Horizon Depth Research Articles

Annual Net Community Production of Particulate and Dissolved Organic Carbon From a Decade of Biogeochemical Profiling Float Observations in the Northeast Pacific

AbstractCarbon export out of the surface ocean via the biological pump is a critical sink for atmospheric carbon dioxide. This process transports organic carbon to the deep ocean through sinking particulate organic carbon (POC) and the downward transport of suspended POC and dissolved organic carbon (DOC). Changes in the relative contribution of each pathway can significantly affect the magnitude and efficiency of carbon export to depth. Net community production (NCP), an analog of carbon export under steady state assumptions, is typically estimated using budgets of biologically important chemical tracers in the upper ocean constrained by ship‐board or autonomous platform observations. In this study, we use measurements from biogeochemical profiling floats, the Ocean Station Papa mooring, and recently developed algorithms for carbonate system parameters to constrain budgets for three tracers (nitrate, dissolved inorganic carbon, and total alkalinity) and estimate NCP in the Northeast Pacific from 2009 to 2017. Using our multiple‐tracer approach, and constraining end‐member nutrient ratios of the POC and DOC produced, we not only calculate regional NCP throughout the annual cycle and across multiple depth horizons, but also partition this quantity into particulate and dissolved portions. We also use a particle backscatter‐based approach to estimate POC attenuation with depth and present a new method to constrain particle export across deeper horizons and estimate in situ export efficiency. Our results agree well with previously published estimates of regional carbon export annually and suggest that the approaches presented here could be used to assess the magnitude and efficiency of carbon export in other regions of the world's oceans.

Results of works carried out via electrical exploration method for searching groundwater sources suitable for drinking and household use in the debris cone of Turyanchay river

The paper deals with the exploration works conducted via electrical exploration method for searching groundwater sources suitable for drinking and household use in the debris cone area of Turyanchay river. As a results of carried out studies, the areas with groundwater sources suitable for drinking and household use are marked, lithological content and depth of water horizons specified as well. With the aim of estimation of fresh groundwater reserves in the debris cone area of Turyanchay river suitable for drinking, ρf and geological-geophysical sections have been developed due to the geophysical surveys executed via vertical electrical sounding (VES) methods. To specify the lithology of the rocks and reveal formations with reservoir properties, logging operations have been carried out. The thickness of clay formations comprising the sections increases from the north-west to the south-east; alongside with this due to the alternations of gravel sediments with clay rocks the specific electrical resistence of the rocks decreases. As a result of exploration of water sources suitable for drinking in the debris cone of Turyanchay river, the water content of the rocks in mentioned area has been studied to the depth of 285 m, the prospective zones of fresh and less mineralized groundwater marked, initial reserves estimated and prospective zones for accurate surveys specified as well.

From Sea Surface to Seafloor: A Benthic Allochthonous eDNA Survey for the Abyssal Ocean

Environmental DNA (eDNA) metabarcoding could facilitate rapid and comprehensive biotic surveys in the deep ocean, yet many aspects of the sources and distribution of eDNA in the deep sea are still poorly understood. In order to examine the influence of the water column on benthic eDNA surveys in regions targeted for deep-sea polymetallic nodule mining, we investigated the occurrence of pelagic eDNA across: (1) two different deep-sea habitat types, abyssal plains and seamounts, (2) benthic sample types, including nodules, sediment, and seawater within the benthic boundary layer (BBL), and (3) sediment depth horizons (0-2 cm, 3-5 cm). Little difference was observed between seamounts and the adjacent abyssal plains in the proportion of legacy pelagic eDNA sampled in the benthos, despite an > 1000 m depth difference for these habitats. In terms of both reads and amplicon sequence variants (ASVs), pelagic eDNA was minimal within sediment and nodule samples (< 2 %), and is unlikely to affect benthic surveys that monitor resident organisms at the deep seafloor. However, pelagic eDNA was substantial within the BBL (up to 13 % ASVs, 86% reads), derived both from the high-biomass upper ocean as well as deep pelagic residents. While most pelagic metazoan eDNA found in sediments and on nodules could be sourced from the epipelagic, protist legacy eDNA sampled on these substrates appeared to originate across a range of depths in the water column. Some evidence of eDNA degradation across a vertical sediment profile was observed for protists, with higher diversity in the 0-2 cm layer and a significantly lower proportion of legacy pelagic eDNA in deeper sediments (3-5 cm). Study-wide, our estimated metazoan sampling coverage ranged from 40 % to 74 %, despite relatively large sample size. Future deep-sea eDNA surveys should examine oceanographic influences on eDNA transport and residence times, consider habitat heterogeneity at a range of spatial scales in the abyss, and aim to process large amounts of material per sample (with replication) in order to increase the sampling coverage in these diverse deep ocean communities.

Influence of Forest Shelterbelts on Local Pedodiversity (Belgorod Oblast)

Detailed mapping of soils under a multi-row 4-km-long 50-year-old forest shelterbelt crossing diverse landforms and under adjacent croplands was performed at the key site in Belgorod oblast, in the south of the Central Russian Upland. Samples were collected in 30 points both in the central part of the shelterbelt and at distances of 30 meters on both sides of the shelterbelt. Maps of the depth of humus horizon, organic carbon content, depth of carbonates, and the soil map were compiled; indices of richness, diversity (Shannon, Simpson, Rao) and taxonomic distances (as a quantitative indicator of soil cover contrasts) were calculated. It was shown that soils under the shelterbelt are less contrasting among one another and more diverse than soils of the adjacent croplands. The shelterbelt effect on pedodiversity at the key site extends over adjacent areas affected by periodic waterlogging due to the barrier function of the shelterbelt.

Discovery of an Abundance of Biosynthetic Gene Clusters in Shark Bay Microbial Mats.

Microbial mats are geobiological multilayered ecosystems that have significant evolutionary value in understanding the evolution of early life on Earth. Shark Bay, Australia has some of the best examples of modern microbial mats thriving under harsh conditions of high temperatures, salinity, desiccation, and ultraviolet (UV) radiation. Microorganisms living in extreme ecosystems are thought to potentially encode for secondary metabolites as a survival strategy. Many secondary metabolites are natural products encoded by a grouping of genes known as biosynthetic gene clusters (BGCs). Natural products have diverse chemical structures and functions which provide competitive advantages for microorganisms and can also have biotechnology applications. In the present study, the diversity of BGC were described in detail for the first time from Shark Bay microbial mats. A total of 1477 BGCs were detected in metagenomic data over a 20 mm mat depth horizon, with the surface layer possessing over 200 BGCs and containing the highest relative abundance of BGCs of all mat layers. Terpene and bacteriocin BGCs were highly represented and their natural products are proposed to have important roles in ecosystem function in these mat systems. Interestingly, potentially novel BGCs were detected from Heimdallarchaeota and Lokiarchaeota, two evolutionarily significant archaeal phyla not previously known to possess BGCs. This study provides new insights into how secondary metabolites from BGCs may enable diverse microbial mat communities to adapt to extreme environments.

Distribution of deep-water scleractinian and stylasterid corals across abiotic environmental gradients on three seamounts in the Anegada Passage

In the Caribbean Basin the distribution and diversity patterns of deep-sea scleractinian corals and stylasterid hydrocorals are poorly known compared to their shallow-water relatives. In this study, we examined species distribution and community assembly patterns of scleractinian and stylasterid corals on three high-profile seamounts within the Anegada Passage, a deep-water throughway linking the Caribbean Sea and western North Atlantic. Using remotely operated vehicle surveys conducted on the E/V Nautilus by the ROV Hercules in 2014, we characterized coral assemblages and seawater environmental variables between 162 and 2,157 m on Dog Seamount, Conrad Seamount, and Noroît Seamount. In all, 13 morphospecies of scleractinian and stylasterid corals were identified from video with stylasterids being numerically more abundant than both colonial and solitary scleractinians. Cosmopolitan framework-forming species including Madrepora oculata and Solenosmilia variabilis were present but occurred in patchy distributions among the three seamounts. Framework-forming species occurred at or above the depth of the aragonite saturation horizon with stylasterid hydrocorals being the only coral taxon observed below Ωarag values of 1. Coral assemblage variation was found to be strongly associated with depth and aragonite saturation state, while other environmental variables exerted less influence. This study enhances our understanding of the factors that regulate scleractinian and stylasterid coral distribution in an underreported marginal sea and establishes a baseline for monitoring future environmental changes due to ocean acidification and deoxygenation in the tropical western Atlantic.

Amynthas spp. impacts on seedlings and forest soils are tree species-dependent

Asian jumping worms (Amynthas spp.) are recent invaders of Upper Midwest forests. Research has highlighted the impacts of Amynthas earthworms on soil biogeochemistry and structure, and field observations suggest that Amynthas spp. decrease litter horizon depth and alter plant communities. However, the extent to which Amynthas spp. effects vary among forest types and with worm density and the mechanisms driving these effects are unknown. We conducted a 3-month tree seedling study to evaluate the effects of Amynthas spp. on tree seedling growth and a mesocosm field experiment to evaluate Amynthas spp. effects on soil carbon and nutrient cycling, soil structure, and leaf litter decomposition rates across forest types. In the seedling study, Amynthas spp. enhanced the growth of sugar maple and European buckthorn seedlings and decreased the growth of white oak seedlings. These effects were due to Amynthas spp.-induced changes in soil properties. In the mesocosm study, as Amynthas spp. density increased, carbon mineralization and carbon, nitrogen, and phosphorus availability increased in white oak forest soils and decreased in sugar maple forest soils, while decomposition rates of European buckthorn litter increased as Amynthas spp. density increased. Amynthas spp. altered soil structure similarly across all forest soil types. Taken together, our results suggest that Amynthas spp. have the potential to alter forest ecosystem dynamics via feedbacks among tree species, seedlings, and soil biogeochemistry. However, Amynthas spp. effects on tree seedlings and forest soils are largely context-dependent, and the direction and magnitude of these effects are mediated by tree species.

Global database of ratios of particulate organic carbon to thorium-234 in the ocean: improving estimates of the biological carbon pump

Abstract. The ocean's biological carbon pump (BCP) plays a major role in the global carbon cycle. A fraction of the photosynthetically fixed organic carbon produced in surface waters is exported below the sunlit layer as settling particles (e.g., marine snow). Since the seminal works on the BCP, global estimates of the global strength of the BCP have improved but large uncertainties remain (from 5 to 20 Gt C yr−1 exported below the euphotic zone or mixed-layer depth). The 234Th technique is widely used to measure the downward export of particulate organic carbon (POC). This technique has the advantage of allowing a downward flux to be determined by integrating the deficit of 234Th in the upper water column and coupling it to the POC∕234Th ratio in sinking particles. However, the factors controlling the regional, temporal, and depth variations of POC∕234Th ratios are poorly understood. We present a database of 9318 measurements of the POC∕234Th ratio in the ocean, from the surface down to &gt;5500 m, sampled on three size fractions (∼&gt;0.7 µm, ∼1–50 µm, ∼&gt;50 µm), collected with in situ pumps and bottles, and also from bulk particles collected with sediment traps. The dataset is archived in the data repository PANGAEA® under https://doi.org/10.1594/PANGAEA.911424 (Puigcorbé, 2019). The samples presented in this dataset were collected between 1989 and 2018, and the data have been obtained from published papers and open datasets available online. Unpublished data have also been included. Multiple measurements can be found in most of the open ocean provinces. However, there is an uneven distribution of the data, with some areas highly sampled (e.g., China Sea, Bermuda Atlantic Time Series station) compared to some others that are not well represented, such as the southeastern Atlantic, the south Pacific, and the south Indian oceans. Some coastal areas, although in a much smaller number, are also included in this global compilation. Globally, based on different depth horizons and climate zones, the median POC∕234Th ratios have a wide range, from 0.6 to 18 µmol dpm−1.

Estimating organic surface horizon depth for peat and peaty soils across a Scottish upland catchment using linear mixed models with topographic and geological covariates

AbstractIn order to evaluate and protect ecosystem services provided by peat and peaty soils, accurate estimations for the depth of the surface organic horizon are required. This study uses linear mixed models (LMMs) to test how topographic (elevation, slope, aspect) and superficial geology parameters can contribute to improved depth estimates across a Scottish upland catchment. Mean (n = 5) depth data from 283 sites (representing full covariate ranges) were used to calibrate LMMs, which were tested against a validation dataset. Models were estimated using maximum likelihood, and the Akaike Information Criterion was used to test whether the iterative addition of covariates to a model with constant fixed effects was beneficial. Elevation, slope and certain geology classes were all identified as useful covariates. Upon addition of the random effects (i.e. spatial modelling of residuals), the RMSE for the model with constant‐only fixed effects reduced by 24%. Addition of random effects to a model with topographic covariates (fixed effects = constant, slope, elevation) reduced the RMSE by 13%, whereas the addition of random effects to a model with topographic and geological covariates (fixed effects = constant, slope, elevation, certain geology classes) reduced the RMSE by only 3%. Therefore, much of the spatial pattern in depth was explained by the fixed effects in the latter model. The study contributes to a growing research base demonstrating that widely available topographic (and also here geological) datasets, which have national coverage, can be included in spatial models to improve organic horizon depth estimations.

Soybean yield in relation to environmental and soil properties

Abstract Our goal was to identify soil, plant and climate attributes that are most closely related to soybean [Glycine max (L.) Merr.] yield variation in Pennsylvania. We studied 22 site-years over the 2016 and 2017 growing seasons in two regions. The average yields were 3.4 Mg ha-1 in 2016 (range 1.4 to 5 Mg ha-1) and 5.5 Mg ha-1 in 2017 (range 3.5 to 7.4 Mg ha-1). Solar radiation capture and water availability, both controlled by planting date, were the main predictors of soybean yield. Principal component analysis and Random Forest analysis revealed that the soil predictors of soybean yield were the content of zinc, copper, phosphorus, sulfur, potassium, as well as A horizon depth and total soil depth. The yield response to nutrients is likely a surrogate for a more complex response to animal manure additions. Soybean yield correlated positively with the ratio of soil respiration to soil organic matter, but did not correlate with the physical and biological soil metrics in the comprehensive Cornell Assessment of Soil Health (CASH). Saturated hydraulic conductivity (ksat) and root depth correlated with both soybean yield and each other. Thus, while planting date sets the maximum achievable yield, only soils having the most water and nutrient availability (manured soils with high ksat) expressed yields exceeding 7 Mg ha-1. The ksat appears to be a valuable indicator of soil condition that can be relevant well beyond its association with high soybean grain yield.

Rooting depth and below ground biomass in a freshwater coastal marsh invaded by European Reed (&lt;i&gt;Phragmites australis&lt;/i&gt;) compared with remnant uninvaded sites at Long Point, Ontario

Invasive European Reed (Phragmites australis subsp. australis) outcompetes native vegetation, reducing floristic diversity and habitat value for wildlife. Research in coastal salt marshes has indicated that P. australis invasion may be facilitated by its relatively deep rooting depth, but in freshwater marshes the growth pattern of below ground tissues in relation to water depth is uncertain. To determine if P. australis is rooting more deeply than resident wetland plant species in a freshwater coastal marsh on Lake Erie, Ontario, we measured the vertical distribution of below ground biomass in P. australis invaded marsh sites and compared it to the below ground biomass distribution in nearby sites not yet invaded by P. australis. These invaded and uninvaded sites were paired by water depth, which is known to influence resource allocation and rooting depth. Below ground biomass in invaded sites was greater than in uninvaded sites (t28 = 3.528, P = 0.001), but rooting depth (i.e., the depth at which 90% of total below ground biomass is accounted for) was comparable (t28 = 0.992, P = 0.330). Using water depth and site type, general linear models could predict below ground biomass (F2,55 = 9.115, P &lt; 0.001) but not rooting depth (F2,55 = 1.175, P = 0.316). Rooting depth is likely affected by other factors such as substrate type and the depth of the organic soil horizon.

Analytic formulation for subsurface volumetric estimation

We have developed an analytic formulation for quick and more accurate volumetric estimations of subsurface resource potential. Our formulation is conceptually based on a structurally conformable model built deterministically using known and interpreted reservoir properties from wells, such as net-to-gross, porosity, and hydrocarbon saturation, along with oil-water contact or lowest known oil depth and interpreted seismic top-of-pay depth horizon. We have evaluated an important function, the hydrocarbon pore capacity (HPC), which is a product of net-to-gross, porosity, and hydrocarbon saturation. HPC reflects the heterogeneity of key reservoir rock and fluid properties, particularly in the vertical direction. We calculated the total hydrocarbon pore volume directly from HPC and the top-of-pay horizon, without the explicit need for building a geologic model first. Our efficient solution form can preserve the vertical resolution of wireline logging with transparent parameterization and the least amount of averaging and upscaling. We also provided additional formulation for incorporating different HPC regimes for cases of multiple existing wells in the reservoir. We demonstrate the practical application of the formulation with a data example from a Cretaceous carbonate reservoir in the southern Gulf of Mexico offshore and with comparisons to other common approaches. In the application example, we determine that the most common approach of using single-average-values can underestimate the reserve upside by as much as 30%, whereas the stochastic modeling approach provided improved estimates when simulating porosity with a lognormal distribution and preserving the net-to-gross log in its original vertical resolution.

Microbial Biomass, Carbon Stocks, and CO2 Emission in Soils of Franz Josef Land: High-Arctic Tundra or Polar Deserts?

The biomass of prokaryotes and fungi, organic carbon stocks, and CO2 emission were studied in the Cryosols and Leptosols of Franz Josef Land. The highest carbon stocks were found in the Eutric Leptosols (Loamic, Humic) formed in the wind-sheltered areas (23.2 kg C/m2 in the upper 50 cm), as well as in Turbic Cryosols (Humiс) that contained organic matter buried by cryoturbation (13.7–20.7 kg C/m2). The number of prokaryotes varied between 0.14 and 2.10 billion cells/g of soil, and the maximum values of their biomass were found in the litter. The fungal biomass varied from tens to hundreds of mg/g of soil depending on the type of soil and biotope. The share of spores was more than a half of the total fungal biomass in 80% of cases. Spores and mycelium were mainly represented by small forms with a diameter of up to 2–3 microns. The length of the fungal mycelium ranged from 4 to 272 m/g of soil. The maximum development of fungi was observed in the lichen biocrusts and moss litters. The fungal biomass decreased exponentially with the depth of horizons, and at the same time the share of prokaryotes in microbial biomass increased by several times. The share of microbial carbon in the total organic carbon was higher in soils of barrens (the most extreme habitats among the studied ones) as compared with the soils of local tundra areas (12.7 versus 2.5%, respectively). The levels of СО2 emission from the surface of undisturbed soils varied in the range of 1.6–91.7 mg C–CО2/m2 per hour and differed by tens of times between barrens and tundra areas. The studied soils are close to the soils of the Arctic tundra when compared by their carbon stocks and CO2 emission values; however, their microbial biomass values and their distribution are close to the soils of Antarctica and hot deserts.

АНАЛІЗ ГІДРОГЕОЛОГІЧНИХ І ГЕОТЕРМІЧНИХ ХАРАКТЕРИСТИК ГЕОТЕРМАЛЬНИХ ОБ’ЄКТІВ УКРАЇНИ

На основі матеріалів «Державного інформаційного геологічного фонду України» створено базу даних геотермальних об’єктів, в яку увійшло 655 об’єкта, які охоплюють 12 адміністративних областей України і близько 54 % існуючих родовищ вуглеводнів. Основними геотермічними і гідрогеологічними характеристиками об’єктів бази даних є: глибина залягання, літологія і склад порід, геологічний вік порід, товщина продуктивного горизонту, пластова температура і пластовий тиск, дебіт свердловини, зниження рівня води у водоносному горизонті під час випробування, мінералізація, газовий склад і вміст природного газу у підземних водах.&#x0D; Аналіз гідрогеологічних і геотермічних характеристик геотермальних об’єктів виконано на основі структурно-гідрогеологічного принципу, тобто усі об’єкти розглядались стосовно крупних гідрогеологічних структур з єдиними регіональними межами і умовами формування родовищ підземних вод. Було проаналізовано чотири гідрогеологічні структури: Закарпатський внутрішній прогин, Прикарпатський передгірний прогини, Дніпровсько-Донецький артезіанський басейн та Причорноморський артезіанський басейн. Для кожної структури побудовано діаграми розподілу пластових температур, глибин залягання і мінералізації підземних вод в геотермальних об'єктах бази даних.&#x0D; Аналіз показав, що умови формування геотермальних родовищ в першу чергу залежать від теплового фону земних надр, але на процеси формування родовищ дуже істотний вплив має глибина залягання кристалічного фундаменту, розташування областей живлення і розвантаження термоводоносних горизонтів, глибина сучасного водообміну, літологічний склад водовмісних порід.&#x0D; Створена база даних геотермальних об’єктів України може бути використана під час вибору першочергових проектів освоєння геотермальних ресурсів, а також для стратегічного планування геотермальної галузі в цілому. Бібл. 10, рис. 14.

Modelling soil properties from horizon depth functions and terrain attributes: An example with cation exchange capacity

The objective of this study was to, through the distribution of some soil properties, model cation exchange capacity (CEC) in soils formed on gently undulating coastal plain sands of southeastern Nigeria using genetic horizon functions and terrain attributes. A total of 19 profile pits were prepared, described and 104 genetic horizons were identified and sampled, processed and analysed in the laboratory. Data were generated on the soil characteristics, including particle size fractions, hydraulic conductivity, bulk density, organic carbon, pH and electrical conductivity. Terrain attributes that were generated from digital elevation model include aspect, compound topographic index (CTI), Flow direction, curvatures, slope and stream power index (SPI). Data generated were analysed using descriptive statistics, correlation and regression. The terrain attributes were modified with genetic horizon depths, bulk density and clay content for the modelling process. Sand content, bulk density and cation exchange capacity possess geogenic rather than pedogenic characteristics and were normally distributed. The indication is that the two groups of terrain attributes depended on the mass per unit area of soil and clay content in their influence on these ultisol profiles. Paired comparison, root mean square error and normalized root mean square error indicated that the model was a good fit and could be useful in the prediction of soil properties and management of coastal plain sands.

Impacts of Varying Dam Outflow Elevations on Water Temperature, Dissolved Oxygen, and Nutrient Distributions in a Large Prairie Reservoir

Dam operations are known to have significant impacts on reservoir hydrodynamics and solute transport processes. The Gardiner Dam, one of the structures that forms the Lake Diefenbaker reservoir located in the Canadian Prairies, is managed for hydropower generation and agricultural irrigation and is known to have widely altering temperature regimes and nutrient circulations. This study applies the hydrodynamic and nutrient CE-QUAL-W2 model to explore how various withdrawal depths (5, 15, 25, 35, 45, and 55 m) influence the concentrations and distribution of nutrients, temperature, and dissolved oxygen (DO) within the Lake Diefenbaker reservoir. As expected, the highest dissolved nutrient (phosphate, and nitrate, ) concentrations were associated with hypoxic depth horizons in both studied years. During summer high flow period spillway operations impact the distribution of nutrients, water temperatures, and DO as increased epilimnion flow velocities route the incoming water through the surface of the reservoir and reduce mixing and surface warming. This reduces reservoir concentrations but can lead to increased outflow nitrogen (N) and phosphorus (P) concentrations. Lower withdrawal elevations pull warmer surface water deeper within the reservoir and decrease reservoir DO during summer stratification. During fall turnover low outflow elevations increase water column mixing and draws warmer water deeper, leading to slightly higher temperatures and nutrient concentrations than shallow withdrawal elevations. The 15 m depth (540 m above sea level) outflow generally provided the best compromise for overall reservoir and outflow nutrient reduction.

Selective Preservation of Coccolith Calcite in Ontong‐Java Plateau Sediments

AbstractDissolution of calcite in deep ocean sediments, which is required to balance global marine CaCO3 production and burial fluxes, is still a poorly understood process. In order to assess the mechanisms of dissolution in sediments, we analyzed four multicore tops taken along a depth transect on the Ontong‐Java Plateau. These cores were taken directly on the equator, and span water column calcite saturation states from ∼0.93 to ∼0.74, allowing us to assess the effect of dissolution on carbonate sediment composition. The top 2 cm of each multicore was sectioned and sieved to separate coccolith from foraminiferal calcite, and the %CaCO3, δ13C, Δ14C, and Mg/Ca were evaluated. The mass ratio of coccoliths to foraminifera increases by a factor of 3 as a function of water depth, reflecting the preferential dissolution of foraminifera. Carbon isotope (δ13C and Δ14C) data suggest that most dissolution takes place at the sediment‐water interface and primarily affects foraminifera. Mg/Ca analyses indicate that the Mg content of the entire foraminiferal assemblage decreases as a function of dissolution. In contrast, coccolith dissolution takes place within the sediments, rather than at the interface. Together these two processes cause coccoliths to be up to 1,000 radiocarbon years younger than foraminifera from the same depth horizon. Despite this within‐sediment coccolith dissolution flux, sediments below the calcite saturation horizon remain enriched in coccolith calcite. Combined with global seafloor hypsometry and calcium carbonate content, this enrichment suggests that globally, coccoliths may outweigh foraminifera in deep ocean sediments by a factor of 1.8.

Influence of Tropical Climate Parameters on Properties of Acid Sulfate Soils for Sustainable Oil Palm Cultivation

To promote effective oil palm plantation and environmental sustainability, this research assessed influence of climatic parameters on physicochemical properties of Thai acid sulfate soils (ASSs). ASSs under oil palm planting areas (Topsoil: Ap, Subsoil-1: Ap-60 cm, Subsoil-2: 60–100 cm, and Rootzone: sum of the three depth levels) and historical climate data in tropical savanna and tropical monsoon were investigated. Stepwise approach of multiple regression analysis from component defining variable of principal component analysis revealed that, in tropical savanna, daily solar radiation influenced clay content (p&lt;0.05) in Topsoil, cation exchange capacity (p&lt;0.05) in Subsoil-1, soil pH by water (p&lt;0.01) in Subsoil-2, and silt content (p&lt;0.001) in Rootzone. In tropical monsoon, daily solar radiation influenced exchangeable magnesium (p&lt;0.01) in Subsoil-2, and exchangeable sodium (p&lt;0.01) and silt content (p&lt;0.01) in Rootzone. We concluded that daily solar radiation is the most influential climatic parameter on soil properties due to the transport of heat in soils, whereas particle size distribution is mostly influenced by climatic parameters due to their clay and silt fractions. OPP in ASSs under these climates should include management of water usage by using raised beds with irrigation canals, considering the rooting depth and depth of acidic horizon before applying fertilizer or amendment and liming along with integrated organic material management to raise soil pH.

Fractionation distribution of metal Al, Fe, Mn, and microbial population in acidic soil horizon

Acidic mineral soil generally has mild acidic to high acidic reaction or pH ⩽ 5.5, with very low exchangeable bases that can exchanged and rich in oxide as well as Al and Fe hydroxides. Acidized soil can lead to increased toxicity from aluminum, iron, and manganese element to the plants and deficiency of phosphorous, alkaline cation (calcium, potassium, and magnesium), and molybdenum element as well as soil microbial population. This study aimed to observe the fractionation distribution of metal aluminum (Al), iron (Fe), and manganese (Mn) and soil microbial population in acidic soil horizon. Al fraction parameters included exchangeable Al (Al-exc), non-crystalline Al (Al-o), inorganic non-crystalline Al (Al-po), Organically Bound Al (Al-p), Low- and Medium- Stability Complexes with Organic Matter (Al-Cu) and High-Stability Complexes with Organic Matter (Al-pCu), exchangeable fractionation of Fe and Mn (Fe/Mn-exc), Fe and Mn from Bound to Carbonates/Acid- extractable, Bound to Fe-Mn Oxides/Reducible, Bound to Organic Matter Fe Mn/Oxidizible, Fe- Mn Residual and soil microbial population (total microbes and Acidithiobacillus bacteria). The results, distribution of Al fraction on the upper horizon of Jasinga and Lebak were dominated by stabilized organic amorphous Al fraction with fluctuative decrease of organic matter (Al-pCu), while the lower horizon tended to be inorganic amorphous Al (Al-op). The fractionation distribution of Fe fractionation on Jasinga and Lebak was dominated by Oxidizible Fe fraction. Mn fraction distribution on Jasinga and Lebak were dominated by Mn-residual fraction in each acidic soil horizon. The total population of Microbes and Acidithiobacillus.sp in each soil horizon decreased along with the alteration of soil chemical properties in each soil depth horizon.

The study of Aluminum (Al) fractionation on forest land, agroforestry, and dryland agriculture in west java

The aims of this study were to evaluate the distribution of Aluminum fraction (Al) on the horizon of forest land, agroforestry, and dryland agriculture in West Java highland soils and looking correlation with soil chemical fertility, is pH, CEC, organic-C, total N, total P, available P and soil texture. The evaluation was carried out on the results of the analysis of soil samples taken at four soil horizons (Ao or Ap, A1 or A2, B1, and B2) in each land use. Al fractionation using extraction methods with different chemicals to find exchangeable Al (Alex), amorphous Al (Alo), amorphous Al organic (Alp), amorphous Al bound weakly to organically (Alcu), Amorphous Al bound strongly to organic (Alop), and amorphous Al inorganic (Alpcu). The results showed that the Alo fraction dominated the other Al fractions in each land use. In forest land Alo fraction (> 58.61%) with a fluctuating distribution pattern, in agroforestry (54.45%) with a declining distribution at the depth of the soil horizon, then on dryland agriculture (> 89.86%) it increases fluctuatively with the depth of the soil horizon. The addition of organic material/compost must be done to increase the organic-C content in the soil.