Geographical factors were also identified as key secondary influences, affecting moss community structures both directly and indirectly by creating suitable microenvironments and influencing climate and soil properties. Additionally, the study highlights the indirect impact of spatial factors on these environmental variables, which in turn shape the structure of biological communities. The findings indicate that the annual temperature range is a key factor influencing the distribution and formation of moss community structures. The findings provide new insights into the ecological adaptation of mosses in diverse environmental settings and lay a crucial foundation for biodiversity conservation and ecosystem management in the Qinhuangdao area.

Insights from Fertilization and Cultivation Management for Interpreting the Variations in the Quantity and Quality of Dissolved Organic Carbon and Microbial Community Structure on Purple Soil Sloping Farmland in Southwest China

It is crucial to comprehend how fertilization and cultivation management alter the composition of dissolved organic carbon (DOC) and microbial communities to regulate the biogeochemical cycling of soil nutrients and mitigate adverse impacts on soil–water quality. Based on 15 years of long-term field trials conducted in purple soil on farmland with a slope of 15° in southwestern China, the following five treatments were examined: CK (no fertilizer was applied), T1 (NPK plus organic manure and downslope cultivation), T2 (NPK and downslope cultivation), T3 (1.5-fold NPK and downslope cultivation), and T4 (NPK and contour cultivation). Soil samples were obtained from summer maize at two soil depths (0–10 and 10–20 cm) and from rhizospheric soil, and the changes in the DOC content, UV–visible (UV–Vis) absorptivity, and phospholipid fatty acids (PLFAs) were assessed. Our results revealed a significant change in the DOC content following fertilization, especially in T1, as it was 136.0%, 179.4%, and 132.2% higher, respectively, than that in CK at the 0–10 and 10–20 cm depths and rhizospheric soil. Fertilization decreased the UV–Vis absorptivity variables of DOC (i.e., SUVA254, SUVA260, SUVA400, SUVA465, SUVA665, and C:C ratio) and raised the E4:E6 ratio (fulvic acid to humic acid in DOC), regardless of T2 and T3 at the 10–20 cm depth and in the rhizospheric soil compared with those in CK, respectively. Fertilization significantly increased the total PLFA content and selected microbial groups relative to CK. Among the treatments, T1 significantly increased the total PLFA content by 50.6%, 59.0%, and 46.2%, respectively, relative to CK, at the 0–10 and 10–20 cm depths and in the rhizospheric soil. The microbial community structure in contour cultivation (T4) was significantly greater than in downslope cultivation (T2). Random forest analysis (RFA) revealed that SOC and DOC were likely the primary variables for regulating the total PLFAs in the examined soil. Partial least squares path modeling (PLS-PM) further indicated that the DOC content and the ratio of E4:E6 among DOC compositions had greater effects on the soil microbial community structure in the examined soil. These observations suggested that long-term fertilization and cultivation management are effective approaches to regulating the soil microbial community structure by altering the composition of DOC in sloping farmland.

Carbon Source in Tertiary Denitrification Regulates Dissolved Organic Nitrogen in Wastewater Effluent.

With global eutrophication and increasingly stringent nitrogen discharge restrictions, dissolved organic nitrogen (DON) holds considerable potential to upgrade advanced wastewater denitrification because of its large contribution to low-nitrogen effluents and stronger stimulation effect for algae. Here, we show that DON from the postdenitrification systems dominates effluent eutrophication potential under different carbon sources. Methanol resulted in significantly lower DON concentrations (0.84 ± 0.03 mg/L) compared with the total nitrogen removal-preferred acetate (1.11 ± 0.02 mg/L) (p < 0.05, ANOVA). With our well-developed mathematical model (R2 = 0.867-0.958), produced DON instead of shared (persist in both influent and effluent) and/or removed DON was identified as the key component for effluent DON variation (Pearson r = 0.992, p < 0.01). The partial least-squares path modeling analysis showed that it is the microbial community (r = 0.947, p < 0.01) rather than the predicted metabolic functions (r = 0.040, p > 0.1) that affected produced DON. Carbon sources rebuild the microorganism-DON interaction by affecting the structure of microbial communities with different abilities to generate and recapture produced DON to finally regulate effluent DON. This study revalues the importance of carbon source selection and overturns the current rationality of pursuing only the total nitrogen removal efficiency by emphasizing DON.

Body size induced changes in metabolic carbon of soil nematodes under N deposition and precipitation regime change in a temperate grassland

Abstract Background Global climate change has resulted in precipitation regimes exhibiting an increasing trend in rainfall intensity but a reduction in its frequency. Nitrogen (N) deposition is a crucial component of the global N cycling. Nematode body size is a trait that responds to climate change and is used as a standard trait-based indicator in soil community analysis. Variations in body size influence metabolic carbon (C). We examined the ways by which body size and metabolic C of nematodes respond to changing precipitation regimes and how N deposition regulates these responses by an 8-year manipulative experiment. Methods Nematode body size was indicated by the community-weighted mean (CWM) mass. We quantified C metabolism components of soil nematodes including production C, respiration C, and corresponding C use efficiency (CUE) under different precipitation intensities and N addition in a semi-arid steppe on the Mongolian Plateau. The Mantel test was used to determine the correlations between CWM, CUE and environmental factors. The partial least squares path modeling (PLS-PM) was conducted to quantify direct or indirect contributions among latent variables. Results We found that heavy precipitation intensity increased the CWM mass of total nematodes and omnivores-predators without N addition. N addition decreased CWM mass of bacterivores across all the precipitation intensity treatments. Stronger precipitation intensities might be favorable for nematode production and respiration C. Variations in the nematode CWM mass drove the CUE to change with N addition. Conclusions Our findings provide new insights into the mechanisms underlying nematode body size and C metabolism, and highlight that explorative studies, such as manipulative experiments, are needed to identify traits underlying size-related effects and to investigate how they affect CUE of nematodes. These efforts may increase our understanding of how changes in precipitation regimes and N deposition may alter soil nematode communities in grassland ecosystems.

Impact of uranium on antibiotic resistance in activated sludge

The emergence of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in the environment is well established as a human health crisis. The impact of radioactive heavy metals on ecosystems and ultimately on human health has become a global issue, especially for the regions suffering various nuclear activities or accidents. However, whether the radionuclides can affect the fate of antibiotic resistance in bacteria remains poorly understood. Here, the dynamics of ARB, three forms of ARGs—intracellular ARGs (iARGs), adsorbed extracellular ARGs (aeARGs), and free extracellular ARGs (feARGs)—and microbial communities were investigated following exposure to uranium (U), a representative radioactive heavy metal. The results showed that 90-d of U exposure at environmentally relevant concentrations of 0.05 mg/L or 5 mg/L significantly increased the ARB concentration in activated sludge (p < 0.05). Furthermore, 90-d of U exposure slightly elevated the absolute abundance of aeARGs (except tetO) and sulfonamide iARGs, but decreased tetracycline iARGs. Regarding feARGs, the abundance of tetC, tetO, and sul1 decreased after 90-d of U stress, whereas sul2 showed the opposite trend. Partial least-squares path model analysis revealed that the abundance of aeARGs and iARGs under U stress was predominantly driven by increased cell membrane permeability/intI1 abundance and cell membrane permeability/reactive oxygen species concentration, respectively. Conversely, the changes in feARGs abundance depended on the composition of the microbial community and the expression of efflux pumps. Our findings shed light on the variations of ARGs and ARB in activated sludge under U exposure, providing a more comprehensive understanding of antibiotic resistance risks aggravated by radioactive heavy metal-containing wastewater.

Societal sustainable development and long‐run economic growth: How do we stand?

AbstractThe United Nations' 2030 Agenda for Sustainable Development proposes the ambitious goal of an inclusive and sustainable economy. Thus, a realistic assessment of individual countries' possibilities to implement the Sustainable Development Goals might provide helpful insights. We seek to contribute to the existing literature by proposing a working framework for assessing, at the individual country level, the impact of long‐run economic growth on societal sustainable development. The framework is based on composite models from the Structural Equation Modeling‐SEM with a Partial Least Squares Path Modeling (PLS‐PM) estimator. In contrast, societal sustainable development is viewed as emerging from its various dimensions (environmental protection, human development and public health). Based on the analyses of an extended sample of 99 countries, including data for thirty years (from 1990 to 2019), we find that economic growth matters in explaining societal sustainable development, and different countries have benefited unequally from this situation. The key finding reveals that countries aiming to follow the SDGs should recognize their significant disparities and engage in profound structural, institutional, functional and cultural transformations. Thus, a more holistic approach to societal sustainable development is currently needed to enhance government effectiveness as a transmission channel for the impact of growth. In addition, governments need to adjust their economic mechanisms to internalize the costs of environmental degradation and negative externalities for human development and public health.

Enhancing Salt Tolerance in Poplar Seedlings through Arbuscular Mycorrhizal Fungi Symbiosis.

Poplar (Populus spp.) is a valuable tree species with multiple applications in afforestation. However, its growth in saline areas, including coastal regions, is limited. This study aimed to investigate the physiological mechanisms of arbuscular mycorrhizal fungi (AMF) symbiosis with 84K (P. alba × P. tremula var. glandulosa) poplar under salt stress. We conducted pot experiments using NaCl solutions of 0 mM (control), 100 mM (moderate stress), and 200 mM (severe stress) and evaluated the colonization of AMF and various physiological parameters of plants, including photosynthesis, biomass, antioxidant enzyme activity, nutrients, and ion concentration. Partial least squares path modeling (PLS-PM) was employed to elucidate how AMF can improve salt tolerance in poplar. The results demonstrated that AMF successfully colonized the roots of plants under salt stress, effectively alleviated water loss by increasing the transpiration rate, and significantly enhanced the biomass of poplar seedlings. Mycorrhiza reduced proline and malondialdehyde accumulation while enhancing the activity of antioxidant enzymes, thus improving plasma membrane stability. Additionally, AMF mitigated Na+ accumulation in plants, contributing to the maintenance of a favorable ion balance. These findings highlight the effectiveness of using suitable AMF to improve conditions for economically significant tree species in salt-affected areas, thereby promoting their utilization.

Unraveling the impacts of multiscale landscape patterns and socioeconomic development on water quality: A case study of the National Sustainable Development Agenda Innovation Demonstration Zone in Lincang City, Southwest China

Study regionNational Sustainable Development Agenda Innovation Demonstration Zone in Lincang City, Southwest China Study focusRevealing the current water quality status in rivers and reservoirs and its drivers is crucial to achieving the United Nations Sustainable Development Goal 6 (SDG 6). We assessed the spatial-temporal dynamics and influence of natural and socioeconomic factors on the water quality index (WQI) and water quality parameters of rivers and reservoirs using redundancy analysis (RDA) and the partial least squares path model (PLSPM). New hydrological insights for the regionThe results indicate the following. (1) The annual average values of the WQI in Lincang City from 2018 to 2020 were 92.26, 92.06, and 92.45, respectively. The WQI values in spring, summer, autumn, and winter were 92.48, 90.38, 92.68, and 93.49, respectively. The annual and seasonal water quality levels were good or higher. However, spatial heterogeneity exists for some water quality parameters in Lincang City. (2) The influence of natural and socioeconomic factors on the WQI and water quality parameters is highly complex. The landscape composition, landscape configuration, and pollutant discharges are key factors affecting the water quality of rivers and reservoirs annually and seasonally, and a spatial scale dependence is observed. (3) Chemical and physical factors directly affect the WQI, particularly at small scales (100 m and 500 m buffer zones). Chemical factors have a strong inhibitory effect on the WQI of reservoirs (−0.79, −0.78) and rivers (−0.56, −0.72), whereas physical factors have a weak promoting effect (0.05–0.13). Landscape composition and landscape configuration and indirectly affect the WQI. In contrast, socioeconomic factors and pollution discharge indirectly impact the WQI of rivers and reservoirs through their influence on chemical and physical factors. These findings demonstrate that natural and social factors interact in multiple ways, impacting the water quality of rivers and reservoirs. This interaction depends on the spatial scale. Therefore, it is crucial to consider the appropriate distance from rivers and reservoirs in future land use planning, particularly in the landscape design and planning in Lincang City. Moreover, controlling wastewater discharge from industrial and agricultural activities and domestic water usage is vital for ensuring high water quality.