Maize straw increases while its biochar decreases native organic carbon mineralization in a subtropical forest soil.

Organic soil amendments have been widely adopted to enhance soil organic carbon (SOC) stocks in agroforestry ecosystems. However, the contrasting impacts of pyrogenic and fresh organic matter on native SOC mineralization and the underlying mechanisms mediating those processes remain poorly understood. Here, an 80-day experiment was conducted to compare the effects of maize straw and its derived biochar on native SOC mineralization within a Moso bamboo (Phyllostachys edulis) forest soil. The quantity and quality of SOC, the expression of microbial functional genes concerning soil C cycling, and the activity of associated enzymes were determined. Maize straw enhanced while its biochar decreased the emissions of native SOC-derived CO2. The addition of maize straw (cf. control) enhanced the O-alkyl C proportion, activities of ß-glucosidase (BG), cellobiohydrolase (CBH) and dehydrogenase (DH), and abundances of GH48 and cbhI genes, while lowered aromatic C proportion, RubisCO enzyme activity, and cbbL abundance; the application of biochar induced the opposite effects. In all treatments, the cumulative native SOC-derived CO2 efflux increased with enhanced O-alkyl C proportion, activities of BG, CBH, and DH, and abundances of GH48 and cbhI genes, and with decreases in aromatic C, RubisCO enzyme activity and cbbL gene abundance. The enhanced emissions of native SOC-derived CO2 by the maize straw were associated with a higher O-alkyl C proportion, activities of BG and CBH, and abundance of GH48 and cbhI genes, as well as a lower aromatic C proportion and cbbL gene abundance, while biochar induced the opposite effects. We concluded that maize straw induced positive priming, while its biochar induced negative priming within a subtropical forest soil, due to the contrasting microbial responses resulted from changes in SOC speciation and compositions. Our findings highlight that biochar application is an effective approach for enhancing soil C stocks in subtropical forests.

Distinct effects of canopy vs understory and organic vs inorganic N deposition on root resource acquisition strategies of subtropical Moso bamboo plants.

Atmospheric nitrogen (N) deposition inevitably alters soil nutrient status, subsequently prompting plants to modify their root morphology (i.e., adopting a do-it-yourself strategy), mycorrhizal symbioses (i.e., outsourcing strategy), and root exudation (i.e., nutrient-mining strategy) linking with resource acquisition. However, how N deposition influences the integrated pattern of these resource-acquisition strategies remains unclear. Furthermore, most studies in forest ecosystems have focused on understory N and inorganic N deposition, neglecting canopy-associated processes (e.g., N interception and assimilation) and the impacts of organic N on root functional traits. In this study, we compared the effects of canopy vs understory, organic vs inorganic N deposition on eight root functional traits of Moso bamboo plants. Our results showed that N deposition significantly decreased arbuscular mycorrhizal fungi (AMF) colonization, altered root exudation rate and root foraging traits (branching intensity, specific root area, and length), but did not influence root tissue density and N concentration. Moreover, the impacts of N deposition on root functional traits varied significantly with deposition approach (canopy vs. understory), form (organic vs. inorganic), and their interaction, showing variations in both intensity and direction (positive/negative). Furthermore, specific root area and length were positively correlated with AMF colonization under canopy N deposition and root exudation rate in understory N deposition. Root trait variation under understory N deposition, but not under canopy N deposition, was classified into the collaboration gradient and the conservation gradient. These findings imply that coordination of nutrient-acquisition strategies dependent on N deposition approach. Overall, this study provides a holistic understanding of the impacts of N deposition on root resource-acquisition strategies. Our results indicate that the evaluation of N deposition on fine roots in forest ecosystems might be biased if N is added understory.

Microplastics affect the ecological stoichiometry of plant, soil and microbes in a greenhouse vegetable system.

Microplastic (MP) pollution is a growing global issue due to its potential threat to ecosystem and human health. Low-density polyethylene (LDPE) MP is the most common type of plastics polluting agricultural soils, negatively affecting soil-microbial-plant systems. However, the effects of LDPE MPs on the carbon (C): nitrogen (N): phosphorus (P) of soil-microbial-plant systems have not been well elucidated. Thus, we conducted a pot experiment with varying LDPE MP concentrations (w/w) (control without MPs; 0.2 % MPs (PE1); 5 % MPs (PE2); and 10 % MPs (PE3)) to study their effects on soil-microbial-plant C-N-P stoichiometry. Soil C:N ratio increased 2.3 and 3.4 times in PE2 and PE3, respectively. Soil C:P ratio increased 2.2 and 3.6 times in PE2 and PE3, respectively. Soil microbial C:N ratios decreased by 46.2 % in PE1, while C:P ratios decreased by 59.2, 38.6, and 67.9 % in PE1, PE2, and PE3, respectively. Soil microbial N:P ratio decreased in PE1 (17.2) and PE3 (59.1 %). MPs increased shoot C content and C:N ratios, particularly at the 5 % MP addition rate. MP addition altered dissolved organic C, N, and P concentrations, depending on the MP addition rate. Microbial community responses to MP exposure were complex, leading to variable effects on different microbial groups at different MP addition rates. Structural equation modeling showed that MP addition had a direct positive effect (ß = 0.96) on soil C-N-P stoichiometry and a direct negative effect (ß = -1.34) on microbial C-N-P stoichiometry. These findings demonstrate the complex interactions between MPs, soil microorganisms, and nutrient dynamics, highlighting the need for further research to better understand the ecological implications of MP pollution in terrestrial ecosystems.

Meta-analysis shows the impacts of ecological restoration on greenhouse gas emissions.

International initiatives set ambitious targets for ecological restoration, which is considered a promising greenhouse gas mitigation strategy. Here, we conduct a meta-analysis to quantify the impacts of ecological restoration on greenhouse gas emissions using a dataset compiled from 253 articles. Our findings reveal that forest and grassland restoration increase CH4 uptake by 90.0% and 30.8%, respectively, mainly due to changes in soil properties. Conversely, wetland restoration increases CH4 emissions by 544.4%, primarily attributable to elevated water table depth. Forest and grassland restoration have no significant effect on N2O emissions, while wetland restoration reduces N2O emissions by 68.6%. Wetland restoration enhances net CO2 uptake, and the transition from net CO2 sources to net sinks takes approximately 4 years following restoration. The net ecosystem CO2 exchange of the restored forests decreases with restoration age, and the transition from net CO2 sources to net sinks takes about 3-5 years for afforestation and reforestation sites, and 6-13 years for clear-cutting and post-fire sites. Overall, forest, grassland and wetland restoration decrease the global warming potentials by 327.7%, 157.7% and 62.0% compared with their paired control ecosystems, respectively. Our findings suggest that afforestation, reforestation, rewetting drained wetlands, and restoring degraded grasslands through grazing exclusion, reducing grazing intensity, or converting croplands to grasslands can effectively mitigate greenhouse gas emissions.

Biochar and soil properties affect remediation of Zn contamination by biochar: A global meta-analysis.

Zinc (Zn) is one of the most common heavy metals that pollute soils and can threaten both environmental and human health. Biochar is a potential solution for remediating soil Zn contamination. This meta-analysis investigates the effect of biochar application on the remediation of Zn-contaminated soils and the factors affecting the remediation efficiency. We found that biochar application in Zn-contaminated soils reduced Zn bioavailability by up to 77.2% in urban soils, 55.1% in acidic soils, and 50.8% in coarse textured soils. Moreover, the remediation efficiency depends on the biochar production condition, with crop straw and sewage sludge feedstocks, high pyrolysis temperature (450-550 °C), low heating rate (<10 °C min-1), and short residence time (<180 min) producing high performing biochars. Biochar affects soil Zn bioavailability by changing soil pH and organic carbon, as well as through its high surface area, ash content, and O-containing surface functional groups. Our findings highlight the role of biochar as a promising and environmentally friendly material for remediating Zn contamination in acidic and/or coarse textured soils. We conclude that soil properties must be considered when selecting biochars for remediating soil Zn contamination.

[Short-term nitrogen deposition changes chemical composition of litter and soil organic matter in a Moso bamboo forest]. / 短期氮沉降改变毛竹林凋落物和土壤有机质化学组成.

To investigate the effects of short-term nitrogen (N) deposition on organic matter composition of litter and soil in Moso bamboo (Phyllostachys edulis) forests, we established a N-addition treatments (50 kg N·hm-2·a-1) to simulate the ambient and N deposition in a subtropical Moso bamboo forest from July 2020 to January 2022. We analyzed the organic matter composition of Moso bamboo leaf/root litter and soil by using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) technique. The results showed that short-term N deposition significantly increased the relative content of soil phenols by 50.9%, while significantly decreased fatty acids by 26.3%. The rela-tive content of alkanes & alkenes and lignin in leaf litter was significantly increased by 51.9% and 33.5%, respectively, while that of phenols and polysaccharides significantly decreased by 52.2% and 56.3%. In root litter, eleva-ted N significantly decreased the relative content of polycyclic aromatic hydrocarbons by 16.6%. Moreover, the relative content of fatty acids in soil organic matter was significantly positively correlated with the relative content of poly-saccharides in leaf litter. The relative content of phenols in soil organic matter was significantly positively correlated with the relative content of lignin, and negatively correlated with the relative content of polysaccharides in leaf litter. Our results demonstrated that short-term N deposition did not change the concentration of total organic carbon, total nitrogen, and C/N of the soil, leaf litter, and root litter, but significantly altered the chemical composition of organic matter. In addition, the changes in chemical composition of organic matter in soil under short-term N deposition were affected by the composition of organic matter in leaf litter.

Effects of maize straw and its biochar application on soil organic carbon chemical composition and carbon degradation genes in a Moso bamboo forest.

We investigated the effects of maize straw and its biochar application on soil organic carbon chemical composition, the abundance of carbon degradation genes (cbhI) and the composition of cbhI gene community in a Moso bamboo forest, to provide the theoretical and scientific basis for enhancing carbon sequestration. We conducted a one-year field experiment in a subtropical Moso bamboo forest with three treatments: control (0 t C·hm-2), maize straw (5 t C·hm-2), and maize straw biochar (5 t C·hm-2). Soil samples were collected at the 3rd and 12th months after the treatment. Soil organic carbon chemical composition, the abundance and community composition of cbhI gene were determined by solid-state 13C NMR, real-time fluorescence quantitative PCR, and high-throughput sequencing, respectively. The results showed that compared with the control, maize straw treatment significantly increased the content of O-alkyl C and decreased aromatic C content, while maize straw biochar treatment showed an opposite effect. Maize straw treatment significantly increased the abundance of cbhI gene and the relative abundance of Penicillium, Gaeumannomyces and Marasmius. However, maize straw biochar treatment reduced the abundance of this gene. The relative abundance of dominant cbhI in soils was positively correlated with the content of O-alkyl C and negatively correlated with the content of aromatic C. Results of redundancy analysis showed that maize straw treatment had a significant effect on the microbial community composition of cbhI gene by changing soil O-alkyl C content, while maize straw biochar affected the microbial community composition of cbhI gene by changing soil pH, organic carbon, and aromatic C content. Maize straw biochar treatment was more effective in increasing soil organic carbon stability and reducing microbial activity associated with carbon degradation in the subtropical Moso bamboo forest ecosystem compared with maize straw treatment. Therefore, the application of biochar has positive significance for maintaining soil carbon storage in subtropical forest ecosystems.

Patterns and abiotic drivers of soil organic carbon in perennial tea (Camellia sinensis L.) plantation system of China.

Understanding soil organic carbon (SOC), the largest carbon (C) pool of a terrestrial ecosystem, is essential for mitigating climate change. Currently, the spatial patterns and drivers of SOC in the plantations of tea, a perennial leaf crop, remain unclear. Therefore, the present study surveyed SOC across the main tea-producing areas of China, which is the largest tea producer in the world. We analyzed the soil samples from tea plantations under different scenarios, such as provinces, regions [southwest China (SW), south China (SC), south Yangtze (SY), and north Yangtze (NY)], climatic zones (temperate, subtropical, and tropical), and cultivars [large-leaf (LL) and middle or small-leaf (ML) cultivars]. Preliminary analysis revealed that most tea-producing areas (45%) had SOC content ranging from 10 to 20 g kg-1. The highest SOC was recorded for Yunnan among the various provinces, the SW tea-producing area among the four regions, the tropical region among the different climatic zones, and the areas with LL cultivars compared to those with ML cultivars. Further Pearson correlation analysis demonstrated significant associations between SOC and soil variables and random forest modeling (RF) identified that total nitrogen (TN) and available aluminum [Ava(Al)] of soil explained the maximum differences in SOC. Besides, a large indirect effect of geography (latitude and altitude) on SOC was detected through partial least squares path modeling (PLS-PM) analysis. Thus, the study revealed a high spatial heterogeneity in SOC across the major tea-producing areas of China. The findings also serve as a basis for planning fertilization strategies and C sequestration policies for tea plantations.

[Effects of Low-density Polyethylene Microplastics on the Growth and Physiology Characteristics of Ipomoea aquatica Forsk].

Microplastic pollution in soil and its toxicological effects have attracted increasing attention from researchers, but the mechanisms of microplastics affecting crop growth and physiology remain unclear. A pot experiment was conducted to evaluate the impacts of various mass concentrations (0%, 0.2%, 5%, and 10%) of low-density polyethylene microplastics (LDPE MPs) on the germination rate, photosynthetic pigment content, biomass, antioxidant enzyme activity, soluble protein, and soluble sugar content of water spinach (Ipomoea aquatica Forsk). The results showed that LDPE MPs significantly inhibited (P<0.05) the seed vigor of water spinach, and the inhibitory effect increased with increasing concentration of LDPE MPs. However, the 5% LDPE MPs significantly promoted the aboveground biomass of water spinach. The 0.2% and 10% LDPE MPs significantly improved the superoxide dismutase (SOD) activity and catalase (CAT) and peroxidase (POD) activities, respectively. Further, malondialdehyde (MDA) content decreased with increasing concentration of LDPE MPs, and the reductions reached 15.53%-27.39% in comparison to that in the control. The LDPE MPs also significantly increased the soluble sugar content of water spinach leaves. In summary, LDPE MPs could inhibit the seed vigor and promote biomass accumulation in water spinach. Water spinach could relieve the oxidative stress caused by LDPE MPs by regulating antioxidant enzyme activity and soluble protein content. Therefore, this study may provide basic information for assessing the influences of microplastics on vegetables.

Nitrogen addition reduces phosphorus availability and induces a shift in soil phosphorus cycling microbial community in a tea (Camellia sinensis L.) plantation.

Nitrogen (N) and phosphorus (P) are two important nutrient elements that limit the growth of plants and microorganisms. The effect of the N supply on soil P cycling and its mechanism remain poorly known. Here, we characterized the effects of different N application rates on soil P availability, the abundances of P-cycling functional genes, and microbial communities involved in P-cycling following the application of N for 13 years in a tea plantation. Soil available P (AP) decreased significantly under N application. The opposite pattern was observed for the activity of soil phosphatases including alkaline (ALP) and acid phosphatase (ACP). Furthermore, N addition increased the abundance of ppa but decreased the abundance of phoD in soil. Both ppa- and phoD-harboring communities varied with N application levels. Redundancy analysis (RDA) showed that soil pH was a key variable modulating ppa-harboring and phoD-harboring microbial communities. Partial least squares path modeling (PLS-PM) revealed that long-term N application indirectly reduced soil P availability by altering the abundances of phoD-harboring biomarker taxa. Overall, our findings indicated that N-induced reductions in AP increased microbial competition for P by selecting microbes with P uptake and starvation response genes or those with phosphatases in tea plantation system. This suggests that tea plantations should be periodically supplemented with P under N application, especially under high N application levels.

Biogeochemical behaviour and toxicology of chromium in the soil-water-human nexus: A review.

Chromium (Cr) affects human health if it accumulates in organs to elevated concentrations. The toxicity risk of Cr in the ecosphere depends upon the dominant Cr species and their bioavailability in the lithosphere, hydrosphere, and biosphere. However, the soil-water-human nexus that controls the biogeochemical behaviour of Cr and its potential toxicity is not fully understood. This paper synthesizes information on different dimensions of Cr ecotoxicological hazards in the soil and water and their subsequent effects on human health. The various routes of environmental exposure of Cr to humans and other organisms are also discussed. Human exposure to Cr(VI) causes both carcinogenic and non-carcinogenic health effects via complicated reactions that include oxidative stress, chromosomal and DNA damage, and mutagenesis. Chromium(VI) inhalation can cause lung cancer; however, incidences of other types of cancer following Cr(VI) exposure are low but probable. The non-carcinogenic health consequences of Cr(VI) exposure are primarily respiratory and cutaneous. Research on the biogeochemical behaviour of Cr and its toxicological hazards on human and other biological routes is therefore urgently needed to develop a holistic approach to understanding the soil-water-human nexus that controls the toxicological hazards of Cr and its detoxification.

Converting food waste into soil amendments for improving soil sustainability and crop productivity: A review.

One-third of the annual food produced globally is wasted and much of the food waste (FW) is unutilized; however, FW can be valorized into value-added industrial products such as biofuel, chemicals, and biomaterials. Converting FW into soil amendments such as compost, vermicompost, anaerobic digestate, biofertilizer, biochar, and engineered biochar is one of the best nutrient recovery and FW reuse approaches. The soil application of FW-based amendments can improve soil fertility, increase crop production, and reduce contaminants by altering soil's chemical, physical, microbial, and faunal properties. However, the efficiency of the amendment for improving ecosystem sustainability depends on the type of FW, conversion method, application rate, soil type, and crop type. Engineered biochar/biochar composite materials produced using FW have been identified as promising amendments for soil remediation, reducing commercial fertilizer usage, and increasing soil nutrient use efficiency. The development of quality standards and implementation of policies and regulations at all stages of the food supply chain are necessary to manage (reduce and re-use) FW.

Effects of plant residues on C:N:P of soil, microbial biomass, and extracellular enzyme in an alpine mea-dow on the Qinghai-Tibetan Plateau, China.

Plant residues can affect C:N:P of soil, microbial biomass, and extracellular enzyme, but the effects are still unclear. We conducted a field experiment in an alpine meadow on the eastern part of the Qinghai-Tibetan Plateau to explore the effects of removing aboveground plant or roots and adding plant residues on the C:N:P of soil, microbial biomass, and extracellular enzyme. The results showed that removing aboveground plant biomass significantly decreased soil C:N (the change was -23.7%, the same below) and C:P (-14.7%), microbial biomass C:P and N:P, while significantly increased microbial biomass C:N, and enzyme C:N:P compared with meadow without human disturbance. Removing all plant biomass (aboveground and roots) significantly reduced soil C:N (-11.6%), C:P (-24.0%), N:P (-23.3%) and microbial biomass C:N in comparison to removing aboveground plant, while significantly improved microbial biomass N:P and enzyme N:P. Adding plant residues after removing aboveground plant significantly increased microbial biomass C:N and C:P, enzyme C:N compared with removing aboveground plant, while significantly decreased enzyme N:P. Compared with removing all the plant, adding plant residues after removing whole plant significantly reduced soil C:N (-16.4%), microbial biomass C:P, N:P and enzyme N:P, while significantly increased enzyme C:N. Our results suggest that removal of plants could have a strong effect on C:N:P of soil, microbial biomass, and extracellular enzyme, and C:N:P of microbial biomass and that extracellular enzyme woule be more sensitive to plant residues. Roots could play a key role in stabilizing C:N:P of soil, microbial biomass, and extracellular enzyme under plant residues addition. Adding plant residues could be a suitable solution for restoring alpine meadows under the circumstance of intact roots, which was conducive to soil C storage, but might not be suitable for alpine meadows with serious root damage, which would increase soil CO2 emission.

Microplastic pollution destabilized the osmoregulatory metabolism but did not affect intestinal microbial biodiversity of earthworms in soil.

Metabolomic and gut microbial responses of soil fauna to environmentally relevant concentrations of microplastics indicate the potential molecular toxicity of microplastics; however, limited data exist on these responses. In this study, earthworms (Eisenia fetida) were exposed to spherical (25-30 µm diameter) polystyrene microplastic-contaminated soil (0.02%, w:w) for 14 days. Changes in weight, survival rate, intestinal microbiota and metabolic responses of the earthworms were assessed. The results showed that polystyrene microplastics did not influence the weight, survival rate, or biodiversity of the gut microbiota, but significantly decreased the relative abundance of Bacteroidetes at the phylum level. Moreover, polystyrene microplastics disturbed the osmoregulatory metabolism of earthworms, as indicated by the significantly decreased betaine, myo-inositol and lactate, and increased 2-hexyl-5-ethyl-furan-3-sulfonic acid at the metabolic level. This study provides important insights into the molecular toxicity of environmentally relevant concentrations of polystyrene microplastics on soil fauna.

Mechanistic insights into the selective adsorption of phosphorus from wastewater by MgO(100)-functionalized cellulose sponge.

Metal oxides have remained state-of-the-art adsorbents for recovering phosphorus from aqueous solutions, but their practical application is still limited by their unsatisfactory adsorption capacities and selectivities in wastewater. Here, using MgO as a model metal oxide, the strategy of employing porous cellulose sponge to support metal oxides featuring exposed specific crystal facets was proposed to develop promising phosphate adsorbents. The phosphate adsorption isotherms and kinetics were measured and the phosphate adsorption mechanism was explored. The results show that cellulose sponge-supported MgO(100) (C-MgO(100)) has a saturation capacity of 28.3 mg P/g, over ten times higher than MgO(100) particles. Importantly, the phosphate adsorption properties of C-MgO(100) are almost not affected in wastewater, demonstrating its exceptional selectivity for phosphate adsorption. In contrast, the saturation capacity of MgO(111)-functionalized cellulose sponge is obviously declined in wastewater. Experimental together with theoretical analyses indicate that phosphate is chemically adsorbed on C-MgO(100) with obvious electrons transfer from the p-orbital of phosphate, and the adsorption energy of C-MgO(100) towards phosphate is maintained in the presence of coexisting anions. Ultimately, regeneration experiments reveal that a regenerant formulation composed of KOH (wt.1 %) and tap water is suitable for the regeneration of C-MgO(100) with >82.6 % phosphate desorption efficiencies after 5 cycles, further confirming its potential in practical application for the treatment of real water.

Relationships between denitrification rates and functional gene abundance in a wetland: The roles of single- and multiple-species plant communities.

Wetland soil denitrification removes excess inorganic nitrogen (N) and prevents eutrophication in aquatic ecosystems. Wetland plants have been considered the key factors determining the capacity of wetland soil denitrification to remove N pollutants in aquatic ecosystems. However, the influences of various plant communities on wetland soil denitrification remain unknown. In the present study, we measured variations in soil denitrification under different herbaceous plant communities including single Phragmites karka (PK), single Paspalum thunbergia (PT), single Zizania latifolia (ZL), a mixture of Paspalum thunbergia plus Phragmites karka (PTPK), a mixture of Paspalum thunbergia plus Zizania latifolia (PTZL), and bare soil (CK) in the Estuary of Nantiaoxi River, the largest tributary of Qingshan Lake in Hangzhou, China. The soil denitrification rate was significantly higher in the surface (0-10 cm) than the subsurface (10-20 cm) layer. Wetland plant growth increased the soil denitrification rate by significantly increasing the soil water content, nitrate concentration, and ln(nirS) + ln(nirK). A structural equation model (SEM) showed that wetland plants indirectly regulated soil denitrification by altering the aboveground and belowground plant biomass, nitrate concentration, abundances of denitrifying functional genes, and denitrification potential. There was no significant difference in soil denitrification rates among PT, PK and ZL. The soil denitrification rate was significantly lower in PTZL than PTPK. Two-plant communities did not necessarily enhance the denitrification rate compared to single planting, the former had a greater competitiveness on N uptake and consequently reduced the amount of nitrate available for denitrification. As PTPK had the highest denitrification rate, co-planting P. thunbergia and P. karka could effectively improve N removal efficiency and help mitigate eutrophication in adjacent aquatic ecosystems. The results of this investigation provide useful information guiding the selection of appropriate wetland herbaceous plant species for wetland construction and the removal of N pollutants in aquatic ecosystems.

Metagenomics reveals N-induced changes in carbon-degrading genes and microbial communities of tea (Camellia sinensis L.) plantation soil under long-term fertilization.

Soil organic carbon (SOC) is an important C pool of the global ecosystem and is affected by various agricultural practices including fertilization. Excessive nitrogen (N) application is an important field management measure in tea plantation systems. However, the mechanism underlying the impact of N fertilization on SOC, especially the microscopic mechanism remain unclear. The present study explored the effects of N fertilization on C-cycling genes, SOC-degrading enzymes and microbes expressing these enzymes by using a metagenomic approach in a tea plantation under long-term fertilization with different N rates. Results showed that N application significantly changed the abundance of C-cycling genes, SOC-degrading enzymes, especially those associated with labile and recalcitrant C degradation. In addition, the beta-glucosidase and chitinase-expressing microbial communities showed a significant difference under different N rates. At the phylum level, microbial taxa involved in C degradation were highly similar and abundant, while at the genus level, only specific taxa performed labile and recalcitrant C degradation; these SOC-degrading microbes were significantly enriched under N application. Redundancy analysis (RDA) revealed that the soil and pruned litter properties greatly influenced the SOC-degrading communities; pH and DOC of the soil and biomass and total polyphenol (TP) of the pruned litter exerted significant effects. Additionally, the random forest (RF) algorithm revealed that soil pH and dominant taxa efficiently predicted the beta-glucosidase abundance, while soil pH and DOC, pruned litter TP, and the highly abundant microbial taxa efficiently predicted chitinase abundance. Our study indicated that long-term N fertilization exerted a significant positive effect on SOC-degrading enzymes and microbes expressing these enzymes, resulting in potential impact on soil C storage in a perennial tea plantation ecosystem.

Long-term nitrogen addition increases denitrification potential and functional gene abundance and changes denitrifying communities in acidic tea plantation soil.

The response of soil denitrification to nitrogen (N) addition in the acidic and perennial agriculture systems and its underlying mechanisms remain poorly understood. Therefore, a long-term (12 years) field trial was conducted to explore the effects of different N application rates on the soil denitrification potential (DP), functional genes, and denitrifying microbial communities of a tea plantation. The study found that N application to the soil significantly increased the DP and the absolute abundance of denitrifying genes, such as narG, nirK, norB, and nosZ. The diversity of denitrifying communities (genus level) significantly decreased with increasing N rates. Moreover, the denitrifying communities composition significantly differed among the soils with different rates of N fertilization. Further variance partitioning analysis (VPA) revealed that the soil (39.04%) and pruned litter (32.53%) properties largely contributed to the variation in the denitrifying communities. Dissolved organic carbon (DOC) and soil pH, pruned litter's total crude fiber (TCF) content and total polyphenols to total N ratio (TP/TN), and narG and nirK abundance significantly (VIP >1.0) influenced the DP. Finally, partial least squares path modeling (PLS-PM) revealed that N addition indirectly affected the DP by changing specific soil and pruned litter properties and functional gene abundance. Thus, the findings suggest that tea plantation is a major source of N2O emissions that significantly enhance under N application and provide theoretical support for N fertilizer management in an acidic tea plantation system.

Nanoplastics induce molecular toxicity in earthworm: Integrated multi-omics, morphological, and intestinal microorganism analyses.

The toxicity of nanoplastics (NPs) at relatively low concentrations to soil fauna at different organismal levels is poorly understood. We investigated the responses of earthworm (Eisenia fetida) to polystyrene NPs (90-110 nm) contaminated soil at a relatively low concentration (0.02 % w:w) based on multi-omics, morphological, and intestinal microorganism analyses. Results showed that NPs accumulated in earthworms' intestinal tissues. The NPs damaged earthworms' digestive and immune systems based on injuries of the intestinal epithelium and chloragogenous tissues (tissue level) and increased the number of changed genes in the digestive and immune systems (transcriptome level). The NPs reduced gut microorganisms' diversity (Shannon index) and species richness (Chao 1 index). Proteomic, transcriptome, and histopathological analyses showed that earthworms suffered from oxidative and inflammatory stresses. Moreover, NPs influenced the osmoregulatory metabolism of earthworms as NPs damaged intestinal epithelium (tissue level), increased aldosterone-regulated sodium reabsorption (transcriptome level), inositol phosphate metabolism (proteomic level) and 2-hexyl-5-ethyl-furan-3-sulfonic acid, and decreased betaine and myo-inositol concentrations (metabolic level). Transcriptional-metabolic and transcriptional-proteomic analyses revealed that NPs disrupted earthworm carbohydrate and arachidonic acid metabolisms. Our multi-level investigation indicates that NPs at a relatively low concentration induced toxicity to earthworms and suggests that NPs pollution has significant environmental toxicity risks for soil fauna.