Base Cation Concentrations Research Articles

Soil available phosphorous and potassium stocks related to environmental properties, land uses and soils

Abstract Soil available phosphorus (SAP) and potassium (SAK) are indispensable for crops, and their stocks are important for food production needed for a growing global population. This study analysed 991 soil profiles across a large part of Romania covering forestland, grassland and cropland in almost all ecological regions. This study investigated SAP and SAK stocks for different soil depths and characterized their magnitude and variability within land uses under different environmental ecosystems, soil classes and soil types, for a better soil and land management under a temperate-continental climate. Cropland soils present the highest SAP and SAK stocks. Chernozems, Phaeozems and Vertosols possess the highest SAP and SAK stocks in Romania, representing the largest country's pool. Both SAP stocks and SAK stocks are significantly correlated with basic environmental properties, existing direct correlations between SAP, SAK, soil organic carbon (SOC) and total nitrogen (TN) stocks. For all land uses, SAP and SAK stocks correlated significantly and directly with each other, as well as with annual temperature, clay content, pH and sum of base cations, and inversely with altitude, slope and annual precipitation. The best predictive values using multiple regression models and basic environmental driving factors were found for forestland stocks of SAP and SAK, followed by grassland stocks, while the lowest prediction occurred for cropland stocks, probably due to the long-term additional nutrient input performed by farmers in cropland that changed the natural conditions otherwise present in grassland, and especially in forestland. Based on these results some management measures are discussed.

Global limited effects of the conversion of multiple ecosystem types to tree and shrub plantations on soil base cation concentration and exchangeable capacity

Global limited effects of the conversion of multiple ecosystem types to tree and shrub plantations on soil base cation concentration and exchangeable capacity

Are pools created when restoring extracted peatlands biogeochemically similar to natural peatland pools?

In the last 25 years, several degraded peatlands in eastern Canada have been restored toward their natural structure. Pools are common in natural peatlands and are important habitats for unique flora and fauna. Because of their ecological value, pools have been created in some restored peatland sites. Nevertheless, the biogeochemistry of created pools in a restoration context has seldom been studied. The objective of our study is to characterize the biogeochemistry of created pools from restored peatlands and compare them with natural pools along a chronosequence since their creation. We measured different biogeochemical variables (pH, concentrations of nitrogen (N), phosphorus (P), dissolved organic carbon (DOC), dissolved organic matter (DOM), base cations-calcium (Ca), sodium (Na), magnesium (Mg), and potassium (K)-and dissolved gases-methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O)-) in 61 pools distributed over seven peatlands in eastern Canada. The sites represent a range of conditions, from natural to restored peatlands with pools ranging from 3 to 22 years old. Created and natural pools had distinctive biogeochemistry, with created pools being generally less acidic (pH >5) and 2.5 times more concentrated in nutrients (N and P) than in natural pools. DOC, N, P, dissolved gases, and base cations concentrations were lower in natural pools than in created pools, and varied between created sites. The oldest created pools (age >17 years) tend to approach the biogeochemical characteristics of natural pools, indicating that created pools may, over time, provide habitats with similar conditions to natural pools. A return of created pools to a natural pool-like biogeochemistry could thus inform on the success of peatland restoration.

Species–soil relationships across Amazonia: Niche specificity and consistency in understorey ferns

AbstractAimsKnowledge about species niches along environmental gradients is needed to understand community assembly and spatial variation in floristic composition and species richness. In Amazonian rainforests, such knowledge is largely lacking, although ferns have been used to infer overall floristic and edaphic patterns. Here we explore fern species distributions along an important edaphic gradient, how narrow their realised niches are and how sensitive inferences are to species commonness, data quality and the region being sampled.LocationAmazonia.MethodsWe used a large data set (1,215 transects across lowland Amazonia) to explore the realised niches of 54 species of two fern genera (Adiantum and Lindsaea) along a soil base cation concentration gradient. We used weighted averaging to estimate species optima and niche widths, and Huisman–Olff–Fresco modelling to assess species response shapes.ResultsOverall, species optima were rather evenly spread along the soil base cation concentration gradient, but Lindsaea optima were limited to the lower half of the gradient, whereas Adiantum optima were more often in the upper half. Most species had unimodal response curves. Mean niche width was ca. 25% of the observed gradient length for Adiantum and 17% for Lindsaea and was only weakly or not at all related to different aspects of species commonness. Species optima were robust to different modelling approaches and consistent across regional subsets. However, the central Amazonian data contained no transects with high soil base cation concentration, so species with high optima were either absent or obtained a lower optimum than in the NW and SW regions.ConclusionsOur results support niche‐related species sorting as an important process that defines species co‐occurrence, turnover and richness patterns within Amazonian rainforests. All Adiantum and Lindsaea species, including the most abundant ones, had narrow enough realised niches to be considered useful indicators of edaphic and floristic variation within the rainforest.

Enhanced Hydrologic Connectivity and Solute Dynamics Following Wildfire and Drought in a Contaminated Temperate Peatland Catchment

AbstractIntact peatlands provide hydrological ecosystem services, such as regulating water regimes and immobilizing pollutants within catchments. Climate change impacts including drought and wildfire may impair their functioning, potentially impacting ecosystem service delivery. Here we investigate stream water quality changes following the combined impacts of a summer drought and wildfire in a peat‐dominated catchment in the UK during 2018. The study catchment stores legacy pollutants (i.e., metals) due to past industrial activity, thus making it particularly susceptible to pollutant release during wildfires. We quantified changes in water chemistry during five storm events over a 9‐month period following the wildfire. Concentration‐discharge (C‐Q) relationships for nine solutes were analyzed to explore changes in activation and connectivity of solute source zones. Hysteresis and flushing indices of C‐Q responses further described solute dynamics during storm events. We found that most nutrient and base cation concentrations in the stream discharge were highest in the immediate post‐fire storm events and decreased during subsequent autumn and spring storms. Metal concentrations increased during autumn and spring storms, indicating delayed mobilization from within‐peat or distal headwater sources. Our findings suggest that seasonal re‐wetting and hydrologic connectivity following disturbance influenced solute source zone activation and transport in the study catchment. Water quality responses associated with wildfire and drought were primarily observed in the months following the wildfire, suggesting mobilization of pollutants peaks shortly after fire. Our results contribute to a critical understanding of the future of water quality risks in temperate peatland catchments subject to disturbances exacerbated by climate change.

Exploring the Role of Shrubs in Modulating Heavy Metal Accumulation in Forest Soils in Single-Species Pine Stands

Heavy metals accumulate and bind strongly in soil, making them difficult to eliminate. The objective of this study was to evaluate the effect of alder buckthorn (Frangula alnus) and European hazelnut (Coryllus avellana) admixtures in pine monocultures on the accumulation and vertical distribution of heavy metals in soil surface horizons. Ten sites each of pine stands admixed with alder buckthorn, pine stands admixed with European hazelnut, and pine monocultures in the Rybnik Forest District in southern Poland were selected for each variant. For the study, soil samples were taken from each site from the organic and mineral horizons and analysed for N and C contents, C/N ratio, pHH2O, base cation contents, and heavy metal contents. For all three stand compositions, the organic horizons showed a significant accumulation of heavy metals compared to the mineral horizons. Heavy metal content was correlated with pH, N and C contents, C/N ratio, and base cation contents. The admixture of shrubs, especially European hazelnut, positively affected soil organic matter quality and, consequently, the accumulation of heavy metals. European hazelnut had the most beneficial soil effects on the tested soil, which confirms that this species can be used in planning species composition, particularly in regions prone to heavy pollutant deposition.

Contribution of emissions from the oil sands activities in Alberta, Canada to atmospheric concentration and deposition of nitrogen and sulfur species at a downwind site

Oil sands activities in the Athabasca Oil Sands Region in Alberta, Canada, are large sources of atmospheric NOx and SO2. This study investigated the impact of oil sands emissions on the atmospheric deposition of nitrogen and sulfur species at a downwind site, about 350 km from the oil sands facilities. Measurement data are from the Canadian Air and Precipitation Monitoring Network (CAPMoN) from 2015 to 2019, including ambient concentrations of HNO3, pNO3-, NO2, pNH4+, NH3, SO2, pSO42− and base cations, as well as concentrations of NO3−, SO42−, NH4+, and base cations in precipitation. Sector analysis of air mass back trajectories was conducted to distinguish measurements with different air mass origins. Median atmospheric concentrations and dry deposition fluxes of HNO3, pNO3-, NO2, pNH4+, pSO42−, and SO2 on days when the air masses came from the oil sands sector were significantly greater than those with the “Clean” sector by 34–67%, whereas the difference in NH3 concentration was not significant. Contributions of the oil sands emissions to dry deposition fluxes of these species ranged from 3.8 to 13.1%. The precipitation-weighted mean concentrations of NO3−, SO42−, and NH4+ in samples with the oil sands sector were 76 %, 65 % and 81 % greater than those with the “Clean” sector, respectively. Contributions of the oil sands emissions to wet deposition of NO3−, SO42−, and NH4+ were 12.5 ± 8.9 %, 8.7 ± 4.4 %, and 6.0 ± 3.3 %, respectively. The annual total deposition of nitrogen and sulfur were 1.9 kg-N ha−1 and 0.74 kg-S ha−1, respectively, of which 8.0 ± 3.5 % and 8.7 ± 3.6 % were from oil sands emissions. The total deposition of sulfur and nitrogen did not exceed the critical loads (CL) of acidity, but nitrogen deposition exceeded the CLs of nutrient nitrogen in the region.

The influence of atmospheric deposition and climate change driven catchment internal processes on the recovery from acidification of high-altitude Alpine lakes

The impact of atmospheric deposition and environmental factors on catchment processes and water chemistry of 20 high-altitude Alpine lakes in Southern Switzerland was investigated over four decades. Through the analysis of input-output budgets of sulphur (S), nitrogen (N), base cations and alkalinity significant trends emerged. Notably, S and N input concentrations significantly declined since the 1980s, by approximately 78 % and 22 %, respectively, with N primarily declining after 2000. Recovery from acidification was slightly delayed, likely due to the increased release of S, possibly originating from legacy S pools, alongside the simultaneous reduction in leaching of base cations from exchange sites. Catchments heavily impacted by thawing cryospheric features increasingly released S and base cations due to enhanced weathering processes, with hardly any impact on the recovery process, as evidenced by the balanced releases of S and base cations. N output concentrations followed the decrease of N input concentrations, while the relative N retention in the catchments remained relatively stable. Recently, both input concentrations of S and N have stabilised, while output concentrations of base cations began to increase across all catchments. The trend likely arises from the stabilisation of S and N input concentrations and/or the ongoing increase in weathering rates induced by climate change. Consequently, there was a consistent rise in alkalinity output concentrations even after the stabilisation of the S and N input concentrations. Ion ratio analysis suggests that carbonation primarily drives weathering processes in catchment areas unaffected by thawing cryosphere, while in areas impacted by thawing cryosphere, sulphide oxidation (or sulphate dissolution) is the dominant process. Further recovery depends on future N deposition and the effects of climate change.

Major drivers of soil acidification over 30 years differ in paddy and upland soils in China

Elevated nitrogen (N) fertilization has largely increased crop production in China, but also increased acidification risks, thereby threatening crop yields. However, natural soil acidification due to bicarbonate (HCO3) leaching and base cation (BC) removal by crop harvest also affect soil acidity whereas the input of HCO3 and BC via fertilizers and manure counteract soil acidification. Insights in rates and drivers of soil acidification in different land use types is too limited to support crop- and site-specific mitigation strategies. In this study, we assessed the historical changes in cropland acidification rates and their drivers for the period 1985–2019 at 151 sites in a typical Chinese county with the combined nutrient and soil acidification model VSD+. VSD+ could well reproduce long-term changes in pH and in the BC concentrations of calcium, magnesium and potassium between 1985 and 2019 in non-calcareous soils. In paddy soils, the acidity production rate decreased from 1985 onwards, mainly driven by a pH-induced reduction in HCO3 leaching and N transformations. In upland soils, however, acidity production was mainly driven by N transformations and hardly changed over time. Crop BC removal by harvesting played a minor role in both paddy and upland soils, but its relative importance increased in paddy soils. The acidity input was partly neutralized by HCO3 input from fertilizers and manure, which decreased over time due to a change from ammonia bicarbonate to urea. Soil buffering by both BC and aluminium release decreased in paddy soils due to a reduction in net acidity production, while it stayed relatively constant in upland soils. We conclude that acidification management in paddy soils requires a focus on avoiding high HCO3 leaching whereas the management in upland soils should focus on balancing N with recycling organic manure and crop residues.

Effects of extreme precipitation on bacterial communities and bioaerosol composition: Dispersion in urban outdoor environments and health risks

Concerns about contaminants dispersed by seasonal precipitation have grown due to their potential hazards to outdoor environments and human health. However, studies on the crucial environmental factors influencing dispersion changes in bacterial communities are limited. This research adopted four-season in situ monitoring and sequencing techniques to examine the regional distribution profiles of bioaerosols, bacterial communities, and risks associated with extreme snowfall versus rainfall events in two monsoon cities. In the early-hours of winter snowfall, airborne cultivable bioaerosol concentrations were 4.1 times higher than the reference exposure limit (500 CFU/m3). The concentration of ambient particles (2.5 μm) exceeded 24,910 particles/L (97 μg/m3), positively correlating with the prevalence of cultivable bioaerosols. These bioaerosols contained cultivable bacterial species such as pathogenic Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, and Escherichia coli. Bioaerosol concentrations increased by 53.0% during 50-mm snow extremes. Taxonomic analysis revealed that Pseudomonas, Staphylococcus, and Veillonella were the most abundant bacterial taxa in the initial snowmelt samples during winter precipitation. However, their abundance decreased by 87.6% as snowing continued (24 h). Reduced water base cation concentration also led to a 1.15-fold increase in the Shannon index, indicating a similar yet heightened bacterial diversity. Seasonally, Pedobacter and Massilia showed higher relative abundance (25% and 18%, respectively), presenting increased bacterial transmission to the soil. Furthermore, Pseudomonas was identified in 60% of spring snowstorm samples, suggesting long-distance dispersal of pathogenic bacteria. When these atmospheric aerosol particles carrying biological entities (0.65–1.1 μm) penetrated human alveoli, the calculated hazard ratio was 0.55, which as observed in inhalation exposures. Consequently, this study underscores the risk of seasonal precipitation-enhanced ambient bacterial transmission.

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.

Exploring adsorption capacity and mechanisms involved in cadmium removal from aqueous solutions by biochar derived from euhalophyte

Biochar has shown potential as a sorbent for reducing Cd levels in water. Euhalophytes, which thrive in saline-alkali soils containing high concentrations of metal ions and anions, present an intriguing opportunity for producing biochar with inherent metal adsorption properties. This study focused on biochar derived from the euhalophyte Salicornia europaea and aimed to investigate its Cd adsorption capacity through adsorption kinetics and isotherm experiments. The results demonstrated that S. europaea biochar exhibited a high specific surface area, substantial base cation content, and a low negative surface charge, making it a highly effective adsorbent for Cd. The adsorption data fit well with the Langmuir isotherm model, revealing a maximum adsorption capacity of 108.54 mg g−1 at 25 °C. The adsorption process involved both surface adsorption and intraparticle diffusion. The Cd adsorption mechanism on the biochar encompassed precipitation, ion exchange, functional group complexation, and cation-π interactions. Notably, the precipitation of Cd2+ with CO32− in the biochar played a dominant role, accounting for 73.7% of the overall removal mechanism. These findings underscore the potential of euhalophytes such as S. europaea as a promising solution for remediating Cd contamination in aquatic environments.

Evaluating soil acidification risk and its effects on biodiversity–ecosystem multifunctionality relationships in the drylands of China

BackgroundSoil acidification caused by anthropogenic activities may affect soil biochemical cycling, biodiversity, productivity, and multiple ecosystem-related functions in drylands. However, to date, such information is lacking to support this hypothesis. MethodsBased on a transect survey of 78 naturally assembled shrub communities, we calculated acid deposition flux in Northwest China and evaluated its likely ecological effects by testing three alternative hypotheses, namely: niche complementarity, mass ratio, and vegetation quantity hypotheses. Rao's quadratic entropy and community-weighted mean traits were employed to represent the complementary aspect of niche complementarity and mass ratio effects, respectively. ResultsWe observed that in the past four decades, the concentrations of exchangeable base cations in soil in Northwest China have decreased significantly to the extent of having faced the risk of depletion, whereas changes in the calcium carbonate content and pH of soil were not significant. Acid deposition primarily increased the aboveground biomass and shrub density in shrublands but had no significant effect on shrub richness and ecosystem multifunctionality (EMF), indicating that acid deposition had positive but weak ecological effects on dryland ecosystems. Community weighted mean of functional traits (representing the mass ratio hypothesis) correlated negatively with EMF, whereas both Rao's quadratic entropy (representing the niche complementarity hypothesis) and aboveground biomass (representing the vegetation quantity hypothesis) correlated positively but insignificantly with EMF. These biodiversity–EMF relationships highlight the fragility and instability of drylands relative to forest ecosystems. ConclusionsThe findings from this study serve as important reference points to understand the risk of soil acidification in arid regions and its impacts on biodiversity–EMF relationships.

Wooded biocorridors substantially improve soil properties in low-altitude rural benchlands

This study examines soil properties in 30- and 60-year-old agricultural biocorridors and provides a comparative overview with neighbouring farmland. Both mixed and undisturbed soil samples were collected from six farmland/biocorridor study areas to assess a wide spectrum of physical, hydrophysical, chemical and biological soil properties. Biocorridor soils were characterised by higher water retention capacities, porosity, aeration and soil carbon stock, the latter increasing with depth. On the other hand, biocorridor bulk density under forest vegetation cover was lower, indicating progressive soil restoration. Slightly lower soil reactions in biocorridor soils disproved the hypothesis that nutrient-rich soils under biocorridors would form substrates with a high base cation content, leading to soil acidification. Biological activity, expressed through respiration coefficients, was generally low due to unfavourable physical conditions (clayey or silty-clay substrates), with the lowest levels in biocorridors. Nevertheless, biocorridor soil microbiota displayed more effective utilisation of organic matter as a carbon and nitrogen source, with lighter-textured soils tending to show more effective organic matter utilisation after excluding the influence of land use. Our results confirm biocorridors as an important landscape component, contributing to both soil stability and local revitalisation of soil environments and further emphasising their potential as climate-change mitigation tools in their role as carbon sinks.

Organic Inputs Positively Alter the Bacteriome of Post-Agricultural Soils

Agriculture can degrade soils and reduce microbial diversity. The reduction in microbial diversity of degraded soils is due to their long-term agricultural use. In most cases, such areas are afforested but rarely succeed in converting them into first-generation pine forests without adequately revitalizing the soils and restoring the natural relationships characteristic of forest habitats. This is possible thanks to the positive changes in soil biodiversity. To facilitate and enhance this phenomenon in the present experiment, various forms of organic matter were added to the soil: pine bark compost scattered on the soil surface (BCS) or placed under the roots of the seedlings at planting (BCR), woody debris (WW) and sawdust (S), while the control plot was not treated. The studies started in 2001 on two experimental plots, a poorer one in Bielsk and a more fertile one in Czarne Człuchowskie (eastern and northern Poland, respectively). The following year, 2-year-old pine seedlings (Pinus sylvestris L.) were planted on the plots. After 20 years, the physicochemical properties of the soil and its microbial composition were determined and compared with the control. The results encourage the use of organic matter for established pine forest crops on post-agricultural land for revitalization: C, N, and P content increased both in the organic layer and in the topsoil (up to 40 cm), where most fine roots are located. The total content of exchangeable base cations (Ca, Mg, K) and the sorption capacity of the soils (a measure of the ion binding capacity of the soil) also improved. The genetic analyses carried out using the molecular method (NGS) showed positive changes in the composition of the soil microbiome. Compared to poorer soil conditions in richer habitats, the number of taxa increases when organic matter is added, leading to significant qualitative changes in the bacteriome. The addition of organic material from the forest had a positive effect on the bacterial communities, which in turn accelerated the changes in the diversity of bacteriomes characteristic of agricultural soils and brought them closer to the forest ecosystem. The organic horizon was restored, and at the same time, the biodiversity of the soil microbiome increased, which is important for the health and sustainability of pine stands on formerly agricultural land.

Liming remediates soil acidity and improves crop yield and profitability - a meta-analysis

Soil acidity reduces base cations required for plant growth and may result in phytotoxic concentrations of soluble aluminum. Liming acidic soils is generally promoted as an effective management practice to increase soil pH, base cation concentrations, and ameliorate toxicity caused by aluminum and manganese. Through a global literature review using data published from field experiments on liming, the objective of this paper is to understand the effects of liming on soil pH, crop yields, and economic profitability. The results show that liming positively influenced crop yields and soil pH, implying that various lime sources can increase soil pH and crop productivity. The effect sizes of liming on crop yields when lime was incorporated into soils were higher than surface application irrespective of tillage practice. Liming under no-tillage (NT) compared to conventional tillage (CT) management showed higher effect sizes for crop yields. Liming increased effect sizes for crop yields in fertilized compared with unfertilized trials. Gypsum, calcium hydroxide and calcium carbonate showed higher effect sizes when compared with Cement Klin Dust (CKD), dolomite and wood ash. The results show that liming increased yields for all crops except potatoes and oats. Liming generally increases soil pH and changes in soil pH increased with higher lime application rates and yield increases were proportional to the magnitude of increases in soil pH. The profitability of liming differed with crop type and liming rate, being more profitable at lower liming rates. Overall, this meta-analysis shows that liming decreases soil acidity and improves crop yields. Attaining maximum gains from liming agricultural crops under acidic soil conditions requires an understanding of the appropriate lime rates required for specific crops and soil types to ensure overall profitability for producers and sustainable improvement of soil health.

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.

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.

Temporal changes in soil chemical compositions in acidified mountain forest soils of Czech Republic

The study aimed to investigate the temporal changes of pH, sorption complex, and structure of soil organic matter through the forest soil profile under beech and spruce forests located in Jizera mountains (Czech Republic) and affected by natural and anthropogenic acidification. Soil samples were collected in four different years (2008, 2013, 2015, and 2020) in each horizon: fermented horizons (F), humified horizons (H), organo-mineral horizons (A), and subsurface mineral horizons (B) (cambic or spodic). The cation exchange capacity (CEC), base saturation (BS), exchangeable element contents, pH, and soil organic carbon content (SOC) were determined. The infrared soil spectra were used to calculate indices of potential wettability, aromaticity, and decomposition. Our results showed that most nutrients and aliphatic compounds were retained in the uppermost soil layers. The aromaticity of organic matter increased with depth, while polysaccharides, regarding the decomposition compound, disappeared through the soil horizons. In a long-term observation, SOC content had constantly increased under beech, while spruce remained stable in the organic horizons. Exchangeable element contents increased in each horizon, except for Al and Fe; their content quickly decreased in F horizons and slowly decreased in H horizon under both forest tree species, while the deeper horizons remained constant, but increased in A horizon under spruce. Continuously increasing base cations concentrations in sorption complex of both forest tree species during the study period revealed the effect of forest stand types on acid deposition reduction and mitigation. The temporal changes in CEC, BS, SOC, and soil wettability are more intensive in beech than in spruce forest floor.

Four decades of regional wet deposition, local bulk deposition, and stream-water chemistry show the influence of nearby land use on forested streams in Central Appalachia

Hydrologic monitoring began on two headwater streams (<1 km2) on the University of Kentucky's Robinson Forest in 1971. We evaluated stream-water (1974–2013) and bulk-deposition (wet + dust) (1984–2013) chemistry in the context of regional wet-deposition patterns that showed decreases in both sulfate and nitrate concentrations as well as proximal surface-mine expansion. Decadal time steps (1974–83, 1984–93, 1994–2003, 2004–2013) were used to quantify change. Comparison of the first two decades showed similarly decreased sulfate (minimum flow-adjusted annual-mean concentration of ≈13.5 mg/L in 1982 to 8.8 mg/L in 1992) and increased pH (6.6–6.8) in both streams, reflecting contemporaneous changes in both bulk and wet deposition. In contrast, concentrations of nitrate (0.14 to >0.25 mg/L) and base cations increased between these two decades, coinciding with expansion of surface mining between 1985 and 1995. In 2004, stream-water pH (6.7 in 2004), sulfate (9.2 mg/L), and nitrate (>0.11 mg/L) were similar to 1982, despite wet-deposition concentrations being lower. Base-cation concentrations were higher in the stream adjacent to ongoing surface mining relative to the stream situated near the middle of the experimental forest. However, pH decreased to approximately 5.7 by 2013 for both streams, which, combined with a shift in dominant cations from calcium to magnesium and potassium, indicates that the soil-buffering capacity of this landscape has been exceeded. Ratios of bulk deposition and stream-water concentrations indicate enrichment of sulfate (1.7–25.2) and cations (0.5–64.8), but not nitrogen (0.1–5.6), indicating that the Forest is not nitrogen saturated and that ongoing changes in water-quality are sulfate driven. When concentrations were adjusted to account for changes in streamflow (climate) over the 4 decades, external influences (land management/regulation) explained most change. The amount and direction of change differed among constituents, both between consecutive decades and between the first and last decades, reflecting the influence of localized surface mining even as regional wet deposition continued to improve due to the Clean Air Act. The implication is that localized stressors have the potential to out-pace the benefits of national environmental policies for communities that depend on local water-resources in similar environments.