Nutrient Dynamics Research Articles

Study of nitrogen and phosphorus nutrient dynamics in concentrated marine fish farming water environment in Long Son - Vung Tau

The nutritional content of N and P in concentrated marine fish farming water in the Cha Va - Long Son - Vung Tau estuary area increased sharply during 2013–2016; notably, the N-NH4+ content increased in 2017–2019. The N-NO2- and N-NO3- content in the dry season (0.051 mg/L and 0.190 mg/L) was higher than in the rainy season (0.044 mg/L and 0.133 mg/L). In contrast, the N-NH4+ and P-PO43- contents in the rainy season (0.321 mg/L and 0.1 mg/L) are higher than in the dry season (0.154 mg/L and 0.093 mg/L). The N and P nutrient dynamics in water fluctuate according to the semi-diurnal tide regime; the nutrient content decreases during high water - daytime, increases during low water in the evening, and is high during high water at night and in the morning, early the next day. In dry and rainy seasons, the N-NH4+ content is always the highest (0.024–0.761 mg/L) among the nitrogen-based nutritional parameters. N and P nutrients in water are correlated: N-NH4+ parameter pairs with Total P, N-NO2- with Total P, Total N with Total P, N-NO2- and N-NO3-, P-PO43- with Total P, and the parameter pair N-NO2- with P-PO43- have low positive correlation coefficients (r), from 0.1–0.21. Conversely, the parameter pairs N-NO3- and Total N, N-NO3- and N-NH4+, and N-NO2- and N-NH4+ have low negative correlation coefficients (r), from -0.12 to -0.26. From 2010–2021, the number of cages increased beyond planning, causing environmental pollution in the water in the farming area. The nutritional RQ value of the water is high at level 4 every year (very high risk of environmental pollution).

Effects of storm events on nutrient characteristics in a stratified drinking water reservoir: Behavior, transmission pathways and management strategy

Storm events result in nutrient fluctuations and deterioration of reservoir water supply quality. Understanding of nutrient dynamics (e.g., concentration, composition, loads and transport pathways) and adoption of effective management strategies are critical for safeguarding water quality. A comprehensive monitoring was conducted for three storm events during the rainy season in 2023. Results showed nitrogen (N) and phosphorus (P) dynamics demonstrate a significant response to hydrological process. Rainfall resulted in the highest event mean concentrations (EMCs) of total nitrogen (TN), nitrate nitrogen (NO3−-N), ammonia nitrogen (NH4+-N), total phosphorus (TP), and particulate phosphorus (PP) in the runoff being 1.97, 2.15, 2.30, 44.17, and 62.38 times higher than those observed in baseflow. On average, NO3−-N/PP accounted for 82 %/96 % of N/P exports. Hysteresis analyses reveal that NH4+-N and PP were mainly transported by surface runoff from over-land sources, whereas TN and NO3−-N were primarily delivered by subsurface runoff. Additionally, nutrient concentrations were significantly higher in the intrusive layer in reservoir compared to the pre-storm period, which gradually decreased from the tail to the head as particulate sedimentation and water column mixing occurred. Water-lifting-aerators (WLAs) were employed to alter the reservoir thermal stratification regime via artificial mixing to affect the intrusive layer of storm runoff. Comparison of the intrusive layer for three storms reveals that WLAs triggers the storm runoff to form an underflow via increasing the reservoir bottom water temperature above that the runoff, ensuring that water quality at the intake position remains unaffected by inflows. These findings serve as a reference for the response of reservoir eutrophication levels to storm events and present practical engineering experience for enhancing water quality safety during the rainy season.

Soil Fertility Dynamics and Identify the Most Limiting Nutrients Affecting Walnut Productivity in Nepal

This study aimed to assess the soil nutrient status in walnut orchards of different ages in Jajarkot district, Nepal, to understand soil fertility dynamics and identify the most limiting nutrients affecting walnut productivity. The research employed a randomized complete block design (RCBD) with three treatments representing different age groups of walnut orchards (1-5 years, 6-10 years, and 11-15 years), each replicated seven times across various municipalities. The study was conducted in Jajarkot district, Karnali Province, Nepal, encompassing municipalities including Nalgad, Junichadey, and Barekot, from March to April 2023. Soil samples were collected from multiple depths (1, 2, and 3 feet) in each orchard and analyzed for pH, soil organic matter (SOM), total nitrogen, available phosphorus, and available potassium. Data analysis included descriptive statistics, one-way analysis of variance (ANOVA), and correlation analyses to explore relationships between soil parameters and orchard age. The study showed that significant variations were observed among different age groups of walnut orchards for soil pH, SOM, nitrogen, phosphorus, and potassium levels. Soil pH decreased with orchard age, while SOM, nitrogen, and phosphorus tended to increase with orchard age. Phosphorus was identified as the most limiting nutrient across all sampled soils, followed by nitrogen and potassium. Moreover, strong correlations were found between orchard age and soil N (r = 0.894, p < 0.01) and P (r = 0.776, p < 0.01), underscoring age-dependent nutrient dynamics. The study highlights the critical role of orchard age in shaping soil nutrient dynamics in walnut orchards. Older orchards exhibited higher levels of SOM, nitrogen, and phosphorus, indicating the accumulation of organic matter and nutrients over time. Phosphorus emerged as the primary limiting nutrient, essential for root growth, flowering, and fruiting in walnut trees. These findings underscore the importance of targeted fertilization strategies to optimize soil fertility and sustain long-term walnut productivity in the region.

Improving the identification of pollution source areas with catchment-resolution sensitivity analysis

The significant impacts of total nitrogen (TN) and total phosphorus (TP) on riverine ecosystems underscores the critical need to identify the primary nutrient source areas in watersheds. This study aims to unravel the influences of terrain and land use types on mean monthly TN (TNM) and mean monthly TP (TPM) export across varying catchment resolutions in the Qiantang River Watershed of China. The findings of this study illuminated the critical role of topography in understanding nutrient dynamics, wielding a profound influence over water flow patterns and nutrient dispersion. Both land slope and Stream Power Index (SPI) displayed substantial negative correlations (r < −0.6) with TNM and TPM concentrations, whereas the Topographic Wetness Index (TWI) showed positive correlations with the nutrient indexes. In addition to terrain characteristics, impervious land surfaces had a positive correlation with nutrient concentrations, while grassland and forest areas exhibited negative correlations. Results further underscored the substantial influence of catchment resolution on correlations between watershed properties and riverine nutrient concentrations. It was imperative to choose an effective catchment resolution in watershed delineation – not too coarse, nor too fine – to accurately capture the topographic and land use impacts on nutrient dynamics. With the most appropriate catchment size (Catchment 700 km2), the critical pollution source areas for TN and TP pollution were identified, and thus could be used to guide future pollution reduction efforts. The study not only highlights the importance of identifying an appropriate catchment size for water pollution, but also emphasizes the necessity of effectively extracting critical pollution source areas to mitigate water nutrient pollution and increase the ecological integrity of the Qiantang River Watershed.

Effects of Low-Phosphorus Stress on Use of Leaf Intracellular Water and Nutrients, Photosynthesis, and Growth of Brassica napus L.

Phosphorus (P) deficiency is one of the main reasons limiting plant production of Brassica napus L. Exploring the dynamics of leaf intracellular substances and the correlations with photosynthesis and growth helps to understand the response mechanisms of B. napus L. to P deficiency. This study conducted experiments on B. napus L. plants by measuring the leaf electrophysiological parameters, leaf structure, elastic modulus (Em), photosynthesis, and growth indices under different P treatment conditions. The dynamics of leaf intracellular water and nutrients of B. napus L. were calculated and analyzed by using the electrophysiological parameters, and the plant tolerance threshold to low-P stress was discovered. The results indicated that the status of the leaf intracellular water and nutrients remained stable when the P concentration was not lower than 0.250 mmol·L−1, but maximized the photosynthesis and growth at a P level of 0.250 mmol·L−1. The 0.125 mmol·L−1 P concentration significantly decreased the mesophyll cell volume, and the palisade–sponge ratio and tightness degree of leaf tissue structure were remarkably increased. This led to an increase in cell elastic modulus, and significantly improved the water retention capacity of leaf cells. At the same time, the intracellular water use efficiency and total nutrient transport capacity of leaves remained stable. As a result, the photosynthesis and growth of plants were maintained at the same level as that of the control group. However, photosynthesis and growth were clearly inhibited with a further decrease in P concentration. Therefore, 0.125 mmol·L−1 was the tolerance threshold of B. napus L. to low P. With the help of electrophysiological information, the effects of the dynamics of intracellular substances on photosynthesis and growth of B. napus L. under low-P stress can be investigated, and the plant’s adaptive response can be revealed. However, the findings of the current hydroponic study are not directly applicable to field conditions with naturally P-deficient soils.

Dynamics and correlations of maximum water age zones and nutrients in the Changjiang Estuary, China

The hydrological process dominates the spatial and temporal concentrations of nutrients and other biogeochemical compounds in the large estuary where river and ocean meet. Water age is a measure of water renewal timescale and a characteristic parameter of hydrodynamics and contaminant transport. A large-scale river-sea linked and multi-process coupled 2D EFDC model was constructed from Datong hydrometric station of Changjiang River to the East China Sea. The effects of changes in river discharge on hydrodynamics and nutrients in the Changjiang Estuary were simulated and analyzed. Pollutant loads to the Changjiang Estuary are mainly from upstream inflows and local inputs. The proportion of total phosphorus (TP) loads from upstream is greater than the total nitrogen (TN) loads, accounting for about 90% and 78%, respectively. As the river discharge decreases, TN concentrations decrease in most regions, except for near large sewage discharges where TN concentrations increase while TP concentrations show a decreasing trend. When the river flow drops from over 60000 m3/s to a relatively low value of 10000 m3/s, the average TN concentration in the southern channel of the Shanghai section of the Changjiang Estuary increases by nearly 13%, while TP concentration decreases by nearly 5%. The model results show that the water age inside the river mouth is inversely proportional to the flow rate. In contrast, the water age outside the mouth is negatively with the river discharge. The water age maximum zones (WAMZ) are found in the estuary, ranging from within the estuary to 90 km from the mouth, and are likely to coincide with the positions of the turbidity maximum zones (TMZ), which move seawards or landwards with the increase or decrease of river discharge in the Changjiang Estuary. In addition to location, the value of water age maxima varies negatively with river discharge, which is also relevant to turbidity intensity likely. Water age and WAMZ can be the indicators to predict the changes in the water environment and nutrient sinks in the Changjiang Estuary.

Impact of seasonality and forest stand age on ion deposition inrehabilitated forests.

This study examines the critical interaction between seasonal precipitation variability and forest maturity in determining ion deposition patterns in rehabilitated forest ecosystems. This research was conducted in rehabilitated forest sites in Bintulu, Sarawak, Malaysia that had ecologically similar plant distribution, species, and age in each planting area. This facilitated the standardization of rainfall deposition in the different study plots which streamlined the study of these specific facets of ecosystem dynamics. The goal is to understand how seasonal changes and the age of the forest influence the chemical composition of the flux that relates to the movement and deposition of nutrients through the forest ecosystem. This flux is a key factor in the health of the forest ecosystem and nutrient cycling. Using ion exchange resin (IER) samplers, we accurately measured and compared the deposition of different ions (Ca2+, Na+, Fe2+, Cu2+, NO3 -, NH4 + and SO4 2-) across different seasons and forest ages. The deposition of Ca2+ and NH₄+ was significantly lower in the low-precipitation season than in the high-precipitation season in all forest stands, regardless of the year they were established (1996, 1999, 2002, 2005, and 2009). In contrast, ions such as Na+, Fe2+, Cu2+, NO3 - and SO4 2- showed no clear seasonal fluctuations. In addition, the study shows that through-fall in forest stands from 2002, 2005 and 2009 had higher concentrations of Ca2+ in both seasons than in 1996 and 1999. Interestingly, forest stands from 2009 and 2002 had elevated levels of Na+ and SO₄2- in seasons with low precipitation, while stands from 1996 had higher levels in seasons with high precipitation. Our results emphasize the crucial role of precipitation amount and canopy age in determining ion deposition in forest ecosystems. By demonstrating the significant influence of precipitation seasonality and forest maturity on the chemical composition of throughfall, this study contributes to a deeper understanding of nutrient dynamics in developing forest landscapes and provides valuable insights for ecological restoration measures.

Phosphorus addition stimulates overall carbon acquisition enzymes but suppresses overall phosphorus acquisition enzymes: A global meta-analysis

Of the total land worldwide, 43 % is phosphorus (P)-constrained, which is significantly greater than the proportion of nitrogen-constrained land (18 %). However, there are some uncertainties regarding the responses of enzyme activities to P addition on a global scale. We collected data from 99 publications and performed a meta-analysis to assess the responses of 11 extracellular enzymes, including carbon, nitrogen, and phosphorus acquisition enzymes, and oxidases. P addition significantly increased the activities of β-1, 4-glucosidase, sucrase, cellobiohydrolase, and alkaline phosphatase, while lowering the activities of acid phosphatase and phosphodiesterase. The responses of enzyme activities to P addition differed considerably across the three ecosystems (forest, grassland, and cropland). P addition significantly decreased the activities of acid phosphatase, phosphodiesterase, and P-acquisition enzymes in forests, but increased the activities of leucine aminopeptidase, carbon acquisition enzymes, and nitrogen acquisition enzymes in grasslands. Sucrase, β-1,4-glucosidase, N-acetyl-β-glucosaminidase, alkaline phosphatase, and carbon acquisition enzymes were significantly stimulated in croplands. In addition, all P addition rates significantly increased the activity of alkaline phosphatase, a P-acquisition enzyme, in croplands. Ca(H2PO4)2 had a greater effect on enzyme activity than other fertilizer types, possibly because Ca2+ can improve the soil structure and enhance microbial metabolic activities. Furthermore, structural equation models revealed that mean annual precipitation and ecosystem type had significant impacts on the response of P-acquisition enzymes, but no factor could directly influence the response of carbon-acquisition enzymes. Our investigation of enzyme activities in response to P addition complements the biogeochemical model and helps forecast soil nutrient dynamics. We propose that rather than focusing on a single factor, P fertilizer addition programs should take into account the effects of mean annual precipitation, ecosystem type, and nutrient interactions, which could also reduce P pollution.

Analysis of the Soil Fertility Condition in Jiliba Village, Ganjam District, Odisha

An assessment of soil fertility was conducted in Jiliba village, situated in the Bellaguntha block of Ganjam district in the North-Eastern agroclimatic zone of Odisha, India. Analysis of physical and chemical properties was conducted on soil samples obtained at a depth ranging from 0 to 15 cm. The findings indicate that the predominant soil texture in the hamlet under study consisted of sandy loam and clay loam. The soil hue ranged from Dark Grey at 10 years old to Yellowish brown at 10 years old. The pH of the soil varied from somewhat acidic (5.5-6) to neutral (6.5-7.5). The electrical conductivity of the whole research area remained uniformly below 0.74 dSm-1. Approximately 77.5% of the research region exhibited soil organic carbon (SOC) levels below 0.5%. The available nitrogen concentration was insufficient, varying from 87.8 to 150.5 kg/ha, indicating a possible requirement for nitrogen fertilization to adequately sustain crop development. The phosphorus content in Brays exhibited significant variation, ranging from 4.7 to 198.2 kg/ha, providing evidence of geographic heterogeneity in phosphorus availability throughout the hamlet. The soil potassium level exhibited significant variation, ranging from 54.6 to 435.6 kg/ha, potentially impacting the absorption of nutrients and the production of crops. The Nutrient Index readings for nitrogen (1.0) and phosphorus (1.32) were below expected levels, suggesting the necessity of implementing nutrient management strategies to enhance soil fertility. The potassium Nutrient Index value of 1.87 indicates a moderate level of potassium availability in comparison to nitrogen and phosphorus. The extractable soil sulphur from calcium chloride (CaCl2) ranged from 6.4 to 126.7 kg/ha, underscoring the significance of sulphur for crop fertilization. Modest variations in exchangeable calcium (Ca2+) and magnesium (Mg2+) levels suggest differences in soil cation exchange capacity and nutrient availability. The micronutrient levels exhibited variation, with copper (Cu) concentration ranging from 2.026 to 4.210 parts per million (ppm), zinc (Zn) concentration ranging from 0.736 to 4.440 ppm, manganese (Mn) concentration ranging from 19.0 to 79.0 ppm, and iron (Fe) concentration ranging from 44.36 to 160.64 ppm. The concentration of boron soluble in hot water varied from extremely low to medium (0.15 to 0.68 mg/kg), suggesting different degrees of boron accessibility for plant absorption. Finally, it is essential to fill the research gaps concerning soil fertility and nutrient dynamics in order to establish sustainable agricultural practices and guarantee food security in the region.

Influence of Native Woody Understory on Invasive Grasses and Soil Nitrogen Dynamics Under Plantation and Remnant Montane Tropical Trees

While the influence of canopy trees on soils in natural and restored forest environments is well studied, the influence of understory species is not. Here, we evaluate the effects of outplanted native woody understory on invasive grass biomass and soil nutrient properties in heavily grass-invaded 30 + year-old plantations of a native N-fixing tree Acacia koa in Hawai‘i. We analyze soils from under A. koa trees with versus without planted woody understory and compare these to soils from under remnant pasture trees of the pre-deforestation dominant, Metrosideros polymorpha where passive recruitment of native woody understory has occurred since the cessation of grazing. Simultaneously, we experimentally planted understory species at three times the density used by managers to see if this could quickly decrease grass biomass and change soil nutrient dynamics. We found that invasive grass biomass declined with understory planting in surveyed and experimental sites. Yet, woody understory abundance had no effect on N cycling. Short-term N availability and nitrification potential were higher under A. koa than M. polymorpha trees regardless of understory. Net N mineralization either did not differ (~ 1 mo) between canopy species or was higher (171 day incubations) under remnant M. polymorpha where organic matter was also higher. The only influence of understory on soil was a positive correlation with loss-on-ignition (organic matter) under M. polymorpha. We also demonstrate differential controls over N cycling under the two canopy tree species. Overall, understory restoration has not changed soil characteristics even as invasive grass biomass declines.

Nutrient dynamics study and yield optimization for soybean through integrated nutrient and weed management

Soybean production faces many constraints with several factors, such as biotic and abiotic factors, and the crop management practices where inadequate nutrient management leads to a decline in production potential of the crop. Among the biotic factors, exploitation of resources by weeds not only causes a decline in production but also decreases the crop quality. Managing the weeds during the critical period of crop weed competition plays outstanding role in maximizing soybean production. In order to study the influence of integrated nutrient and weed management on nutrient dynamics and yield optimization of soybean an experiment was conducted in Split Plot Design with three nutrient management treatments in main plot {100% recommended dose of fertilizer (RDF), 75% RDF + 25% N through farmyard manure (FYM) + Phosphate solubilizing bacteria (PSB) and 50% RDF + Rhizobium + PSB} and five weed management treatments in the sub-plot (Hand weeding at 15, 30 and 45 DAS, Mechanical weeding at 20 and 40 DAS, Pendimethalin @ 1 kg a.i. ha−1 PE fb Hand weeding at 30 DAS, Propaquizafop @ 0.075 kg a.i. ha−1 PoE fb Hand weeding at 45 DAS, and Weedy check as control). The results indicated that application of 75% RDF + 25% N through FYM + PSB recorded the highest seed yield, nutrient content in seed and uptake of N, P, K, and S in the seed and stover, microbial population, and soil nutrient status. Highest partial factor productivity was recorded under 50% RDF + Rhizobium + PSB. Under weed management, hand weeding recorded the highest growth, yield attributes and nutrient content, but was found to be at par with Pendimethalin @ 1 kg a.i. ha−1 PE fb Hand weeding at 30 DAS and Propaquizafop @ 0.075 kg a.i. ha−1 PoE fb Hand weeding at 45 DAS. Application of 75% RDF + 25% N through FYM + PSB and pendimethalin @ 1 kg a.i. ha−1 fb hand weeding at 30 DAS proves to be an effective strategy for soybean cultivation. The experiment was conducted at the experimental farm of School of Agricultural Sciences, Nagaland University, Medziphema, India.

Benthic metabolism and nutrient dynamics of a hyperturbid and hypernutrified estuary

Benthic metabolism and nutrient dynamics of a hyperturbid and hypernutrified estuary

Production of industrial-interest colorants in microalgae and cyanobacteria: leveraging nutrient dynamics and photoperiod optimization

La exploración de la biodiversidad de cianobacterias y microalgas es muy prometedora para la obtención de pigmentos de interés industrial. Este estudio se centra en la bioprospección de estos organismos para obtener pigmentos de interés industrial junto con biomasa enriquecida. Investigamos el impacto del fotoperiodo y la concentración de fuentes de nutrientes C/N/P en cultivos heterótrofos, controlando variables específicas como la intensidad luminosa, volumen, pH, temperatura, flujo de aire y tiempo para la producción de ficobiliproteínas en Arthrospira sp.y carotenoides totales en Scenedesmus sp. Empleando un diseño Plackett‒Burman no factorial en el software STATISTICA 7.0. La concentración de biomasa fue determinada por peso seco, mientras que la concentración de ficocianinas y carotenoides fueron determinadas espectrofotométricamente a longitudes de onda específicas. Los cultivos heterótrofos demostraron una productividad superior, alcanzando las ficocianinas y los carotenoides porcentajes del 7% y el 0,4% (% p/p) respectivamente, y un notable valor R2 de 0,99. Entre los parámetros influyentes, el difosfato potásico y el bicarbonato sódico desempeñaron papeles fundamentales en la deposición final de carotenoides y ficocianinas, respectivamente, alcanzando concentraciones de 96,5 mg/L de ficocianinas y 6,5 mg/L de carotenoides.

Relationships between Wheat Development, Soil Properties, and Rhizosphere Mycobiota.

Wheat is a vital global food crop, yet it faces challenges in saline-alkali soils where Fusarium crown rot significantly impacts growth. Variations in wheat growth across regions are often attributed to uneven terrain. To explore these disparities, we examined well-growing and poorly growing wheat samples and their rhizosphere soils. Measurements included wheat height, root length, fresh weight, and Fusarium crown rot severity. Well-growing wheat exhibited greater height, root length, and fresh weight, with a lower Fusarium crown rot disease index compared to poorly growing wheat. Analysis of rhizosphere soil revealed higher alkalinity; lower nutrient levels; and elevated Na, K, and Ca levels in poorly growing wheat compared to well-growing wheat. High-throughput sequencing identified a higher proportion of unique operational taxonomic units (OTUs) in poorly growing wheat, suggesting selection for distinct fungal species under stress. FUNGuild analysis indicated a higher prevalence of pathogenic microbial communities in poorly growing wheat rhizosphere soil. This study underscores how uneven terrains in saline-alkali soils affect pH, nutrient dynamics, mineral content, wheat health, and rhizosphere fungal community structure.

Mapping Soil-crop Nutrient Dynamics in Continuous Cotton Cultivation Areas of Sangareddy District, Telangana

A soil-crop nutrient survey was conducted in Sangareddy district, Telangana during Rabi, 2023 to study the fertility status of cotton growing soils at 0-15 cm and 15-30 cm depth. Georeferenced soil and leaf samples were collected from 112 sites covering 23 mandals during flowering stage. Soil physical and physico-chemical properties and cotton leaf nutrient content were analysed. In the study area, bulk density, sand, silt and clay content ranged from 1.36-1.66 Mg m-3, 41.84-78.02 %, 6.74-29.60 % and 10.76-42.76 %, respectively. The soils were strongly acidic to slightly alkaline in reaction (4.25-7.98; 4.44-7.97), non-saline (0.026-0.254 dS m-1; 0.020-0.241 dS m-1) and low to high in organic carbon (2.03 to 11.52 g kg-1; 1.13 to 8.24 g kg-1) at 0-15 cm and 15-30 cm depths, respectively. Soil Nutrient Status: Available nitrogen, phosphorus, potassium and exchangeable magnesium contents ranged from 101 to 448 kg ha-1, 7 to 41 kg ha-1, and 154 to 763 kg ha-1 at 0-15 cm depth, respectively while 91 to 319 kg ha-1, 4 to 39 kg ha-1, and 142 to 730 kg ha-1 at 15-30 cm depth, respectively. Crop Nutrient Status: Total nitrogen, phosphorus, potassium and magnesium contents in the collected cotton leaves ranged from 0.53 to 3.64 %, 0.12 to 0.68 %, 0.80 to 1.84 % and 0.27 to 0.92 %, respectively. Soil Fertility Mapping: Soil fertility maps were prepared considering the low/deficient, medium and high/sufficient range of soil macronutrients (N, P, K and Mg) at the depth of 0-15 cm under QGIS 3.36.1. Soil fertility maps showed that soils of the study area were mostly low in available nitrogen, medium in available phosphorus, high in available potassium and sufficient in exchangeable magnesium. Regular soil testing is crucial to monitor the variations in nutrient levels and formulation of appropriate management strategies to address it.

Variability of soil enzyme activities and nutrients with forest gap renewal interacting with soil depths in degraded karst forests

Forest gaps serve as crucial starting points for forest self-renewal. Within these gaps, soil enzymes play an essential role in driving nutrient transformation and species renewal. However, how forest gap renewal regulates soil fertility through soil enzyme across various soil depths remains unclear. This investigation delved into the dynamics of soil enzymes and nutrients within karst forest gaps at four developmental age stages: Infancy (<10 years), Youth (10–20 years), Middlescence (20–30 years), and Elder (>30 years) across different soil depths (0–10 cm, 10–20 cm, and 20–30 cm). The study determined the contents of CNP and the activities of soil enzymes such as polyphenol oxidase, catalase, protease, and alkaline phosphatase. Two-way ANOVA was employed to assess the variations in gap ages and soil depths, along with their interaction. Redundancy analysis (RDA) was used to reveal the correlations between soil enzyme activities and CNP fertility indicators. The results indicated that gap age significantly influenced the activities of alkaline phosphatase, polyphenol oxidase, and protease, as well as the contents of total and available nitrogen, phosphorus, and organic carbon, alongside the ratios of N/P, C/N, and C/P. Catalase activity, however, did not vary significantly with gap age, although soil depth influenced these parameters, excluding total phosphorus and the C/N ratio. Notably, in the 0–10 cm soil layer, alkaline phosphatase activity, total nitrogen, available nitrogen, and organic carbon contents significantly increased with gap age increase, followed by a significant decrease after the middlescence stage. In the 10–20 cm and 20–30 cm soil layers, Alkaline phosphatase and polyphenol oxidase activities, along with N/P and C/N ratios initially decreased and then increased with gap age increase. During the Infancy, Youth, and Middlescence stages, Polyphenol oxidase and protease activities, CNP contents, as well as N/P and C/P ratios generally decreased with soil depth increase or after an increase in the 10–20 cm soil layer. RDA highlighted the variational positive and negative correlations between soil enzyme activities and CNP fertility indicators across soil depths during forest gap renewal, with explanatory rates ranging from 88.05 % to 94.67 % across soil layers. Overall, this study suggests that forest gap renewal significantly influences soil enzymes, CNP content and stoichiometry, modifying soil CNP content through stoichiometric regulation across different soil depths, and ultimately sustaining soil fertility via soil enzymes.

Anthropogenic Influence and Climate Change on Water and Nutrient Dynamics in the Kebir-Rhumel Basin, (Northeastern Algeria)

&lt;p&gt;This study investigates the Anthropogenic Influence and Climate Change: Water and Nutrient Dynamics in the Kebir-Rhumel Basin in Northeastern Algeria. Utilizing an advanced methodology and integrating 10 physicochemical variables, this research provides a novel insight into the environmental factors shaping the basin's ecosystem. By employing a PCA analysis, it highlights two distinct factors accounting for 80.90% of the total variance and identifies a strong positive correlation between various variables, particularly NH4+ and PO43-. Two contrasting river areas were noted: Oued Radjas and Oued Rhumel rivers, displaying evidence of anthropogenic activities, and Oued Kebir and Oued El-Kotone rivers, indicative of pristine conditions. Seasonal fluctuations were noted in atmospheric temperature, precipitation, humidity, and wind speed, as well as in physical parameters and nutrient concentrations of surface water, revealing new details about the potential impact of human activities on water quality and ecosystem health. The findings here are not only significant in understanding the dynamics of water quality but also crucial in devising effective management strategies. High EC and TDS values in the Oued Radjas River point to anthropogenic pollution, and high nitrogen nutrient concentrations in the Oued El-Kotonne River hint at potential eutrophication. The study underscores the importance of understanding the interplay between human activities and natural processes in managing water resources and ecosystems. This research contributes to the existing body of knowledge by shedding light on specific aspects of water quality in the region, paving the way for more focused investigations and policy interventions for sustainable development.&lt;/p&gt;

Soil heavy metal pollution promotes extracellular enzyme production by mediating microbial community structure during vegetation restoration of metallic tailing reservoir

Vegetation restoration in metallic tailing reservoirs is imperative to restore the post-mining degraded ecosystems. Extracellular enzymes determine microbial resource acquisition in soils, yet the mechanisms controlling the enzyme activity and stoichiometry during vegetation restoration in metallic tailing reservoirs remain elusive. Here, we investigated the variations and drivers of C-, N- and P-acquiring enzymes together with microbial community along a 50-year vegetation restoration chronosequence in the China's largest vanadium titano-magnetite tailing reservoir. We found a parabolic pattern in the enzyme activity and efficiency along the chronosequence, peaking at the middle restoration stage (∼30 years) with approximately six-fold increase relative to the initial 1-year site. The enzyme ratios of C:P and N:P decreased by 33 % and 68 % along the chronosequence, respectively, indicating a higher microbial demand of C and N at the early stage and a higher demand of P at the later stage. Soil nutrients directly determined the enzyme activities and stoichiometry, whereas microbial biomass and community structure regulated the temporal pattern of the enzyme efficiency. Surprisingly, increased heavy metal pollution imposed a positive effect on the enzyme efficiency indirectly by altering microbial community structure. This was evidenced by the increased microbial diversity and the conversion of copiotrophic to oligotrophic and stress-tolerant taxa along the chronosequence. Our findings provide new insights into microbial functioning in soil nutrient dynamics during vegetation restoration under increasing heavy metal pollution.

Litter decomposition in pure and mixed plantations on the Loess Plateau, China: Lack of home-field advantage

Litter decomposition plays a critical role in the nutrient cycling of terrestrial ecosystems. According to the home-field advantage (HFA) hypothesis, litter decomposes more rapidly in its home habitat (where it originates) compared to other habitats (referred to as away). Although this hypothesis has been widely tested in natural forests, it remains controversial and lacks support for plantations, especially in dry ecosystems where microbial activities are limited. To clarify it, the present study investigated litter mass loss, nutrient dynamics, and decomposer communities in a 549-day reciprocal transplant experiment of litter decomposition in Robinia pseudoacacia (RP) and Hippophae rhamnoides (HR) pure plantations and their mixed plantations (5:5 and 8:2 ratios) on the Loess Plateau, China. The rate of mass, carbon (C), nitrogen (N) and phosphorus (P) loss in litter differed depending on litter type of species component and plantation type they were placed in. HR litter lost mass and released C, N, and P fastest, irrespective of plantation type. The overall mass loss of the four litter types were the fastest under 5:5 mixed plantations. However, litter did not decompose more rapidly in its home soil compared to the away soil. The structural equation modeling revealed that initial litter quality played a significant role in regulating the loss of C and N across decomposition stages, while the climate variations and microbial chemistry also contributed to the process. The similarity in soil microbial communities across plantation types, along with the limited interaction between litter and microbes in arid environments, could help elucidate the lack of HFA, with other factors such as the litter type exerting a minor influence. In summary, this study does not substantiate the hypothesis of home-field advantage but supports its context-dependency. Thus, regional heterogeneity should be taken into account when predicting the carbon cycle of forest ecosystems in future studies.

Marine redox and nutrient dynamics linked to the Cambrian radiation of animals

Abstract The early Cambrian witnessed an increase in metazoan ecosystem complexity, likely linked to enhanced oxygen and nutrient availability. However, while improved stratigraphic and geochemical records suggest that the Cambrian explosion occurred under highly dynamic redox conditions, mechanistic links to nutrient availability and early Cambrian evolutionary innovations are poorly constrained. Here, we report paleoredox and nutrient data for two drill cores documenting late Cambrian Stage 2 to Stage 3 (ca. 522–514 Ma) strata from the Yangtze block, South China. The development of water-column euxinia during Cambrian Stage 2 led to extensive recycling of P, fueling elevated primary production and hence an increase in atmospheric and shallow-marine oxygen concentrations. The resulting expansion of oxygenated shelf area promoted sedimentary P retention and, in combination with a diminished supply of P from upwelling, drove a transition to oligotrophic shallow-marine conditions during Cambrian Stage 3. Reduced primary production and limited water-column oxygen consumption allowed for the stabilization of oxygenated continental shelf habitats that supported a burgeoning biotic complexity.