Base Cations Research Articles

Relationship between edaphoclimatic attributes and productivity of loblolly pine (Pinus taeda L.) in southern Brazil

The productivity of loblolly pine in southern Brazil is one of the highest in the world, in part because of genetic breeding programs but also as consequence of the species adaptation to the edaphoclimatic conditions and of the right silvicultural management. Thus, the understanding of the relationship between wood productivity and soil attributes is very important and can serve as a basis for guiding management practices in forest plantations. This research aimed to identify which are the natural factors related to the productivity of Pinus taeda planted on different geological formations in southern Brazil. The selection of the study plots was carried out based on site productivity, altitude, soil maps and geological maps. In the selected plots, soil profiles were opened to classify and characterize the physical and chemical attributes of the soils. The soil attributes evaluated were depth of the A and B soil horizons, pH, clay content, carbon, phosphorus, basic cations and potential acidity. Mean annual precipitation and mean temperature of coldest and warmest quarter of the year were collected for all the study sites. Productivity was represented by the mean annual increment (MAI) and by the site index (SI). To identify the relationship between soil attributes and productivity, correlation analysis was performed. The plots showed MAI varying from 27.2 to 44.5 m3 ha−1 year−1, and SI varying from 9.0 and 26.6 m. Among the climatic parameters, the temperature of the warmest quarter of the year (Tmax) showed positive correlation with SI, and among the soil attributes the best correlation was between MAI and clay content. Another important result was the correlation between clay and carbon content in the whole soil profile which combination seemed to present a high influence on the loblolly productivity in southern Brazil.

Short-term effects of Sulla residues and farmyard manure amendments on soil properties: cation exchange capacity (CEC), base cations (BC), and percentage base saturation (PBS)

Short-term effects of Sulla residues and farmyard manure amendments on soil properties: cation exchange capacity (CEC), base cations (BC), and percentage base saturation (PBS)

High-resolution maps of critical loads for sulfur and nitrogen in China

The critical load concept is an important scientific guideline for acid deposition control. It was not only a crucial scientific basis to determine the emission reduction targets in Europe, but also used in China’s air pollution control, especially the designation of two control zones. Currently, critical loads of sulfur and nitrogen are still exceeded in Europe, America, and East Asia (mainly in China), and need to be continuously updated to meet the demands of further emission reductions. Critical loads of China were calculated and mapped in the 2000s, but are not sufficiently accurate due to methodological and data limitations. Here we present the latest high-quality critical loads for China, based on high-resolution basic data on soil, vegetation, and atmospheric base cations deposition, and up-to-date knowledge on important parameters. Our data, which is going to be included in GAINS-China, can be used to assess the ecological benefits of nitrogen and sulfur reductions in China at a regional or national scale, and to develop mitigation strategies in the future.

Evaluating the use of Ca/Sr and 87Sr/86Sr ratios to track Ca sources in sugar maple in Ontario

Decades of acidic deposition and timber harvesting have depleted calcium (Ca) stocks in soils, especially at base-poor soils characterized by low base cation weathering rates. One approach to tracking Ca sources from soil is by using Ca/Sr ratios in vegetation, while 87Sr/86Sr ratios have also been used to estimate mineral weathering rates. To evaluate the uses of Ca/Sr ratios and Sr isotopes in identifying Ca sources in sugar maple ( Acer saccharum Marsh.) trees, three base-poor sites on the Canadian Shield and three limestone sites in southern Ontario were sampled for Ca, Sr, and 87Sr/86Sr ratios. Higher Ca/Sr ratios in soil extracts and sugar maple tissues at base-rich sites compared with base-poor sites reflect different minerology among regions, while the Ca/Sr discrimination factor between roots and foliage indicated that internal cycling exerts a major control on Ca/Sr ratios in sugar maple. At the three off-shield sites, 87Sr/86Sr ratios in soil and tree tissues were higher than precipitation but were indistinguishable for off-shield sites. Mixing models using a 1.0 mol L−1 HCl soil extract as the weathering endmember indicated that a lower proportion of weathering Ca compared with other geochemical approaches. One potential explanation is that the extraction method dissolves more recalcitrant minerals to a greater extent than under field conditions, leading to a higher weathering rate endmember value used in the mixing model.

Exploration of the amphoteric transition of Al2O3 on melt structure and viscosity of silicate slag

The amphoteric oxide Al2O3 has different behaviors in different chemical environments. In an acidic environment, Al3+ breaks the network structure while in an alkaline environment, Al3+ forms a three-dimensional network like Si4+. In this paper, the amphoteric effect of Al2O3 on the structure and viscosity of a five-oxide silicate system (SiO2–Al2O3–FeO–CaO–MgO) is studied. The viscosities with different Al2O3 contents were experimented on an inclined plane and compared by the flow length of liquid slags. The study shows that the melt viscosity increases and then decreases with increasing Al2O3 content. As Al2O3 increases, the coordination number of the basic cations increases, changing from a network destruction ion to a charge balance ion. And the coordination number of Al3+ has a higher shift from four to five. The detailed reaction pathways of the structural units are revealed through the variation of oxygen types. The addition of Al2O3 leads to the replacement of [SiO4]4- by [AlO4]5-, with a decrease in the contents of Si–O–Si and Si–O-M while an increase of Si–O–Al, Al–O–Al and TO. Therefore, the network strength increases first and then decreases which is consistent with the tendency of viscosity.

Managing Soil Acidity, Not Soil Balancing, Affects Yield

AbstractIt can be hard to convince people of something when they think their lived experience suggests otherwise. That’s the challenge facing scientists trying to convince organic farmers that soil balancing—specifically through the base cation saturation ratio method—doesn’t actually improve crop yield. New research echoes previous work showing crop yields are affected by pH but not the calcium‐magnesium ratio soil balancing. Earn 0.5 CEUs in Soil & Water Management by reading this article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Introducing a map of soil base cation concentration, an ecologically relevant GIS-layer for Amazonian forests

Soil maps are crucial for habitat and species distribution modeling under present and future conditions, thereby providing relevant background information for conservation planning. In Amazonia, soil conditions are highly heterogeneous, which has important implications for the distribution and dynamics of the area's exceptional biodiversity. Unfortunately, available soil maps for this region suffer from inaccuracies and lack of ecologically relevant variables. Here, we develop a map of the sum of exchangeable base cation concentration (SB) in the surface soil by applying machine learning to a comprehensive set of over 10,000 field data points of SB values directly measured from soil samples or inferred using indicator plant species occurrences. As predictors, we used rasters of soil type probabilities, elevation, biomass and reflectance values from Landsat satellite images. Random Forest (RF) models were trained and tested using two different cross-validation strategies. We also assessed in which areas the map was more reliable using the area of applicability approach and compared the results with two other soil layers. The best predictors of SB variation were Landsat bands 7, 4 and 3, elevation, and probability of Histosols. The regional patterns observed across Amazonia were consistent with current geological understanding; lower SB values tended to occur in central Amazonian soils and higher values in western Amazonian soils, with considerable variation within each region. The model was found applicable over most of the Amazonian biome, especially in non-inundated (terra-firme) forest, but not over coastal areas, floodplains of major rivers and wetlands, which were poorly represented in the training data. Our new SB map over performed previous SB map and represent an accurate and ecologically meaningful variable. It is available as a digital GIS layer and can be used in habitat mapping and in modeling the current or future distributions of biological communities and species. This will advance general understanding of Amazonian biogeography and help in conservation planning.

Assessing impacts of sulfur deposition on aquatic ecosystems: A decision support system for the Southern Appalachians

AbstractWith climate change and ongoing impacts from human development and resource extraction, US federal land management agencies are acutely concerned with managing for healthy aquatic ecosystems in the Southern Appalachian Mountain (SAM) Region. Here, we describe development of a spatial decision support application to assess the biological and ecological impacts of atmospheric S and N deposition on aquatic ecosystems of the region. We first summarize foundational published work to predict continuous maps of surface water acid neutralizing capacity (ANC) and soil base cation weathering (BCw). We use the predicted ANC and BCw maps to estimate steady‐state critical loads (CLs) of atmospheric S and N deposition. We included estimated CLs of atmospheric N to get a complete picture of CLs and potential exceedances. We then present a logic‐based decision support model for assessing effects of S and N deposition based on statistically modeled stream ANC and CL exceedance. The model is easily modified for continuous monitoring of CL exceedance patterns as new S and N deposition and ANC data become available. We present mapped model results for the SAM study area and an important subset of the region, the Great Smoky Mountains National Park. ANC modeling results revealed that predicted acid sensitivity was spatially variable, with areas of relatively low stream ANC (<50 μeq · L−1) and soil BCw (<50 meq · m−2 · year−1) predominantly found in certain critical areas. Within the Great Smoky Mountains National Park, evidence for S CL exceedance based on an ANC criterion of 50 μeq · L−1 was strong at locations where ambient S deposition was at least two times the CL. We also predicted likely impacts of CL exceedances on aquatic insect species richness and native fish abundance. Responses for insect species richness and fish impact showed variability similar to CL exceedance, with increasing impact positively correlated with elevation. Finally, we discuss ways that the decision support system can be used to prioritize management across the region.

Peculiarities of Modified Ceramics (Na0.5Bi0.5)TiO3–BaTiO3–(K0.5Na0.5)NbO3

Single-phase ceramic samples with new compositions (1 – x – у)(Na0.5Bi0.5)TiO3–хBaTiO3–у(K0.5Na0.5)NbO3 (x = 0.05, у = 0–0.15) modified with ZnO and GeO2 additions were obtained by solid-phase synthesis. Their crystal structure, microstructure, and dielectric and local piezoelectric properties were studied. A phase with a perovskite structure with a pseudocubic unit cell was found to form in all of the synthesized samples; it was shown that the unit cell volume increased as a result of the partial replacement of base cations by complex additive cations. The ferroelectric phase transitions were confirmed by dielectric spectroscopy. Residual piezoelectric hysteresis loops were obtained for the synthesized samples in the polarization switching spectroscopy mode, which confirmed the switching of ferroelectric polarization.

Characteristics and acidic soil amelioration effects of biochar derived from a typical halophyte Salicornia europaea L. (common glasswort).

Glycophyte biomass - derived biochars have proven to be effective in the amelioration of acidic soil. However, there is scarce information on the characteristics and soil amelioration effects of halophyte-derived biochars. In this study, a typical halophyte Salicornia europaea, which is mainly distributed in the saline soils and salt-lake shores of China, and a glycophyte Zea mays, which is widely planted in the north of China, were selected to produce biochars with a pyrolysis process at 500°C for 2h. S. europaea-derived and Z. mays-derived biochars were characterized in elemental content, pores, surface area, and surface functional groups, and then by using a pot experiment their potential utilizable value as acidic soil conditioner was evaluated. The results showed that compared with Z. mays-derived biochar, S. europaea-derived biochar displayed higher pH, ash contents, base cations (K+, Ca2+, Na+, and Mg2+) contents and exhibited more larger surface area and pore volume than Z. mays-derived biochar. Both biochars had abundant oxygen-containing functional groups. Upon treating the acidic soil, the pH of acidic soil was increased by 0.98, 2.76, and 3.36 units after the addition of 1%, 2%, and 4% S. europaea-derived biochar, while it was increased only by 0.10, 0.22, and 0.56 units at 1%, 2%, and 4% Z. mays-derived biochar. High alkalinity in S. europaea-derived biochar was the main reason for the increase of pH value and base cations in acidic soil. Thus, application of halophyte biochar such as S. europaea-derived biochar is an alternative method for the amelioration of acidic soils.

An 11,000 year record of plant community stability and paludification in a patterned rich fen in northeastern Alberta, Canada

Patterned rich fens have a diverse flora and are maintained by unidirectional inflowing water with high concentrations of base cations, along with high pH and limited nutrients. Rich fens are among the most threatened ecosystems in Europe, but are not uncommon across the western boreal forest zone of Canada. Utilizing 10 radiocarbon dated cores extracted from the wetland, we investigated the Holocene developmental history of a large patterned rich fen in northeastern Alberta (McClelland Wetland). Organic matter accumulation began around 11,457 cal yr BP as primary peat formation on recently deglaciated substrates. Over the 10,000+ years history of McClelland Wetland, the central portions of the wetland have been remarkably resistant to change, with little alteration in dominant species. The resistance to change is set against a background of fluctuations in regional Holocene climate and local varying water balance. The dominant bryophyte species ( Hamatocaulis vernicosus and Scorpidium scorpioides) continued to play a foundational role on site for the duration of the Holocene, dependent on a persistent long-term ground water source. Accumulation rates of organic matter have remained steady once the dominant bryophyte layer was established, but with accumulation rates at paludifying marginal sites lower than those of the central moss-graminoid-dominated areas.

Inorganic amendments improve acidic paddy soils: Effects on soil properties, Al fractions, and microbial communities

Alkaline soil inorganic amendments (SIAs) have been extensively used to improve acidic soils. In this study, we arranged 9 treatments of low, medium, and high application dosages of silicon calcium magnesium potassium fertilizer, calcium magnesium phosphate fertilizer, and lime in the field to study the mechanism of SIAs in improving acidic soils. The Al sequential extraction experiment showed that the application of SIAs tended to transform from active to stable fractions of Al. By amplicon sequencing, it was observed that the application of SIAs significantly affected microbial community compositions in rhizosphere soils. With the decrease in soil acidity, the microbial function was also enhanced, especially the activity of dehydrogenase. In this study, the acidity-related indicators in soils (pH, exchangeable acid, and exchangeable base cations) were first integrated into an index-AIV (acidity improvement value), which was used to assess the relationship with other soil properties. The redundancy analysis and correlation network between soil chemical and biological indexes indicated that SIAs did not greatly affect the fungi community structure, while greatly increased or decreased the abundance of bacteria, especially Acidobacteria, Nitrospirae, and Crenarchaeota. Our data revealed the SIAs optimized soil environment for rice growth jointly by decreasing Al mobility, improving soil microbial function, and increasing soil fertility.

The impacts of landscape positions and land management practices on soil physicochemical properties in Mancha Galgo watershed, Rift Valley Basin of Ethiopia

ABSTRACT The utmost pervasive and harmful procedure of land degradation is soil erosion by water. This study’s objective was to evaluate fanya juu affected particular soil characteristics and landscape positions in the Mancha Galgo watershed. Five-year-old fanya juu structure-treated fields were compared to un-conserved nearby land and assessed under slope gradients. The top 0–20 cm of the soil was sampled for a total of 18 composite soil samples, which were reproduced three times for each treatment in an “X” design square plot measuring 10 m × 10 m. Data were evaluated using the SPSS 20 version through one-way analysis of variance (ANOVA). Most of the examined soil characteristics, including clay, silt, sand, soil moisture content (SMC), soil organic matter (SOM), total nitrogen (TN), available phosphorus, exchangeable cations, and cation exchange capacity (CEC), showed significant (P≤0.05) changes between Fanya Juu-conserved land and the control plot. Regarding landscape positions, clay, silt, sand, BD, SOM, TN, available phosphorus, exchangeable basic cations, and CEC each demonstrated a significant variance (P≤0.05). For deeper knowledge of the impacts of ecological use of land, additional studies focused on the combined effects of both physical and biological SWC techniques through the inclusion of socio-economic factors are needed.

Chemical Weathering Rates of Soils Developed on Eocene Marls and Sandstones in a Mediterranean Catchment (Istria, Croatia)

Physical and chemical weathering, together with biological and biochemical processes, form soil from bedrock and strongly influence the chemical composition of natural waters. Erosive processes, primarily through the agents of running water and wind, remove the products of weathering from catchments. The aim was to determine the chemical weathering of minerals because of changes in land-use and natural forestation in two small neighboring catchments of the rivers Argilla and Bazuja. Agricultural land-use practice is very intense in the Argilla catchment, while the Bazuja catchment’s arable land is mostly abandoned, with progressive forestation. Chemical weathering in soils and sediments was evaluated with the aid of bulk chemistry analysis focused on major elements, trace elements, and zirconium. Weathering indices, mass balance, and strain were calculated. The abandonment of arable land and intense forestation in the Bazuja catchment caused increased chemical weathering with the loss of base cations (Ca and Mg) and enrichment of conservative elements (Zr and Ti) in surface horizons. EIC and MTF values are positive (enrichment) in areas with agricultural activities, while forested areas show negative values (loss). A comparison of the oldest and youngest parts of the overbank sediment profiles in the swallow hole zone and stream sediments shows that chemical and mechanical weathering in the Bazuja catchment was similar to present weathering in the Argilla catchment, while agriculture was active in the Bazuja catchment. The integrated knowledge gained in small catchment studies can be broadly applicable to larger systems.

Contribution of modified P-enriched biochar on pH buffering capacity of acidic soil

Biochar can directly hold cations in soil because of the negative charge that exists on its surfaces. Besides, improving soil cation exchange capacity, the negative charges on biochar surfaces can buffer acid soil by protonation and deprotonation mechanisms. Moreover, biochar ameliorates soil acidity due to the presence of oxides, carbonates, and hydroxides of its basic cations (Ca, Na, K, and Mg). Both biochar surface functional group and basic cation concentrations can be altered by modification with chemical agents which can affect its soil pH buffering capacity. However, the impact of modified biochar application on soil pH buffering capacity is still scanty. This study investigated the pH buffering capacity of acidic soil amended with three P-enriched modified Douglas fir biochars and compared this buffering capacity to amendment with untreated Douglas fir biochar. These three P-enriched biochars, were prepared by treating Douglas fir biochar (DFB), respectively, with: 1) anhydrous calcium chloride (CaCl2) and potassium phosphate monobasic (KH2PO4), 2) calcium carbonate (CaCO3) and diammonium phosphate {(NH4)2HPO4} and 3) an aqueous solution of magnesium sulfate (MgSO4), potassium hydroxide (KOH) and potassium phosphate monobasic (KH2PO4). The three P-enriched biochars were designated as CCPP, CAPP and MSPP, respectively. The soil pH buffering abilities were largely dependent on the added biochar's alkalinity and ash contents. The residual soil CEC was highly correlated (r ≥ 0.9), with the soil buffering capacity. Both alkalinity and pH buffering capacity improved following the order CCAP > CCPP > MSPP > DFB, while residual soil CEC followed the order CAPP > MSPP > CCPP > DFB. The pH buffering capacity of the soil after amendments with 10% CAPP, CCPP MSPP and BFB rose by 84.8, 58.3, 3.0 and 2.5%, respectively. Whereas MSPP had higher concentrations of K+ and Mg2+, greater concentrations of Ca2+ were present in CCAP and CCPP than MSPP. So, Ca2+ concentrations in biochar exerts a greater influence on alkalinity and buffering capacity than Mg2+ and K+ because of 1) its smaller effective hydration radius and larger charge density. 2) calcium hydroxide has a greater water solubility than magnesium hydroxide providing more available base. Since pH buffering capacity depends on cation exchange sites, soil additives containing Ca2+ are prone to create greater impacts than Mg2+ and K+ additives.

Morphological Characters and Soil Characteristics of Potential Horticultural Plants Growing in the Wild

This study investigated the variations observed in morphology of four (4) potential horticultural plants: Callichilia stenosepala Stapf, Clerodendrum splendens G. Don, Combretum bracteatum Herb. Madr. ex Wall and Combretum indicum (L.) Defillips and the soil characteristics of their habitats. Plants samples were obtained within University of Uyo Main Campus, Use Offot village in Uyo Local Government Area and Ifiayong Usuk Village in Uruan L.G.A. of Akwa Ibom State. Soil samples were obtained around the base of the studied plants before collection. Plants' morphological characters were extensively described and the soil samples analyzed using standard methods. The results revealed that these plants thrive on slightly acidic soils (6.31±0.07 to 6.75±0.05). Soils supporting Callichila stenosepala recorded the highest electrical conductivity (18.2±4.10), organic carbon (5.28±0.80), total nitrogen (4.86±0.52), calcium (164.00±10.20), magnesium (74.36±6.21) and exchange acidity (2.88±0.07) values, soils supporting Clerodendrum splendens recorded the highest pH (6.75±0.05), bulk density (1.88±0.004), phosphorus (2.08±0.003), sodium (18.40±4.09), potassium (32.18±7.02) and clay (34.00±6.10). Also, Combretum indicum was supported by soils having higher sand (62.00±7.10) and silt (23.00±4.30) contents while Combretum bracteatum occurred on soils with lower values of base cations, basic nutrient elements and soil physical properties. In conclusion, there are plants with potential horticultural values found within the study area and there are significant differences in the soil properties at the locations in which they are found. A better ecological investigation is needed in order to provide useful insights needed for the adoption, management, mass production, and better utilization of these potential horticultural plants within the study area.

Normative Mineralogy of 1170 Soil Profiles across Canada

Weathering of soil minerals provides base cations that buffer against acidity, and nutrients that support plant growth. In general, direct observations of soil minerals are rare; however, their abundance can be determined indirectly through soil geochemistry using normative-calculation procedures. This study compiled a data set of major oxide content from published and archived soil geochemical observations for 1170 sites across Canada (averaged over the soil profile [A, B, and C horizons], weighted by depth and bulk density to a maximum depth of 50 cm). Quantitative soil mineralogy (wt%) was systematically determined at each site using the normative method, ‘Analysis to Mineralogy’ (A2M); the efficacy of the approach was evaluated by comparison to X-ray Diffraction (XRD) mineralogy available for a subset of the study sites. At these sites, predicted A2M mineralogy was significantly related to estimated XRD, showing a strong linear relationship for plagioclase, quartz, and K-feldspar, and a moderate linear relationship for chlorite and muscovite. Further, the predicted A2M plagioclase content was almost identical to the estimated XRD soil mineralogy, showing no statistical difference. The Canada-wide predicted quantitative soil mineralogy was consistent with the underlying bedrock geology, such as in north-western Saskatchewan and north-eastern Alberta, which had high amounts of quartz due to the Western Canadian Sedimentary Basin. Other soil minerals (plagioclase, potassium feldspar, chlorite, and muscovite) varied greatly in response to changing bedrock geology across Canada. Normative approaches, such as A2M, provide a reliable approach for national-scale determination of quantitative soil mineralogy, which is essential for the assessment of soil weathering rates.

Influence of Nitrogen Fertilizer Application on Soil Acidification Characteristics of Tea Plantations in Karst Areas of Southwest China

Nitrogen (N) fertilizer application is one of the causes of soil acidification at tea plantations. However, the effect of N fertilizer application on the soil acidification characteristics of tea plantations with different acidities remains unclear. In this study, field experiments were conducted to investigate the effects of different nitrogen fertilizer application rates on the pH, pH buffer capacity (pHBC), exchangeable total acidity (ETA), exchangeable base cations (EBCs), and cation exchange capacity (CEC) in the topsoil of non-acidified (NA), mildly acidified (MA), and heavily acidified (HA) tea plantations. The results showed that the exchangeable Al3+ (E-Al) and CEC were HA > MA > NA in all tea plantations, whereas the EBCs and base saturation percentage (BSP) were HA < MA < NA. In the tea plantations with pH > 4.0, the pH, EBCs, and BSP showed decreasing trends with increasing N fertilizer application, whereas E-Al showed an increasing trend. In the tea plantations with pH < 4.0, the soil pH showed a small increasing trend with the increase in N fertilizer application, whereas the soil exchangeable H+ (E-H), E-Al, and CEC showed decreasing trends. Meanwhile, in the pH range of 4–6, the soil acid–base buffer curve rose sharply, and an excessive application of N fertilizer (N900) significantly reduced the pHBC. In addition, a stepwise regression analysis showed that the BSP, EBCs, and exchangeable Mg2+ (E-Mg) had significant direct effects on the soil pH, whereas the CEC and N application had significant direct effects on the soil pHBC. In conclusion, a decrease in the BSP and an increase in E-Al were the main mechanisms of acidification at tea plantations, whereas a decrease in the BSP caused by the application of N fertilizer was the main cause of exacerbated soil acidification in non-acidified tea plantations.

A 200-year snapshot of soil development in pyroclastic deposits derived from the 1815 super explosive eruption of Mount Tambora in Indonesia

Early-stage pedogenic processes and formation rates on completely obliterated volcanic landscapes, such as the super explosive 1815 Mount Tambora eruption, have not previously been robustly explored. The objectives of this study were to determine (i) the mineralogical composition of the sand fraction, selected physical and chemical soil properties and potential nutrient reserves after 200 years of pedogenesis, and (ii) chemical weathering indices, rate of soil formation, and rates of C and N accretion. Soil formation was examined for five soil profiles on stable plain/foot slope positions representing the diversity of soils in these landscape positions, which are important for agricultural production. Results showed that the soil mineralogical composition of the sand fraction was dominated by easily weatherable minerals (e.g., labradorite and augite volcanic glass) indicating high potential nutrient reserves (e.g., Ca2+, Mg2+, K+, P) as confirmed by X-ray fluorescence (XRF) analyses. Allophanic material formation was minimal (<2.3%) owing to the preferential accumulation of Al3+ into Al-humic complexes. The low contents of allophanic materials and metal-humus complexes resulted in low P-retention (17.5–43.4%) within the soil solum, with the highest value in surface horizons (33–43%). Morphological features showed rapid solum (A + B horizons) development of 22 to 107 cm. Shallow soils occurred on shallow eruption deposits (consisting of pyroclastic flow underlain by pumice), whereas the deepest soils were found on thick deposit consisting of either trachyandesite pyroclastic or basaltic andesite materials. The chemical index of alteration (CIA) followed the order of A horizons (48.4 ± 4.6) > B horizons (45.4 ± 2.4) > C horizons (43.8 ± 4.2) ≈ tephra/lava (43.1), indicating accumulation of Al oxides and depletion of base cations in the upper horizons. Similarly, the base depletion index (BDI) showed a trend of A horizons (1.13 ± 0.18) < B horizons (1.25 ± 0.09) < C horizons (1.34 ± 0.20) ≈ tephra/lava (1.35), indicating depletion of base cations (Ca2+, Mg2+, K+, Na+) from the soil surface to C horizons. Based on solum depths (A + B horizons) and 200 years of post-eruption soil development, the solum formation rate ranged from 1.2 to 5.3 mm yr−1. Appreciable stocks of SOC (2.3–12.8 kg C m−2) and SON (0.21–0.77 kg m−2) accumulated over the 200 year period. Eruption materials from the Mt. Tambora eruption with a precisely known timescale contributed new pedological insights documenting rapid soil formation rates from pyroclastic materials leading to a rapid recovery of soil functions to support agricultural production.

Geochemical Characteristics of Typical Karst Soil Profiles in Anhui Province, Southeastern China

The geographical distributions of Cd and several other heavy metals (HMs) (Hg, Cu, Ni, Pb, Zn, Cr, As, Co, and V) were characterized in 90 (p &gt; 0.05) terra rossa samples across the Anhui karst area. Significant enrichment of HM was observed in this soil, mainly associated with the weathering of Cd-enriched carbonate rocks. Then, this enrichment was developed in 31 profiles. Our investigations revealed pedogenic processes as the dominant factors accounting for the enrichment of Hg, Cu, Ni, As, Co, and V. We also observed that all soil samples had a silty clay texture, with a pH scope of 4.08–8.04 and a median value of 6.50. In addition, the soil samples had relatively high saturation, with basic cations over 6.68%. The enrichment of the HMs based on their distinct factors were as follows: Cd (3.92) &gt; As (2.55) &gt; Zn (1.62) &gt; Ni (1.50) &gt; Cu (1.47) &gt; Pb (1.47) &gt; V (1.43) &gt; Cr (1.23) &gt; Co (1.19) &gt; Hg (1.12). Finally, terra rossa samples derived from carbonate rocks were categorized as Cambisols, Luvisols, and Regosols. The soil profiles of Cambisols and Luvisolsis were less developed, so the HM concentrations were relatively low. The Regosols profile contained the highest total Cd concentration and exhibited a higher capacity to immobilize Cd compared with other soil profiles. Regosols are also characterized by high pH values (scope of 7.05 to 8.22, with an average value of 7.56). The contents of HM also exhibited minor changes across the Regosol, Cambisol, and Luvisol profiles, implying that the karst development degrees of weathering in Anhui were relatively low.