Nutrient availability in the initial stages of surface mine spoil reclamation — Impact on plant growth

The aim of this study was to characterise nutrient availability in the initial stages of reclamation and its impact on the growth of Secale multicaule L., the typical cover crop in newly established Pinus silvestris L. stands. A field experiment testing different levels of nutrient supply (N, P, K) was conducted on a carboniferous and a non-carboniferous sandy mine spoil representing typical mine spoils in the open-cast lignite mining district of Lower Lusatia. On both types of mine spoils, primarily N and P limited plant growth. On non-carboniferous mine spoil, low P availability to plants was alleviated by mineral fertiliser application while on carboniferous mine spoil, due to P immobilisation, P availability was still limiting plant growth after similar levels of P fertilisation. The elevated N_min content in carboniferous mine spoil compared to non-carboniferous mine spoil is probably the result of less N leaching as the dominant N form in carboniferous mine spoil is NH₄⁺ while the highly mobile NO₃^— is prevailing in the non-carboniferous mine spoil. N release from geogenic organic matter in carboniferous mine spoil as suggested by comparable N_t contents in pedogenetically formed soil organic matter is less likely.     

南京幕府山矿区废弃地自然恢复植被的构树种群及其伴生树种生态位研究

以南京幕府山矿区废弃地自然恢复的植被优势种群为对象，对构树及其伴生树种的生态位宽度和生态位重叠进行了研究。结果表明：研究的9个树种的生态位总体比较接近，都有比较宽的生态位，从群落形成的时间分析，这些树种是在矿区废弃地上的先锋树种，对废弃地有较强的适应能力。因此，在人工恢复这一地区矿区废弃地植被时，可以选用这些树种。构树的生态位较宽。而其与其他树种的生态位重叠却不是很大，构树在一定时期内，还是矿区废弃地上植物群落的最主要的优势树种，是矿区废弃地最适应的树种之一，可以作为本地区矿区废弃地植被恢复的首选树种。     

Influence of Different Forms of Iron and Aluminum on the Nature of Soil Acidity of Some Inceptisols,Alfisols, and Ultisols

Abstract

Fifteen acid soils of Mizoram representing Ultisols and Inceptisols, and Madhya Pradesh, representing Alfisols, were studied to characterize the nature of acidity in relation to different forms of iron (Fe) and aluminum (Al). The mean contents of Fe and Al were extracted by various extracting reagents and were found to be in descending order as followed: dithionite>oxalate>pyrophosphate>ammonium acetate>KCl. The electrostatically bonded EB‐H⁺ and EB‐Al³⁺ acidity comprised 28.3 and 71.7% of exchangeable acidity whereas EB‐H⁺, EB‐Al³⁺, exchangeable, and pH‐dependent acidities comprised 9.8, 30.7, 40.5, and 59.5% of total potential acidity. All forms, of acidity showed significant correlation with pH_k and organic carbon. Among the different forms, Fe and Al caused most of the variations in different forms of soil acidity but the effect of different forms of Al are more active and directly participate in the formation of EB‐H⁺, EB‐Al³⁺, and exchangeable acidity.     

Variation in the acid-base parameters of automorphic loamy soils in the taiga and tundra zones of the Komi Republic

A database for the main genetic horizons of loamy automorphic soddy-podzolic, typical podzolic, gley-podzolic, and surface-gley tundra soils of the Komi Republic was developed on the basis of the available archive and literature data and unpublished results of the authors. The database included the following parameters: the pH_water and pH_KCl, the exchangeable and total acidity, and the degree of SEC saturation. All the parameters were characterized by normal distribution types. The variation coefficients V for the pH_water and pH_KCl were <10%. For the exchangeable and total acidities and the degree of SEC saturation, the V values varied among the soils and horizons in the range of 10–50%. The greatest differences in the acid-base properties of all the soils were revealed between the groups of organic horizons, the eluvial horizons, and the B horizon by the cluster analysis. Between the separate subtypes of podzolic soils, the maximum differences were observed in the organic and, to a lesser extent, eluvial horizons; the B horizons of the different soils in the taiga and tundra zones did not significantly differ in these terms. For the entire profiles, the highest similarity was found between the typical podzolic and gley-podzolic soils, which were more similar to the automorphic soils of the tundra zone than to soddy-podzolic soils.     

Weathering Processes in a Lignite Mine Spoil Treated with a CaCo3-Rich Waste Slurry under Two Moisture Programmes

Chemical processes affecting the acidity of asulphide-rich lignite mine spoil treated with high orlow doses of a CaCO₃-rich industrial waste slurrywere studied in the laboratory under two moistureprogrammes (cycles of alternate waterlogging anddrying, and percolation) so as to determine the slurrydose neutralizing spoil acidity and the possibledetrimental effects of high doses. The most importantacidity-reducing process was the dissolution ofapplied calcium carbonate, and CaCO₃ consumptionwas greater under percolation conditions than underwaterlogging and drying conditions. The most importantacidity-increasing process was the oxidation ofsulphides, which was again more intense underpercolation. Under waterlogging and drying conditions,the formation of hydroxysulphates may also havecontributed to acidification.     

Modifications of the phosphorus cycle with development of lignite mine soils

Various aspects of the P cycle in four and seven year old soils from the Meirama lignite mine (northwest Spain) were studied. With increasing soil age, The organic P (P_o) content increased in parallel with the organic matter content. the observed increase in secondary inorganic P (Bic—P_i + NaOH-P_i + us-NaOH P_i) is related to the increase in the retention capacity for P with soil age. the observed increase in the HCl-P fraction can be attributed to a gradual dissolution of the non-extractable forms of P produced from fertilizers added in the course of spoil management. Both the C:P_o ratio and phosphatase activity also increased with soil age, suggesting that biochemical mineralization processes are taking place and indicating a need for the hydrolysis of phosphate esters to ensure an adequate phosphorus supply to plants. All these findings suggest that in the long term plants May, suffer a pronounced P deficiency.     

Lipid biomarkers and their environmental significance in mine soils from Eastern Europe

The present study describes signature lipid biomarkers in reclaimed mine soils (RMSs), an unreclaimed spoil and a natural soil (Vertisol) for a major coal mine basin in Eastern Europe. Alkanes, fatty acids and fatty alcohols, as well as coal biomarkers were abundant in the mine soils and the unreclaimed spoil. The alkanes distribution in the RMSs was bimodal with maxima at C₁₈ and C₂₉/C₃₁ and points at two origins for the alkanes, terrigenous plants, including soil borne and from the coal source. Fatty acid carbon preference indices (CPI_even/odd = 10.4 and 8.1 for the mine soils under pine and grass vegetation) reflect the increasing role of terrestrial vegetation in the formation of organic matter. The higher concentrations of the long-chain alkanes, fatty acids and alcohols are speculated as the reason for the severe and extreme water repellency observed with the Vertisol and the unreclaimed spoil. The presence of terrigenous steroid and triterpenoid markers in the RMSs is an indication of the ongoing soil formation processes. The analysis of lipid extracts allowed for the assessment of sensitive molecular indicators of biogenic terrigenous and coal origin and the degree of soil recovery following >20 years of spoils reclamation.     

Long-term dynamics of heavy metals in the upper horizons of soils in the region of a copper smelter impacts during the period of reduced emission

The 23-year-long dynamics of actual acidity (pH_water) and acid-soluble heavy metals (Cu, Pb, Cd, Zn) in the forest litter and humus horizon of soils in spruce-fir forests were studied in the area subjected to the long-term (since 1940) pollution with atmospheric emissions from the Middle Ural Copper Smelter (Revda, Sverdlovsk oblast). For this purpose, 25 permanent sample plots were established on lower slopes at different distances from the enterprise (30, 7, 4, 2, and 1 km; 5 plots at each distance) in 1989. The emissions from the smelter have decreased since the early 1990s. In 2012, the emissions of sulfur dioxide and dust decreased by 100 and 40 times, respectively, as compared with the emissions in 1980. Samples of litter and humus horizons were collected on permanent plots in 1989, 1999, and 2012. The results indicate that the pH of the litter and humus horizons restored to the background level 10 and 23 years after the beginning of the reduction in emissions, respectively. However, these characteristics in the impact zone still somewhat differ from those in the background area. In 2012, the content of Cu in the litter decreased compared to 1989 on all the plots; the content of Cu in the humus horizon decreased only in the close vicinity of the smelter. The contents of other metals in the litter and humus horizons remain constant or increased (probably because of the pH-dependent decrease in migration capacity). The absence of pronounced removal of metals from soils results in the retention of high contamination risk and the conservation of the suppressed state of biota within the impact zone.     

Rehabilitation of lands mined for limestone in the Indian desert

In the Indian desert, the economics of mining is second only to agriculture in importance. However, research on the rehabilitation of land disturbed by mining has only recently received serious attention. An attempt has been made to determine both the qualitative and quantitative success of rehabilitation plans used to revegetate limestone mine spoils in an area near Barna, northwest arid India. Rehabilitation success was achieved using a combination of rainwater harvesting techniques, soil amendment application approaches, plant establishment methods and the selection of appropriate germplasm material (trees, shrubs and grasses). It is expected that the resulting vegetative cover will be capable of self‐perpetuation under natural conditions while at the same time meeting the land‐use needs of the local people. The minespoils have adequate levels of the major nutrients (except P, Mo and Se) for proper plant and grazing animal health. Levels of organic matter are low whereas total B concentrations are exceptionally high. Also, the population of soil fungi, Azotobactor, and nitrifying bacteria is negligible. Enhanced plant growth was achieved in treated plots, compared to control plots, where spoil moisture storage was improved by 5 – 45 per cent. Due to the decomposition of farmyard manure and nitrogen fixation by planted leguminous plant species, the electrical conductance of treated mine spoils increased threefold, CaCO₃ content decreased from 20·0 to 5·2 per cent, and organic carbon, P, K, and biological activity increased significantly. The rehabilitation protocol used at the site appears to have been successful because plant self‐regeneration is occurring. The increased diversity of woody perennials resulted in ‘dominance’ being better shared among species and ‘evenness’ being increased within the plant community elements. The early to mid‐successional trends are continuing for six years following initial rehabilitation. This study developed methods for the rehabilitation of lands mined for limestone and has also resulted in an understanding of rehabilitation processes in arid regions with an emphasis on the long‐term monitoring of rehabilitation success. Copyright © 2000 John Wiley & Sons, Ltd.     

Cation exchange properties of acid forest soils of the northeastern USA

Negative correlations between soil pH and cation exchange capacity (CEC) or base saturation in soils of the northeastern USA and Scandinavia have raised questions regarding the nature of cation exchange in acid forest soils. Using data from three small‐catchment studies and an extensive regional survey of soils in the northeastern USA, I examined relationships among total carbon, effective CEC (CEC_e), soil pH_s (in 0.01 m CaCl₂) and base saturation. Organic matter is the predominant source of soil surface charge in these coarse‐grained, glacially derived soils. Correlation coefficients (r) between total carbon and CEC_e ranged from 0.43 to 0.74 in organic horizons and from 0.46 to 0.83 in mineral horizons. In all cases, the intercepts of functional relations between CEC_e and total C were near zero. In O horizons, the CEC_e per unit mass of organic carbon (CEC_e:C) was positively correlated with pH_s in three of the four data sets, consistent with the weak‐acid behaviour of the organic matter. However, CEC_e:C was negatively correlated with pH_s in mineral soils in two data sets, and uncorrelated in the other two. The CEC_e in mineral soils represents the portion of total CEC not occupied by organically bound Al. The negative correlations between CEC_e:C and pH_s can therefore be explained by increased Al binding at higher pH_s. Aluminium behaves like a base cation in these soils. When Al was considered a base cation, the relation between base saturation and pH_s could be effectively modelled by the extended Henderson–Hasselbalch equation. When modelled without Al as a base cation, however, there were no consistent relationships between pH_s and base saturation across sites or soil horizons. Because of the non‐acidic behaviour of Al, it is difficult to predict the effect of ongoing reductions in acid deposition on the base status of soils in the northeastern USA.     

Effect of crop residue biochar on soil acidity amelioration in strongly acidic tea garden soils

Strongly acidic soil (e.g. pH < 5.0) is detrimental to tea productivity and quality. Wheat, rice and peanut biochar produced at low temperature (max 300 °C) and differing in alkalinity content were incorporated into Xuan‐cheng (Ultisol; initial pH_{soil/water = 1/2.5} 4.12) and Ying‐tan soil (Ultisol; initial pH _{soil/water = 1/2.5} 4.75) at 10 and 20 g/kg (w/w) to quantify their liming effect and evaluate their effectiveness for acidity amelioration of tea garden soils. After a 65‐day incubation at 25 °C, biochar application significantly (P < 0.05) increased soil pH and exchangeable cations and reduced Al saturation of both tea soils. Association of H⁺ ions with biochar and decarboxylation processes was likely to be the main factor neutralizing soil acidity. Further, biochar application reduced acidity production from the N cycle. Significant (P < 0.05) increases in exchangeable cations and reductions in exchangeable acidity and Al saturation were observed as the rate of biochar increased, but there were no further effects on soil pH. The lack of change in soil pH at the higher biochar rate may be due to the displacement of exchangeable acidity and the high buffering capacity of biochar, thereby retarding a further liming effect. Hence, a significant linear correlation between reduced exchangeable acidity and alkalinity balance was found in biochar‐amended soils (P < 0.05). Low‐temperature biochar of crop residues is suggested as a potential amendment to ameliorate acidic tea garden soils.     

Mycorrhizal status of plant species colonizing a magnesite mine spoil in India

Summary The present study reports the vesicular arbuscular mycorrhizal fungal association with 14 plant species colonizing a magnesite mine spoil in Salem, Tamil Nadu state, India. The soil was poor in Olsen-available P (5–45 kg/ha^-1). Hyphal, arbuscular and vesicular infection was noticed. Infection ranged from 32 to 82%. Thirteen VAM fungal species were identified. Spores of Glomus fasciculatum and Gigaspora gigantea were commonly found in the magnesite mine spoil.     

Ameliorative effect of Lantana camara biochar on coal mine spoil and growth of maize (Zea mays)

The aftermath of surface mining is a wasteland deprived of vegetation, soil structure and biodiversity. The unearthed overburden material is nutrient deprived and can only support the growth of invasive weeds such as Lantana camera which often cause allelopathy. The aim of the study is to prepare biochar from these noxious weeds and use it as an amendment for the mine spoil reclamation. Lantana biochar (LB) was prepared and applied to mine spoil, and Zea mays L. growth on biochar amended mine spoil was monitored for three months. Biochar application in a coal mine spoil using LB is comparatively de novo approach for reclamation practitioners. LB was prepared at varying temperature (250, 350 and 450℃) and residence times (30, 45 and 60 min) and characterized. After characterization, the most recalcitrant biochar at 450℃ for 60 min was chosen for application for the study. A pot trial was conducted to study the effect of LB at 0, 5, 10, 20 and 30 g kg⁻¹ dosage on the yield of Zea mays and mine spoil properties. Significant ameliorative effects were observed with increase in organic carbon content (2.9 times), cation exchange capacity (2 times), water holding capacity (0.13 times) and decrease in bulk density (0.5 times) in the mine spoil. The seedling vigour index and germination also increased significantly (p < .05) at 30 g kg⁻¹ biochar treatment compared to control. The study concluded that LB has the potential to remediate coal mine spoils and promote re-vegetation in degraded land.     

Limiting factors for reforestation of mine spoils from Galicia (Spain)

Mined areas are a continuing source of heavy metals and acidity that move off site in response to erosion. Revegetation of the mine tailings could limit the spread of these heavy metals and acidity. This study was conducted to evaluate, at four tailings on opencast mines of Galicia (Touro: copper mine; and Meirama: lignite mine, NW Spain), the chemical and physical soil quality indicators and limiting edaphic factors concerning forest production. Selected zones were: (1) The tailings formed by the waste materials from the depleted Touro mine; (2) the decantation site of deposited sludge coming from the copper extraction in the flotation stage; (3) and (4) tailings of 3 and 10 years old of the Meirama lignite mine. The main physical limitations of the mine soils are the low effective depth (<50 cm), high stoniness (>30 per cent) and high porosity (>60 per cent); which make them vulnerable to soil erosion and seriously interferes with the forest production. Soils coming from the decantation site of copper mine do not have physical limitations. The main chemical limitations of mine soils are their acidity (pH from 3·62 to 5·71), and aluminium saturation (>60 per cent in copper mine soils, and >20 per cent in lignite mine soils), low CECe (from 5·34 to 9·47 cmol₍₊₎ kg⁻¹), organic carbon (from 0·47 to 7·52 mg kg⁻¹) and Ca²⁺ and Mg²⁺ contents, and imbalance between exchange bases. Mine soils coming from the decantation site of copper mine soils are strongly limited by the high Cu content (1218 mg kg⁻¹). Lime and organic amendments are the most important factors in providing a suitable medium for plant growth. Copyright © 2004 John Wiley & Sons, Ltd.     

Sensitivity of Scottish Upland Moorland Podzols Derived from Sandstones and Quartzites to Acidification: the Potential Importance of the Mobile Anion Effect

Soil samples were collected from the main horizons of Scottish upland moorland podzols derived from quartzite or Devonian and Torridonian sandstones. The soils were subjected to routine chemical analysis and the results studied in relation to potential acidification effects of atmospheric deposition. Stronger correlations were observed for soil pH_water than for soil pH in CaCl₂ with wet deposition fluxes of mobile strong-acid anions. Exchangeable Al³⁺ correlated more strongly with wet deposition fluxes of mobile strong-acid anions than with H⁺ deposition flux. It is suggested that the direct effects of mobile anion enhancement upon soil pH_water must be taken into account when assessing damage to, and hence critical loads of, acidification-sensitive mineral soils.     

Inhibition of acidification of kaolinite and an Alfisol by aluminum oxides through electrical double‐layer interaction and coating

Soil chemical properties are affected significantly by surface charge characteristics of the soil. Interaction between oppositely charged particles in variable‐charge soils plays an important role in variation of soil electrochemical properties. In this study, the effects of Al oxides on surface charge and acidity properties of kaolinite and an Alfisol during electrodialysis were investigated. The results indicated that Al oxides, when mixed into kaolinite or the Alfisol, decreased the effective cation exchange capacity (ECEC) and exchangeable acidity and inhibited the decrease in pH. Gibbsite had less effect than γ‐Al₂O₃ and amorphous Al(OH)₃ in reducing the ECEC and acidity of kaolinite and the Alfisol; γ‐Al₂O₃ and amorphous Al(OH)₃ displayed comparable effects. However, this effect is inconsistent with the order of the surface positive charge per unit mass that the Al oxides carried. Their effect on the ECEC of kaolinite and Alfisol varied irreversibly with ionic strength of the bathing solutions. X‐ray diffraction spectra indicated that amorphous Al(OH)₃ and γ‐Al₂O₃ were more effective than gibbsite in decreasing peak intensity of electro‐dialyzed kaolinite when mixed with these Al oxides at the same rate. The results demonstrated that Al oxides could decrease the effective negative charge and inhibit acidification of kaolinite and an Alfisol through diffuse‐double‐layer overlapping between oppositely charged particles and coating of Al oxides on these materials. Both mechanisms intensified with increasing rate of added Al oxides, which can therefore act as anti‐acidification agents in variable‐charge soils.     

Total and soluble fluorine concentrations in relation to properties of soils in New Zealand

Soil fluorine (F) concentrations continue to increase in agricultural soils receiving regular applications of phosphatic fertilizer. Continued accumulation of soil F poses a risk to grazing ruminants and may pose a future risk to groundwater quality. This paper examines the range of total F (F_t) concentrations and forms of soluble F species and their relationship to selected soil properties in New Zealand agricultural soils. The F_t and soluble F (soil F extracted with water (F_water) and 0.01 m KCl (F_KCl)) concentrations in 27 soil samples (0–75 mm depth) taken from predominantly pasture sites in the North and South Islands of New Zealand were much less than those reported in the literature for sites contaminated with F from industry. The F_t concentrations ranged from 212 to 617 µg F g^?1 soil. The F‐toxicity risk to grazing animals in farms at these sites through soil ingestion is small at present, but farms with very large F_t concentrations (i.e. > 500 µg F g^?1) need to adopt suitable grazing and fertilizer management practices to avoid future F‐toxicity risk. The F_t concentration had very strong positive correlations with both total soil P and total soil Cd concentrations, reflecting the link between P fertilizer use and F accumulation in the soils. It also had significant positive correlations with organic matter and amorphous Al oxides contents, indicating that F is strongly bound to Al polymers adsorbed to organic matter and amorphous Al oxides. The F_water and F_KCl concentrations and free F^– ion concentrations in water (F^–_water) and 0.01 m KCl (F^–_KCl) extracts were generally two and three orders of magnitude, respectively, less than the F_t concentrations and were much less than the concentrations considered phytotoxic. The F_water and F_KCl concentrations were positively related to soil organic matter content and negatively related to soil pH. Regression models relating F_water and F_KCl concentrations to soil organic matter content and soil pH suggest that F can be very soluble in extremely acidic soils (pH(water) < 4.9) with large organic matter contents and therefore F potentially may contaminate groundwater if these soils are also coarse‐textured and the water table is shallow.     

Comparison of ammonium bicarbonate‐DTPA,ammonium carbonate,and ammonium oxalate to assess the availability of molybdenum in mine spoils and soils

Abstract

A variety of extractants has been used to assess the availability of molybdenum (Mo) in soils. Most of the extractants have been studied from a deficiency aspect rather than for soils with Mo toxicity, and none of them have been used to extract available Mo from mine spoils. The purpose of this study was to examine the potential of different chemical extractants for assessing the availability of Mo in mine spoils and soils. One mine spoil and three soils were treated with sodium molybdate and then subjected to wetting and drying cycles for two months. These spoil/soils were extracted with ammonium bicarbonate DTPA (AB‐DTPA), ammonium carbonate, and ammonium oxalate solution for available Mo. Crested wheatgrass (Agropyron cristatum) and alfalfa (Medicago sativa) were grown in the spoil/soils in a greenhouse to determine plant uptake of Mo. Additionally, four mine spoils and six soils were extracted and analyzed for available Mo as mentioned above. The results obtained by these three extractants were highly correlated. It was found that ammonium oxalate extracts the greatest amount of Mo among the three extractants from spoil/soils since it dissolves some adsorbed Mo from Fe‐oxide and Al‐oxide. The changes in pH of spoil/soils did not have a significant effect on the amount of Mo extracted by any of these methods. The relationships between Mo uptake and Mo extracted by each method were all significant at 1% level. None of the extractants were clearly better or worse than the others. All three methods can be used to assess Mo availability, and potential toxicity from plant uptake of Mo from reclaimed spoils.     

Ameliorating acidity of an extensively‐managed permanent pasture soil

Acid soil amelioration was measured annually over an 11 year experiment. Lime, and superphosphate were surface‐applied under combinations of three rates of lime, viz. nil, lime to raise pH_{C a} of 0–10 cm to 5.0 (low rate) and 5.5 (high rate) respectively, two rates of superphosphate (125 kg/ha every 2 to 3 yr, 250 kg/ha/yr) and two sheep stocking rates. Soils were sampled at 0–2.5, 2.5–5, 5–7.5, 7.5–10, 10–15 and 15–20 cm. Soil pH stratification developed after lime application. By 11 yr lime had not raised pH_{C a} to either 5.0 or 5.5 in the 5–10 cm profile. However, pH_{C a} >5.0 or >5.5 were observed in the 0–5 cm profile. Under high P, low lime application, soil pH_{C a} was higher in the 0–2.5 cm profile at low stocking rate. Effects of applied lime on pH_{C a} declined with time and depth under low lime and the relationship with Al_ex which increased as pH_{C a} declined, was modelled. A rarely reported relationship showed that as soil C increased the apparent solubility of Al decreased. At the lowest pH_{C a} considered, there was a strong negative association between Al_ex and total C, becoming weaker with positive pH_{C a} increments. Higher P rates increased pH_{C a} under low lime contrasting with lesser effects on pH_{C a} under low P at the same lime rate. Slow and limited lime movement means that farmers growing acid sensitive plants must apply lime early enough and at rates and frequencies sufficient to ensure downward movement.     

Effects of Natural Soil Acidification on Biodiversity in Boreal Forest Ecosystems

Variations in soil acidity and in biodiversity were analysed in the National Natural Park "Russian North", European Russia. Improving soil quality from podzol, podzolic soil, derno-podzolic soil, brown earth to pararendzina leads to increase in diversity and changes in floristical composition, followed by changing of pine and spruce forest to mixed and birch forests. In PCA ordination species diversity, richness and evenness of trees, shrubs and vascular plants are closely connected with each other, and are represented by the first principal component. They are strongly correlated to the thickness of Al horizon, pH_H20 and pH_CaC12 in organic, surface and subsurface mineral horizons. Only bryophyte species richness and diversity are directly related to the thickness and weight of organic horizon, soil exchangeable acidity, and inversely related to the thickness of Al horizon and pH. Thus, the ordination of the major species diversity variables is highly related to soil pH, suggesting that pH is the best soil related predictor of species diversity parameters. Our study shows that plants notably respond to soil acidification in boreal forest ecosystems.