Nutrient Distribution Patterns Research Articles

The Contrasting Role of Marine- and Land-Terminating Glaciers on Biogeochemical Cycles in Kongsfjorden, Svalbard.

This case study of Kongsfjorden, western coastal Svalbard, provides insights on how freshwater runoff from marine- and land-terminating glaciers influences the biogeochemical cycles and distribution patterns of carbon, nutrients, and trace elements in an Arctic fjord system. We collected samples from the water column at stations along the fjord axis and proglacial river catchments, and analyzed concentrations of dissolved trace elements, together with dissolved nutrients, as well as alkalinity and dissolved inorganic carbon. Statistical tools were applied to identify and quantify biogeochemical processes within the fjord that govern the constituent distributions. Our results suggest that the glacier type affects nutrient availability and, therefore, primary production. Glacial discharge from both marine-terminating glaciers and riverine discharge from land-terminating glaciers are important sources of dissolved trace elements (dAl, dMn, dCo, dNi, dCu, and dPb) that are involved in biological and scavenging processes within marine systems. We identified benthic fluxes across the sediment-water interface to supply fjord waters with silicate, dFe, dCu, and dZn. Our data show that intensive carbonate weathering in proglacial catchments supplies fjord waters with additional dissolved carbonates and, therefore, attenuates reduced buffering capacities caused by glacial runoff. Our study provides valuable insight into biogeochemical processes and carbon cycling within a climate-sensitive, high-latitude fjord region, which may help predict Arctic ecosystem changes in the future.

Nutrient Distribution Patterns in Soil Across Various Locations in Muzaffarnagar and Ghaziabad Districts of Uttar Pradesh under a Rice-Sugarcane Cropping Sequence

A study was conducted to evaluate the macro and micronutrient levels in the soil under the sugarcane-wheat cropping sequence and its relationship with soil characteristics. Understanding the nutrient status is vital for the efficient application of fertilizers, as widespread deficiencies in both macro and micronutrients are being reported in the soils of Uttar Pradesh. The rice-sugarcane cropping sequence is a prominent practice in the northwestern plains of Uttar Pradesh and Uttarakhand, covering 10-11% of the net cultivated area in these regions. Over recent years, sugarcane and wheat yields have plateaued in these areas due to declining factor productivity. Soil samples were collected from depths of 0-15 cm, 15-30 cm, and 30-45 cm at four locations in the Muzaffarnagar and Ghaziabad districts under the rice-sugarcane sequence. The available zinc content in the surface soil (0-15 cm) ranged from 0.605 to 0.883 mg/kg, and in the sub-surface soil (30-45 cm), it varied between 0.111 to 0.629 mg/kg, with an average of 0.083 mg/kg in surface soil and 0.435 mg/kg in sub-surface soil. A correlation analysis between various soil properties across different locations at three soil depths (0-15 cm, 15-30 cm, and 30-45 cm) was also conducted. The findings indicated that the soils are generally low in nitrogen, low to medium in phosphorus and potassium, and sufficiently supplied with copper, iron, manganese, and zinc in the surface layer. Future research on nutrient distribution in these areas will help advance precision agriculture, improve fertilizer management, and boost crop productivity while minimizing environmental harm. This research will contribute to sustainable soil management, economic benefits for farmers, and provide valuable insights for regional agricultural policies, further supporting food security.

Assessment of Vertical Nutrient Stratification in Paddy Cultivating Soils in Vepurikota Microwatershed of Andhra Pradesh, India

A thorough soil investigation was conducted to assess the soil's ability to supply nutrients by examining the vertical nutrient distribution pattern in the pedons of paddy growing areas in the Vepurikota microwatershed in Andhra Pradesh. The results revealed that soils were low in available nitrogen and medium to high in available P2O5, low to high in available K2O and deficient to sufficient in available S. In both the surface and subsurface horizons of every pedon, the DTPA extractable Cu was revealed sufficient in the soils. All pedons in the surface and subsurface horizons had deficient to sufficient amounts of available Zn, while all pedons except pedon 4 had sufficient quantities of available Fe and Mn that were above critical levels.

Heavy metals and nutrients mediate the distribution of soil microbial community in a typical contaminated farmland of South China

The effects of heavy metals on soil microbial communities have been extensively investigated, whereas the combined effects of heavy metals and nutrients on soil microbial communities and their interactions are rarely understood. In this study, we investigated the distribution patterns of heavy metals, nutrients and microbial communities in a typical contaminated farmland and explored their interaction mechanisms. The results showed that Cd and Pb were the main pollutants in this area, which mainly came from the smelter. Canonical correspondence analysis and variance decomposition analysis showed that the heavy metals played a more important role in restraining the microbial community structure of soils than other soil properties. Soil Cd, Pb, pH and available K content were the most important environmental factors affecting the microbial community structures in soil. Major Cd tolerant bacteria and fungi were detected including Actinobacteriota, Gemmatimonadota, Entorrhizomycota and Mortierellomycota. The analyses of molecular ecological networks showed that there were 84.1 % of negative correlations among microorganisms. Cd could regulate the abundance of key nodes in Cd-tolerant network modules, and these key nodes could improve the adaptability of the whole module to heavy metals through competition with other microorganisms. This study provides insights into the ecological effects of heavy metals and nutrients on soil microbial communities and will help to develop the bio-remediation technologies for contaminated soils.

Rhizobox Technology for Sustainable Agriculture–Acquired Implications

Evaluation on the effect of rhizobox technology in the rhizosphre soil of agricultural crops is necessary for sound and safe agriculture. This article confers the rhizobox technology-induced information about rhizosphere so far conducted since 1987s and on. Combined with its special features and construction technique, rhizobox-affected rhizosphere processes like pH changes, patterns of nutrient distribution, heavy metal movement and microbial activities are extensively analyzed. Finally, the established rhizobox model of 1987 encompassing its modified versions are detailed, followed by its potential application in rhizosphere studies of plant nutrition, soil chemistry, and soil biology for sustainable agriculture.

Elucidation of the dominant factors influencing N2O emission in water-level fluctuation zones in a karst canyon reservoir, southwest China

The water-level fluctuations zones (WLFZs) are crucial transitional interfaces within river-reservoir systems, serving as hotspots for N2O emission. However, the comprehension of response patterns and mechanisms governing N2O emission under hydrological fluctuation remains limited, especially in karstic canyon reservoirs, which introduces significant uncertainty to N2O flux assessments. Soil samples were collected from the WLFZs of the Hongjiadu (HJD) Reservoir along the water flow direction from transition zone (T1 and T2) to lacustrine zone (T3, T4 and T5) at three elevations for each site. These soil columns were used to conduct simulation experiments under various water-filled pore space gradients (WFPSs) to investigate the potential N2O flux pattern and elucidate the underlying mechanism. Our results showed that nutrient distribution and N2O flux pattern differed significantly between two zones, with the highest N2O fluxes in the transition zone sites and lacustrine zone sites were found at 75 % and 95 % WFPS, respectively. Soil nutrient loss in lower elevation areas is influenced by prolonged impoundment durations. The higher N2O fluxes in the lacustrine zone can be attributed to increased nutrient levels resulting from anthropogenic activities. Furthermore, correlation analysis revealed that soil bulk density significantly impacted N2O fluxes across all sites, while NO3−and SOC facilitated N2O emissions in T1-T2 and T4-T5, respectively. It was evident that N2O production primarily contributed to nitrification in the transition zone and was constrained by the mineralization process, whereas denitrification dominated in the lacustrine zone. Notably, the annual N2O efflux from WLFZs accounted for 27 % of that from the water-air interface in HJD Reservoir, indicating a considerably lower contribution than anticipated. Nevertheless, this study highlights the significance of WLFZs as a vital potential source of N2O emission, particularly under the influence of anthropogenic activities and high WFPS gradient.

Assessing Shrub Patch Characteristics and Soil Nutrient Distribution Patterns of Four Typical Alpine Shrub Plants in the Eastern Qilian Mountains

Shrub patches have an impact on soil fertility and vegetation, influencing species composition and diversity. The unique context of the Eastern Qilian Mountains provides insights into alpine ecosystems’ responses to environmental challenges. This study aimed to evaluate the physical characteristics and soil nutrient contents of shrub patches for four different shrub species (Salix oritrepha (SO), Spiraea alpina (SA), Rhododendron capitatum (RC), and Potentilla fruticosa (PF)). We assessed their patch characteristics and soil nutrients at different depths within three patch microsites (the center (CS), the edge (ES), and the midpoint between the center and the edge of the shrub patch (BC)). Soil samples were collected and analyzed for organic matter, nitrogen, phosphorus, and potassium content. Statistical analyses were conducted to evaluate differences among shrub species and locations within the shrub patches. Our results showed that the shrub species exhibited variations in patch characteristics and soil nutrient distribution. Soil nutrient content varied by depth and location within the shrub patches, with higher concentrations at the center. The relative interaction intensity (RII) revealed nutrient aggregation or dispersion trends. The study highlighted the complex interactions between shrub characteristics and soil nutrients, emphasizing their influence on nutrient cycling, vegetation dynamics, and soil properties. These findings contribute to our understanding of alpine ecosystem dynamics and inform conservation, sustainability, and management strategies.

Nutrient allocation patterns in different aboveground organs at different reproductive stages of four introduced Calligonum species in a common garden in northwestern China.

The Calligonum species is a typical shrub with assimilative branches (ABs) in arid regions in Central Asia. The nutrient distribution patterns at different reproductive stages are of great significance for further understanding the ecological adaptation and survival strategies of plants. In the present study, a common garden experiment was employed to avoid interference by environmental heterogeneity. Furthermore, the nitrogen (N), phosphorus (P), and potassium (K) allocation characteristics in the supporting organs (mature branches), photosynthetic organs (ABs), and reproductive organs (flowers and fruits) of Calligonum caput-medusae (CC), Calligonum arborescens (CA), Calligonum rubicundum (CR), and Calligonum klementzii (CK) during the flowering, unripe fruit, and ripe fruit phases were systematically analyzed. Aboveground organs were the main factors affecting the variation of N, P, and K concentrations and their stoichiometric ratios, and the reproductive stages were secondary factors affecting N, P, and the P:K ratio and species were secondary factors affecting K and the N:P and N:K ratios. Meanwhile, significant interactions were found for all three of the aforementioned factors. The N and P concentrations in the ABs of the four species were highest during the flowering phase, while the N:P ratio was lowest, which then gradually decreased and increased, respectively, during plant growth. This result supported the growth rate hypothesis, i.e., that the growth rate is highest during the early growth stage. In the growth period, the N, P, and K concentrations in each organ of the four Calligonum species followed the power law, with the allocation rates of N and P being generally higher than K. There were differences among the species as the N-P scaling exponent in the ABs of CR was only 0.256; according to the scaling exponent law, this species was the least stressed and had the strongest environmental adaptability. Overall, the adaptability of the four species could be ranked as CR > CA > CC > CK. In conclusion, there were significant differences in nutrient traits among different aboveground organs, species, and reproductive stages. The results of this study contribute to a deeper understanding of the nutrient allocation strategies of different Calligonum species and provide scientific evidence for the ex-situ conservation and fixation application of these species.

Field Baseflow Eluting SOM-Rich Sandy Soil to Exacerbate Non-Point Source Pollution of Lake Erhai, Southwest China

Excessive nutrient loss from farmland located on the west bank of Erhai Lake has resulted in significant non-point source pollution within the Lake Erhai basin. However, mitigating this issue proves challenging due to the intricate nature of soil properties and environmental factors. Here, during the rainy season in the Lake Erhai basin, we collected and analyzed soil profile samples, 35 topsoil (0–20 cm) samples, and more than 300 field baseflow samples. Our objective was to explore the influences of soil properties, field baseflow, and agricultural management measures on the spatiotemporal migration of nutrients. The results indicated that the concentration of soil organic matter (SOM) has a significant impact on the spatial patterns of nutrient distribution in sandy soil. Consequently, this leads to a substantial reduction in the potential for nutrient loss in the Lake Erhai basin. The vegetable-field baseflow exhibited the highest concentrations of nitrogen and phosphorus when subjected to high fertilization and flood irrigation. The concentrations of TN and TP in baseflow increase by a factor of 2 and 7.7, respectively, during rainfall compared to periods of no rainfall. Optimizing agricultural measures, such as replacing chemical fertilizers with organic fertilizers and modifying irrigation methods to enhance the organic content of sandy soil and minimize baseflow elution, has a beneficial impact on mitigating agricultural non-point source pollution in the Erhai Lake basin. The research results can enable us to have a more systematic understanding of the problem of non-point source pollution in the Erhai River Basin, and provide a theoretical basis for developing targeted agricultural non-point source pollution mitigation plans. Simultaneously, optimizing agricultural management models to strike a balance between agricultural economic development and ecological protection issues holds significant practical significance for managers.

Assessment of Spatial Variability of Soil Properties Using Geospatial Techniques for Enhanced Productive Capacity of Agricultural Systems in India

Soil is an important source of available nutrients. Either shortage or surplus of available nutrients in the soil would limit growth of crops. Understanding the spatial variability and distribution patterns of soil available nutrients is essential for soil management with respect to fertilizer application. A total of 111 geo-referenced soil samples were collected on 300 m x 300 m grid at a depth of 0–15 cm, processed and analyzed for pH, EC, soil organic carbon (SOC), available nitrogen (AN), available phosphorus (AP), available potassium (AK), available sulphur (AS), available iron (Fe), available manganese (Mn), available zinc (Zn) and available copper (Cu). Soil properties coefficients of variation (CVs) of soil properties widely varied from low (5.22%) to moderate (49.28%). The geostatistics and geographic information system (GIS) techniques were applied. Ordinary kriging and semivariogram analysis showed differed spatial variability patterns for the studied soil properties with spatial dependence ranged from moderate to strong. The semivariograms for the soil properties were best fitted with spherical model. The range of influence for available N, P, K and S were 268, 287, 497 and 706 m, respectively. The spatial ranges of available Fe, Mn, Zn and Cu were 1050, 1150, 1470, and 1430 m, respectively. The spatial dependence class was strong for EC, SOC, available P, K and was moderate for available N, S, Fe, Mn, Zn and Cu. The available N and P is categorized as low (<280 kg ha-1) and low (<11 kg ha-1) to medium (<22 kg ha-1), respectively were the main limiting factors in crop production. The availability K was categorized as medium (118-280 kg ha-1) to high (> 280 kg ha -1). The soil nutrient maps generated would help to provide precise fertilizer recommendations for sustainable production and environmental conservation.

Seasonal variations in carbon, nitrogen, and phosphorus of Pinus yunnanenis at different stand ages.

The seasonal variations in carbon (C), nitrogen (N), and phosphorus (P) at the organ level of Pinus yunnanenis during different season are poorly understood. In this study, the C, N, P, and their stoichiometric ratios in various organs of P. yunnanensis during the four seasons are discussed. The middle and young aged P. yunnanensis forests in central Yunnan province, China were chosen, and the contents of C, N, and P in fine roots (<2mm), stems, needles, and branches were analyzed. The results showed that the C, N, P contents and their ratios in P. yunnanensis were significantly influenced by season and organ, less affected by age. The C content of the middle-aged and young forests decreased continuously from spring to winter, whereas N and P first decreased and then increased. No significant allometric growth relationships were observed between P-C of the branches or stems in the young and middle-aged forests, whereas a significant allometric growth relationship existed for N-P of needles in the young stands, indicating that the P-C and N-P nutrient distribution patterns shows different trends in the organ level in different age stands. The pattern of P allocation between organs shows differences in stand age, with more allocation to needles in middle-aged stands and more allocation to fine roots in young stands. The N:P ratio in needles was less than 14, indicating that P. yunnanensis was mainly limited by N and increasing the application of N fertilizer would be beneficial for the productivity of this stand. The results will be helpful to nutrient management in P. yunnanensis plantation.

Soil Nutrient Distribution and Preferential Flow Transport Patterns in Robinia Pseudoacacia Communities of Degraded Wetlands

The Yellow River Delta wetlands in the Yellow River Delta National Nature Reserve are facing serious degradation due to water scarcity and soil salinization. This study aims to investigate the mechanism of wetland degradation by analyzing the small-scale distribution of soil nutrients and preferential flow transport patterns in the Robinia Pseudoacacia community, which is a typical vegetation community in degraded wetlands. Soil physical and chemical properties based on field staining experiments were analyzed, and indoor solute penetration experiments were conducted to investigate the distribution of soil nutrients and hydrological characteristics. The results showed that the contents of soil organic carbon, organic matter, total nitrogen, and available phosphorus decreased with increasing soil depth, with higher contents in the preferential flow area than in the matrix flow area. Soil organic carbon, organic matter, total nitrogen, total phosphorus, and available phosphorus showed positive correlations with each other, while soil pH and conductivity exhibited negative correlations with the above nutrients. The efflux rate of the Acacia community exhibited a gradual decline as soil depth increased, and the relative concentration of the solution exhibited a non-monotonic pattern of decrease, increase, and subsequent decrease with increasing soil depth. The findings could provide valuable guidance for the restoration and management of degraded wetlands in the Yellow River Delta.

Variation in Plant Community Composition and Biomass to Macro and Micronutrients and Salinity across Egypt’s Five Major Coastal Lakes

To better assess the relationship between excess nutrient runoff and plant species diversity in the Egyptian northern coastal lakes, the relationships between aboveground biomass, species diversity, and both micro and macronutrient concentrations in sediment, water, and plant materials were investigated. A total of 38 sampling sites were established for the five Egyptian northern lakes (8 for Bardawil, 10 for Manzala, 8 for Burullus, and 6 for each of Edku and Mariut). Sediment, water, and plant materials were collected and analyzed for both micro and macronutrients including nitrogen (N), phosphorus (P), sulfur (S), magnesium (Mg), calcium (Ca), potassium (K), iron (Fe), boron (B), sodium (Na), and aluminum (Al). Based on the Sørensen similarity index, Burullus and Mariut lakes were very similar (0.70) in their vegetation composition, while Bardawil Lake had no similarity with the rest of the lakes. In sediment, Mariut Lake had the highest total P concentrations (1.3 g kg−1), while Bardawil Lake had the lowest (0.3 g kg−1). Bardawil, a hypersaline lake, had the highest concentrations for both Na and B (9.6 and 0.1 g kg−1, respectively). Among the deltaic lakes, Mariut Lake water bodies had the lowest plant species richness. The current study indicated that the excessive agricultural and industrial nutrient runoff had a greater impact on the nutrient distribution pattern and negatively impacted plant species diversity at the Egyptian coastal lakes. An integrated management plan, including establishing more pretreatment facilities for runoff and wastewater, should be implemented to reduce the nutrient loads from the main industrial and agricultural runoff sources. Moreover, periodic monitoring and assessment for nutrient runoff reaching the lakes are necessary to help reduce eutrophication levels.

Both Zn biofortification and nutrient distribution pattern in cherry tomato plants are influenced by the application of ZnO nanofertilizer

A pot experiment was conducted to determine the influence of commercial nanoparticles (ZnO-NPs) at different doses for use as nanofertilizer on nutrient uptake and its distribution in cherry tomato (Solanum lycopersicum L var. cerasiforme) plants in an acidic (soil pH 5.5) and calcareous soil (soil pH 8.5) from the Mediterranean area. We determined crop yield; macro- (N, P, K, Mg, S and Ca) and micro-nutrient (B, Cu, Fe, Mn, Na and Zn) concentrations in the different parts of the crop (root, stem, leaves and tomato fruits) and the extent of nutrient translocation to the aerial part of the plant. The concentrations of macronutrients N, P, K and Mg in tomato fruits grown in both soils can be considered adequate in terms of nutritional requirements. However, the Ca concentration in tomato fruits grown in the calcareous soil did not reach the required concentration to be considered sufficient. This effect was related to the characteristics of this calcareous soil. Although different concentrations of ZnO-NPs did not affect Fe and Na concentrations in tomato fruit, B concentration in tomato fruits increased with the application of ZnO-NPs. In addition, Cu concentration decreased with the application of ZnO-NPs compared to treatments without any Zn application (Nil-ZnO NP) in the calcareous soil. Manganese concentrations decreased with ZnO-NPs application in both soils. The effect of the application of ZnO-NPs depends on soil characteristics. Zinc applied as a nanofertilizer in the form of ZnO-NPs can be used to increase the crop yield and to obtain an adequate Zn biofortification in cherry tomato crop. The Zn concentrations in tomato fruits reached ranges of 4.5–4.8 mg Zn kg−1 in the acidic soil and 2.5–3,5 mg Zn kg−1 in the calcareous soil. Nutrient concentrations in these fruits following biofortification are adequate for human consumption.

Impact of COVID-19 Infection and Persistent Lingering Symptoms on Patient Reported Indicators of Nutritional Risk and Malnutrition.

Persistent malnutrition after COVID-19 infection may worsen outcomes, including delayed recovery and increased risk of rehospitalization. This study aimed to determine dietary intakes and nutrient distribution patterns after acute COVID-19 illness. Findings were also compared to national standards for intake of energy, protein, fruit, and vegetables, as well as protein intake distribution recommendations. Participants (≥18 years old, n = 92) were enrolled after baseline visit at the Post-COVID Recovery Clinic. The broad screening battery included nutritional assessment and 24-h dietary recall. Participants were, on average, 53 years old, 63% female, 69% non-Hispanic White, and 59% obese/morbidly obese. Participants at risk for malnutrition (48%) experienced significantly greater symptoms, such as gastric intestinal issues, loss of smell, loss of taste, or shortness of breath; in addition, they consumed significantly fewer calories. Most participants did not meet recommendations for fruit or vegetables. Less than 39% met the 1.2 g/kg/day proposed optimal protein intake for recovery from illness. Protein distribution throughout the day was skewed; only 3% met the recommendation at all meals, while over 30% never met the threshold at any meal. Our findings highlight the need for nutritional education and support for patients to account for lingering symptoms and optimize recovery after COVID-19 infection.

Dietary Intake Patterns of Community-Dwelling Older Adults After Acute Hospitalization.

Malnutrition and sarcopenia are a growing concern in community-dwelling older adults. Hospitalization increases the risk of malnutrition and leads to a decline in functional and nutritional status at discharge. Persistent malnutrition after hospital discharge may worsen posthospital outcomes, including readmissions. The aim of this study was to determine dietary intakes and nutrient distribution patterns of community-dwelling older adults after acute hospitalization. Participants (65 years and older, n = 85) were enrolled during acute hospitalization and dietary 24-hour recalls were collected weekly for 1 month postdischarge. Analysis included change in dietary intake over recovery timeframe; daily intake of energy, protein, fruit, vegetables, and fluids; comparison of intake to recommendations; distribution of energy and protein across mealtimes; and analysis of most common food choices. Most participants did not meet current recommendations for energy, fruit, vegetables, or fluids. Average protein consumption was significantly higher than the current recommendation of 0.8 g/kg/d; however, only 55% of participants met this goal and less than 18% met the 1.2 g/kg/d proposed optimal protein intake for older adults. The protein distribution throughout the day was skewed and no one met the 0.4 g/meal protein recommendation at all meals. Our findings indicate that community-dwelling older adults did not meet their nutritional needs during recovery after hospitalization. These data highlight the need for better nutritional evaluation and support of geriatric patients recovering from hospitalization.

Teasing Apart Silvopasture System Components Using Machine Learning for Optimization

Silvopasture systems combine tree and livestock production to minimize market risk and enhance ecological services. Our objective was to explore and develop a method for identifying driving factors linked to productivity in a silvopastoral system using machine learning. A multi-variable approach was used to detect factors that affect system-level output (i.e., plant production (tree and forage), soil factors, and animal response based on grazing preference). Variables from a three-year (2017–2019) grazing study, including forage, tree, soil, and terrain attribute parameters, were analyzed. Hierarchical variable clustering and random forest model selected 10 important variables for each of four major clusters. A stepwise multiple linear regression and regression tree approach was used to predict cattle grazing hours per animal unit (h ha−1 AU−1) using 40 variables (10 per cluster) selected from 130 total variables. Overall, the variable ranking method selected more weighted variables for systems-level analysis. The regression tree performed better than stepwise linear regression for interpreting factor-level effects on animal grazing preference. Cattle were more likely to graze forage on soils with Cd levels &lt;0.04 mg kg−1 (126% greater grazing hours per AU), soil Cr &lt;0.098 mg kg−1 (108%), and a SAGA wetness index of &lt;2.7 (57%). Cattle also preferred grazing (88%) native grasses compared to orchardgrass (Dactylis glomerata L.). The result shows water flow within the landscape position (wetness index), and associated metals distribution may be used as an indicator of animal grazing preference. Overall, soil nutrient distribution patterns drove grazing response, although animal grazing preference was also influenced by aboveground (forage and tree), soil, and landscape attributes. Machine learning approaches helped explain pasture use and overall drivers of grazing preference in a multifunctional system.

Changes of the concentrations and stoichiometry of carbon, nitrogen and phosphorus in soil aggregates along different altitudes of Helan Mountains, Northwest China.

Exploring the distribution patterns of soil nutrients in aggregates of forests along different altitudes in arid and semi-arid areas can provide a theoretical basis for understanding nutrient cycling in vulnerable mountain ecosystems. In this study, we analyzed the distribution and stability of aggregates in the 0-20 cm soil layer along different altitudes (1380-2438 m) of Helan Mountains and measured the storage and stoichiometric characteristics of organic carbon, total nitrogen, and total phosphorus in soil aggregates. Results showed that the main soil aggregates of Helan Mountains changed from micro-aggregates (0.25-0.053 mm) to macro-aggregates (>0.25 mm) with increa-sing elevation. The mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates in high altitude (2139-2248 m) were significantly higher than those in low altitude (1380-1650 m). The content and storage of organic carbon and total nitrogen in soil aggregates of different size fractions were positively correlated with altitude, while the content of total phosphorus fluctuated with the increase in elevation and distributed uniformly in aggregates. Macro-aggregates and micro-aggregates had more contribution to soil nutrient storage than the silt and clay fractions, indicating that the proportion of aggregates with different size fractions was the key factor affecting soil nutrient storage and that macro-aggregates and micro-aggregates were the main carriers of soil nutrients. Moreover, the C:N ratio in aggregates of different size fractions did not change across different altitudes, whereas the C:P and N:P ratio were higher at mid and high elevations than those at low elevations. Our results indicated that the mid and high elevations of Helan Mountains had higher nutrient storage in the surface soil layer, and that higher content of macro-aggregates and micro-aggregates would help to retain organic carbon and nutrients in the soil. Soil nitrogen limitation was strong at low altitude in our study, suggesting that the appropriate amount of nitrogen addition in low altitudes could improve total nitrogen status during forest cultivation.

Climate and vegetation together control the vertical distribution of soil carbon, nitrogen and phosphorus in shrublands in China

Carbon (C), nitrogen (N) and phosphorus (P) in soil are characterized by decreasing patterns with soil depth. However, these patterns and their driving factors have rarely been investigated in shrublands. We conducted extensive sampling of the top 100 cm of soil in 1120 shrublands across China to measure the soil organic C (SOC), total N (STN) and total P (STP) concentrations and densities. We found that in shrublands, the geometric means (and geometric standard errors) of SOC, STN and STP concentrations were 5.62 (0.09), 0.66 (0.07), and 0.31 (0.07) mg g−1, respectively, and those of their densities were 5.46 (0.08), 0.67 (0.08), and 0.30 (0.08) kg m−3, respectively. The decrease along soil depth for nutrients could be parameterized by a power function. The rates of decrease with depth differed between shrubland types and were negatively correlated with temperature but positively correlated with biomass. Climatic factors tended to have a relatively stronger effect than vegetation factors on the vertical distribution patterns of soil nutrients. Our findings reveal nutrient limitations in shrublands in terms of the total pools, suggest the necessity of soil protection for vegetation conservation and restoration, and provide an important supplement for the accurate prediction of terrestrial element cycles.

Nitrogen application mitigates drought-induced metabolic changes in Alhagi sparsifolia seedlings by regulating nutrient and biomass allocation patterns

Groundwater and its associated nutrients sustain the establishment and persistence of phreatophytes. Rapid root elongation immediately after germination is vital for desert species to access deep water sources to avoid water-deficit stress. However, the growth strategy and responses to nutrients and water of young phreatophyte seedlings before their roots reach the water table are poorly understood, especially in the scenarios of nitrogen (N) deposition and drought. We investigated how simulated N deposition and drought affect the plasticity of Alhagi sparsifolia seedlings by multiple eco-physiological mechanisms. Seedlings were planted under drought-stressed or well-watered conditions and subjected to various levels of N addition (0, 3.0, 6.0, or 9.0 gN·m−2 yr−1). The amounts of N and water independently or interactively affected the photosynthetic traits, drought tolerance characteristics, morphological traits, biomass allocation strategy, and nutrient distribution patterns among the plant organs. Moreover, changes mediated by N addition at the leaf level reflected the drought acclimation of the seedlings, which may be related to biomass and nutrient partitioning between organs. The roots were found to be more sensitive to variation of the N:phosphorus (P) ratio, and greater proportions of biomass, N, and P were allocated to resource-acquiring organs (i.e., leaves and fine roots) than to other tissues. A. sparsifolia adopts numerous strategies to tolerate drought, and additional N input was crucial to enhance the growth of drought-stressed A. sparsifolia, which was mainly attributable to its positive impact on the N and P uptake capacity mediated by increased biomass allocation to the roots.