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Urban forests are crucial for biodiversity and climate resilience. This study investigated the impact of human disturbances on carbon (C) stocks in un-conserved forests of Entoto Mountain, Addis Ababa, Ethiopia, focusing on forest structure: important value index (IVI), species diversity (H’), regeneration pattern status, and C storage in aboveground biomass (AGB), belowground biomass (BGB), litter biomass (LB), and soil. Field data were collected from 35 quadrats across two altitudes, and human disturbances were observed, including firewood collection, tree cutting, soil excavation, and road and infrastructure inside the sample plot. Results indicate low species diversity dominated by Eucalyptus globulus Labill and Juniperus procera Hoechst. Ex Endl., with fair regeneration. Higher altitudes showed greater measured C stock (572.62 tC ha−1) than lower altitudes (495.03 tC ha−1), attributed to larger trees. C values in the upper altitude for AGB, BGB, LB, and soil (0–30 cm) were higher than at lower altitudes. The IVI showed a significant positive correlation with C in aboveground biomass, C in belowground biomass, and total C stock, whereas H’ also showed a significant (p < 0.05) positive correlation with the total number of trees. It is concluded that forest structures contribute to the C stock of this area. Given the importance of the un-conserved Entoto Mountain forest, it is recommended to prioritize the conservation of old-growth forest species in the area, as they demonstrate the highest capacity for C accumulation.

Immobilisation of lead (Pb) and toxic elements in contaminated soils is of importance due to their persistence in the environment. Herein, we investigated the effects of sugarcane filter cake biochar (SFCB) and sugarcane bagasse ash (SBA) on the extractability of Pb and some toxic and potentially toxic elements (As, Cd, Cu, and Zn) in polluted mine soil samples from Lower Klity Creek, Thailand. The soil was equilibrated with the SFCB and SBA at the respective rates of 0, 1, and 5% (w/w) for 120 days at field capacity. The results revealed that both SFCB and SBA materials significantly (P < 0.05) decreased Pb extractability in the studied soil, and it stabilised after 56 days of incubation. At 120 days, the SFCB and SBA application at the rates of 5% SFCB, 5% SBA, 1% SFCB, and 1% SBA decreased the extractable Pb contents by 50.35, 40.81, 29.42, and 19.27%, respectively, compared to unamended soil. The SFCB and SBA materials also improved soil chemical properties by increasing the soil pH, available phosphorus, and extractable sulfur. At 5%, SFCB decreased As extractability and increased organic carbon in the studied soil. The Zn availability in the studied soil was also improved by SFCB and SBA addition. This study highlights the potential use of biochar and ash from the sugarcane industry to stabilise Pb and As in contaminated soils.

Managing phosphorus (P) in acidic paddy soils is crucial for sustaining rice yields. However, the effects of combined humic acid (HA) and flue gas desulfurization gypsum (FG), a by-product of coal-fired power plants, on P forms remain poorly understood. This study examined P forms using a sequential extraction procedure and XANES spectroscopy following the application of HA, FG, and HA + FG. HA increased organic labile P, while FG and HA + FG promoted HCl-extractable Pi and humic Po, respectively. XANES data revealed that P associated with aluminum (Al) (hydr)oxides was dominant in acidic paddy soils. Brushite (CaHPO4·2(H2O)) accounted for 25% and 19% of total P in the FG- and HA + FG-treated soil, respectively. Iron (Fe)-bound P was absent in control and FG-treated soils but was present as strengite (FePO4·2H2O) in HA- and HA + FG-treated soils (23% and 30% of the total P, respectively). Inositol hexakisphosphate (IHP), a non-labile Po, was in HA- and HA + FG-treated soil (12% and 31% of the total P, respectively). Archerite (KH2PO4) was 40% and 20% of the total P in HA- and HA + FG-treated soil, respectively. HA alone is an effective soil amendment that enhances P cycling and availability by increasing organic P mineralization, boosting rice yield in acidic paddy soil.

The impact of arbuscular mycorrhiza fungi (AMF) on root-shoot scaling strategies under zinc and phosphorus deficiency remains poorly understood in maize. The aims of this study were (i) To quantify the effects of zinc/phosphorus deficiency on AMF colonization, (ii) to quantify biomass accumulation in different plant parts in the presence of AMF, and (iii) to characterize how AMF alter root-shoot allometric scaling under zinc/phosphorus deficiency. We conducted a pot experiment arranged in RCBD split plot with 6 replications. SUWAN 5819 maize seeds were grown for 22 days under five Hoagland's solution-based nutrient regimes (+Zn+P, -Zn-P, +Zn-P, -Zn+P, and deionized water), with and without AMF. AMF colonization was highest (49.6%) under -Zn+P contrary to hypothesis 1 which predicted highest colonization under dual deficiency, while the deionized water treatment had the lowest colonization (30.1%). Phosphorus was the dominant factor affecting biomass accumulation with a 2-4-fold reduction in organ dry weights for phosphorus-deficient treatments compared to phosphorus-sufficient treatments. AMF colonization significantly reduced dry weights in +Zn+P by 8.6%, 19.0%, and 47.5% in the leaf, stem, and roots, respectively, consistent with mycorrhiza-induced growth depression (MGD). Nutrient deficiency resulted in root biomass accumulation, consistent with the optimal partitioning theory. AMF increased shoot mass fraction from 50% to 63% in +Zn+P, and from 41% to 52.5% in -Zn-P, suggesting AMF role in modulating biomass accumulation. Root-shoot scaling slopes derived from LMM revealed that zinc deficiency caused negative scaling trajectory, and AMF was associated with positive root-shoot scaling trajectory in the -Zn+P treatment, though the scaling relationship was not confirmed by SMA analysis. These findings highlight nutrient specific AMF-mediated growth dynamics in early vegetative stage.

Purpose:This study characterized the chemical components and nutrient release patterns of filter cake, filter cake biochar, and sugarcane bagasse ash—by-products of the sugarcane industry, a globally significant crop.Method:The chemical composition of each material was analyzed, nutrient release kinetics were examined using water extraction during 336 h, and kinetic models were applied.Results:The studied materials were rich in various elements and exhibited alkaline properties. Carbon and Si were the primary components, followed by Ca, Al, P, and K. All materials released substantial amounts of K and P, with minimal N release. Filter cake had the highest cumulative release of water-soluble P (7,701±87.4 mg/kg), followed by filter cake biochar (2,982±27.3 mg/kg) and sugarcane bagasse ash (1,194±3.66 mg/kg), representing 32.2%, 7.8%, and 21.7%, respectively, of total P. Conversely, the cumulative release of water-soluble K was highest in sugarcane bagasse ash (7,295±418 mg/kg), followed by filter cake (3,999±124 mg/kg) and filter cake biochar (2,312±107 mg/kg), accounting for 23.3%, 30.3%, and 11.0%, respectively, of total K. The nutrient release kinetics showed that the magnitude of release was controlled by the inherent elemental concentrations of each material and exhibited good fits with the Elovich and power function models (R² = 0.836–0.990 and 0.810–0.996). Nutrient release depended mainly on diffusion through heterogeneous and homogeneous surfaces.Conclusion:These sugarcane by-products have the potential to improve soil fertility through nutrient releases. Transforming filter cake into biochar slows the initial release of nutrients while ensuring a more sustained and steady long-term release.Highlight· Filter cake, its biochar and sugarcane bagasse ash are alkaline and rich in C and Si.· Filter cake releases the most water-soluble P among the three materials.· Sugarcane bagasse ash shows the highest cumulative release of water-soluble K.· Each material shows distinct nutrient release influencing agricultural use.Biochar transformation of filter cake slows nutrient release for long-term use.

Urban forests have a role in climate regulation by managing greenhouse gas emissions. The aim of this study was to assess the potential carbon (C) stock of both above ground biomass (AGB) and below-ground biomass (BGB) in the un-conserved Entoto mount forest and to determine their contribution to mitigating climate change and enhancing ecosystem services. The selected study sites recorded a total of 417 trees, with Eucalyptus globulus covering 45.08% of the species and Juniperus procera covering 38.13%. The average AGB was 114.28 ton/hectare (t/ha), while BGB it was 22.28 t/ha. The average C content in the AGB was 53.73 t/ha, while in the BGB it was 10.81 t/ha. This study enhances the comprehension of the forest’s present ecological condition and facilitates decision-making processes for conservation and sustainable development.

Vehicle emissions have been known to cause trace metal contamination in soils. The extent of such contaminations in soils, and of the effects of traffic density and distance from highways on the concentration of trace metals in roadside agricultural soils is largely unknown. This study examined the total concentrations of common trace metals (Cd, Co, Cr, Cu, Ni, Pb, V, and Zn) in roadside agricultural soils from Thailand with diverse traffic densities (approximately 30–200 million vehicles/kilometer/year), roadside distances (0, 10, 20, 50, and 100 m from the road edge), and crops (rice, maize, and sugarcane). Cadmium, Cu, Pb, and Zn concentrations significantly decreased with increasing distance away from the roads (p < 0.05). However, the concentrations of these metals were not correlated with traffic density, probably due to extensive road maintenance and expansion. The contamination factor demonstrated that the road edge soils were moderately- to highly-polluted with Cd, Cu, Pb, and Zn. The safest distance to minimize metal pollution for agricultural production is proposed to be greater than 10 m away from the road edge.

Rice productivity in acid sulfate soils are frequently limited due primarily to strong acidity, low phosphorus (P) availability and metal toxicity. A recent study has documented that the use of sodium bentonite (NaB), non-hazardous material uses in natural gas pipeline construction, could be a promising soil amendment for mitigating major concerns experiencing in acid sulfate soils. Here we examined the effects of NaB and dolomite (DL) on dynamics in dissolved contents of both nutrient and associated elements in an acid sulfate soil and rice yield from paddy field in natural gas pipeline Rights-of-Way. The results demonstrated that the NaB and DL utilization significantly alleviated soil acidity and metal (Al, Fe, and Mn) toxicity (α = 0.05). Both soil amendments also significantly improved readily available P. Nonetheless, the soil NaB incorporation did elevate soluble sodium and did plummet soluble K, Ca, and Mg. Therefore, appropriate ratios and amounts of the K, Ca, and Mg along with N fertilizers are indisputable needed to maintain the nutrient balance when applying NaB as a soil amendment. Our finding implies that combined use of NaB and DL are suggested to soil amendment and could alleviate nutrient imbalance as compared to the sole NaB utilization.

Soil Pb extractability and critical Pb levels in soils were examined for three leafy vegetables grown in artificially Pb-contaminated soils at different Pb concentrations in a greenhouse experiment. Soil Pb extractability was quantified using eight extractants, and the Pb concentration was determined in two different parts of the leafy vegetables (edible parts and roots). The results showed that the extracted Pb concentrations in soils using aqua regia, DTPA, EDTA, 0.5 M HCl, Mehlich-3, and 0.43 M HNO3 had significant (p < 0.01) relationships with Pb concentrations in the edible parts and roots of the leafy vegetables. The results indicated that these extractants were highly suitable for estimating the critical Pb level in soils and describing the maximum allowable level of Pb in leafy vegetables (0.3 mg kg−1). Based on the quality of the linear models (R2 = 0.535–0.649) and the extracted Pb in the soils, we proposed the Mehlich-3 soil test as the standard for soil quality for leafy vegetable production, with the calculated critical level of Pb in soils for growing leafy vegetables, based on this test being 61.39 mg kg−1. Furthermore, the results indicated that Pb is more easily transferred from soil to root than from root to shoot, preventing Pb accumulation in the edible part of leafy vegetables.

Accurate prediction of cadmium (Cd) ecotoxicity to and accumulation in soil biota is important in soil health. However, very limited information on Cd ecotoxicity on naturally contaminated soils. Herein, we investigated soil Cd ecotoxicity using Folsomia candida , a standard single-species test animal, in 28 naturally Cd-contaminated soils, and the back-propagation neural network (BPNN) model was used to predict Cd ecotoxicity to and accumulation in F. candida . Soil total Cd and pH were the primary soil properties affecting Cd toxicity. However, soil pH was the main factor when the total Cd concentration was < 3 mg kg −1 . Interestingly, correlation analysis and the K-spiked test confirmed nutrient potassium (K) was essential for Cd accumulation, highlighting the significance of studying K in Cd accumulation. The BPNN model showed greater prediction accuracy of collembolan survival rate ( R 2  = 0.797), reproduction inhibitory rate ( R 2  = 0.827), body Cd concentration ( R 2  = 0.961), and Cd bioaccumulation factor ( R 2  = 0.964) than multiple linear regression models. Then the developed BPNN model was used to predict Cd ecological risks in 57 soils in southern China. Compared to multiple linear regression models, the BPNN models can better identify high-risk regions. This study highlights the potential of BPNN as a novel and rapid tool for the evaluation and monitoring of Cd ecotoxicity in naturally contaminated soils.