Floodplain Soils Research Articles

Microbial Biomass and Rhizosphere Soil Properties in Response to Heavy Metal-Contaminated Flooding

Mining and metallurgy are the main sources of soil contamination with harmful metals, posing a significant threat to human health and ecosystems. River floodplains in the vicinity of metal mines or industrial plants are often subject to flooding with sediments containing heavy metals, which can be harmful to the soil ecosystem. This study aimed to investigate the microbial properties of the soil at a metal-contaminated site and to determine the significant relationships between the biological and chemical properties of the soil. The study site was located near the village of Gyöngyösoroszi, in the Mátra mountain region of Northwest Hungary. A phytoremediation experiment was conducted in a metal-polluted floodplain using willow and corn plantations. The soil basal respiration, substrate-induced respiration, soil microbial biomass carbon (MBC), acid phosphatase activities, and soil chemical properties were measured. The soil of the contaminated sites had significantly higher levels of As, Pb, Zn, Cu, Cd, and Ca, whereas the unpolluted sites had significantly higher levels of phosphorus and potassium. The substrate-induced respiration showed a positive correlation with MBC and negative correlations with the metabolic quotient (qCO2). The soil plasticity index and phosphorus showed a positive correlation with MBC, whereas salinity and the presence of Cd, Pb, Zn, As, and Cu showed a negative correlation. Acid phosphomonoesterase activity negatively correlated with the plant-available phosphorus content and MBC, but was positively correlated with the contents of toxic elements, including cadmium, lead, zinc, arsenic, and copper. This study found a significant correlation between the qCO2 and the toxic element content. This suggests that an enhanced metabolic quotient (qCO2), together with a decreased MBC/SOC ratio, could be used to indicate the harmful effect of soil contamination by heavy metals in floodplain soils.

The coupling of sulfide and Fe-Mn mineral promotes the migration of lead and zinc in the redox cycle of high pH floodplain soils

In this study, we investigated the impact of fluctuating water levels on the distribution of lead (Pb) and zinc (Zn) in soil and sediments at a historical Pb-Zn smelting site along the Xiangjiang River. Despite the high pH levels (7 to 11) in the study area, which generally inhibits heavy metal solubility, we found that regular changes in water levels still affect Pb-Zn movement. Soil analysis revealed distinct redox zones within the unconfined aquifer, as shown by the variable Fe/Mn and Ce/Ce* ratios. Advanced techniques such as Mn K-edge XAFS, Mössbauer spectroscopy, and TOF-SIMS indicated persistent Fe-Mn redox cycling and highlighted the presence of Pb and Zn-rich manganese oxides near sulfur-bearing minerals. These findings suggest that acidic microzones produced by the oxidation of sulfur-bearing minerals become "refuges" for microbial and heavy metal activity. Considering that sulfur-containing minerals are widespread waste types in nonferrous metal smelting sites, these findings are instructive for a better understanding of the transformation mechanisms of heavy metal ions in nonferrous metal smelting-polluted environments and for guiding pollution remediation strategies.

Risk assessment of trace elements in vegetables grown in river Yamuna floodplain in Delhi.

Urban agriculture is common in fertile river floodplains of many developing countries. However, there is a risk of contamination in highly polluted regions. This study quantifies health risks associated with the consumption of vegetables grown in the floodplain of the urban river 'Yamuna' in the highly polluted yet data-scarce megacity Delhi, India. Six trace elements are analyzed in five kinds of vegetable samples. Soil samples from the cultivation area are also analyzed for elemental contamination. Ni, Mn, and Co are observed to be higher in leafy vegetables than others. Fruit and inflorescence vegetables are found to have higher concentrations of Cr, Pb, and Zn as compared to root vegetables. Transfer Factor indicates that Cr and Co have the highest and least mobility, respectively. Vegetable Pollution Index indicates that contamination levels follow as Cr > Ni > Pb > Zn. Higher Metal Pollution Index of leafy and inflorescence vegetables than root and fruit vegetables indicate that atmospheric deposition is the predominant source. Principal Component Analysis indicates that Pb and Cr have similar sources and patterns in accumulation. Among the analyzed vegetables, radish may pose a non-carcinogenic risk to the age group of 1-5year. Carcinogenic risk is found to be potentially high due to Ni and Cr accumulation. Consumption of leafy vegetables was found to have relatively less risk than other vegetables due to lower Cr accumulation. Remediation of Cr and Ni in floodplain soil and regular monitoring of elemental contamination is a priority.

Smectite Characterization of The River Nile Floodplain Soils, Sohag Governorate, Egypt

Smectite Characterization of The River Nile Floodplain Soils, Sohag Governorate, Egypt

Porewater microbiomes in buried wetland soils: Synergic effects of water chemistry and redox gradients associated with hydrological processes

Abstract Interstitial water or pore water occupies the space between soil particles and provides “hotspots” and “fluvial networks” for microbial activities in floodplain soil. However, to date, we know very little about the microorganisms living in pore water and how they respond to environmental changes. This study aimed to understand microbial distribution and assemblage in riparian pore waters, and how they respond to water chemistry and redox gradients associated with hydrological processes. We analysed the annual changes of porewater microbial communities from the east and west banks of the White Clay Creek, a site at the Christina River Basin – Critical Zone Observatory, Pennsylvania, USA. Microbial abundances were quantified by epifluorescence microscopy and detailed community structures were characterised by high‐throughput sequencing. Water chemistry and redox gradients were also monitored and recorded, and their interactions with porewater microbiomes were analysed using correlations and multivariate analyses. Abundance of microbial cells increased during summer and late autumn. Wetland porewater microbiomes mainly contained Acidobacteria, Bacteroidetes, Nitrospirae and Proteobacteria, and microbiome structures were easily distinguishable from those in the underlying hyporheic gravel layer. Seasonal dynamics of bacterial community structure in the east and west wetlands were distinct, responding to floodplain topography and associated hydrological/geochemical processes. Iron (Fe)‐cycling bacteria (mainly Gallionellaceae and Rhodoferax spp.) dominated the porewater microbiome, and their relative abundance was significantly higher in the east than the west wetland. Furthermore, Fe‐oxidising bacteria (Gallionellaceae) were negatively correlated with Fe‐reducing bacteria (Rhodoferax spp.) at the east wetland. Microbial abundances (cell density) in pore waters showed similar seasonal patterns across stream banks, but microbial community structure did not. Microbiome assembly in pore water is correlated with water chemistry and redox gradients primarily associated with local hydrological processes. As a consequence of their significance for carbon (C) mineralisation and Fe reduction at terrestrial–aquatic interfaces, microbiomes in riparian pore waters and associated microbial activity play an essential role in C and mineral dynamics. These findings will inform future studies of the response of freshwater ecosystems to hydrological dynamics influenced by global climate change.

Synergistic Benefits of Combined Application of Manures and Chemical Fertilizers: Enhancing Growth and Yield of Rice and Wheat

The incorporation of compost and manure with chemical fertilizer has become a key concern to sustain soil fertility. Because the nutrients are continuously depleting from the soil and consequently creating a risk to preserving soil health. Aims: This study assesses the response of different doses of cowdung (CD), municipal solid waste compost (MSWC), oil cake (OC), and poultry manure (PM), incorporated with fertilizers on the growth, yield and protein content of BRRI dhan49 rice and BARI Gom-24. Study Design: RCBD with 8 treatments and 3 replications. Place and Duration of Study: Field experiment and nutrient analysis were carried out at Bangladesh Agricultural University (BAU), Mymensingh. Wheat was grown during the rabi season from October 2018 to March 2019. Again, rice was cultivated during kharif II season from August 2019 to December 2019 on the same field. Then the laboratory analysis was performed till June 2020. Methodology: Eight treatments i.e., T0 Control (no fertilizer), T1 Recommended Fertilizer Dose, T2 (CD + NPK), T3 (MSWC + NPK), T4 (OC + NPK), T5 (PM + N), T6 (MSWC + N), T7: (CD + OC) were accommodated. Data on the growth parameters including grain and straw yields were documented after the harvest of the fully matured crop simultaneously determining the nitrogen (N) and protein content. Results: Adoption of various combinations of compost and manures with fertilizer accorded an increase in yield contributing characters as well as the N and protein content. Integrating MSWC @ 10 t ha-1+N projected the highest grain yield (7.11 t ha-1 in rice; 4.84 t ha-1 in wheat) and straw yield (8.8 t ha-1 in rice; 5.55 t ha-1 in wheat). It also promisingly secured the highest protein content compared to all other treatments. Conclusion: The appliance of MSWC @ 10 t ha-1 with the recommended dose of N may be endorsed for rice and wheat cultivation in the AEZ-9 region and retaining the physicochemical properties of Old Brahmaputra Floodplain soils.

Characterizing River Manafwa Floodplain and Adjacent Soils

The objective of this study was to characterise Manafwa River floodplain and adjacent soils. Soil samples were collected from 0 - 20 cm depth in fallowed and cultivated Manafwa floodplain soils for laboratory analysis. Treatments included upland (control), floodplains fallowed for a year, floodplains fallowed for over a year, cultivated floodplains within 5 m and 50 m away from the river banks. Each treatment was replicated three times (3 blocks), and samples collected were analysed for K, Na, available P, total N, exchangeable acidity, pH, organic matter, moisture content, sand, silt, and clay. The soil sampling results were subjected to statistical Analysis of Variance (ANOVA) using Randomised Complete Block Design (RCBD), and the difference between treatment means were dictated using F-, student’s t and F-LSD/pairwise comparison tests. There was statistically no significant (p > 0.05) difference among different floodplains and uplands studied. Upland soils posted 71.67% for the highest pH and 0.09%, 0.87%, 9.74 ppm, 2.23 ppm and 7.264% for the lowest available N, organic matter, Phosphorous, Sodium and Moisture Content, respectively. Cultivated floodplain soil posted highest total P at 29.16 ppm and pH at 6.39% while fallowed floodplains lowest pH at 5.34%, highest available N at 0.32%, highest organic matter at 4.02%, highest K at 21.33%, highest Na at 13.93%, highest exchangeable acidity at 2.32 Cmol/Kg, highest clay content at 14.33%, lowest sand composition at 38.00%, highest silt composition at 54.8% and highest Moisture Content of 32.472%. As depicted by soil fertility analysis results, Manafwa River floodplain and adjacent soils have the capacity to accommodate and boost crop production and productivity. Any nutrients lost to leaching could be gained from subsequent fallowing and sustainable soil fertility management, proper drainage, crop rotation, adding organic manure, and cover cropping, among others

Microbially Induced Soil Colloidal Phosphorus Mobilization Under Anoxic Conditions.

Understanding the behavior of colloidal phosphorus (Pcoll) under anoxic conditions is pivotal for addressing soil phosphorus (P) mobilization and transport and its impact on nutrient cycling. Our study investigated Pcoll dynamics in acidic floodplain soil during a 30-day flooding event. The sudden oxic-to-anoxic shift led to a significant rise in pore-water Pcoll levels, which exceeded soluble P levels by more than 2.7-fold. Colloidal fractions transitioned from dispersed forms (<220 nm) to colloid-associated microaggregates (>220 nm), as confirmed by electron microscopy. The observed increase in colloidal sizes was paralleled by their heightened ability to form aggregates. Compared to sterile control conditions, anoxia prompted the transformation of initially dispersed colloids into larger particles through microbial activity. Curiously, the 16S rRNA and ITS microbial diversity analysis indicated that fungi were more strongly associated with anoxia-induced colloidal release than bacteria. These microbially induced shifts in Pcoll lead to its higher mobility and transport, with direct implications for P release from soil into floodwaters.

Comparative Performance of Different Fertilizer Recommendation Methods on Growth and Yield of Rice (Oryza sativa) in Old Brahmaputra Floodplain Soils

Improving rice productivity is the challenge for the farmer due to rapid soil health deterioration in intensive agricultural system. Therefore, the present study was conducted to evaluate comparative performance of different nutrient management practices in rice production in Bangladesh. The experiment was laid out in a randomized complete block design with three replications. There were six treatments namely, T1 (Control-no fertilizer), T2 (Farmer’s Practice), T3 (Fertilizer Recommendation Guide-2018), T4 (BAU Soil Testing Kit), T5 (Soil Test Basis) and T6 (Rice Crop Manager). The results revealed that all the treatments showed better performances over control (T1). Treatment T4 (BAU Soil Testing Kit) produced the highest value of plant height (90.18 cm), panicle length (24.90), filled grains panicle-1 (122.60) and 1000-grain weight (26.67g) while T5 (Soil Test Basis) produced maximum effective tillers hill-1 (12.80). The highest grain yield (6.29 t ha-1) and straw yield (7.73 t ha-1) were recorded in treatment T4 (BAU Soil Testing Kit). Treatment T4 (BAU Soil Testing Kit) also showed the highest grain yield increase (61.49%) and straw yield increase (90.49%) over control. The highest total N, P and K uptake (108.84 kg ha-1, 24.54 kg ha-1 and 128.17 kg ha-1) were obtained in the treatment T4 (BAU Soil Testing Kit). Control treatment T1 (No fertilizers) showed minimum performances in all the cases compared to other treatments. The overall result demonstrated that the application of fertilizers following BAU Soil Testing Kit method of fertilizer application system is a better option for rice production.

Antimony release and volatilization from organic-rich and iron-rich submerged soils

Antimony (Sb) is an poorly understood, increasingly common pollutant, especially in soils susceptible to waterlogging. We investigated the impact of waterlogging on Sb release, methylation, and volatilization from an organic-rich wetland soil and an iron (Fe)-rich floodplain soil in a 27-day microcosm experiment. The release of Sb into the porewaters of the organic-rich soil was environmentally relevant and immediate with waterlogging (3.2 to 3.5 mg L−1), and likely associated with a complex interplay of sulfide precipitation, sorption with organic matter and manganese (Mn) (oxyhydr)oxides in the soil. The release of Sb from the Fe-rich soil was likely associated with Fe-(oxyhydr)oxide reduction and immobilized due to co-precipitation with Fe-sulfides or as Sb-sulfides. Volatile Sb was produced from the soils after waterlogging. The organic-rich soil produced more volatile Sb (409 to 835 ng kgsoil−1), but the Fe-rich soil volatilized Sb more efficiently. The negligible association of Sb volatilization with soil parameters indicates a more complex underlying, potentially microbial, mechanism and that antimony volatilization could be ubiquitous and not dependent on specific soil properties. Future works should investigate the microbial and physiochemical drivers of Sb volatilization in soils as it may be an environmentally relevant part of the biogeochemical cycle.

Fluvial avulsions influence soil fertility in the Pantanal wetlands (Brazil)

River avulsions drive important changes in the Pantanal wetlands, owing to their role in the hydro-sedimentology of the region. Although relevant to numerous ecosystem services, few studies have analyzed the influence of river avulsions on soil fertility in the Pantanal. Here, we use the largest ongoing avulsion in the Taquari River (Caronal region) to evaluate the effects on soil fertility, considering two factors: avulsion stage (1) and aquatic-terrestrial succession (2). Since both factors are influenced by macrophyte abundance, an incident map was created through tasseled cap indices from Sentinel 2 images to guide sampling efforts in flooded soils. The mapped area was split into two zones of alluvial processes, the first from the apex of the Caronal lobe corresponding to the Taquari River megafan (TRM), and the second as the distal Paraguay River floodplain (PRF). Soil macro- and micronutrient levels were evaluated from 42 surface samples (0–0.2 m) distributed across the two alluvial process zones. The macrophyte map's overall accuracy (OA) was analyzed by a confusion matrix using the Sentinel 2 imagery. Finally, we used Random Forest regressions to determine the influence of response variables on soil attributes, including tassel indices, distance from the Caronal crevasse, macrophyte density, and an existing soil fertility map. The macrophyte map obtained an OA of 93 %. Some parameters such as pH (r = −0.62; R2 = 0.57), effective cation exchange capacity (r = −0.49; R2 = 0.79), Mn (r = −0.71; R2 = 0.6), Zn (r = −0.69; R2 = 0.54), and base saturation (r = −0.7; R2 = 0.93) were influenced by the distance or level of maturation of the avulsion stage in the TRM. Our scattering of soil collections was insufficient to test the terrestrialization hypothesis (2). The study results show that river channel avulsions influence the accumulation of mineral and organic nutrients in tropical floodplain soils, which has implications for fertility and biodiversity.

Multi-method analysis of microplastic distribution by flood frequency and local topography in Rhine floodplains

Rivers are important transport pathways for microplastics into the ocean, but they can also be potential sinks due to microplastic deposition in the sediments of the river bed and adjacent floodplains. In particular, floods can (re)mobilise microplastics from sediments and floodplains, (re)deposit and relocate them depending on the floodplain topography. The knowledge about fluvial microplastic input to floodplains, their spatial distribution and their fate in floodplain soils is limited. To investigate this topic, we sampled soil at a depth of 5–20 cm along three transects in three different Rhine floodplains. We analysed the soil samples in tandem with pyrolysis GC/MS and ATR- & μ-FPA-FTIR for their microplastic abundance and mass concentrations. To study the influence of flood frequency on the microplastic abundance in the three floodplains, we fitted a hydrodynamic flood model (MIKE 21, DHI, Hørsholm, Denmark) and related the results to the respective spatial microplastic distribution. We found similar microplastic distribution patterns in each floodplain. The highest microplastic abundance (8516–70,124 microplastics kg−1) and mass concentration (46.2–141.6 mg kg−1) were consistently found in the farthest transects from the Rhine in a topographical depression. This microplastic distribution pattern is detectable with both, pyrolysis GC/MS and FTIR. The strongest correlation between the results of both methods was found for small, abundant microplastic particles. Our results suggest that the spatial distribution of microplastics in floodplains is related to the combination of flood frequency and local topography, that ought to be explicitly considered in future studies conducted in floodplains. Finally, our results indicate that pyrolysis GC/MS and FTIR data are comparable under certain conditions, which may help in the decision for the analytical method and sampling design in future studies.

Mercury distribution in organisms, litter, and soils of the Middle Araguaia floodplain in Brazil.

Mercury (Hg) is a chemical element that, depending on its concentration, may become toxic to living organisms due to the ability of Hg to bioaccumulate in food chains. In this study, we collected samples of soil, litter, and organisms in the Middle Araguaia floodplain, Brazil. Total mercury (THg) concentrations in litter were significantly higher (p < 0.0001) than that in soil, ranging from 10.68 ± 0.55 to 48.94 ± 0.13 and 20.80 ± 1.07 to 55 .19 ± 1.59 ng g-1, respectively. Total mercury concentration levels in soil showed a linear, inversely proportional relationship with soil organic matter (SOM) contents and soil pH, consistent with the geochemical behavior of chemical elements in flooded environments. Ten orders of organisms were identified, and the average THg concentrations determined in their bodies were up to 20 times higher than those in soil and litter. We found a significant linear relationship between the levels of THg in litter and those found in soil organisms, thereby allowing the prediction of THg concentration levels in soil organisms through the analysis of litter at the sample units. The different dynamics and feeding habits of soil organisms and the concentration of THg in these organisms may be influenced by the river's course. This study provides evidence of the bioaccumulation of THg in soil organisms in the floodplain of the Middle Araguaia River, an important river basin in the Brazilian savanna.

Can Exclusion of Feral Ecosystem Engineers Improve Coastal Floodplain Resilience to Climate Change? Insight from a Case Study in North East Arnhem Land, Australia

Global climate change can interact with local drivers, such as ecosystem engineers, to exacerbate changes in ecosystem structure and function, with socio-ecological consequences. For regions of Indigenous interest, there may also be cultural consequences if species and areas affected are culturally significant. Here we describe a participatory approach between the Indigenous (Yolngu) Yirralka Rangers and non-Indigenous researchers that explored the interaction between sea level rise and feral ungulate ecosystem engineers on culturally significant floodplains in the Laynhapuy Indigenous Protected Area (IPA), northern Australia. A feral ungulate exclusion fence array (12 fenced and 12 unfenced plots) was stratified by elevation/salinity to disentangle the effects of salinity and ungulates on floodplain soil and vegetation. We found that exclusion of feral ungulates improved ground cover vegetation, which, according to our literature-derived ecosystem process model, may enhance soil trapping and reduce evapotranspiration to provide the antecedent conditions needed to improve floodplain resilience to sea level rise. The mid-zone of the supratidal floodplain study site was suggested as the region where the benefits of fencing were most pronounced after two years and ground cover species diversity was highest. Ongoing monitoring is required to investigate whether removal of feral ungulates can increase resilience against sea level rise and recruitment of eco-culturally significant Melaleuca species. An interview with a key Yolngu Traditional Owner of the study site demonstrated the importance and effectiveness of the partnership. Yolngu land owners and rangers were active co-researchers and will decide if, when and how to integrate results into feral ungulate management and climate adaptation responses, highlighting the importance of industry-university partnerships in maximising biocultural conservation outcomes.

Short‐ and long‐term legacies of carbon sequestration, and nutrient burial in floodplain wetlands of agricultural and forested catchments, Indiana, United States

AbstractSoil organic carbon (C) sequestration and nitrogen (N) and phosphorus (P) burial were measured in two floodplain wetlands' soils of the West Fork of the White River watershed (Indiana, United States) whose catchments differed in land use to better understand how land use practices affect wetland C and nutrient retention. The catchment of one floodplain, Upper West Fork, is dominated by row crop agriculture (61%) whereas the second catchment, Beanblossom Creek, is mostly forested (85%). Soils (0–30 cm) of the two floodplain wetlands had similar bulk density (1.23 g/cm3). Soil organic C and N were low in both floodplains but the percent organic C and N was two times greater (3.3% C, 0.22% N) in the agricultural floodplain than in the floodplain in the forested catchment (1.5% C, 0.14% N). Soil P was three times greater in the agricultural (1100 μg/g) than in the forested floodplain (350 μg/g). Recent soil accretion based on 137Cs which provides a historical record since 1964 (60 years), was two times greater in the agricultural floodplain (2.2 mm/year) than in the forested catchment (1.0 mm/year). Sediment deposition (2500 g/m2/year), C sequestration (90 g/m2/year), and N burial (7.5 g/m2/year) were three times greater in the agricultural floodplain and P burial was seven times greater (3.0 vs. 0.41 g/m2/year). Long‐term measurements (100 years) based on 210Pb did not show large differences in C sequestration and N burial between the two floodplains though soil accretion and sediment deposition were greater in the forested floodplain. We attribute these higher rates to greater erosion in the watershed before 1950 when the catchment had more agricultural land and before instruction on best management practices to reduce soil erosion. These findings confirm previously published studies that show that P enrichment and accumulation in floodplain soils represent legacy effects of agricultural land use in the catchment.

Fertility Assessment of Nun River Floodplain Soils in Bayelsa State, Southern Nigeria for Agricultural Productivity

Following massive crude oil exploitation in Bayelsa State, arable land is shrinking and a food crisis, looming. To stop this trend, information on soil fertility status and management strategies becomes important for policy development. This paper assesses fertility status of the Nun River floodplain soils in Bayelsa State using newly developed indices for sustainable agricultural productivity and food security. Nun River plain alluvial soils of different landforms were collected from the genetic horizons of nine profiles, and analysed for physicochemical characteristics and soil fertility assessed using soil fertility index. (SFI) and soil evaluation factor (SEF). ). Silt-sized particles dominated Odi (ODI), Koroama (KRM) and Niger Delta University (NDU 1) soils, except in NDU2 and NDU3, pH was moderate to slightly acidic (5.64–6.30), available P, low to high (0.6–22 mg/kg), organic C (0.31–5.35%), and total nitrogen (0.01–0.45%) low to high while calcium dominated the exchange complex. Correlation between Organic matter and total N (r = 0.366, p ‹ 0.001) and available P (r = - 0.310, p ‹ 0.01) was highly positively, suggesting that organic matter dictates availability of N and P. The SFI values were higher (p ‹0.05) than SEF except in NUD2 and NDU3, pH, organic matter and available phosphorus contributing more. Of paramount importance is conservation of organic matter as the accumulation of biomass greatly improved physical properties and fertility of the soil.

Soil, climate, and landscape drivers of base cation concentrations in green stormwater infrastructure soils

Deicing practices and infrastructure weathering can impact plants, soil, and water quality through the input and transport of base cations. Base cation accumulation in green stormwater infrastructure (GSI) soils has the potential to decrease soil infiltration rates and plant water uptake or to promote leaching of metals and nutrients. To understand base cation retention in GSI soils and its drivers, we sampled 14 GSI soils of different age, contributing areas, and infiltration areas, across 3 years. We hypothesized that soil, climate, and landscape drivers explain the spatial and temporal variability of GSI soil base cation concentrations. Sodium (Na), Calcium (Ca), and Magnesium (Mg) concentrations in GSI soils were higher than in reference soils, while Ca and Mg were similar to an urban floodplain soil. Neither the contributing area, contributing impervious area, nor their ratios to infiltration area predicted base cation concentrations. Age predicted the spatial variability of Potassium (K) concentrations. Ca and Mg were moderately predicted by sand and silt, while clay predicted Mg, and sand predicted K. However, no soil characteristics predicted Na concentrations. A subset of sites had elevated Na in Fall 2019, which followed a winter with many freezing events and higher-than-average deicer salt application. K in sites with elevated Na was lower than in non-elevated sites, suggesting that transient spikes of Na driven by deicer salt decreased the ability of GSI soils to accumulate K. These findings demonstrate the large variability of GSI soil base cation concentrations and the relative importance of soil, climate, and landscape drivers of base cation dynamics. High variability in GSI soil data is commonly observed and further research is needed to reduce uncertainties for modeling studies and design. Improved understanding of how GSI soil properties evolve over time, and their relation to GSI performance, will benefit GSI design and maintenance practices.

Carbon Stocks and Potential Greenhouse Gas Production of Permafrost‐Affected Active Floodplains in the Lena River Delta

AbstractArctic warming increases the degradation of permafrost soils but little is known about floodplain soils in the permafrost region. This study quantifies soil organic carbon (SOC) and soil nitrogen stocks, and the potential CH4 and CO2 production from seven cores in the active floodplains in the Lena River Delta, Russia. The soils were sandy but highly heterogeneous, containing deep, organic rich deposits with &gt;60% SOC stored below 30 cm. The mean SOC stocks in the top 1 m were 12.9 ± 6.0 kg C m−2. Grain size analysis and radiocarbon ages indicated highly dynamic environments with sediment re‐working. Potential CH4 and CO2 production from active floodplains was assessed using a 1‐year incubation at 20°C under aerobic and anaerobic conditions. Cumulative aerobic CO2 production mineralized a mean 4.6 ± 2.8% of initial SOC. The mean cumulative aerobic:anaerobic C production ratio was 2.3 ± 0.9. Anaerobic CH4 production comprised 50 ± 9% of anaerobic C mineralization; rates were comparable or exceeded those for permafrost region organic soils. Potential C production from the incubations was correlated with total organic carbon and varied strongly over space (among cores) and depth (active layer vs. permafrost). This study provides valuable information on the carbon cycle dynamics from active floodplains in the Lena River Delta and highlights the key spatial variability, both among sites and with depth, and the need to include these dynamic permafrost environments in future estimates of the permafrost carbon‐climate feedback.

Assessment of the humus state of hortically suitable soils Northwest Caucasus

The laying of intensive industrial gardens in Russia is carried out according to special projects, which are based on complex works that begin the selection and assessment of the soil suitability of land plots. The levels of total humus and its labile forms have been established for the main horticultural soils of the Krasnodar Territory on the basis of long-term studies. The use of these criteria makes it possible to assess the degree of cultivation or degradation processes of the soil cover of each specific garden plot. Studies have shown that, in all surveyed soils of the region, the profile distribution of humus is gradually decreasing. The most informative soil layer for assessing fertility can be considered the upper 30 cm layer. The greatest quantitative and qualitative changes of organic matter occur in this layer. Different gardening zones of the region differ in the content of total humus in the main types of soils, a decrease is observed from ordinary chernozems (northern zone) to alluvial meadow soils (river valleys of the foothill zone). The humus content in the natural cenoses of Kuban chernozems reached 5.5 %, and in heavily plowed soil up to 3.5 %, a similar situation was observed in floodplain soils, these values corresponded to 4.0 % and 2.0 %. All other types of soils occupied an intermediate position in terms of humus content.

ИЗМЕНЕНИЕ ПАРАМЕТРОВ ПЛОДОРОДИЯ АЛЛЮВИАЛЬНЫХ ПОЧВ МЕЛИОРИРОВАННОЙ ПОЙМЫ Р. ДЕСНЫ ПРИ ИСПОЛЬЗОВАНИИ В КАЧЕСТВЕ СЕНОКОСА

Purpose: to study the features of changes in agrochemical parameters of reclaimed soils of the Desna river floodplain when used as haymaking. Materials and methods. The studies were carried out on a reclaimed section of the Desna river floodplain located between communities Negotino and Ovstug, Zhukovsky district, Bryansk region. Soil samples were collected in 2005 and 2021 using the method of soil keys by genetic horizons. Agrochemical indicators were determined by generally accepted methods. Results. Monitoring observations were carried out in the reclaimed area of the Desna river floodplain. It was noted that the recommended fertilizer system is not used, liming is not carried out, and reclamation channels are not maintained in proper condition. It was shown that there was a sharp decrease in the organic matter and total nitrogen content in the humus horizon in all key areas. An ambiguous change in acidity was noted. At site R-22, a decrease in pH (KCl) down the soil profile by 0.4 and 0.1 units was noted. In the key area R-23 pH (KCl) decreased by 1.0 units in the humus horizon, for the underlying horizons by 0.8 and 1.2 units, respectively. At site R-24, acidity decreased by 0.3 and 0.4 units for horizons down the soil profile. At site R-25, the acidity in the humus horizon did not change, but in the underlying horizon there was an increase in pH (KCl) by 0.6 units. In areas R-22 and R-24, the content of mobile phosphorus compounds in the humus horizon increased from 4.8 to 22.7 % and decreased in the underlying one. At site R-23, the content of available phosphorus decreased. In the R-25 area in the humus horizon it increased by 51.6 %, in the underlying one it decreased by 58.6 %. The dynamics of the mobile potassium distribution is generally similar to that of mobile phosphorus. Conclusions: ignoring the recommendations on the fertilizer and liming system, the neglect of reclamation canals, combined with the climatic features of the observed period, led to changes in soil properties, mainly of a degradation nature.