Variation In Soil pH Research Articles

Characterization of the physiological parameters, effective components, and transcriptional profiles of Polygonum multiflorum Thunb. Under pH stress

Polygonum multiflorum Thunb. is a traditional Chinese medicine with extensive distribution and robust adaptability, but comprehensive research on its acid and alkali resistance is presently lacking. This study aimed to analyze the effects of 5 months of continuous pH stress on the physiological and photosynthetic parameters of P. multiflorum, and the content of effective components. Results revealed that pH stress significantly influenced the normal growth, physiological functions, and photosynthetic indicators of P. multiflorum. At soil pH 4.5, the tubers of P. multiflorum exhibited the highest levels of 2,3,5,4′-tetrahydroxy stilbene-2-O-β-d-glucoside (THSG) and total anthraquinones at 5.41% and 0.38%, respectively. However, increased soil pH significantly reduced the content of THSG and total anthraquinones. Reference-free transcriptome analysis was further conducted on P. multiflorum treated at pH 4.5 and 9.5, generating a total of 47,305 unigenes with an N50 of 2118 bp, of which 31,058 (65.65%) were annotated. Additionally, 2472 differentially expressed genes (DEGs) were identified. Among them, 17 DEGs associated with the biosynthesis of THSG and anthraquinones were screened. A comprehensive analysis of differential gene expression and effective component content demonstrated a significant positive correlation between the content of effective components and the 14 DEGs’ expression but a negative correlation with soil pH. This study highlighted the influence of varying soil pH values on the effective component content of P. multiflorum. Specific acidic conditions proved beneficial for the synthesis and accumulation of THSG and total anthraquinones in P. multiflorum, thereby enhancing the quality of the medicinal material.

Changes in Soil Chemical Properties and Rhizosphere Bacterial Community Induced by Soil Amendments Associated with Reduction in Cadmium Accumulation by Rice

Soil amendments have been extensively employed for the purpose of remediating soils contaminated with cadmium (Cd). However, the potential impacts of soil amendments on soil chemical properties, soil Cd bioavailability, total Cd accumulation by rice, and rhizosphere bacterial community in Cd-contaminated paddy fields located in a tropical region is still at its infancy. In this study, a commercial MgO-CaO-SiO2 conditioner (A), biochar (B), and a combination of the commercial MgO-CaO-SiO2 conditioner and biochar with a ratio of 1:1 (C) were applied at two different doses [2250 kg ha−1 (A150, B150, C150), 4500 kg ha−1 (A300, B300, C300)] to investigate their impacts on soil Cd stabilization and total Cd uptake of rice straw and grain in a Cd-contaminated remediation field experiment. Rhizosphere bacterial community diversity and composition were also assessed using high-throughput sequencing based on 16S rRNA genes. Compared with non-amendment treatment (CK), soil pH, cation exchange capacity (CEC), organic matter (OM), total nitrogen (TN), available nitrogen (AN), and nitrate (NO3−) concentrations were significantly elevated, whereas ammonium (NH4+) and soil available Cd concentrations were reduced by soil amendment treatments. Meanwhile, soil amendments significantly decreased concentrations of total Cd in both rice straw and grain, with the lowest Cd concentration in the C300 treatment. Soil pH and CEC were significantly and negatively associated with soil Cd availability and rice straw and grain Cd concentrations, while NH4+ concentration was positively correlated with soil available Cd concentration, and OM, TN, and NO3− concentrations were positively linked with rice grain Cd concentration. Soil amendments significantly increased bacterial Chao 1 and Shannon indexes and altered bacterial community composition in rhizosphere soil, due to changes in the composition of the community primarily influenced by variations in soil pH, CEC, and soil available Cd, NH4+, available phosphorous (AP) and available Potassium (AK) concentrations. Furthermore, the abundant bacterial species (Pseudomonas) and rare bacterial species (Bacillus, Candidatus_Solibacter and Streptomyces) have been up-regulated by different soil amendments, which might be in favour of soil Cd immobilization. A structural equation model also showed that soil amendments could improve bacterial diversity and change soil pH and CEC, which were conducive to hindering the removal and conversion of Cd. Overall, these results indicate that biochar-(MgO-CaO-SiO2) mixed amendments at high dosage exerted better performance compared with single application soil amendment A and B. The changes in soil chemical properties, available Cd content, and rhizosphere bacterial community assembly induced by soil amendments are closely correlated with the decrease in rice’s ability to accumulate Cd.

Quantitative relationship between soil pH and electrical conductivity values and cadmium phytoavailability for Chinese cabbage under simulated conditions

Pot experiments were conducted to investigate the impacts of continuous addition of different concentrations of calcium chloride (CaCl2) and/or low-molecular-weight organic acids (LMWOAs) on soil pH, electrical conductivity (EC), and cadmium (Cd) transformation. These factors subsequently affected Cd phytoavailability in a system consisting of Cd-contaminated soil and Chinese cabbage (Brassica chinensis L.). The results indicate that CaCl2 addition had a greater impact on reducing soil pH value, increasing soil EC value, and enhancing Cd phytoaccumulation in Chinese cabbage compared to LMWOAs. When soil pH dropped by 0.3 unit and the soil EC increased by 500 µS cm−1, the Cd concentration in the Chinese cabbage shoots was 3 times higher than that in the control group. Throughout two planting terms of Chinese cabbage, the addition of CaCl2 (1.6–3.2 g kg−1) and LMWOAs (≤ 1.0 g kg−1) led to phytoextracted Cd concentration exceeding exchangeable Cd concentration in soil samples before the pot experiment. Regarding phytoextracted Cd, desorption from carbonate-bound Cd contributes more than desorption from bound to organic matter Cd and adsorption to Fe/Mn oxide Cd. This study underscores the influence of soil pH and EC value variations and Cd transformation on Cd phytoavailability. Special attention should be given to leafy vegetables grown in Cd-contaminated soil, as the phytoavailable Cd concentration reaches approximately 2.0 µg kg−1, which may lead to Cd levels surpassing acceptable limits for Chinese cabbage.

Soil pH Variability in Mangu, Bokkos and Pankshin Local Government Areas of Plateau State

This paper investigates soil pH variability in three local government areas (LGAs) in Plateau State, Nigeria: Bokkos, Mangu, and Pankshin. Soil pH is a crucial factor influencing soil biogeochemical properties, which in turn affect crop yield, soil nutrient levels, and microbial activity. The study utilized Stratified Random Sampling to collect soil samples, and employed IDW (Inverse Distance Weighted) interpolation for analysis. The results revealed a pH range of 4.5 to 7.07, categorized into five classes: very strongly acidic (4.5 - 5.05), strongly acidic (5.05 - 5.35), moderately acidic (5.35 - 5.58), slightly acidic (5.58 - 5.83), and neutral (5.83 - 7.07). Slightly acidic and moderately acidic soils were predominant across the entire study area, covering 1643.96 Km² and 1444.41 Km² respectively. Noteworthy variations in pH were observed between the LGAs, with Bokkos and Mangu exhibiting more acidic soils, while Pankshin had soils tending towards neutrality. These variations were attributed to the local topography and geology. The pH variations also play a significant role in determining suitable crops for cultivation. Bokkos and Mangu are conducive for extensive farming of maize and Irish potatoes, while Pankshin is better suited for millet and sorghum cultivation. Given the global implications of events like the Russia-Ukrainian war on food supply, the study recommends that relevant government agencies identify areas with similar soil characteristics and invest in extensive cultivation of crops well-suited to those soils. This could contribute significantly to enhancing food security on a global scale]

Comparison of Soil Properties in Different Fertilizer Input Systems in Lowland Rice at the Third Year in Transition

Synthetic inorganic fertilizers (SIF) have the potential to impose detrimental environmental effects and are frequently utilized in Sri Lankan conventional rice farming. To maximize rice yield while maintaining soil health, soil nutrient management is vital. In this study, the soil properties of rice fields maintained using conventional (as recommended by the Department of Agriculture (DOA), 2013), reduced (50% DOA + 50% organic), and organic Input Management Systems (IMSs) were studied. The Rajarata University of Sri Lanka's Faculty of Agriculture established this experiment during the Maha season of 2020–2021 utilizing a Randomized Complete Block Design. At the initial, 50% flowering, and harvesting stages, soil samples were obtained from three distinct IMSs with three replicates at surface (0 - 15 cm) and subsurface (15 - 30 cm) soil depths. The data were analyzed using linear mixed effect models followed by Tukey's mean comparison. Three IMSs and three different stages of rice growth exhibited substantially varying soil pH, EC, available P, and exchangeable K values in this third transition year (p<0.05). Despite being highly varying across IMSs, soil CEC was not significantly different (p>0.05) among the stages of rice growth. Three IMSs' soil available N did not change significantly (p>0.05) yet differed across growth stages (p<0.05). In comparison to those obtained with conventional IMS, rice grain yield with organic IMS produced levels that were noticeably similar. The highest grain yield was produced with reduced IMS (p<0.05). This illustrates the possibility of boosting yields and sustaining soil fertility by substituting organic manure for 50% of SIF.

Predicting Dynamics of Soil Salinity and Sodicity Using Remote Sensing Techniques: A Landscape-Scale Assessment in the Northeastern Egypt

Traditional mapping of salt affected soils (SAS) is very costly and cannot precisely depict the space–time dynamics of soil salts over landscapes. Therefore, we tested the capacity of Landsat 8 Operational Land Imager (OLI) data to retrieve soil salinity and sodicity during the wet and dry seasons in an arid landscape. Seventy geo-referenced soil samples (0–30 cm) were collected during March (wet period) and September to be analyzed for pH, electrical conductivity (EC), and exchangeable sodium percentage (ESP). Using 70% of soil and band reflectance data, stepwise linear regression models were constructed to estimate soil pH, EC, and ESP. The models were validated using the remaining 30% in terms of the determination coefficient (R2) and residual prediction deviation (RPD). Results revealed the weak variability of soil pH, while EC and ESP had large variabilities. The three indicators (pH, EC, and ESP) increased from the wet to dry period. During the two seasons, the OLI bands had weak associations with soil pH, while the near-infrared (NIR) band could effectively discriminate soil salinity and sodicity levels. The EC and ESP predictive models in the wet period were developed with the NIR band, achieving adequate outcomes (an R2 of 0.65 and 0.61 and an RPD of 1.44 and 1.43, respectively). In the dry period, the best-fitted models were constructed with deep blue and NIR bands, yielding an R2 of 0.59 and 0.60 and an RPD of 1.49 and 1.50, respectively. The SAS covered 50% of the study area during the wet period, of which 14 and 36% were saline and saline-sodic soils, respectively. The extent increased up to 59% during the dry period, including saline soils (12%) and saline-sodic soils (47%). Our findings would facilitate precise, rapid, and cost-effective monitoring of soil salinity and sodicity over large areas.

White-rot fungi scavenge reactive oxygen species, which drives pH-dependent exo-enzymatic mechanisms and promotes CO2 efflux.

Soil organic matter (SOM) decomposition mechanisms in rainforest ecosystems are governed by biotic and abiotic procedures which depend on available oxygen in the soil. White-rot fungi (WRF) play an important role in the primary decomposition of SOM via enzymatic mechanisms (biotic mechanism), which are linked to abiotic oxidative reactions (e.g., Fenton reaction), where both processes are dependent on reactive oxygen species (ROS) and soil pH variation, which has yet been studied. In humid temperate forest soils, we hypothesize that soil pH is a determining factor that regulates the production and consumption of ROS during biotic and abiotic SOM decomposition. Three soils from different parent materials and WRF inoculum were considered for this study: granitic (Nahuelbuta, Schizophyllum commune), metamorphic (Alerce Costero, Stereum hirsutum), and volcanic-allophanic (Puyehue, Galerina patagonica). CO2 fluxes, lignin peroxidase, manganese peroxidase, and dye-decolorizing peroxidase levels were all determined. Likewise, the production of superoxide anion (O2•-), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH) were assessed in soils microcosms after 36 days of anaerobic incubation with WRF inoculum and induced Fenton reaction under pH variations ranging from 2.5 to 5.1. ROS significantly increased biotic and abiotic CO2 emissions in all tested soils, according to the findings. The highest values (217.45 mg C kg-1) were found during the anaerobic incubation of sterilized and inoculated soils with WRF at a natural pH of 4.5. At pH 4.0, the lowest levels of C mineralization (82 mg C kg-1) were found in Nahuelbuta soil. Enzyme activities showed different trends as pH changed. The Fenton reaction consumed more H2O2 between pH 3 and 4, but less between pH 4.5 and 2.5. The mechanisms that oxidized SOM are extremely sensitive to variations in soil pH and the stability of oxidant radical and non-radical compounds, according to our findings.

Parthenium hysterophorus Weed Fecundity and Seed Survival at Different Soil pH and Burial Conditions

Parthenium hysterophorus L. is regarded as one of the most invasive weed species. This study evaluated the effect of soil pH on P. hyterophorus weed growth and fecundity, as well as the effect of burial depths on P. hyterophorus seed survival and emergence. The first study evaluated five soil pH levels (acidic, sub-acidic, neutral, sub-basic, and basic) in a randomised complete block design. Seed germinability and subsequent seedling growth (height, leaf area, biomass, and seed number/plant) were evaluated. This study showed that P. hysterophorus seeds have a similar germination capacity under varying soil pH conditions. However, acidic soil indicated accelerated growth (25% higher biomass with 15.2% more leaf area) and fecundity (13.4% faster to enter the flowering stage at 74 days after sowing). In the second study, two factors were tested; burial depths (0.5, 5, 10, and 20 cm) being nested into seven burial durations (0, 2, 4, 6, 8, 10, and 12 months). Seed viability (final germination percentage and germination rate index), electrical conductance, and emergence percentage were assessed with the burial conditions. The results showed that only seed buried at 0.5 cm depth indicated emergence (81.3% of cumulative emergence). Forty per cent of the seeds remained viable after exhumation at 0.5–5 cm depth, while only 19–27% survived as the burial depth increased beyond 10 cm depth within 12 months. The seed remained viable for more than 12 months as a seed bank, despite faster deterioration at increasing soil depth.

Cell-Free Supernatant (CFS) from Bacillus subtilis EB2004S and Lactobacillus helveticus EL2006H Cultured at a Range of pH Levels Modulates Potato Plant Growth under Greenhouse Conditions.

Agriculture involving industrial fertilizers is another major human made contributing factor to soil pH variation after natural factors such as soil parent rock, weathering time span, climate, and vegetation. The current study assessed the potential effect of cell-free supernatant (CFS) obtained from Bacillus subtilis EB2004S and Lactobacillus helveticus EL2006H cultured at three pH levels (5, 7, and 8) on potato (var Goldrush) growth enhancement in a greenhouse pot experiment. The results showed that CFSs obtained from B. subtilis EB2004S and L. helveticus EL2006H cultured at pH 5 significantly improved photosynthetic rates, stomatal conductance, root fresh weight, and whole plant fresh weight. interactive effects of pot pH and that of CFSs obtained from pH 5 influenced chlorophyll, plant height, and shoot and whole plant fresh weight. Moreover, treatment 52EB2004S~0.4% initiated early tuberization for potato grown at pH 7 and 8. Potato grown at pH 5, which received a 72EB2004S~0.4% CFS treatment, had greater whole plant fresh and dry weight than that treated with L. helveticus EL2006H CFS and a positive control. Taken together, the findings of this study are unique in that it probed the effect of CFS produced under differing pH conditions which revealed a new possibility to mitigate stresses in plants.

Hysteretic response of N2O reductase activity to soil pH variations after application of lime to an acidic agricultural soil

Hysteretic response of N2O reductase activity to soil pH variations after application of lime to an acidic agricultural soil

Influence of Zinc, Iron and Manganese Applications on Soil Properties, Protein Content and Sedimentation Value of Wheat

Micronutrient insufficiency in plants is becoming increasingly common, particularly in cereals crops around the world. These deficits result in a loss of yield as well as deterioration in the nutritional quality of the crops. The experiment was carried out in screen house for Rabi season of 2017-18, Soil Science Department, CCS HAU, Hisar to measure the impact of methods and dosages of zinc (Zn), iron (Fe) and manganese (Mn) application on post-harvest soil characteristics and wheat quality. The findings of this research illustrated that DTPA-extractable Zn and Mn increased significantly with the addition of Zn and Mn, respectively as compared to control. With the application of micronutrients, the sedimentation value and protein content of wheat both significantly increased in comparison to the control. Maximum increase in sedimentation value (54.0) was found when 0.5 % ZnSO4 + 2.5 % urea was applied. Whereas, maximum increase in protein content (12.2%) was observed when 0.5 % FeSO4 + 3 % urea was applied. Overall, quality of wheat improved with the application of micronutrients but there was no significant effect of these applications on soil parameters. There was no significant variation in soil pH, soil organic carbon (SOC), electrical conductivity (EC), available nitrogen (N), phosphorus (P), potassium (K) and DTPA-extractable Fe when micronutrients were applied as foliar or basal doses.

Contrasting Key Bacteria and Fungi Related to Sugar Beet (Beta vulgaris L.) with Different Resistances to Beet Rot under Two Farming Modes

Sugar beet production is threatened by beetroot rot, which can be triggered by consecutive monoculture. Previous studies have shown the beneficial function of microbes affiliated with different plant compartments in inhibiting various plant pathogens. However, whether sugar beet root can recruit particular microbes at the risk of beet rot is still unclear. Therefore, this study explored the composition and community structure of bacteria and fungi of the different compartments (endosphere root, rhizosphere, bulk soil) under two farming modes (monoculture and rotation). Our result showed that the farming mode significantly affected the community structure of bacteria and fungi in bulk soil. In the rhizosphere, the community structures of bacteria between the two varieties were similar under rotation mode, and markedly different under monoculture mode. The bacterial and fungal diversity in the rhizosphere and endophytic root of the rot-suppressive variety was higher than in the rot-conducive variety. Under monoculture mode, the beneficial microbes as biomarkers were enriched in the rot-resistant variety, e.g., operational taxonomic units (OTUs) affiliated to the genus of Sordariomycetes, Cordycipitaceae, Lecanicillium, Plectosphaerellaceae, S085, Pedosphaeraceae in the rhizosphere and the genus of Actinobacteria, and Pseudonocardia, Exobasidiomycetes in the endophytic root, while for the rot-conducive variety, OTUs affiliated to the genus of Chitinophagaceae, Flavisolibacter in the rhizosphere and the Novosphingobium, Sphingobacterium, Tilletiopsis_washingtonensis, and Flavobacterium in the endophytic root. The network analysis showed that OTUs affiliated to the order of Saccharimonadales, Anaerolineae, the family of Saprospiraceae, the genus of Subgroup_10 (belonging to the family of Thermoanaerobaculaceae), Lysobacter, and AKYG587 were the keystone taxa in the rot-suppressive variety, while both beneficial and harmful microbes in the rot-conducive variety, such as Pedobacter, Ferruginibacter, and P3OB-42, were present. The variation in soil pH was shown to be the critical contributor to the microbial difference. In summary, the farming mode is critical in shaping bulk soil microbial structure by changing soil pH. Under monoculture mode, the rot-suppressive variety has more microbial diversity in both the rhizosphere and endophytic root, and enriched different beneficial microbes relative to the rot-conducive variety; the underlying mechanisms and associations of critical microbes are worth further investigation.

Spatio-Temporal Variations in Soil pH and Aluminum Toxicity in Sub-Saharan African Croplands (1980–2050)

Soil acidity threatens food production in the tropics. The effect of increasing ammonium-based fertilizer (INF) on soil pH was assessed in sub-Saharan Africa (SSA). A total of 9043 soil data from Africa soil information services, past INF use, and two future scenarios of INF use (business as usual (BAU) and equitable diet (EqD)) were used to determine soil pH variations from 1980 to 2022 and to predict soil PH variations from 2022 to 2050. Random forest and extreme gradient boosting algorithms and soil-forming factor covariates were used for the spatio-temporal soil pH predictions. Topsoil acidification was shown to be significant, with mean annual decrements of 0.014, 0.024, and 0.048 from 1980 to 2022, 2022 to 2050 (BAU), and 2022 to 2050 (EqD), respectively. Over the past 42 years, croplands with soil pH < 6.5 have declined significantly, and soil acidification is predicted to become severe by 2050 in the BAU and EqD scenarios. This was indicated by a predicted 3% increase in croplands at risk of aluminum toxicity (soil pH < 5.5) from 66 × 106 ha in 2022 to 78.5 × 106 ha in 2050. The drivers of the spatial variations in the soil pH between 1980 and 2050 were the MAP, basic cation, clay content, SOC, and nitrogen fertilizers. The evaluation metrics of the 10-fold cross-validation showed that the root mean squared errors (RMSEs) of the soil pH from 1980 to 2022, as well as the predicted soil PH from 2022 to 2050 (BAU) and 2022 to 2050 (EqD), were 0.53 pH units, 0.54 pH units, and 0.56 pH units, respectively, with coefficients of determination (R2) of 0.63, 0.64, and 0.66. The findings of this study can be used for the establishment of management strategies for increasing INF use in acidic soils.

Urban forest soil is becoming alkaline under rapid urbanization: A case study of Changchun, northeast China

Soil pH in natural ecosystems is experiencing outstanding changes because of acid deposition, especially in the background of global climate change, which significantly alters the ecological material cycle and affects ecosystem function. However, in urban ecosystems, the direction and pattern of forest soil pH variation affected by urbanization are still unclear. In this study, we obtained the level of urbanization by remote sensing and combined it with urban forest soil properties obtained from field sampling to ascertain the effects of urbanization on the soil in Changchun city, Northeast China. Our results showed that the urban soil pH of urban forests was significantly higher than that in suburban (+3%) and outside-city forests (+33 %, p < 0.001) and that it increased with an increasing level of urbanization (p < 0.001). The other soil physical–chemical properties of urban forests in urban areas, such as soil electrical conductivity and EC (+41 %, p < 0.001; +172 %, p < 0.001) and soil water content and SWC (-9%; p > 0.05; −27 %, p < 0.001), were also significantly different from those in suburban and outside-city forests, but there were no evident changes in soil bulk density. Urbanization has caused topsoil soil water deficits and serious soil alkalization. The expansion of total impervious surface coverage (TISC) is the main influencing factor that has both direct (TISC-pH) and indirect effects (TISC-BD-SWC-EC-pH chain) on urban forest soil alkalization. Our findings highlight that urbanization possibly reverses the urban forest soil acidification risk and that its significance should be considered in global biogeochemical cycling.

The vertical distribution and control factor of microbial biomass and bacterial community at macroecological scales

Microorganisms exist throughout the soil profile and those microorganisms living in deeper soil horizons likely play key roles in regulating biogeochemical processes. However, the vertical differentiations of microbes along soil depth and their global biogeographical patterns remain poorly understood. Herein, we conducted a global meta-analysis to clarify the vertical changes of microbial biomass, diversity, and microbial relative abundance across the soil profiles. Data was collected from 43 peer-reviewed articles of 110 soil profiles (467 observations in total) from around the world. We found soil microbial biomass and bacterial diversity decreased with depth in soils. Among examined edaphic factors, the depth variation in soil pH exhibited significant negative associations with the depth change in microbial biomass and bacterial Shannon index, while soil total organic carbon (TOC) and total nitrogen (TN) exhibited significant positive associations. For the major bacteria phyla, the relative abundances of Proteobacteria and Bacteroidetes decreased with soil depth, while Chloroflexi, Gemmatimonadetes, and Nitrospirae increased. We found both parallels and differences in the biogeographical patterns of microbial attribute of topsoil vs. subsoil. Microbial biomass was significantly controlled by the soil nutrient concentrations in both topsoil and subsoil compared with climatic factors, while bacterial Shannon index was significantly controlled by the edaphic factors and across latitudes or climatic factors. Moreover, mean annual precipitation can also be used as a predictor of microbial biomass in subsoil which is different from topsoil. Collectively, our results provide a novel integrative view of how microbial biomass and bacterial community response to soil depth change and clarify the controlling factors of the global distribution patterns of microbial biomass and diversity, which are critical to enhance ecosystem simulation models and for formulating sustainable ecosystem management and conservation policies.

Mapping soil pH levels across Europe: An analysis of LUCAS topsoil data using random forest kriging (RFK)

AbstractSoil pH affects food production, pollution control and ecosystem services. Mapping soil pH levels, therefore, provides policymakers with crucial information for developing sustainable soil use and management policies. In this study, we used the LUCAS 2015 TOPSOIL data to map soil pH at a European level. We used random forest kriging (RFK) to build a predictive model of spatial variability of soil pH, as well as random forest (RF) without co‐kriging and boosted regression trees (BRT) modelling techniques. Model accuracy was evaluated using a ten‐fold cross‐validation procedure. While we found that all methods accurately predicted soil pH, the accuracy of the RFK method was best with regression performance metrics of: R2 = 0.81 for pH (H2O) and pH (CaCl2); RMSE = 0.59 for pH (H2O) and RMSE = 0.61 in pH (CaCl2); MAE = 0.41 for pH (H2O) and MAE = 0.43 in pH (CaCl2). Dominant explanatory variables in the RF and BRT modelling were topography and remote sensing variables, respectively. The generated maps broadly depicted similar spatial patterns of soil pH, with an increasing gradient of soil pH from north to south Europe, with the highest values mainly concentrated along the Mediterranean coast. The mapping could provide spatial reference for soil pH assessment and dynamic monitoring.

Evaluating Soil Nutrient Status of Mandarin Orchards across Varied Altitudes in Gorkha, Nepal

Mandarin, a prominent crop in Nepal, exhibits remarkable adaptability to different altitudes, resulting in diverse soil and nutrient conditions in orchards. Understanding these variations is crucial for optimizing orchard management practices and ensuring sustainable fruit production. This research endeavor sought to assess the nutritional profile of the soil in mandarin positioned at diverse elevations in Gorkha district, Nepal. The orchards were classified into five elevation groups: 800 masl, 900 masl, 1000 masl, 1100 masl, and 1200 masl. Using randomized complete block design (RCBD), each altitude contained ten composite soil samples, and was then subjected to chemical analysis to assess their properties. The results showed that soil pH increased with altitude, with the highest pH (6.66±0.045) and soil organic matter (OM) (5.88±0.12%) at 1200 masl and the lowest pH (5.5±0.045) and OM (1.92±0.12%) at 800 masl. Soil acidity was observed 5.79±0.045 at 900 masl and 5.5±0.045 at 800 masl, while all other altitudes had neutral soils. Nitrogen content followed a similar trend, with the highest at 1200 masl (0.32±0.007%) and the lowest at 800 masl (0.10±0.007%). Phosphorus and potassium showed no significant variation with altitude. Available phosphorus was the highest at 1000 masl (72.93±2.02 kg ha-1) and the lowest at 800 masl (51.61±2.02 kg ha-1). Maximum available potassium (365.34±6.84 kg ha-1) was observed at 1100 masl, while the minimum (337.63±6.84 kg ha-1) was recorded at 800 masl. In 18% of the samples, nitrogen exhibited the lowest concentration, while phosphorus was limiting in 12% of the samples. Potassium was not found to be a limiting nutrient in any of the samples. Variations in soil pH, OM, and nutrient content call for altitude-specific nutrient management to optimize mandarin production. Further studies are required in diverse ecology to characterize nutrient requirements and enhance sustainable mandarin cultivation practices.

Quantitative climatic reconstruction and prehistoric human subsistence strategy evolution since the mid-Holocene in Nenjiang river Basin, Northeastern China

Quantitative paleoclimate reconstructions can provide crucial climate context to test the hypothesis of climatic impact on prehistoric human activities. However, the climate change in Nenjiang River Basin is poorly understood due to the lack of reliable paleoclimate records. In this study, we report paired quantitative temperature (MAAT0) and soil pH records based on the branched glycerol dialkyl glycerol tetraether (brGDGTs) since the mid-Holocene in an alluvial sedimentary sequence near the Honghe Neolithic site in the middle reaches of Nenjiang River Basin. The result of MAAT0 shows an obvious cooling interval at 6.5–4.0 kyr BP, which is consistent with paleotemperature reconstruction results in EASM margin. The strengthened westerlies may play a crucial role in shaping the cooling mid-Holocene in EASM margin. The soil pH variations yield a peak at 6.0–3.5 kyr BP, which is roughly consistent with other precipitation reconstruction from northeastern China. From the middle Neolithic to Bronze period, the prehistoric humans gradually settled in Nenjiang River Basin. Cool-wet climate during 6.0–4.0 kyr BP provide enough water & wildlife resources and broader space for human survival and thus prompted the settlement and cultivation development. With the deterioration of the climate since 4.0 kyr BP, the ancient inhabitants have to move southward along the Nenjiang River to lower reaches to find more suitable places for settlement.

Microbial cell membrane properties and intracellular metabolism regulate individual level microbial responses to acid stress

Community- and individual-level soil microbial traits greatly depend on environmental conditions, especially soil pH. Given substantial spatio-temporal variations in soil pH, microorganisms exhibit acid tolerance to some extent, although the underlying mechanisms of microbial tolerance capacities remain understudied. In this study, ten microbial species with different functions (plant growth promoting, pathogen biocontrol, and nutrient cycling functions) were cultured under different acid treatments to investigate the acid tolerance capacity and the underlying physiological mechanisms for acid tolerance of these microbial species. Microbial species exhibited substantially different acid tolerance capacities, making them survival at pH from 3.5 to 5.0. Cellular physiological assays further indicated that three aspects could contribute to the acid tolerance capacity of soil microorganisms in the present study, i.e., shield effect by regulating the fluidity of cell membrane to prevent H+ from entering into cells, neutralizing effect by promoting the internal metabolic activities to produce metabolic chemicals such as amino acids and urea that could consume more intracellular H+, and pumping effect by regulating the H+-ATPase activity to extrude H+ out of cells, although it cannot be denied that other pathways may also function. However, these pathways did not make the same contribution to the acid tolerance capacity of different microbial species, suggesting that the regulators and underlying mechanisms depended greatly on microbial species. Further studies that combine omics technologies to discern tradeoff among microbial traits such as resource allocation, stress tolerance, etc., would be helpful to clarify the molecular mechanisms underlying microbial tolerance to the environmental stressors such as soil acidification.

Predicting Habitat Properties Using Remote Sensing Data: Soil pH and Moisture, and Ground Vegetation Cover

Remote sensing data comprise a valuable information source for many ecological landscape studies that may be under-utilized because of an overwhelming amount of processing methods and derived variables. These complexities, combined with a scarcity of quality control studies, make the selection of appropriate remote sensed variables challenging. Quality control studies are necessary to evaluate the predictive power of remote sensing data and also to develop parsimonious models underpinned by functional variables, i.e., cause rather than solely correlation. Cause-based models yield superior model transferability across different landscapes and ecological settings. We propose two basic guidelines for conducting such quality control studies that increase transferability and predictive power. The first is to favor predictors that are causally related to the response. The second is to include additional variables controlling variation in the property of interest and testing for optimum processing method and/or scale. Here, we evaluated these principles in predicting ground vegetation cover, soil moisture and pH under challenging conditions with forest canopies hindering direct remote sensing of the ground. Our model using lidar data combined with natural resource maps explained most of the observed variation in soil pH and moisture, and somewhat less variation of ground vegetation cover. Soil pH was best predicted by topographic position, sediment type and site index (R2 = 0.90). Soil moisture was best predicted by topographic position, radiation load, sediment type and site index (R2 = 0.83). The best model for predicting ground vegetation cover was a combination of lidar-based estimates for light availability below canopy and forest type, including an interaction between these two variables (R2 = 0.65).