Phosphorus Cycling Research Articles

The effect of combined application of biochar and phosphate fertilizers on phosphorus transformation in saline-alkali soil and its microbiological mechanism

This study investigated the effects of combining Phragmites australis-based biochar, prepared at 400 °C, with various types of phosphate fertilizers—soluble, insoluble, and organic—on the content and transformation of phosphorus fractions in saline-alkali soil. Additionally, we explored microbiological mechanisms driving these transformations. The results showed that this combination significantly increased the concentrations of dicalcium phosphate (Ca2P), octacalcium phosphate (Ca8P), aluminum phosphate (AlP), moderately labile organic phosphorus (MLOP), and resistant organic phosphorus (MROP) in soil. Conversely, the levels of hydroxyapatite (Ca10P) and highly resistant organic phosphorus (HROP) decreased. The increase in labile organic phosphorus (LOP) content or decrease in iron phosphate (FeP) was found to effectively enhance the availability of Olsen phosphorus (Olsen-P) in soil. Furthermore, the study revealed that biochar mixed with organic phosphate fertilizers increased the activity of soil acid phosphatase (ACP) and neutral phosphatase (NEP), while reducing alkaline phosphatase (ALP) activity. In contrast, biochar combined with soluble and insoluble phosphate fertilizers decreased the activity of ACP (22.59 % and 28.57 %, respectively) and NEP (62.50 % and 11.11 %, respectively), with the combination with insoluble fertilizers also reducing ALP activity by 55.84 %, whereas the soluble combination increased it by 190.34 %. Additionally, the co-application of biochar and phosphate fertilizers altered the composition and abundance of the gene phoD-harboring microbial community, enhancing the abundance of Proteobacteria and reducing that of Actinobacteria. Correlation analysis between phoD-functional microbial species and various phosphorus fractions showed that Rhodopseudomonas was significantly associated with several phosphorus components, exhibiting a positive correlation with Ca2P, Ca8P, AlP, LOP, MLOP, and MROP, but a negative relationship with Ca10P. These findings suggest that the combined application of biochar and phosphate fertilizers could change the abundance of Rhodopseudomonas, potentially influencing phosphorus cycling in the soil. This research provides a strong scientific foundation for the efficient combined use of biochar and phosphate fertilizers in managing saline-alkali soil.

Contrasting fertilization and phenological stages shape microbial-mediated phosphorus cycling in a maize agroecosystem

Phosphorus (P) is essential for plants but often limited in soils, with microbes playing a key role in its cycling. P deficiency in crops can be mitigated by applying by-products like sludge and struvite to enhance yield and sustainability. Here, we evaluated the contribution of four different types of fertilizers: i) conventional NPK; ii) sludge; iii) struvite; and iv) struvite+sludge in a semiarid maize plantation to the availability of P and the responses of the soil microbiome. We investigated the effects of these treatments on the relative abundance of bacterial and archaeal genes and proteins related to organic P mineralization, inorganic P solubilization, and the P starvation response regulation through a multi-omic approach. Moreover, we explored the impact of maize phenology by collecting samples at germination and flowering stages. Our findings suggest that the phenological stage has a notable impact on the abundance of P cycle genes within bacterial and archaeal communities, particularly regarding the solubilization of inorganic P. Furthermore, significant variations were observed in the relative abundance of genes associated with different P cycles in response to various fertilizer treatments. Sludge and struvite application improved P availability, which was related to an increase in the relative abundance of Sphingomonas (Proteobacteria) and Luteitalea (Acidobacteria) respectively, and genes related to inorganic P solubilization. Furthermore, we observed a substantial taxonomic clustering of functional processes associated with the P cycle. Among the dominant bacterial populations containing P-related genes, those microbes possessing genes linked to the solubilization of inorganic P typically did not harbor genes associated with the mineralization of organic P. This phenomenon was particularly evident among members of Actinobacteria. Overall, we reveal important shifts in bacterial and archaeal communities and associated molecular processes, stressing the intricate interplay between fertilization, phenology, and P cycling in agroecosystems.

In Situ Evolution of Ionic Sites at Clay Mineral Interfaces Facilitates Fluoride and Phosphorus Mineralization.

Soil minerals influence the biogeochemical cycles of fluoride (F) and phosphorus (P), impacting soil quality and bioavailability to plants. However, the cooperative mechanisms of soil minerals in governing F and P in the soil environment remain a grand challenge. Here, we reveal the essential role of a typical soil mineral, montmorillonite (Mt), in the cycling and fate of F and P. The results show that the enrichment of metal sites on the Mt surface promotes the mineralization of F to the fluorapatite (FAP) phase, thereby remaining stable in the environment, simultaneously promoting P release. This differential behavior leads to a reduction in the level of F pollution and an enhancement of P availability. Moreover, solid-state NMR and HRTEM observations confirm the existence of metastable F-Ca-F intermediates, emphasizing the pivotal role of Mt surface sites in regulating crystallization pathways and crystal growth of FAP. Furthermore, the in situ atomic force microscopy and theoretical calculations reveal molecular fractionation mechanisms and adsorption processes. It is observed that a competitive relationship exists between F and P at the Mt interface, highlighting the thermodynamically advantageous pathway of forming metastable intermediates, thereby governing the activity of F and P in the soil environment at a molecular level. This work paves the way to reveal the important role of clay minerals as a mineralization matrix for soil quality management and offers new strategies for modulating F and P dynamics in soil ecosystems.

Organic management improved the multifunctionality in recolonization soil by increasing microbial diversity and function

Abstract Organic management enhances the formation of distinct and stable soil microbial communities, however, its influence on the temporal recovery of microbiome and multifunctionality of sterilized soil remains poorly understood. We used amplicon sequencing and metagenomic sequencing to investigate the effects of microbial communities in long‐term organic and conventional managed soils on restoring soil microbiome and functionality. We calculated multifunctionality of soils at days 30 and 90 of recolonization using the averaging approach. Results showed that organic management (O) significantly increased alpha diversity, niche width and network complexity of microbial community compared to conventional management (C). The alpha diversity, niche width and network complexity of microbial community in soils with organic soil suspension were significantly increased compared to conventional management at days 30 and 90 of recolonization. Soil multifunctionality of sterilized organic managed soil inoculated with organic soil suspension (OO) was 14.6% to 70.6% higher than that of the rest treatments. Macrogenomic analysis revealed that O significantly enriched functional pathways of ABC transporters, carbon metabolism, biosynthesis of amino acids, two‐component and nitrogen metabolism as well as most of the functional genes for carbon degradation, carbon fixation, nitrogen cycling and phosphorus cycles compared to C. These functional pathways and genes were also significantly enriched in soils with organic soil suspension at day 30 and 90 of recolonization. Furthermore, alpha diversity, niche width, network complexity, functional pathways and functional genes of microbiome correlated positively with soil multifunctionality. Synthesis and applications. Our results emphasize the importance of organic management induced changes in diversity, network complexity, and functionality of microbial communities for promoting recovery to soil microbial and functional losses, providing the theoretical basis for sustainable impact of organic management in agronomic production on soil microbiome and function. Read the free Plain Language Summary for this article on the Journal blog.

Ecotoxicological effects of microplastic types and concentrations in combination with Cd on the bioenergy plant sweet sorghum: Growth and rhizosphere microbiome analysis

Complex interactions occur when microplastics (MPs) and heavy metals cooccur as pollutants, and these interactions have become a popular research topic. However, there is a lack of research examining the impact of concurrent pollution from MPs and heavy metals on the soil microbial community and its roles in nitrogen and phosphorus cycling. Therefore, in this study, we investigated the effects of composite pollution from cadmium (Cd) and different types of MPs (e.g., PVC, PE, and PP) at different concentrations (0.1 % and 0.5 %) on the growth of sweet sorghum, an energy plant, and evaluated Cd accumulation in sweet sorghum and the expression of genes related to soil nitrogen and phosphorus cycling. The results indicated that the growth of sweet sorghum was negatively impacted by combined treatment with the three types of microplastics and Cd, with the composite stress trend being 0.5 % > 0.1 %. The contents of mineral nutrients such as nitrogen, phosphorus, and potassium in the soil decreased due to MP+Cd pollution. Cocontamination with MP and Cd significantly affected the microbial community composition and increased the activity of enzymes such as urease. MP+Cd pollution affected the composition and abundance of functional genes related to nitrogen and phosphorus cycling. The type and concentration of microplastics were identified as the primary factors influencing the composition and abundance of functional genes. Bacteria belonging to Acidobacteria and Actinobacteria are key to soil nitrogen cycling, while Acidobacteria plays crucial roles in soil phosphorus cycling. Metagenomic analysis was performed in this study to determine the impact of microplastic–heavy metal pollution on soil microbial communities and functions and to provide a reference for the environmental assessment of soils contaminated by both microplastics and heavy metals.

Unveiling the unknown viral world in groundwater

Viruses as the prevailing biological entities are poorly understood in underground realms. Here, we establish the first metagenomic Groundwater Virome Catalogue (GWVC) comprising 280,420 viral species ( ≥ 5 kb) detected from 607 monitored wells in seven geo-environmental zones throughout China. In expanding ~10-fold the global portfolio of known groundwater viruses, we uncover over 99% novel viruses and about 95% novel viral clusters. By linking viruses to hosts from 119 prokaryotic phyla, we double the number of microbial phyla known to be virus-infected in groundwater. As keystone ultrasmall symbionts in aquifers, CPR bacteria and DPANN archaea are susceptible to virulent viruses. Certain complete CPR viruses even likely infect non-CPR bacteria, while partial CPR/DPANN viruses harbor cell-surface modification genes that assist symbiont cell adhesion to free-living microbes. This study reveals the unknown viral world and auxiliary metabolism associated with methane, nitrogen, sulfur, and phosphorus cycling in groundwater, and highlights the importance of subsurface virosphere in viral ecology.

Decoupled cycling of particulate cadmium and phosphorus in the subtropical Northwest Pacific

AbstractWe examined the spatial variation in size‐fractionated (0.8–51 and > 51 μm) particulate cadmium (Cd) and phosphorus (P) based on a large dataset collected during a GEOTRACES Section cruise (GP09) in the North Pacific Subtropical Gyre (NPSG) to better understand the interrelationship between Cd and P biogeochemical cycles. Concentrations of particulate Cd (0.06–2.15 pmol L−1) and P (0.33–10.19 nmol L−1) showed an initial increase with depth followed by a decrease, and were among the lowest observed in the global ocean. Bulk particulate Cd : P ratios in the euphotic zone, indicative of phytoplankton Cd assimilation, showed strong geographic variability averaging 0.05 ± 0.02 within the NPSG interior vs. 0.14 ± 0.04 pmol nmol−1 at the southern boundary. Cadmium to P remineralization ratio in the mesopelagic zone had a roughly similar stoichiometry as what was produced in the euphotic zone, being ~ 0.05 ± 0.01 in the NPSG interior vs. 0.21 ± 0.04 pmol nmol−1 at the southern boundary. Cd–P decoupling was reflected in the elements' vertical distribution, showing unsynchronized changes through the water column, consistent with Cd–P differential remineralization resulting from multiple Cd and P pools. The Cd–P relationship also differed between small and large particles, suggesting differences in Cd assimilation among phytoplankton assemblages as well as particle dynamic processes. Our results highlight complex processes fractionating Cd from P in the oligotrophic ocean and complicate the use of Cd as a palaeo‐phosphate proxy.

Supplementary bird feeding as an overlooked contribution to local phosphorus cycles

Supplementary feeding of garden birds and gamebirds is a common practice worldwide. Bird feed is rich in phosphorus (P), which plays a key role in animal health and ecosystem function. However, much of the P in bird feed originates from mined rock deposits, which is then transported thousands of kilometers to feeder stations, where it represents an external source of nutrients for recipient ecosystems. Here, we demonstrate that diffusion of P by birds and other animals from feeder stations to ecosystems can represent a nontrivial contribution to local biogeochemical cycles. Using the UK as a case study, we show that supplementary bird feeding supplies 2.4 (range: 1.9–3.0) gigagrams of P per year across the UK, a flux similar in magnitude to atmospheric deposition. Phosphorus provided to garden birds alone is equal to that supplied through the application of garden fertilizers. In natural and semi‐natural ecosystems, additional feeder‐derived P inputs may exacerbate eutrophication at the local scale and adversely impact biodiversity.

Single-cell exploration of active phosphate-solubilizing bacteria across diverse soil matrices for sustainable phosphorus management.

Phosphate-solubilizing bacteria (PSB) are crucial for enhancing phosphorus bioavailability and regulating phosphorus transformation processes. However, the in situ phosphorus-solubilizing activity and the link between phenotypes and genotypes for PSB remain unidentified. Here we employed single-cell Raman spectroscopy combined with heavy water to discern and quantify soil active PSB. Our results reveal that PSB abundance and in situ activity differed significantly between soil types and fertilization treatments. Inorganic fertilizer input was the key driver for active PSB distribution. Targeted single-cell sorting and metagenomic sequencing of active PSB uncovered several low-abundance genera that are easily overlooked within bulk soil microbiota. We elucidate the underlying functional genes and metabolic pathway, and the interplay between phosphorus and carbon cycling involved in high phosphorus solubilization activity. Our study provides a single-cell approach to exploring PSB from native environments, enabling the development of a microbial solution for the efficient agronomic use of phosphorus and mitigating the phosphorus crisis.

Repercussions of Prolonged Pesticide Use on Natural Soil Microbiome Dynamics Using Metagenomics Approach.

The residual pesticides in soil can affect the natural microbiome composition and genetic profile that drive nutrient cycling and soil fertility. In the present study, metagenomic approach was leveraged to determine modulations in nutrient cycling and microbial composition along with connected nexus of pesticide, antibiotic, and heavy metal resistance in selected crop and fallow soils having history of consistent pesticide applications. GC-MS analysis estimated residuals of chlorpyrifos, hexachlorbenzene, and dieldrin showing persistent nature of pesticides that pose selective pressure for microbial adaptation. Taxonomic profiling showed increased abundance of pesticide degrading Streptomyces, Xanthomonas, Cupriavidus, and Pseudomonas across the selected soils. Genes encoding for pesticide degrading cytochrome p450, organophosphorus hydrolase, aldehyde dehydrogenase, and oxidase were predominant and positively correlated with Bacillus, Sphingobium, and Burkholderia. Nitrogen-fixing genes (nifH, narB, and nir) were relatively less abundant in crop soils, correlating to the decrease in nitrogen-fixing bacteria (Anabaena, Pantoea, and Azotobacter). Microbial enzymes involved in carbon (pfkA, gap, pgi, and tpiA) and phosphorus cycle (gmbh and phnJ) were significantly higher in crop soils indicating extensive utilization of pesticide residuals as a nutrient source by the indigenous soil microbiota. Additionally, presence of antibiotic and heavy metal resistance genes suggested potential cross-resistance under pressure from pesticide residues. The results implied selective increase in pesticide degrading microbes with decrease in beneficial bacteria that resulted in reduced soil health and fertility. The assessment of agricultural soil microbial profile will provide a framework to develop sustainable agriculture practices to conserve soil health and fertility.

Global distribution pattern of soil phosphorus-cycling microbes under the influence of human activities.

Human activities have profoundly altered the Earth's phosphorus (P) cycling process and its associated microbial communities, yet their global distribution pattern and response to human influences remain unclear. Here, we estimated the abundances of P-cycling genes from 3321 global soil metagenomic samples and mapped the global distribution of five key P-cycling processes, that is, organic phosphoester hydrolysis, inorganic phosphorus solubilization, two-component system, phosphotransferase system, and transporters. Structural equation modeling and random forest analysis were employed to assess the impact of anthropogenic and environmental factors on the abundance of P-cycling genes. Our findings suggest that although less significant than the climate and soil profile, human-related factors, such as economic activities and population, are important drivers for the variations in P-cycling gene abundance. Notably, the gene abundances were increased parallel to the extent of human intervention, but generally at low and moderate levels of human activities. Furthermore, we identified critical genera, such as Pseudomonas and Lysobacter, which were sensitive to the changes in human activities. This study provides insights into the responses of P-cycling microbes to human activities at a global scale, enhancing our understanding of soil microbial P cycling and underscoring the importance of sustainable human activities in the Earth's biogeochemical cycle.

Sex-specific phosphorus acquisition strategies and cycling in dioecious Populus euphratica forests along a natural water availability gradient.

Soil phosphorus (P) availability affects plant growth and distribution. However, it is still unknown how sex-specific variation in functional traits affects plants' P acquisition and soil P transformation. On wet sites, female poplars had a greater specific root length (SRL), and a higher diversity of arbuscular mycorrhizal fungi (AMF) and phosphate-solubilizing bacteria (PSB). Male poplars living on wet sites increased the abundance of AMF and PSB communities and enhanced moderately labile and highly resistant organic P mineralisation via increased phosphatase activity. In contrast, on the dry site, the abundance and diversity of AMF and PSB communities increased in females, enhancing moderately labile and highly resistant organic P mineralisation via elevating phosphatase activities. Males maintained greater SRL and promoted Ca-P mobilisation via the release of root carboxylic acids and rhizosphere acidification on the dry site. The AMF community diversity followed a similar pattern as that of the PSB community when altering the P availability of different-sex plants. Our results indicated that organic P and Ca-P are the major sources of plant-available P in natural P. euphratica forests. Seasonal shifts and geographic locations affected the share of organic and inorganic P pools, and AMF and PSB diversities, ultimately altering sex-specific P acquisition strategies of plants.

Phosphate Influx and Dust Deposition Create Zonal and Meridional Biogeochemical Gradients in Trichodesmium Abundance

AbstractTrichodesmium plays a key role in the biogeochemical cycling of carbon, nitrogen and phosphorus in the Tropical Atlantic Ocean. A complex interplay of physicochemical factors control the growth of Trichodesmium. However, owing to the large spatial and temporal variability, the relative influence of these factors in controlling Trichodesmium distribution and abundance remains unclear. In this study, we examined the basin‐scale distribution pattern of Trichodesmium in the upper 200 m water column of the Atlantic Ocean (25°N–30°S and 70°W–20°E) using a large data set (n = 33,235) and tried to constrain the distribution based on various physicochemical parameters. We suggest that the combined effect of warm temperatures and phosphate (PO43−) availability determines the zonal spatial extent and the abundance of Trichodesmium in the Tropical North Atlantic Ocean. However, the availability of dissolved iron, along with high sea surface temperatures and meteorological parameters such as the wind direction and precipitation, likely govern the meridional distribution of Trichodesmium across the Atlantic Ocean. Excess PO43− at the surface rules out the possibility of PO43− limitation in regulating the meridional distribution of the Trichodesmium. Depth‐integrated nitrogen fixation rates, based on a multiple linear regression, vary from 0.07 to 306 μmol N m−2 d−1. The presence of Trichodesmium colonies down to a depth of 200 m and the depth‐integrated nitrogen fixation rates reflect the pivotal role of Trichodesmium in the nitrogen budget of this region.

Dolostone-barite-phosphorite sequence in the basal Doushantuo Formation: Origin and implications for post-Marinoan ocean chemistry and phosphogenesis

Barite (BaSO4) represents a major component of many post-Marinoan cap dolostones worldwide, recording important information on climate upheavals during the terminal Neoproterozoic. However, its origins and relations with other lithofacies remain to be explored. Here we report new occurrences of barite in the basal Ediacaran Doushantuo Formation at a major phosphate mine in Weng'an, South China, and present results of detailed petrographic and geochemical investigations on the barites and related phases. At the outcrop scale, barite is mainly present as a 1–2 cm-thick layer at the contact of the cap dolostones and overlying phosphorites. Detailed petrographic observations reveal a lithofacies transition from dolostone through a mixture of barite, dolomite and apatite to barite and finally to granular phosphorite. The barites can be categorized into three generations in stratigraphic order, which are present as loose, randomly-oriented blades (B1), dense aggregates (B2), and radially aligned crystal fans (B3), respectively. B1 is dispersed in a matrix of apatite and dolomite, which has an average δ13Ccarb of −0.61‰. This, along with the common presence of organic matter (OM) in this barite, point to a possible source of Ba from organic degradation. B3 forms a centimeter-scale layer of barite fans that laterally extends over the entire mining pit, whereas B2 is locally distributed between B1 and B3, and occurs as relatively unoriented aggregates. δ34S values of B3 show a narrow range between +25.9‰ and +30.9‰, which is similar to that of contemporaneous seawater and indicate a seawater source of sulfate in barite. Based on the present investigation and a compilation of published data, we propose that B1 is diagenetic barite with a main source of Ba from degradation of organic matter and possibly also from dissolution of previous pelagic barite, whereas B2 and B3 represent seafloor precipitates that resulted from interactions between deep, anoxic Ba-rich waters and oxic, sulfate-rich surface waters during the post-glacial transgression. This episode of barite precipitation was immediately followed by massive accumulations of phosphorites in Weng'an and many areas of South China. The consecutive deposition of cap dolostone, barite and phosphorite signifies the transition from an alkalinity-rich, stagnant anoxic ocean to a dynamic marine regime featuring oxygenated surface waters and upwelling currents. These pH and redox changes likely facilitated the cycling and enrichment of phosphate in the shallow waters that was necessitated by the unprecedented accumulation of Ediacaran phosphorites in South China.

IMPACT OF FOREST CONVERSION TO PASTURE ON SOIL ENZYMATIC ACTIVITY IN THE NORTHERN AMAZON

The conversion of forests to pastures in the Amazon results in deforestation and the loss of environmental services. This practice affects biogeochemical cycles and impairs soil enzyme activity, which is essential for maintaining soil quality. This study aimed to investigate the impact of converting part of the Amazon forest into pastures, focusing on soil enzyme activity. The study was conducted at Fazenda Canto Verde, Roraima, comparing native forest areas and pastures of Brachiaria brizantha and Brachiaria humidicola, established on Haplic acrisol, without fertilization or tillage, under a management regime of 30 days of grazing and 60 days of rest. Sampling involved 12 mini trenches per hectare at two depths, with analysis of enzyme activity post-incubation. Higher activity of carbon cycle enzymes (Cellulase, Invertase, β-Glucosidase) was observed in the forest compared to pastures, especially with B. humidicola. Nitrogen cycle enzymes (Urease, BAA-Protease) were more active in the forest, while B. humidicola showed the highest Casein-Protease activity. In the phosphorus and sulfur cycles, the forest led in Phosphomonoesterase and Phosphodiesterase, while B. humidicola excelled in Arylsulfatase. This study demonstrates that replacing forest with pastures significantly alters soil functionality, impacting biogeochemical cycles and their ecological functions.

Position-Specific Oxygen Isotope Analysis in Inositol Phosphates by Using Electrospray Ionization-Quadrupole-Orbitrap Mass Spectrometry.

Conventional isotope-ratio mass spectrometry measurements obscure position-specific isotope distributions in molecular compounds because these measurements require an initial step that converts compounds into simple gases by combustion or pyrolysis. Here, we used electrospray ionization (ESI)-based Orbitrap mass spectrometry to measure oxygen isotope ratios in the phosphate and hydroxyl moieties of inositol phosphates. A thermal hydrolysis experiment was conducted using 18O-labeled water to examine the position-specific oxygen isotope exchange in inositol hexakisphosphate (IP6) as well as its hydrolysis products IP5, IP3, and PO3 fragments. Measurement precisions of the position-specific and molecular-average oxygen isotope values of inositol phosphates were better than ±1.1‰ and ±0.5‰, respectively. Under optimized ionization and Orbitrap parameters, this level of precision was obtained within 30 min of run time at 60 μM initial concentration of inositol phosphate. The ability to measure phosphate-specific oxygen isotopes in inositol phosphate enabled the quantification of isotope exchange, which did not occur in phosphate on IP6, IP5, IP3, and PO3 fragments, meaning that the change in isotopes should have resulted from hydroxyls in the ring. Isotope mass balance calculations corroborated that hydroxyl oxygens are derived from 18O-labeled water. With the observed sensitivity and precision achieved in this study, Orbitrap IRMS proved to be a promising tool for investigating the position-specific oxygen isotopes in organophosphorus compounds. These outcomes open up numerous potential applications that can expand our understanding of phosphorus cycling in the environment.

Rhizosphere effects and microbial N limitations drive the root N limitations in the rhizosphere during secondary succession in a Pinus tabuliformis forest in North China.

Rhizosphere effects (REs) have recently been identified as important regulators of root and microbial nutrient acquisition and are positively involved in nutrient cycling of belowground carbon (C), nitrogen (N), and phosphorus (P). Nutrient conditions of the fine roots and soil N are likely to influence REs. Still, it is unclear how REs of soil nutrients themselves variably impact the supply of nutrients to plants in terms of the responses to soil N due to succession. In this study, we applied both fine roots and extracellular enzymes for vector analysis and stoichiometry of N:P to explore the metabolic limitations of roots and rhizospheric soil microbes and their relationships with REs across five levels of soil N (0, 5, 10, 15, and 20kg N m-2 year-1) along successional age classes of 42, 55, and 65 years in a Pinus tabuliformis forest. Overall, the metabolism of root and rhizospheric soil microbes was mediated by soil N. N limitation of roots initially decreased before increasing, whereas that of microbes demonstrated opposite trends to the N levels owing to competition for inorganic N between them by REs of NO3 --N. However, N limitations of both roots and microbes were alleviated in young stands and increased with succession after the application of N. In addition, root N limitations were manipulated by REs of three different soil N-related indicators, i.e., total N, NH4 +-N, and NO3 --N. Rhizospheric soil microbial N limitation was almost unaffected by REs due to their strong homeostasis but was an important driver in the regulation of root N limitation. Our results indicated that successional age was the most critical driver that directly and indirectly affected root N metabolism. However, the level of N application had a slight effect on root N limitation. Microbial N limitation and variations in the REs of N indicators regulated root N limitation in the rhizosphere. As a result, roots utilized REs to sequester N to alleviate N limitations. Thesefindings contribute to novel mechanistic perspectives on the sustainability of N nutrition by regulating N cycling in a system of plant-soil-microbes in the rhizosphere to adapt to global N deposition or the heterogeneous distribution of bioavailable soil N with succession.

Pursuing China's provincial sustainable development goals within a safe and just operating space: Past, present and future

As emphasized by the challenging sustainable development agenda, countries are facing a complicated combination of environmental stress and social challenges, leading the Earth system towards an unsustainable path. Therefore, it is crucial to accurately assess past fluctuations contributing to current situations and apprehend plausible future implications. This study integrates safe and just operating space (SJOS) with Sustainable Development Goals to depict multiple “windows” of environmental and social evolution in different historical periods, with 31 provinces in China as a case study. Then, we track the spatiotemporal evolution trajectory of environmental performance and social well-being in each province from 2012 to 2021. The Long Short-Term Memory (LSTM) model is utilized to capture the temporal relationships between various indicators and to forecast the spatial trends of SJOS in the provinces from 2022 to 2030. Research findings indicate that: (1) over the 2012–2021 period, the environmental performance of the majority of provinces far exceeds the warning thresholds, with no province falling within all threshold boundaries simultaneously. The phosphorus cycle is the most challenging boundary, with only 6.8% of provinces within the safe boundary over the past 10 years. In comparison, freshwater use performs the best, with 80% of provinces staying within the threshold. (2) Social well-being generally improves across all provinces from 2012 to 2021, but the spatial and temporal trajectories are more varied. All provinces meet the thresholds for the food security and employment indicators. However, none of the provinces meet the standard for the social equity indicator. (3) Over the 2022–2030 projection period, environmental performance and social well-being trend in opposite directions across provinces. This culminates in no province being entirely within the safe and just space by 2030. Sanitation shows the most significant change compared to other indicators. Xinjiang had the largest improvement at 59.12%, while Tianjin had the most significant downward trend at 53.88%. Adjustments in national policies and priorities are essential if China wants to accomplish the sufficiency of biophysical resources whilst ensuring social equity in the access and exploitation of these resources.

Assembly of root-associated bacterial community and soil health in cadmium-contaminated soil affected by nano/bulk-biochar compost associations

Biochar (BC) has been proven effective in promoting the production of safety food in cadmium (Cd)-polluted soil and the impact can be further enhanced through interaction with compost (CM). However, there existed unclear impacts of biochar with varying particle sizes in conjunction with compost on microbiome composition, rhizosphere functions, and soil health. Hence, in this study, two bulk-biochar derived from wood chips and pig manure were fabricated into nano-biochar using a ball-milling method. Subsequently, in a field experiment, the root-associated bacterial community and microbial functions of lettuce were evaluated in respond to Cd-contaminated soil remediated with nano/bulk-BCCM. The results showed that compared to bulk-BCCM, nano-BCCM significantly reduced the Cd concentration in the edible part of lettuce and the available Cd in the soil. Both nano-BCCM and bulk-BCCM strongly influenced the composition of bacterial communities in the four root-associated niches, and enhanced rhizosphere functions involved in nitrogen, phosphorus, and carbon cycling, as well as the relative abundance and biodiversity of keystone modules in rhizosphere soil. Furthermore, soil quality index analysis indicated that nano-BCCM exhibited greater potential than bulk-BCCM in maintaining soil health. The data revealed that nano-BCCM could regulate the Cd concentration in lettuce shoot by promoting microbial biodiversity of keystone modules in soil-root continuum and rhizosphere bacterial functions. These findings suggest that nano-biochar compost associations can be a superior strategy for enhancing microbial functions, maintaining soil health, and ensuring crop production safety in the Cd-contaminated soil compared to the mix of bulk-biochar and compost.

How do glyphosate and AMPA alter the microbial community structure and phosphorus cycle in rice-crayfish systems?

Glyphosate, a commonly used organophosphorus herbicide in rice-crayfish cropping regions, may alter regional phosphorus cycle processes while affecting the structure of microbial communities. However, the effects of glyphosate residues on rice-crayfish systems remain unclear. In this study, we assessed the spatial and temporal distribution characteristics of glyphosate and its primary degradation products, as well as the impact mechanisms of glyphosate on microbial communities and the phosphorus cycle in rice-crayfish systems such as paddy fields, breeding ditches and recharge rivers. The detection rates of glyphosate and aminomethylphosphonic acid (AMPA) were 100% in rice-crayfish systems. Concentrations of glyphosate in the water phase and soil/sediment were as high as 0.012 μg/L and 7.480 μg/kg, respectively, and concentrations of AMPA were as high as 17.435 μg/L and 13.200 μg/kg, respectively. Glyphosate concentrations were not affected by rainfall or sampling site, but concentrations of AMPA in the water phase of recharge rivers were affected by rainfall. The glyphosate concentration was significantly and positively correlated with RBG-16-58-14 abundance, and the AMPA concentration was significantly and positively correlated with Actinobacteria and Lysobacter abundance, and negatively correlated with Cyanobacteria abundance (P < 0.05). The highest abundances of phoD, phnK, and ppx genes were found in all soils/sediments. Glyphosate concentration in soil/sediment was significantly and positively correlated with the abundance of phoD gene encoding an organophosphorus-degrading enzyme and ppx gene encoding poly inorganic phosphate (Pi) hydrolase (P < 0.05). In addition, the glyphosate concentration was significantly and positively correlated with the Ca-bonded Pi content (P < 0.05). This implies that glyphosate may promote the production of stable Pi in rice-crayfish systems by increasing the abundance of phoD and ppx genes. The results of this study reveal the impact mechanism of glyphosate on the phosphorus cycle in rice-crayfish systems and provide a basis for the risk assessment of glyphosate.