Nutrient Cycling Research Articles

Deciphering the environmental adaptation and functional trait of core and noncore bacterial communities in impacted coral reef seawater

Microorganisms play pivotal roles in different biogeochemical cycles within coral reef waters. Nevertheless, our comprehension of the microbially mediated processes following environmental perturbation is still limited. To gain a deeper insight into the environmental adaptation and nutrient cycling, particularly within core and noncore bacterial communities, it is crucial to understand reef ecosystem functioning. In this study, we delved into the microbial community structure and function of seawater in a coral reef under different degrees of anthropogenic disturbance. To achieve this, we harnessed the power of 16S rRNA gene high-throughput sequencing and metagenomics techniques. The results showed that a continuous temporal succession but little spatial heterogeneity in the bacterial communities of core and noncore taxa and functional profiles involved in nitrogen (N) and phosphorus (P) cycling. Eutrophication state (i.e., nutrient concentration and turbidity) and temperature played pivotal roles in shaping both the microbial community composition and functional traits of coral reef seawater. Within this context, the core subcommunity exhibited a remarkably broader habitat niche breadth, stronger phylogenetic signals and lower environmental sensitivity when compared to the noncore taxa. Null model analysis further revealed that the core subcommunity was governed primarily by stochastic processes, while deterministic processes played a more significant role in shaping the noncore subcommunity. Furthermore, our observations indicated that changes in function related to N cycling were correlated to the variations in noncore taxa, while core taxa played a more substantial role in critical processes such as P cycling. Collectively, these findings facilitated our knowledge about environmental adaptability of core and noncore bacterial taxa and shed light on their respective roles in maintaining diverse nutrient cycling within coral reef ecosystems.

Microbial central carbon metabolism in a tidal freshwater marsh and an upland mixed conifer soil under oxic and anoxic conditions.

The central carbon (C) metabolic network is responsible for most of the production of energy and biosynthesis in microorganisms and is therefore key to a mechanistic understanding of microbial life in soil communities. Many upland soil communities have shown a relatively high C flux through the pentose phosphate (PP) or the Entner-Doudoroff (ED) pathway, thought to be related to oxidative damage control. We tested the hypothesis that the metabolic organization of the central C metabolic network differed between two ecosystems, an anoxic marsh soil and oxic upland soil, and would be affected by altering oxygen concentrations. We expected there to be high PP/ED pathway activity under high oxygen concentrations and in oxic soils and low PP/ED activity in reduced oxygen concentrations and in marsh soil. Although we found high PP/ED activity in the upland soil and low activity in the marsh soil, lowering the oxygen concentration for the upland soil did not reduce the relative PP/ED pathway activity as hypothesized, nor did increasing the oxygen concentration in the marsh soil increase the PP/ED pathway activity. We speculate that the high PP/ED activity in the upland soil, even when exposed to low oxygen concentrations, was related to a high demand for NADPH for biosynthesis, thus reflecting higher microbial growth rates in C-rich soils than in C-poor sediments. Further studies are needed to explain the observed metabolic diversity among soil ecosystems and determine whether it is related to microbial growth rates.IMPORTANCEWe observed that the organization of the central carbon (C) metabolic processes differed between oxic and anoxic soil. However, we also found that the pentose phosphate pathway/Entner-Doudoroff (PP/ED) pathway activity remained high after reducing the oxygen concentration for the upland soil and did not increase in response to an increase in oxygen concentration in the marsh soil. These observations contradicted the hypothesis that oxidative stress is a main driver for high PP/ED activity in soil communities. We suggest that the high PP/ED activity and NADPH production reflect higher anabolic activities and growth rates in the upland soil compared to the anaerobic marsh soil. A greater understanding of the molecular and biochemical processes in soil communities is needed to develop a mechanistic perspective on microbial activities and their relationship to soil C and nutrient cycling. Such an increased mechanistic perspective is ecologically relevant, given that the central carbon metabolic network is intimately tied to the energy metabolism of microbes, the efficiency of new microbial biomass production, and soil organic matter formation.

Sensitivity of root production to long‐term aridity under environmental perturbations in Chihuahuan Desert ecosystems

Abstract Root production influences carbon and nutrient cycles and subsidizes soil biodiversity. However, the long‐term dynamics and drivers of belowground production are poorly understood for most ecosystems. In drylands, fire, eutrophication, and precipitation regimes could affect not only root production but also how roots track interannual variability in climate. We manipulated the intra‐annual precipitation regime, soil nitrogen, and fire in four common Chihuahuan Desert ecosystem types (three grasslands and one shrubland) in New Mexico, USA, where the 100‐year record indicates both long‐term drying and increasing interannual variability in aridity. First, we evaluated how root production tracked aridity over 10–17 years using climate sensitivity functions, which quantify long‐term, nonlinear relationships between biological processes and climate. Next, we determined the degree to which perturbations by fire, nitrogen addition or intra‐annual rainfall altered the sensitivity of root production to both mean and interannual variability in aridity. All ecosystems had nonlinear climate sensitivities that predicted declines in production with increases in the interannual variance of aridity. However, root production was the most sensitive to aridity in Chihuahuan Desert shrubland, with reduced production under drier and more variable aridity. Among the perturbations, only fire altered the sensitivity of root production to aridity. Root production was more than twice as sensitive to declines with aridity following prescribed fire than in unburned conditions. Neither the intra‐annual seasonal rainfall regime nor chronic nitrogen fertilization altered the sensitivity of roots to aridity. Synthesis. Our results yield new insight into how dryland plant roots respond to climate change. Our comparison of dryland ecosystems of the northern Chihuahuan Desert predicted that root production in shrublands would be more sensitive to future climates that are drier and more variable than root production in dry grasslands. Field manipulations revealed that fire could amplify the climate sensitivity of dry grassland root production, but in contrast, the climate sensitivity of root production was largely resistant to changes in the seasonal rainfall regime or increased soil fertilization.

Standing and shed litters alter plant growth in disturbed and undisturbed soils differently

Abstract Plant species affect key ecosystem processes like nutrient cycling and overall ecosystem productivity through their litter. The outcome of litter effects is largely determined by its decomposability, which directly effects soil properties. If litter remains standing or unshed (i.e. marcescent), its final decomposability can be increased by photodegradation of recalcitrant structures (like lignin). If the litter is immediately shed, its decomposability largely depends on its original nutrient content. Moreover, plant species may affect soil also through other, more direct effects. It is however unknown whether marcescent and immediately shed litters affect soil, and by that plants, differently, whether direct effects of plants on soil interact with those of marcescent and shed litters, and whether these interactions are consistent under different soil conditions. We set up a pot experiment, where we tested the effects of originally marcescent and shed litters (both added on the soil surface of the pots) on three grassland species (Bromus erectus, Filipendula vulgaris and Plantago media) in contrasting soils from long‐term stable ancient grassland and grassland restored on arable land 20 years before. We also tested how litter types and plant species affect soil chemical properties and microbial community (characterised by PLFA markers). Marcescent litter contained a lower amount of nutrients, but still increased plant biomass more than shed litter, although only for F. vulgaris (likely due to mobilisation of soil nutrients). The effect of litter on soil chemical properties and microbial community was low. These were largely affected by the plant species growing in the pot. The effect of these species on the microbial community was stronger in the undisturbed soil of ancient grasslands, while plant species affected mainly chemical properties in disturbed soil of restored grasslands. B. erectus slowed down the decomposition of both litter types in restored grassland soil. The effect of marcescent litter on living plants was significant but species‐specific and depended on soil conditions. Marcescence seems to have a stronger effect on plants in disturbed soil, which indicates its importance for recovery of the ecosystem after disturbance. Read the free Plain Language Summary for this article on the Journal blog.

Application of Panchagavya, a Cow-based Liquid Formulation, as a Lever for Sustainable and Enhanced Vegetable Crop Production: A Review

Panchagavya, a fermented liquid bio-formulation derived from cow-based products such as dung, urine, milk, curd and ghee, has recently gained importance in agricultural practices due to its reported effectiveness in enhancing vegetable crop production. Its formulation involves a fermentation process that harnesses the diverse microbial communities present in cow-derived substances, resulting in a potent nutrient-rich solution that is believed to possess plant growth-promoting properties. One of the primary mechanisms underlying its efficacy lies in the diverse array of microorganisms present in the formulation. These microorganisms, including beneficial bacteria, fungi and actinomycetes, play crucial roles in nutrient cycling, disease suppression and soil conditioning. Additionally, Panchagavya contains plant growth-promoting substances such as hormones, enzymes, vitamins and amino acids, which contribute to enhanced nutrient uptake, root development and overall plant vigour. Furthermore, application of Panchagavya has been shown to improve soil health by enhancing microbial activity, increasing organic matter content and improving soil properties. These soil improvements not only benefit the current crop but also have long-term positive implications for soil fertility and sustainability. This multifaceted approach to crop management offers a holistic solution to enhance crop productivity while reducing reliance on synthetic inputs. This review aims to comprehensively analyse the literature on the effects of Panchagavya on vegetable crops, highlighting its mechanisms of action and potential benefits for increased vegetable crop production.

Impact of Fertilizers Application on Leaf Litter Decomposition and Nutrient Cycling in White Poplar (Populus alba L.) Forest Ecosystem

Fertilizer application plays a crucial role in the decomposition of white poplar leaf litter and cycling of nutrients within forest ecosystems. The impact of various fertilizer additions on white poplar leaf litter and nutrient cycling is poorly understood. In this study, seven treatments were conducted at the following levels: Control (CK), no adding mineral fertilizers, N fertilization (+N), N and P fertilization (+NP), N, P, K fertilization (+NPK), P, K (+PK), manure fertilizer (+MF), and bird fertilizers (+BF) in a white poplar plantation in Qadis district, and used the litterbag techniques to measure litter mass remaining. The main objectives of our study were: (1) to explore the response of white poplar leaf litter decomposition to various fertilizers and accelerate the decomposition process; (2) to examine the relationship between C, N, and P concentration and their stoichiometric characteristic in leaf litter and soil. In this investigation, our results showed that white poplar leaf litter was significantly affected by fertilizers, and the decomposition process was greatly accelerated with + MF, +NPK, and + BF. The decay rate constant k (year −1) shows the decomposition rate of white poplar leaf litter as follows: +MF > +NPK > +BF > +PK > +NP > +N > CK (0.56, 0.53, 0.52, 0.51,0.51,0.5, and 0.46). Soil nutrients N, P and K increased significantly during the decomposition time with + MF, +NPK, and + BF, respectively, while C:N, C:P, and N:P ratios were highest in the white poplar leaf litter, and lowest in soil, we observed significant association between nutrients concentrations in soil and white poplar leaf and their stoichiometric. This current study concluded that adding + MF, +NPK and + BF fertilizers might be the preferred management option as they provided potentially beneficial changes in leaf litter decomposition and increased nutrient concentration. The data obtained will be a valuable reference for fertilization management strategies in forest ecosystems.

Tea and Pleurotus ostreatus intercropping modulates structure of soil and root microbial communities.

Intercropping with Pleurotus ostreatus has been demonstrated to increase the tea yield and alleviate soil acidification in tea gardens. However, the underlying mechanisms remain elusive. Here, high-throughput sequencing and Biolog Eco analysis were performed to identify changes in the community structure and abundance of soil microorganisms in the P. ostreatus intercropped tea garden at different seasons (April and September). The results showed that the soil microbial diversity of rhizosphere decreased in April, while rhizosphere and non-rhizosphere soil microbial diversity increased in September in the P. ostreatus intercropped tea garden. The diversity of tea tree root microorganisms increased in both periods. In addition, the number of fungi associated with organic matter decomposition and nutrient cycling, such as Penicillium, Trichoderma, and Trechispora, was significantly higher in the intercropped group than in the control group. Intercropping with P. ostreatus increased the levels of total nitrogen (TN), total phosphorus (TP), and available phosphorus (AP) in the soil. It also improved the content of secondary metabolites, such as tea catechins, and polysaccharides in tea buds. Microbial network analysis showed that Unclassified_o__Helotiales, and Devosia were positively correlated with soil TN and pH, while Lactobacillus, Acidothermus, and Monascus were positively correlated with flavone, AE, and catechins in tea trees. In conclusion, intercropping with P. ostreatus can improve the physical and chemical properties of soil and the composition and structure of microbial communities in tea gardens, which has significant potential for application in monoculture tea gardens with acidic soils.

Geologically younger ecosystems are more dependent on soil biodiversity for supporting function

Soil biodiversity contains the metabolic toolbox supporting organic matter decomposition and nutrient cycling in the soil. However, as soil develops over millions of years, the buildup of plant cover, soil carbon and microbial biomass may relax the dependence of soil functions on soil biodiversity. To test this hypothesis, we evaluate the within-site soil biodiversity and function relationships across 87 globally distributed ecosystems ranging in soil age from centuries to millennia. We found that within-site soil biodiversity and function relationship is negatively correlated with soil age, suggesting a stronger dependence of ecosystem functioning on soil biodiversity in geologically younger than older ecosystems. We further show that increases in plant cover, soil carbon and microbial biomass as ecosystems develop, particularly in wetter conditions, lessen the critical need of soil biodiversity to sustain function. Our work highlights the importance of soil biodiversity for supporting function in drier and geologically younger ecosystems with low microbial biomass.

Soil C:N:P stoichiometric signatures of grasslands differ between tropical and warm temperate climatic zones

AbstractClimate and land management affect nutrient cycling in grassland ecosystems. We aimed to understand whether temperate and tropical grasslands differ in terms of soil organic carbon (SOC), nitrogen (N), and phosphorus (P) concentrations, and their C:N:P stoichiometric ratios in grazed and ungrazed natural grasslands and pastures. For this, we used a meta-analysis approach (1296 records, 241 papers), and regression models to explain the observed patterns in terms of mean annual precipitation (MAP), mean annual temperature (MAT), altitude, and latitude. SOC, N, and P concentrations were higher in temperate regions than in tropical ones, and they negatively correlated with MAT and MAP. The grassland type effect was more significant for tropical regions. In tropical regions, soil C:N ratios were higher in ungrazed than in grazed pastures, and soil N:P ratios in ungrazed sites were higher in pastures than in natural grasslands. Grazing increases soil N and SOC for natural grasslands in temperate regions. Our findings suggest that soil stoichiometric C:N:P stoichiometric signatures in grasslands differed between tropical and temperate regions on a global scale. P is a key element in regulation and restriction on soil C and N cycling in tropical regions but less in the temperate ones. Our findings suggest the direction of effects of grazing or grassland type on C:N:P stoichiometric signature. Since imbalances in soil stoichiometric ratios may have implications for ecosystem functioning, the assessment of these patterns could serve as a valuable tool for management and conservation of grasslands and pastures in both tropical and temperate regions.

Investigation of Fungal Community Structure in the Gut of the Stag Beetle Dorcus hopei (Coleoptera; Lucanidae): Comparisons Among Developmental Stages

Stag beetles, recognized as common saproxylic insects, are valued for their vibrant coloration and distinctive morphology. These beetles play a crucial ecological role in decomposition and nutrient cycling, serving as a vital functional component in ecosystem functioning. Although previous studies have confirmed that stag beetles are predominantly fungivores, the fluctuations in their intestinal fungal communities at different developmental stages remain poorly understood. In the current study, high-throughput sequencing was employed to investigate the dynamic changes within intestinal fungal communities at various developmental stages in the stag beetle Dorcus hopei. Results showed that microbial diversity was higher during the larval stage than during the pupal and adult stages. Furthermore, significant differences were identified in the composition of the intestinal fungal communities across the larval, pupal, and adult stages, suggesting that developmental transitions may be crucial factors contributing to variations in fungal community composition and diversity. Dominant genera included Candida, Scheffersomyces, Phaeoacremonium, and Trichosporon. Functional predictions indicated a greater diversity and relative abundance of endosymbiotic fungi in the larval gut, suggesting a potential dependency of larvae on beneficial gut fungi for nutrient acquisition. Additionally, the application of abundance-based β-null deviation and niche width analyses revealed that the adult gut exerted a stronger selection pressure on its fungal community, favoring certain taxa. This selection process culminates in a more robust co-occurrence network of fungal communities within the adult gut, thereby enhancing their adaptability to environmental fluctuations. This study advances our understanding of the intestinal fungal community structure in stag beetles, providing a crucial theoretical foundation for the development of saproxylic beetle resources, biomass energy utilization, plastic degradation strategies, and beetle conservation efforts.

Aerobic anoxygenic phototrophs play important roles in nutrient cycling within cyanobacterial Microcystis bloom microbiomes

BackgroundDuring the bloom season, the colonial cyanobacterium Microcystis forms complex aggregates which include a diverse microbiome within an exopolymer matrix. Early research postulated a simple mutualism existing with bacteria benefitting from the rich source of fixed carbon and Microcystis receiving recycled nutrients. Researchers have since hypothesized that Microcystis aggregates represent a community of synergistic and interacting species, an interactome, each with unique metabolic capabilities that are critical to the growth, maintenance, and demise of Microcystis blooms. Research has also shown that aggregate-associated bacteria are taxonomically different from free-living bacteria in the surrounding water. Moreover, research has identified little overlap in functional potential between Microcystis and members of its microbiome, further supporting the interactome concept. However, we still lack verification of general interaction and know little about the taxa and metabolic pathways supporting nutrient and metabolite cycling within Microcystis aggregates.ResultsDuring a 7-month study of bacterial communities comparing free-living and aggregate-associated bacteria in Lake Taihu, China, we found that aerobic anoxygenic phototrophic (AAP) bacteria were significantly more abundant within Microcystis aggregates than in free-living samples, suggesting a possible functional role for AAP bacteria in overall aggregate community function. We then analyzed gene composition in 102 high-quality metagenome-assembled genomes (MAGs) of bloom-microbiome bacteria from 10 lakes spanning four continents, compared with 12 complete Microcystis genomes which revealed that microbiome bacteria and Microcystis possessed complementary biochemical pathways that could serve in C, N, S, and P cycling. Mapping published transcripts from Microcystis blooms onto a comprehensive AAP and non-AAP bacteria MAG database (226 MAGs) indicated that observed high levels of expression of genes involved in nutrient cycling pathways were in AAP bacteria.ConclusionsOur results provide strong corroboration of the hypothesized Microcystis interactome and the first evidence that AAP bacteria may play an important role in nutrient cycling within Microcystis aggregate microbiomes.Bqr2Xubb8cMPqvNydLEaxMVideo

Effect of coastal hypoxia on bacterial diversity as elucidated through 16S rRNA amplicon sequencing

The formation of oxygen-depleted zones in the bottom waters is one of the most widespread phenomena in coastal areas. Upwelling episodes along India’s west coast due to the southwest monsoon increase biological productivity, further lowering the dissolved oxygen in the upwelled waters, which intensifies annually between June and October. Here, we have determined the changes in the microbial community in response to the varying oxygen levels and other physicochemical parameters at the Candolim Time Series Station using high-throughput sequencing. Amplicon Sequence Variants across all the samples collected in different seasons were mostly affiliated to the phyla Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Chloroflexi, Firmicutes and Planctomycetes, with the most dominant being Proteobacteria (21-41%). Statistical analysis revealed that microbial diversity differed significantly with changing DO, ammonia, nitrate and nitrite concentrations during different seasons. The microbial community shift due to seasonal hypoxia results in the differential biogeochemical cycling of essential nutrients, with certain years seeing redox conditions up to sulphate reduction while certain years seeing only nitrogen loss. Future global warming scenarios will serve as a big challenge for understanding the role of microbial diversity and its implications in the cycling of natural elements.

Litter decomposition rate response to multiple global change factors: A meta-analysis

Anthropogenic global change fundamentally impacts ecosystem biogeochemical cycling. Although litter decomposition is a crucial component of carbon (C) cycling, its response to diverse global change factors (GCFs) remains uncertain. In this research, we synthesized 1706 observations from 260 peer-reviewed publications to elucidate the effects of GCFs on litter decomposition rate (k) and the contribution of different variables to them. Overall, nitrogen (N) addition and drought significantly decreased k (−3.3 and −17.7%, respectively), phosphorus (P) addition, warming, and increased precipitation significantly increased k (6.7, 8.2, and 11.6%, respectively), while elevated CO2 had an insignificant effect on k (−0.6%). Combined GCFs had no significant effect on k except for warming*drought, and all combined factors mainly exhibited antagonistic interactions. Further analysis showed that k responses to GCFs were influenced by initial litter quality (C, N, C:N, P, cellulose, lignin, and vegetation types), soil properties (soil organic C, soil total N, soil total P, soil respiration and microbial biomass C), environmental factors (latitude, longitude, annual mean temperature, annual mean precipitation, ecosystem type, and climate type), and experimental methods (experiment type, richness, treatment method, fertilizer form, fertilizer rate, and experimental duration). Initial litter quality predominantly governed the k response to N addition (53.5%), while soil properties were more significant in regulating the P addition response (44.8%). Environmental factors largely determined k responses to warming, drought, and increased precipitation (50.6, 54.7, 46.9%). Moreover, the experimental methodology also played an important role in regulating k responses to GCFs, which explained 8.6, 23.6, 31.1, 23.7, and 29.7% of the variation of the responses of k to N addition, P addition, warming, drought, and increased precipitation. This meta-analysis offers improved global-scale nutrient cycling predictions under climate change and underscores the need for long-term, multi-factor, methodologically standardized experiments to accurately predict the influence of GCFs on litter decomposition.

Precessional forcing of biogeochemical and nutrient cycling in the tropical western Pacific during the late Pleistocene

Unravelling the biogenic material export production and its relationship to surface ocean nutrient conditions, along with their external forcing, will provide insights into the ocean carbon biogeochemical cycle. In this study, we present data on coccolith particulate inorganic carbon (PIC) export production, coccolith carbon isotopic vital effects, and planktonic foraminifer cadmium to calcium ratio in the tropical western Pacific over the past 250 kiloyears (kyr). These proxies indicate the strength of the coccolith-based carbonate counter pump or coccolithophore productivity, and phosphate concentration in the surface ocean. Our results show that low phosphate concentration correlates with enhanced coccolith-based carbonate counter pump in the precessional band (a cyclicity of 19–23 kyr). Additionally, low phosphate concentration, which indicates high degree of phosphorus utilization, is coupled with enhanced nitrogen fixation, as shown by a nitrogen isotope record in the tropical western Pacific. Greater precipitation in Papua New Guinea (PNG) can occur during local insolation maxima, suggesting a dominant control of precession. This will in turn drive the biogeochemical and nutrient cycling in the tropical western Pacific. We propose that higher amounts of the PNG riverine input caused by greater precipitation can provide additional nutrients and trace element iron (Fe) for phytoplankton. An increased bioavailable Fe in the surface ocean can promote the growth of nitrogen-fixing diazotrophs, which results in a high degree of phosphorus utilization and relieves a potential nitrogen limitation. This may ultimately lead to increased biological productivity, e.g., the coccolith PIC.

Above- and belowground phenology responses of subtropical Chinese fir (Cunninghamia lanceolata) to soil warming, precipitation exclusion and their interaction

Plant phenology plays an important role in nutrient cycling and carbon balance in forest ecosystems, but its response to the interaction of global warming and precipitation reduction remains unclear. In this study, an experiment with factorial soil warming (ambient, ambient +5 °C) and precipitation exclusion (ambient, ambient −50 %) was conducted in a subtropical Chinese fir (Cunninghamia lanceolata) plantation. We investigated the effects of soil warming, precipitation exclusion, and their interactions on Chinese fir phenology involving tree height and fine root growth. In the meantime, the impact of tree height growth and related climatic factors on fine root production was also assessed. The results showed that: (1) more variable phenology responses were observed in fine root growth than in tree height growth to the climatic treatments; the duration of fine root growth and tree height growth was significantly reduced by the precipitation exclusion and warming treatment, respectively; phenology differences of fine root and tree height growth caused by the solo warming and precipitation exclusion treatment were further enhanced by the combined treatment; and despite the greater inter-annual phenology stability of tree height growth than that of fine root growth, both of them showed insignificant response to all the climate treatments; (2) asynchrony of phenology between tree height and fine root growth was significantly enlarged by solo warming and precipitation exclusion treatments, and further enlarged by the combined treatment; (3) fine root production was significantly and positively correlated with air, and soil temperature, and tree height growth as well, which was altered by warming and precipitation exclusion treatments. Our results demonstrated that climatic changes significantly and differently alter phenology of, and extend the phenology asynchrony between, above and below ground plant components, and also highlight the climate-sensitive and variable nature of root phenology. Overall, these phenology responses to climatic change may weaken the close link between fine root production and tree height growth, which may result in temporal mismatch between nutrient demand and supply in Chinese fir plantation.

General reversal of N-decomposition relationship during long-term decomposition in boreal and temperate forests

Decomposition of dead organic matter is fundamental to carbon (C) and nutrient cycling in terrestrial ecosystems, influencing C fluxes from the biosphere to the atmosphere. Theory predicts and evidence strongly supports that the availability of nitrogen (N) limits litter decomposition. Positive relationships between substrate N concentrations and decomposition have been embedded into ecosystem models. This decomposition paradigm, however, relies on data mostly from short-term studies analyzing controls on early-stage decomposition. We present evidence from three independent long-term decomposition investigations demonstrating that the positive N-decomposition relationship is reversed and becomes negative during later stages of decomposition. First, in a 10-y decomposition experiment across 62 woody species in a temperate forest, leaf litter with higher N concentrations exhibited faster initial decomposition rates but ended up a larger recalcitrant fraction decomposing at a near-zero rate. Second, in a 5-y N-enrichment experiment of two tree species, leaves with experimentally enriched N concentrations had faster decomposition initial rates but ultimately accumulated large slowly decomposing fractions. Measures of amino sugars on harvested litter in two experiments indicated that greater accumulation of microbial residues in N-rich substrates likely contributed to larger slowly decomposing fractions. Finally, a database of 437 measurements from 120 species in 45 boreal and temperate forest sites confirmed that higher N concentrations were associated with a larger slowly decomposing fraction. These results challenge the current treatment of interactions between N and decomposition in many ecosystems and Earth system models and suggest that even the best-supported short-term controls of biogeochemical processes might not predict long-term controls.

Deciphering Nature’s Secret of Seaweed Extract as a Biostimulant on Horticultural Crops: A Review

Seaweed extracts have gained significant attention in horticultural practices due to their diverse range of beneficial effects on plant growth, development, and stress tolerance. The presence of antioxidants and Osm-protectants in seaweed extracts helps mitigate oxidative damage and maintain cellular integrity under adverse conditions. It also holds great promise as a valuable input in horticultural systems, offering a range of benefits including enhanced soil health, and sustainability. This review aims to summarize and analyze the benefits of seaweed extract application on horticultural crops. The extracts derived from seaweed are rich in essential nutrients which are available from through which plants can absorb easily and promote growth. It also contains numerous bioactive compounds including cytokinins, auxins, gibberellins, and betaines, which act as plant growth regulators. The application of seaweed extracts can induce systemic acquired resistance (SAR) in plants, triggering defense mechanisms against pathogens and pests, which can reduce the need for synthetic pesticides and fungicides, promoting sustainable and environmentally friendly horticultural practices. In addition to its direct effects on plants, seaweed extract enhances soil health and microbial activity. It serves as a natural biostimulant, promoting beneficial microbial populations in the rhizosphere, which facilitate nutrient uptake and cycling. Moreover, the humic substances present in seaweed extract contribute to soil structure improvement, water retention, and nutrient availability, fostering a conducive environment for plant growth.

Machine learning and metagenomics identifies uncharacterized taxa inferred to drive biogeochemical cycles in a subtropical hypereutrophic estuary

Abstract Anthropogenic influences have drastically increased nutrient concentrations in many estuaries globally, and microbial communities have adapted to the resulting hypereutrophic ecosystems. However, our knowledge of the dominant microbial taxa and their potential functions in these ecosystems has remained sparse. Here, we study prokaryotic community dynamics in a temporal–spatial dataset, from a subtropical hypereutrophic estuary. Screening 54 water samples across brackish to marine sites revealed that nutrient concentrations and salinity best explained spatial community variations, whereas temperature and dissolved oxygen likely drive seasonal shifts. By combining short and long read sequencing data, we recovered 2459 metagenome-assembled genomes (MAGs), proposed new taxon names for previously uncharacterised lineages, and created an extensive, habitat specific genome reference database. Community profiling based on this genome reference database revealed a diverse prokaryotic community comprising 61 bacterial and 18 archaeal phyla, and resulted in an improved taxonomic resolution at lower ranks down to genus level. We found that the vast majority (61 out of 73) of abundant genus level taxa (>1% average) represented unnamed and novel lineages, and that all genera could be clearly separated into brackish and marine ecotypes with inferred habitat specific functions. Applying supervised machine learning and metabolic reconstruction, we identified several microbial indicator taxa responding directly or indirectly to elevated nitrate and total phosphorus concentrations. In conclusion, our analysis highlights the importance of improved taxonomic resolution, sheds light on the role of previously uncharacterised lineages in estuarine nutrient cycling, and identifies microbial indicators for nutrient levels crucial in estuary health assessments.

Optimal control on ABC fractal fractional order model of micro-plastic pollution in soil and its effect on the nutrient cycle

Micro-plastic pollution is the major ultimatum to contaminate agricultural soils and empirical situation to lessening the soil quality and fertility. In this work the soil pollution due to micro-plastic in the Atangana-Baleanu-Caputo fractal dimension and fractional order inquiry with four compartments namely, Microplastic (P(t)), Soil pollution (S(t)), Remediate or recycling (R(t)) and Soil Nutrients cycle (N(t)). The qualitative analysis of the steady states is explained as locally stable, globally stable and Hyer Ulam stable. The expected equilibrium point appears in a pollution-free equilibrium point and pollution-extinct equilibrium point. Two significant best control strategies (u1(t) and u2(t)) are found to reduce soil pollution. Sensitivity analyses bring off the nature of various deportment of Basic reproduction numbers. Numerical approximation extracted with the help of Newton's Polynomial method. The purpose of precise expected results is demonstrated as a numerical simulation for various orders (0≤α≤0.6) and dimensions.

Soil microbial community responses to long-term experimental warming in an alpine Dryas octopetala heath in Norway

Over the last century, high-altitude and high-latitude regions have experienced global warming at rates higher than the worldwide average. Climate change influences complex soil-microbe-plant-atmosphere interactions, leading to changes in plant-associated soil microbial diversity and functioning and alterations in nutrient cycling, carbon fluxes, and storage. This study analyzed how two decades of global warming simulated by open-top chambers (OTCs) affected soil bacterial and fungal communities in an alpine dwarf-shrub heath dominated by Dryas octopetala in Norway. We collected soil samples from 10 OTCs and 10 control plots and compared their physicochemical properties, microbial biomass, extracellular enzyme activities, and bacterial and fungal community diversity and composition. Warming did not significantly affect the bacterial community despite the tendency to reduce alpha diversity and increase the degree of specialisation. In contrast, two decades of warming significantly affected fungal community composition, which was dominated by ectomycorrhizal Basidiomycota. While there was no significant effect on the total fungal community diversity, a significant shift in saprotrophic Ascomycota taxa was observed between the warmed and control plots. Their positive correlations with oxidative enzymes and fungal biomass suggest that long-term warming might lead to an increase in fungal biomass and the activity of oxidative enzymes, promoting the decomposition of more recalcitrant biopolymers. This may result in an increase in CO2 flux into the atmosphere and a decrease in ecosystem C storage.