Influence of Functional Traits of Dominant Species of Different Life Forms and Plant Communities on Ecological Stoichiometric Traits in Karst Landscapes.

Assessing the functional traits and ecological stoichiometric characteristics of dominant species across different life forms within plant communities in karst environments and investigating the inherent connection between them can provide insights into how species adjust their functional attributes in response to habitat heterogeneity. This approach offers a more comprehensive understanding of ecosystem processes and functions in contrast to examination of the taxonomic diversity of species. This study examines the relationship between the functional characteristics of dominant species in plant communities of various life forms in karst environments, focusing on deciduous leaf-soil ecological stoichiometry. The investigation relies on community science surveys, as well as the determination and calculation of plant functional traits and ecological stoichiometries, in plant communities of various life forms in Guizhou (a province of China). The findings of our study revealed considerable variability in the functional trait characteristics of dominant species across different plant-community life forms. Specifically, strong positive correlations were observed among plant height (PLH), leaf area (LA), leaf dry matter content (LDMC), and specific leaf area (SLA) in the dominant species. Additionally, our results indicated no significant differences in leaf ecological stoichiometry among different life forms. However, we did observe significant differences and strong positive correlations between soil N:P, withered material C:N, and apomictic C:P. Furthermore, our study found that plant height (PLH), leaf area (LA), and specific leaf area (SLA) were particularly sensitive to the ecological stoichiometry of soil and apomixis. The results of our study suggest that the functional traits of diverse plant-community life forms in karst regions are capable of adapting to environmental changes through various expressions and survival strategies. The development of various plant-community life forms in karst areas is particularly vulnerable to phosphorus limitation, and the potential for litter decomposition and soil nutrient mineralization is comparatively weaker. The functional traits of various plant-community life forms in karst regions exhibit greater sensitivity to both the soil's C:N ratio and the C:N ratio of apomictic material. Habitat variations may influence the ecological stoichiometric characteristics of the plant leaf-apomictic soil continuum.

Response of soil-microbe-extracellular enzyme stoichiometric characteristics to nitrogen deposition in a Pinus yunnanensis forest in central Yunnan Province, Southwest China.

To understand the effects of nitrogen deposition on element cycling and nutrient limitation status in forest ecosystems, we examined the effects of nitrogen deposition on the stoichiometric characteristics of forest soil-microbial-extracellular enzymes in Pinus yunnanensis forest. We conducted a field experiment with control (CK, 0 g N·m-2·a-1), low nitrogen (LN, 10 g N·m-2·a-1), medium nitrogen (MN, 20 g N·m-2·a-1) and high nitrogen (HN, 25 g N·m-2·a-1) since 2019. We collected soil samples (0-5 cm, 5-10 cm and 10-20 cm) at September 2022, and measured the contents of soil organic, total nitrogen, total phosphorus, microbial biomass carbon, nitrogen and phosphorus (MBC, MBN, MBP) and the activities of C, N, and P acquisition enzymes. The results showed that nitrogen deposition significantly reduced soil organic content, C:N and C:P by 6.9%-29.8%, 7.6%-45.2% and 6.5%-28.6%, and increased soil total N content and N:P by 10.0%-45.0% and 19.0%-46.0%, respectively. Nitrogen addition did not affect soil total P content. Except for soil C:N and C:P, soil nutrient content and stoichiometric ratio were highest in 0-5 cm soil layer. MN and HN treatments significantly decreased MBN by 11.0%-12.7%. MBC, MBP, and their stoichiometry did not change significantly under nitrogen deposition. Soil microbial nutrient content in 0-5 cm soil layer was significantly higher than that in other soil layers. Nitrogen deposition significantly decreased the activities of cellobiose hydrolase and leucine aminopeptidase (decreased by 14.5%-16.2% and 48.7%-66.3%). HN treatment promoted ß-1,4-glucosidase activity (increased by 68.0%), but inhibited soil enzyme stoichiometric carbon to nitrogen ratio and nitrogen to phosphorus ratio (decreased by 95.4% and 88.4%). LN and MN treatment promoted ß-1,4-N-acetylglucosaminidase activity (increased by 68.3%-116.6%), but inhibited enzyme stoichiometric carbon to phosphorus ratio (decreased by 14.9%-29.4%). Alkaline phosphatase activity had no significant change. Soil enzyme activities were significantly decreased with increasing soil depth. Soil total N and total P and microbial nutrients were negatively correlated with vector angle (representing microbial nitrogen or phosphorus limitation), while vector length (representing microbial carbon limitation) was consistently significantly positively correlated with vector angle, suggesting the synergistic promotion between microbial carbon limitation and phosphorus limitation. Nitrogen deposition gradually shifted to phosphorus limitation while alleviating microbial nitrogen limitation in P. yunnanensis forest. In addition, microbial activities in this region was limited by C availability, and the relationship between microbial C and P limitation was proportional.

Effects of migratory birds activities on the stoichiometry of soil carbon, nitrogen and phosphorus in a Carex-dominated wetland of Poyang Lake.

Studying the stoichiometric characteristics of soil nutrients aids in evaluating soil quality and deciphering the coupling of soil nutrients. The influence of migratory bird activities on the dynamics of wetland soil nutrients and their stoichiometric remains unclear. We classified the central, peripheral and adjacent natural grassy areas as severe, mild, and no bird activity (control), respectively, in Donghu Carex meadow, a representative migratory bird habitat in Poyang Lake, based on flock characteristics and initial surveys. We analyzed the contents and stoichio-metry of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) across soil depths of 0-100 cm under different intensities of migratory bird activities. The results showed that the activities of migratory birds significantly impacted nutrient levels exclusively within 0-30 cm soil. Mild activities markedly enhanced SOC and TN across 0-30 cm soil, while both mild and severe activities significantly raised TP within the same depth. For the 0-100 cm soil profiles, soil C/N ratios were 10.0, 10.8, and 9.9, C/P ratios were 23.5, 30.0, and 22.7, and N/P ratios were 2.3, 2.7, and 2.3 under no, mild, and severe bird activities, respectively. Further, mild activities of migratory birds significantly increased soil C/N, C/P and N/P ratios only within the 0-30 cm depth, while the stoichiometric ratios of all soil layer had no significant difference under severe bird activity. Soil stoichiometric ratios strongly correlated with physicochemical properties. SOC, TN, and TP primarily mediated the effects of migratory bird activity on soil carbon, nitrogen, and phosphorus stoichiometric ratios in Poyang Lake wetland. In conclusion, the influence of migratory bird activity on the stoichiometric ratios of soil carbon, nitrogen, and phosphorus in Poyang Lake wetland exhibited depth threshold (approximately 30 cm), aligning with the "Intermediate Distur-bance Hypothesis". These findings could provide a new perspective for the protection of wetlands and migratory birds.

Shading and Water Addition Alleviate the Elemental Limitations of the Early Restoration Community in a Stressful Environment.

Shading and water addition are essential management measures to improve seed germination and early seedling survival; however, little is known about their effects on leaf stoichiometry and nutrient status. We established 90 plant communities with shading and water addition gradients on a rocky hill; leaves of their dominant woody plant species were collected to measure elemental concentrations, and then, stoichiometric variation and nutrient status were analysed. The results showed that the overall effects of shading and water addition significantly altered the concentrations and ratios of nutrient elements; shading largely affected leaf K and P, while water addition mainly affected leaf N and P. The interactions between shading and water addition were significant for most species but disappeared at the community level. Consequently, the nutrient status in leaves was improved by promoting the concentrations and balances of nutrient elements. However, the responses to shading and water addition were marked by species-specific differences, with some plants forming a sensitive group and others distinguished by conservatism. Our findings show that management of the physical environment could improve nutrient element utilization in leaves and alleviate the nutrient limitations. For our site conditions, mild shading (25-35%) and adequate water addition (30 L·m-2) in the early stage of vegetation restoration is recommended to advance community assembly by improving nutrient physiology, directly diminishing the stress of water scarcity and excessive irradiation. These findings explore the underlying mechanisms of shading and water addition that could promote community development and provide guidance for restoration practice.

Effects of exogenous calcium additions on the ecological stoichiometric characteristics of various organs and soil nutrients and their internal stability in Pinus tabuliformis.

Introduction: Pinus tabuliformis as a crucial afforestation species in semi-arid regions, faces issues such as the reduction of plantations. Calcium plays a significant role in alleviating drought stress and promoting nutrient uptake in plants. Methods: Utilizing a pot experiment approach, seedlings were treated with exogenous calcium at five concentrations (0, 50, 100, 200, and 400 mg•kg-1). The nutrient content of the plants and soil was measured, and their ecological stoichiometric characteristics and internal stability were analyzed. This was followed by a series of related studies. Results: As the concentration of calcium increases, the contents of carbon, nitrogen, phosphorus, and potassium in various organs and the whole plant exhibit a trend of first increasing and then decreasing, peaking at calcium treatment of 50-100 mg•kg-1. Concurrently, the calcium concentration in plant organs and the entire plant gradually increases with the availability of calcium in the soil. The addition of exogenous calcium has a certain impact on the ecological stoichiometric ratios (C:N, C:P, N:P) of Pinus tabuliformis seedlings' leaves, stems, roots, and the whole plant, exhibiting distinct variation characteristics. At calcium concentrations of 50-100 mg•kg-1, the ratios of C:N and C:P are relatively lower. Under calcium concentrations of 0, 50, and 100 mg•kg-1, soil calcium shows a positive correlation with the total carbon (TC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), and calcium contents in leaves, stems, roots, and the entire plant. However, at calcium concentrations of 200 and 400 mg•kg-1, soil calcium exhibits a significant positive correlation with the calcium content in leaves, stems, roots, and the entire plant, and a significant negative correlation with the total phosphorus, total nitrogen, total phosphorus, and total potassium contents. After the addition of exogenous calcium at different concentrations, most stoichiometric indices of various organs of Pinus tabuliformis seedlings demonstrate strong balance. Discussion: Calcium, as an essential structural component and second messenger, regulates the nutrient uptake and utilization in plants, influencing the stoichiometry. However, both low and high concentrations of calcium can be detrimental to plant growth by disrupting nutrient metabolism and internal structures. Consequently, there exists an optimal calcium concentration for nutrient absorption.

The Critical Role of Soil Ecological Stoichiometric Ratios: How Does Reforestation Improve Soil Nitrogen and Phosphorus Availability?

The ecological stoichiometric characteristics of soil elements have greatly enhanced our understanding of the circulation of soil nutrients. However, there is limited knowledge regarding the alteration of carbon, nitrogen, and phosphorus stoichiometric ratios in deep soil after afforestation. To examine the variations in stoichiometric ratios of soil elements with different vegetation types, restoration times, and soil depths, we collected soil samples from grassland, Caragana korshinskii shrubland, and Picea asperata forestland at different stand ages (10a, 25a, and 40a) in Xining City, which is located on the Loess Plateau. Our results showed that, at 25a, the carbon-to-nitrogen (C:N) and carbon-to-phosphorus (C:P) ratios were significantly higher in the grassland soil than under other vegetation types, whereas the nitrogen-to-phosphorus (N:P) ratio had no significant difference among the three vegetation types. At 40a, the ratios of soil C:N, C:P, and N:P in the shrubland were the highest. With the increasing of the restoration time, the ratios of soil C:N, C:P, and N:P in grassland with 25a became higher than for 40a or 10a. The ratios in the shrubland were highest at 40a, followed by 25a and then 10a, while the ratios in the forestland showed no significant difference. At 40a, the soil C:N, C:P, and N:P ratios of shrubland were highest at the soil depth of 40-100 cm. The soil C:N, C:P, and N:P ratios showed positive correlations with soil ammonium nitrogen and nitrate nitrogen, and the soil N:P ratios showed a negative correlation with soil available phosphorus. Plant diversity significantly influenced the soil stoichiometric ratio of the upper soil layer. In the upper soil layer (0-40 cm), species richness showed a positive correlation with soil C:N, C:P, and N:P ratios, and the Margalef index exhibited a positive correlation with soil C:N and C:P ratios. The results of this study indicate that the stoichiometric ratio and nutrient availability of Caragana korshinskii shrubland were the highest over time. Therefore, these findings can be served as a valuable reference for local revegetation and ecological restoration.

Stoichiometric theory in aquatic carbon sequestration under elevated carbon dioxide.

Global climate change projections indicate that the atmospheric concentration of carbon dioxide will increase twofold by the end of this century. However, how the elevated carbon dioxide affects aquatic carbon sequestration and species composition within aquatic microbial communities remains inconclusive. To address this knowledge gap, we formulate a bacteria-algae interaction model to characterize the effects of elevated carbon dioxide on aquatic ecosystems and rigorously derive the thresholds determining the persistence and extinction of algae or bacteria. We explore the impacts of abiotic factors, such as light intensity, nutrient concentration, inorganic carbon concentration and water depth, on algae and bacteria dynamics. The main findings indicate that the elevated atmospheric carbon dioxide will increase algae biomass and thus facilitate carbon sequestration. On the other hand, the elevated atmospheric carbon dioxide will reduce bacterial biomass, and excessive carbon dioxide concentrations can even destroy bacterial communities. Numerical simulations indicate that eutrophication and intensified light intensity can reduce aquatic carbon sequestration, while elevated atmospheric carbon dioxide levels can mitigate eutrophication. Furthermore, higher algae respiration and death rates are detrimental to carbon sequestration, whereas the increased bacterial respiration rates promote carbon sequestration.

Plant traits regulated metal(loid)s in dominant herbs in an antimony mining area of the karst zone, China.

Understanding how plant functional traits respond to mining activities and impact metal(loid)s accumulation in dominant species is crucial for exploring the driving mechanisms behind plant community succession and predicting the ecological restoration potential of these plants. In this study, we investigated four dominant herbaceous species (Artemisia argyi, Miscanthus sinensis, Ficus tikoua, and Ageratina adenophora) growing on antimony (Sb) mining sites (MS) with high Sb and arsenic (As) levels, as well as non-mining sites (NMS). The aim was to analyze the variations in functional traits and their contribution to Sb and As concentrations in plants. Our results indicate that mining activities enhanced soil nitrogen (N) limitation and phosphorus (P) enrichment, while significantly reducing the plant height of three species, except for F. tikoua. The four species absorbed more calcium (Ca) to ensure higher tolerance to Sb and As levels, which is related to the activation of Ca signaling pathways and defense mechanisms. Furthermore, plant Sb and As concentrations were dependent on soil metal(loid) levels and plant element stoichiometry. Overall, these findings highlight the regulatory role of plant element traits in metal(loid) concentrations, warranting widespread attention and further study in the future.

Response of ecological stoichiometry and homeostasis characteristic to nitrogen addition in Hippophae rhamnoides L.

Nitrogen (N) in the atmosphere frequently affects plant growth, ecological stoichiometric equilibrium, and homeostasis stability. However, the effect of N addition application on the growth of Hippophae rhamnoides seedlings remains ambiguous. We investigated the effects of N addition on the ecological stoichiometry and homeostatic characteristics of H. rhamnoides seedlings. Greenhouse cultivation experiments were conducted at five N application levels: 0 kg ha-1 yr-1(CK), 100 kg ha-1 yr-1 (N10), 200 kg ha-1 yr-1 (N20), 400 kg ha-1 yr-1 (N40), 800 kg ha-1 yr-1 (N80). The results showed that pH and available phosphorus (AP) significantly decreased with increasing N, whereas soil C:P and N:P ratios significantly increased under the N40 and N80 treatments. The leaf C:N ratio significantly decreased with increasing N, whereas the N:P ratio increased. With N addition, the C:N ratio of plant stems and roots significantly decreased, whereas the C:P and N:P ratios significantly increased. N addition was significantly correlated with the ecological stoichiometry of plant leaves and soil properties (0.38 and 0.84, respectively). Homeostasis of the organs of H. rhamnoides seedlings exhibited an absolute steady state. The C, N, and C:P ratios of the roots exhibited insensitive states under the N40 treatment. N addition significantly modified both the soil ecological stoichiometry and the stoichiometry of H. rhamnoides seedlings. However, it did not demonstrate a pronounced negative effect on the homeostasis of H. rhamnoides seedlings. This study offers new insights into the ecological adaptation process of H. rhamnoides, particularly concerning its nutrient distribution, utilization strategies, and stability.

Effects of fertilization on soil ecological stoichiometry and fruit quality in Karst pitaya orchard.

Pitaya (Hylocereus undulatus) is a significant cash crop in the karst region of Southwest China. Ecological stoichiometry is an essential method to research biogeochemical cycles and limiting elements. The purpose of this study was to explore the stoichiometric characteristics of C, N, and P in Karst pitaya orchards and fruit quality and to elucidate the mechanism and process of nutrient cycling. The results showed that: (1) Fruit quality was highest under the combination of chemical and organic fertilizers. Compared to the control, the contents of per-fruit weight, vitamin C, and soluble sugar increased significantly by 55.5%, 60.7%, and 23.0%, respectively, while the content of titratable acidity decreased significantly by 22.0%. (2) The content of soil nutrients under fertilization stress showed a downward trend in general, as did microbial biomass and extracellular enzyme activities. (3) Different fertilization treatments significantly affected the soil-microbial stoichiometry C:N ratio, C:P ratio, with research areas being significantly limited by C and P. (4) Spearman and PLS-SEM (partial least squares-structural equation model) analysis results showed that under the influence of fertilization, there was a significant positive effect between microorganisms and soil nutrients, but a significant negative effect between soil nutrients and quality. The results of this study offer an innovative perspective on pitaya quality research in Karst areas.

Leaf carbon, nitrogen, and phosphorus ecological stoichiometry of grassland ecosystems along 2,600-m altitude gradients at the Northern slope of the Tianshan Mountains.

Ecological stoichiometry of terrestrial ecosystems has been a hot issue in current research, with intense focus on the proportional relationships of nutritional elements within plants and between plants and their environment. To clarify these relationships along continuous environmental gradients is essential for a more comprehensive understanding how plants adapt to a changing environment. In arid regions, the varying plant and soil types along altitude gradients offer a unique opportunity to examine the vertical spectrum of plant and soil ecological stoichiometry. In this study, the northern slope of the Tianshan Mountains was selected as the study area to explore the carbon (C), nitrogen (N), and phosphorus (P) ecological stoichiometric characteristics of herbaceous plants along 900-m-3,500-m altitude gradients. We also investigated the variation of ecological stoichiometric characteristics among different grassland types. The results indicated that the mean C, N, and P in leaf of grassland were 342.95 g·kg-1-557.73 g·kg-1, 6.02 g·kg-1-20.97 g·kg-1, and 0.71 g·kg-1-3.14 g·kg-1, respectively. There was no significant change in leaf carbon content along the elevation gradient, and the highest and lowest leaf C concentrations were in the upland meadow and the semidesert grasslands. Both N and P concentrations obtained their highest value in the meadow steppe. The P concentration gradually increased in desert and semidesert grasslands and reached the highest value in the meadow steppe, and then decreased to the lowest value in the upland meadow and subsequently increased in the alpine meadow. The ranges of the C:N ratio, C:P ratio, and N:P ratio were 16.36-155.53, 109.36-786.52, and 2.58-17.34, respectively. Due to fluctuations in the P concentration, the C:P ratio and N:P ratio reached the lowest value in the meadow steppe and obtained their highest value in the upland meadow. Redundancy analysis showed that temperature was the dominant factor affecting the C, N, and P ecological stoichiometry of herbaceous plants, followed by soil organic carbon, mean annual precipitation, soil pH, and soil electrical conductivity. Corresponding results could enhance predictive models of nutrient cycling and ecosystem responses to climate change, particularly in arid and semiarid regions.

Global leaf sulfur stoichiometry and the relationships with nitrogen and phosphorus: phylogeny, growth form and environmental controls.

Sulfur (S) is an essential bioelement with vital roles in serving regulatory and catalytic functions and tightly coupled with N and P in plants. However, globally stoichiometric patterns of leaf S and its relationships to leaf N and P are less well studied. We compiled 31 939 records of leaf-based data for 2600 plant species across 6652 sites worldwide. All plant species were divided into different phylogenetic taxa and growth forms. Standard major axis analysis was employed to fit the bivariate element relationships. A phylogenetic linear mixed-effect model and a multiple-regression model were used to partition the variations of bioelements into phylogeny and environments, and then to estimate the importance of environmental variables. Global geometric mean leaf S, N and P concentrations were 1.44, 15.70 and 1.27 mg g-1, respectively, with significant differences among plant groups. Leaf S-N-P positively correlated with each other, ignoring plant groups. The scaling exponents of LN-LS, LP-LS and LN-LP were 0.64, 0.76 and 0.79, respectively, for all species, but differed among plant groups. Both phylogeny and environments regulated the bioelements. The variability, rather than mean temperature, controlled the bioelements. Phylogeny explained more for the concentrations of all the three bioelements than environments, of which S was the one most affected by phylogenetic taxa.

Temporal Variations in Aboveground Biomass, Nutrient Content, and Ecological Stoichiometry in Young and Middle-Aged Stands of Chinese Fir Forests.

Understanding the ecological dynamics of forest ecosystems, particularly the influence of forest age structure on soil carbon (C), nitrogen (N), and phosphorus (P) content, is crucial for effective forest management and conservation. This study aimed to investigate the nutrient storage and ecological stoichiometry across different-aged stands of Chinese fir forests. Soil samples were collected from various depths (0-15 cm, 15-30 cm, and 30-45 cm) across four age groups of Chinese fir forests (8-year-old, 12-year-old, 20-year-old, and 25-year-old) in the Forest Farm, Pingjiang County, China. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were measured, and their stoichiometries were calculated. The results showed that both individual tree biomass and stand biomass, along with SOC, TN, and TP content, increased with stand age, highlighting the significant importance of stand age on biomass production and nutrient accumulation in forests. Specifically, soil C and P contents significantly increased as the forest aged, while variation in N content was relatively minor. Soil C/N and C/P ratios exhibited variation corresponding to forest age, suggesting alterations in the ecological stoichiometry characteristics of the forests over time. These findings are crucial for understanding the dynamics of ecosystem functioning and nutrient cycling within Chinese fir forests and provide a solid scientific basis for the effective management and conservation of these vital forest ecosystems.

Riparian plant-soil-microbial C:N:P stoichiometry: are they conserved at plant functional group level?

As a consequence of the tight linkages between plants, soil, and microorganisms, we hypothesized the variations in plant species would change soil and microbial stoichiometry. Here, we examined the plant leaf carbon (C):nitrogen (N):phosphorus (P) ratios of nine species coming from three plant functional groups (PFGs) in the riparian zones of Hulunbuir steppe during near-peak biomass. The soil C:N:P, microbial biomass carbon (MBC):microbial biomass nitrogen (MBN), and extracellular enzyme's C:N:P were also assessed using the soils from each species. We found that plant tissue, soil nutrient, microbial, and enzyme activity stoichiometry significantly differed among different PFGs. Plant leaf and soil nutrient ratios tended to be similar (p > 0.05) between different species within the same PFGs. The variations in leaf C:N:P significantly correlated with the changes in soil C:N:P and MBC:MBN ratios. The homeostatic coefficients (H) < 1 suggested the relationships between plants and their resources C:N:P ratios might be non-homeostatic in the examined riparian zone. By assessing plant tissue and its soil nutrient stoichiometry, this study provided a perspective to understand the linkages of plant community, soil nutrient, and microbial characteristics.

Postfire Phosphorus Enrichment Mitigates Nitrogen Loss in Boreal Forests.

Net nitrogen mineralization (Nmin) and nitrification regulate soil N availability and loss after severe wildfires in boreal forests experiencing slow vegetation recovery. Yet, how microorganisms respond to postfire phosphorus (P) enrichment to alter soil N transformations remains unclear in N-limited boreal forests. Here, we investigated postfire N-P interactions using an intensive regional-scale sampling of 17 boreal forests in the Greater Khingan Mountains (Inner Mongolia-China), a laboratory P-addition incubation, and a continental-scale meta-analysis. We found that postfire soils had an increased risk of N loss by accelerated Nmin and nitrification along with low plant N demand, especially during the early vegetation recovery period. The postfire N/P imbalance created by P enrichment acts as a "N retention" strategy by inhibiting Nmin but not nitrification in boreal forests. This strategy is attributed to enhanced microbial N-use efficiency and N immobilization. Importantly, our meta-analysis found that there was a greater risk of N loss in boreal forest soils after fires than in other climatic zones, which was consistent with our results from the 17 soils in the Greater Khingan Mountains. These findings demonstrate that postfire N-P interactions play an essential role in mitigating N limitation and maintaining nutrient balance in boreal forests.

Theory of Stoichiometric Intraguild Predation: Algae, Ciliate, and Daphnia.

Consumers respond differently to external nutrient changes than producers, resulting in a mismatch in elemental composition between them and potentially having a significant impact on their interactions. To explore the responses of herbivores and omnivores to changes in elemental composition in producers, we develop a novel stoichiometric model with an intraguild predation structure. The model is validated using experimental data, and the results show that our model can well capture the growth dynamics of these three species. Theoretical and numerical analyses reveal that the model exhibits complex dynamics, including chaotic-like oscillations and multiple types of bifurcations, and undergoes long transients and regime shifts. Under moderate light intensity and phosphate concentration, these three species can coexist. However, when the light intensity is high or the phosphate concentration is low, the energy enrichment paradox occurs, leading to the extinction of ciliate and Daphnia. Furthermore, if phosphate is sufficient, the competitive effect of ciliate and Daphnia on algae will be dominant, leading to competitive exclusion. Notably, when the phosphorus-to-carbon ratio of ciliate is in a suitable range, the energy enrichment paradox can be avoided, thus promoting the coexistence of species. These findings contribute to a deeper understanding of species coexistence and biodiversity.

Fish stocks as phosphorus sources or sinks: Influenced by nutritional and metabolic variations, not solely by dietary content and stoichiometry.

The study provides a descriptive understanding of when fish (Cyprinus carpio model) are the source or sink of phosphorus. Dissolved reactive phosphorus (DRP; PO4-P) losses (51.1 ± 5.9 % of intake-P) increase at excess of bioavailable P (>0.83 g 100 g-1 dry matter, DM fed) or when food (digestible) N:P mass ratio (≤4.4:1) approaches organismal storage threshold (~4:1). This is known, however, even at a sub-threshold food P content (0.57 g 100 g-1 DM) and food N:P mass ratio (7.3:1), DRP losses (57.8 ± 4.5 % of intake-P) may be extraordinary if two indispensable amino acids are biologically insufficient (lysine ≤1.43 g, methionine ≤0.39 g 100 g-1 DM fed). Given that methionine and lysine are sufficient, DRP losses cease (≈0 %) and even some P from water is absorbed, given there is support from non-protein energy (NPE). Insufficient NPE (<180 kcal 100 g-1 DM fed) may drive DRP losses (81.6 ± 4.3 % of intake-P) beyond expected levels (46-59 % of intake-P) at a given food P content (0.91 g 100 g-1 DM). Natural food seldom fulfills low P, high lysine + methionine, and high NPE contents simultaneously, thus keeping fish in a perpetual P recycling for algae (scaleless carp > scaly carp). Such P recycling ceases only during basal metabolism. During feeding state, the richness of lysine + methionine bound N and lipid + carbohydrate bound C in the food base may enhance the fishes' threshold of P storage. P storage can be diminished when they are insufficient. We show that for fish, the decision of P recycling or not recycling (for algae) may change based on the supply of specific fractions of N or C from the food web or metabolic variations (basal metabolism, presence of scales). NOVELTY STATEMENT: The ecological stoichiometry theory is better connected to fish nutritional bioenergetics for better understanding and biomanipulation of eutrophication processes.

Divvying up the pie: Tissue nutrient content is related to its parasite load.

The nutrient content of host resources can influence the abundance of parasites within an ecosystem, but linking specific nutrients in a host to the abundance of different parasite taxa remains a challenge. Here, we work to forge this link by quantifying the relationship between the nutrient content of specific infection sites and the abundance of multiple parasite taxa within the digestive tract of largemouth bass (Micropterus salmoides) collected from the Mississippi River. To generate a mechanistic understanding of these relationships, we tested four basic predictions: (1) the nutrient content of different host tissues (infection sites) varies within and across hosts, (2) the nutrient content of parasite genera differs from that of their host tissue(s), (3) the nutrient content of parasite genera differ from one another and (4) the nutrient content of host tissues is related to the nutrient content and abundance of parasite genera. We found support for each of these predictions. We found stoichiometric differences between the digestive tissues we examined. We also found that across hosts, intestine and pyloric caeca C:N ratios increased and %N decreased with fish condition factor. Both of the actively feeding parasitic genera we measured had lower C:N ratios compared to both their host tissue and other encysted/non-reproductive genera, suggesting the potential for N limitation of these parasites in the intestines or pyloric caeca of hosts. Consistent with this possibility, we found that the total number of actively feeding parasitic worms in the pyloric caeca increased with that tissue's N:P ratio (but was not related to host condition factor). Our results suggest that parasites encounter significant variation in nutrient content within and across hosts and that this variation may influence the abundance of actively feeding parasites. This work highlights the need for additional empirical comparisons of parasite stoichiometry across tissues and individual hosts.

Deciphering the crop-soil-enzyme C:N:P stoichiometry nexus: A 5-year study on manure-induced changes in soil phosphorus transformation and release risk.

Carbon:nitrogen:phosphorus (C:N:P) stoichiometry plays a vital role in regulating P transformation in agriculture ecosystems. However, the impact of balanced C:N:P stoichiometry in paddy soil, particularly regarding relative soil P transformation, remains unknown. This study explores the response of C:N:P stoichiometry to manure substitution and its regulatory role in soil P transformation, along with the associated release risk to the environment. Based on a 5-year field study, our findings reveal that replacing 30 % of chemical P fertilizer with pig manure (equal total NPK amounts with chemical P fertilizer treatment, named CFM) increased soil total C without altering soil total P, resulting in an elevated soil C:P ratio, despite the homeostasis of crop stoichiometry. This increase promoted microbial diversity and the accumulation of organic P in the soil. The Proteobacteria and Actinobacteria produced lower C:PEEA metabolism together, and enhanced in vivo turnover of P. Additionally, by integrating high-resolution dialysis (HR-Peeper), diffusive gradients in thin films (DGT), DGT-induced fluxes in the soil (DIFS), and sediment P release risk index (SPRRI) models, we observed that, in addition to organic P, CFM simultaneously increased soil Al-P, thereby weakening the diffusion and resupply capacity of P from soil solids to the solution. Consequently, this decrease in P release risk to the environment was demonstrated. Overall, this study establishes a connection between crop-soil-enzyme C:N:P stoichiometry, soil microorganisms, and soil P biogeochemical processes. The study further evaluates the P release risk to the environment, providing a novel perspective on both the direct and indirect effects of manure substitution on soil P cycling.

Understanding stoichiometric constraints on growth using resource use efficiency imbalances.

Growth is a function of the net accrual of resources by an organism. Energy and elemental contents of organisms are dynamically linked through their uptake and allocation to biomass production, yet we lack a full understanding of how these dynamics regulate growth rate. Here, we develop a multivariate imbalance framework, the growth efficiency hypothesis, linking organismal resource contents to growth and metabolic use efficiencies, and demonstrate its effectiveness in predicting consumer growth rates under elemental and food quantity limitation. The relative proportions of carbon (%C), nitrogen (%N), phosphorus (%P), and adenosine triphosphate (%ATP) in consumers differed markedly across resource limitation treatments. Differences in their resource composition were linked to systematic changes in stoichiometric use efficiencies, which served to maintain relatively consistent relationships between elemental and ATP content in consumer tissues and optimize biomass production. Overall, these adjustments were quantitatively linked to growth, enabling highly accurate predictions of consumer growth rates.