Classification schemes for the acidity,base saturation,and acidification status of forest soils in Switzerland

Soil chemical parameters related to soil acidity were determined for 1450 soil samples taken from individual mineral soil horizons in 257 forest soils in Switzerland, 196 developed from carbonate‐containing and 61 from carbonate‐free parent material. The distribution of pH values and exchangeable base cations in corresponding pH ranges were related to the capacity and rate of buffer reactions in the soil. Based on this, five acidity classes for individual soil samples were defined. To describe and classify the status of soil acidity and base saturation (BS) of an entire soil body, the pH and the BS of the total fine earth in the soil were calculated from the pH and BS, respectively, of the individual soil horizons and the estimated volumetric content of fine earth. The status of soil acidification of soil profiles was assessed primarily using the total amount of exchangeable acidic cations in percent of the CEC of the fine earth in the entire soil profile. As a second factor, the gradient between the acidity class of the most acidic soil horizon and the estimated acidity class at the beginning of soil formation was used. The application of these classification schemes to our collection of soil profiles revealed the great influence played by the type of parent material. The acidification status of most soils on carbonate‐containing parent material was classified as very weak to weak, whereas soils on carbonate‐free parent material were found to be strongly to very strongly acidified. In terms of parent rock material, microclimate, and natural vegetation, the results of this study and the proposed classification schemes can be considered appropriate for large parts of Europe.     

The sensitivity of Swiss forest soils to acidification and the risk of aluminum toxicity

In the context of pollution‐control strategies to minimize the detrimental effects of soil acidification, there is a need to know how and to what extent soils respond to acidifying substances. The purposes of this study were to assess the sensitivity of soil to acidification, in particular to a decrease in pH and in base saturation (BS), and the risk of Al toxicity for vulnerable plants using chemical indicators. These indicators were derived from soil data (pH, exchangeable cations, amount of fine earth) measured in the mineral horizons of 257 soil profiles throughout Switzerland. Based on the analysis of the distribution of pH and BS values in the soil collective, we assessed the sensitivity of soils to a decrease in pH and in BS. Soils that were considered sensitive to a decrease in pH had pH values between 4.8 and 7.0. The degree of sensitivity was estimated with the proportion of fine earth in the critical pH range to a depth of 100 cm. Soils that were considered sensitive to a decrease in BS had pH values between 3.6 and 5.5 and a BS between 10% and 95%. Since the effective cation‐exchange capacity (CEC_eff) of the fine earth might dampen the decrease in BS when acidity is added, the disposition for a decrease in BS was related to the relative amount of fine earth in the sensitive BS and to the mean CEC_eff of this fine‐earth fraction. The risk of Al toxicity for vulnerable plants was estimated using the ratio of base cations to Al at the cation‐exchange sites (BC : Al_exc). A BC : Al_exc of 0.2 was taken as a threshold value below which the risk for sensitive plants increases. The degree of risk was based on the proportion of fine earth in the critical BC : Al range (≤0.2) in the soil profile. These indicators taking into account the various aspects of soil acidification are derived from usually available data and represent therefore a cost‐effective tool to assess the sensitivity of soils to an input of acidity.     

Alberta油砂地区在两种水文流域森林土壤酸化敏感性研究

Input of large amounts of N and S compounds into forest ecosystems through atmospheric deposition is a significant risk for soil acidification in the oil sands region of Alberta. We evaluated the sensitivity of forest soils to acidification in two watersheds （Lake 287 and Lake 185） with contrasting hydrological regimes as a part of a larger project assessing the role of N and S cycling in soil acidification in forest ecosystems. Fifty six forest soil samples were collected from the two watersheds by horizon from 10 monitoring plots dominated by either jack pine （Pinus banksiana） or aspen （Populus tremuloides）. Soils in the two watersheds were extremely to moderately acidic with pH （CaCl2） ranging from 2.83 to 4.91. Soil acid-base chemistry variables such as pH, base saturation, Al saturation, and acid-buffering capacity measured using the acetic acid equilibrium procedure indicated that soils in Lake 287 were more acidified than those in Lake 185. Acid-buffering capacity decreased in the order of forest floor 〉 subsurface mineral soil 〉 surface mineral soil. The most dramatic differences in percent Ca and Al saturations between the two watersheds were found in the surface mineral soil horizon. Percent Ca and Al saturation in the surface mineral soil in Lake 287 were 15% and 70%, respectively; the percent Ca saturation value fell within a critical range proposed in the literature that indicates soil acidification. Our results suggest that the soils in the two watersheds have low acid buffering capacity and would be sensitive to increased acidic deposition in the region.     

Acidity,nutrient stocks,and organic‐matter content in soils of a temperate deciduous forest with different abundance of European beech (Fagus sylvatica L.)

The production and composition of leaf litter, soil acidity, exchangeable nutrients, and the amount and distribution of soil organic matter were analyzed in a broad‐leaved mixed forest on loess over limestone in Central Germany. The study aimed at determining the current variability of surface‐soil acidification and nutrient status, and at identifying and evaluating the main factors that contributed to the variability of these soil properties along a gradient of decreasing predominance of European beech (Fagus sylvatica L.) and increasing tree‐species diversity. Analyses were carried out in (1) mature monospecific stands with a predominance of beech (DL 1), (2) mature stands dominated by three deciduous‐tree species (DL 2: beech, ash [Fraxinus excelsior L.], lime [Tilia cordata Mill. and/or T. platyphyllos Scop.]), and (3) mature stands dominated by five deciduous‐tree species (DL 3: beech, ash, lime, hornbeam [Carpinus betulus L.], maple [Acer pseudoplatanus L. and/or A. platanoides L.]). The production of leaf litter was similar in all stands (3.2 to 3.9 Mg dry matter ha^–1 y^–1) but the total quantity of Ca and Mg deposited on the soil surface by leaf litter increased with increasing tree‐species diversity and decreasing abundance of beech (47 to 88 kg Ca ha^–1 y^–1; 3.8 to 7.9 kg Mg ha^–1 y^–1). The soil pH_(H2O) and base saturation (BS) measured at three soil depths down to 30 cm (0–10 cm, 10–20 cm, 20–30 cm) were lower in stands dominated by beech (pH = 4.2 to 4.4, BS = 15% to 20%) than in mixed stands (pH = 5.1 to 6.5, BS = 80% to 100%). The quantities of exchangeable Al and Mn increased with decreasing pH and were highest beneath beech. Total stocks of exchangeable Ca (0–30 cm) were 12 to 15 times larger in mixed stands (6660 to 9650 kg ha^–1) than in beech stands (620 kg ha^–1). Similar results were found for stocks of exchangeable Mg that were 4 to 13 times larger in mixed stands (270 to 864 kg ha^–1) than in beech stands (66 kg ha^–1). Subsoil clay content and differences in litter composition were identified as important factors that contributed to the observed variability of soil acidification and stocks of exchangeable Ca and Mg. Organic‐C accumulation in the humus layer was highest in beech stands (0.81 kg m^–2) and lowest in stands with the highest level of tree‐species diversity and the lowest abundance of beech (0.27 kg m^–2). The results suggest that redistribution of nutrients via leaf litter has a high potential to increase BS in these loess‐derived surface soils that are underlain by limestone. Species‐related differences of the intensity of soil–tree cation cycling can thus influence the rate of soil acidification and the stocks and distribution of nutrients.     

Cold and hot water–extractable organic matter as indicators of litter decomposition in forest soils

Mild extractions were used as indicators of easily decomposable organic matter (OM). However, the chemical composition of extracted OM often remained unclear. Therefore, the composition of cold and hot water–extractable OM was investigated in the O horizons (Oi, Oe, Oa) of a 170 y old beech stand (Fagus sylvatica) in the Ore Mtns., SE Germany. To simulate litter decomposition, the O horizon samples were incubated for 1 week under defined conditions. Cold‐ and hot‐water extracts were analyzed and chemically characterized by pyrolysis–field ionization mass spectrometry (Py‐FIMS). The C and N concentrations were always lower in the cold‐(C: 2.69 to 3.95 g kg^–1; N: 0.14 to 0.29 g kg^–1) than in the hot‐water extracts (C: 13.77 to 15.51 g kg^–1; N: 0.34 to 0.83 g kg^–1). The C : N ratios of both extracts increased with increasing depth. Incubation increased the concentrations of C and N in all water extracts, while C : N ratios of extracts decreased. The molecular‐chemical composition of cold and hot water–extracted OM revealed distinct differences. Generally, cold water–extracted OM was thermally more stable than hot water–extracted OM. The mass spectra of the hot water–extracted organic matter revealed more intensive signals of carbohydrates, phenols, and lignin monomers. Additionally, the n‐C₂₈ fatty acid and the n‐C₃₈–to–n‐C₅₂ alkyl monoesters clearly distinguished the hot‐ from the cold‐water extract. A principle‐component analysis visualized (1) alterations in the molecular‐chemical composition of cold‐ and hot‐water extracts due to previous incubation of the solid O horizon samples and (2) a decomposition from the Oi to the Oh horizon. This provides evidence that the macromorphological litter decomposition was reflected by the chemical composition of water extracts, and that Py‐FIMS is well‐suited to explain at the molecular level why OM decomposability is correlated with water‐extracted C.     

Addition of lignin to lime materials for expedited pH increase and improved vertical mobility of lime in no‐till soils

Soil acidification caused by long‐term nitrogen (N) fertilizer applications has been a growing concern for dryland crop production in both tilled and no‐till soils in the Pacific Northwest (PNW). Many no‐till soils have stratified soil pH in the 5–10 cm depth due to repeated N fertilizer applications at this depth. In the PNW, the practice of liming to correct low soil pH is complicated due to lack of affordable lime sources and because the inherent difficulty in ameliorating stratified soil acidity in no‐till systems. An intact soil‐column incubation study was conducted to investigate whether mixing lime materials with lignin‐containing black liquor—a by‐product from the pulp industry—could elevate soil pH change in both conventional and no‐till systems and expedite vertical downward movement of lime in no‐till system. Results indicate that mixing lime with black liquor has the potential to not only elevate the increase in soil pH in both conventional till and no‐till systems, but also accelerate downward movement of lime to correct soil pH below the soil surface. Mixing agricultural lime or super fine micro lime with black liquor increased soil pH to a depth of 25–30 cm within 147 days after surface application to a no‐till soil.     

The application of biochar on soil acidity and other physico‐chemical properties of soils in southern Ethiopia

The aim of this research was to investigate the effect of biochar amendment on soil acidity and other physico‐chemical properties of soil in Southern Ethiopia using a field experiment of three treatments: (1) biochar made of corn cobs, (2) biochar made of chopped Lantana camara stem, and (3) biochar made of Eucalyptus globulus feedstock and a control, in which neither of the biochar was used. Each treatment had three levels of 6, 12 and 18 t ha⁻¹. The experiment was setup with RCBD in a factorial arrangement with three replications. In this regard, a total of 36 plots (each 2 × 2 m size) were applied with three replications to the depth of 0–15cm. From these 36 plots, composite soil samples were collected to the depth of 0–30 cm and analyzed for bulk density, total porosity, pH, soil organic carbon, total nitrogen, available phosphorus, potassium, and exchangeable acidity using standard procedures before and after biochar application. Two‐way ANOVA was also used to analyze the impact of the biochars on soil acidity and other properties. For the treatments that had significant effects, a mean separation was made using Least Significance Difference (LSD) test. The results showed the application of biochar significantly reduced, soil bulk density and exchangeable acidity when compared with a control (p < 0.05). Moreover, the total soil porosity, soil pH, total nitrogen, soil organic carbon, available phosphorus, and potassium were significantly increased in the soil. From among applied biochar treatments, Lantana camara applied at the level of 18 t ha⁻¹ had a higher impact in changing soil physico‐chemical properties. In general, the study suggests that the soil acidity can be reduced by applying biochar as it can amend other soil physico‐chemical properties.     

A multiscale soil–landform relationship in the glacial‐drift area based on digital terrain analysis and soil attributes

Understanding the linkages between structure and processes in soil landscapes involves analyses across several spatial and temporal scales. The transfer of information between scales requires the (1) identification of respective scale levels and (2) procedures for regionalization. Here, we present a multiparameter delineation of landform units and their attribution with typical Reference Soil Groups (RSG) of a landscape of NE Germany which is representative of young moraine regions. Data sources are a digital elevation model (DEM, 5 m × 5 m), a reference data set from sections of an intensively augered landscape, and expert knowledge. A conceptual digital soil map was constructed in the scale 1:5000 based on the Topographic Position Index (TPI). The methodology is applicable for multiscale analyses. Results are (1) the landform unit classified by digital terrain analysis of a DEM, (2) the attribution of RSG, and (3) the evaluation of the classification. Accuracy of the method was 57% overall, with 70% accuracy on typical erosional sites. The developed method allows identification of terrain‐related soil pattern with high spatial resolution in glacial‐drift areas. The high resolution of soil information can be used for delineation of management zones in precision farming, or as input for process studies and models requiring a translation of typological soil information into relevant soil properties (e.g., by pedotransfer functions).     

Medium‐ and short‐term available organic matter,microbial biomass,and enzyme activities in soils under Pinus sylvestris L. and Robinia pseudoacacia L. in a sandy soil in NE Saxony,Germany

Total, mobile, and easily available C and N fractions, microbial biomass, and enzyme activities in a sandy soil under pine (Pinus sylvestris L.) and black locust (Robinia pseudoacacia L.) stands were investigated in a field study near Riesa, NE Germany. Samples of the organic layers (Oi and Oe‐Oa) and the mineral soil (0–5, 5–10, 10–20, and 10–30 cm) were taken in fall 1999 and analyzed for their contents of organic C and total N, hot‐water‐extractable organic C and N (HWC and HWN), KCl‐extractable organic C and N (C_org(KCl) and N_org(KCl)), NH ‐N and NO ‐N, microbial‐biomass C and N, and activities of β‐glucosidase and L‐asparaginase. With exception of the HWC, all investigated C and N pools showed a clear response to tilling, which was most pronounced in the Oi horizon. Compared to soils under pine, those under black locust had higher contents of medium‐ and short‐term available C (HWC, C_org(KCl)) and N (HWN, N_org(KCl)), mineral N (NH ‐N, NO ‐N), microbial‐biomass C and N, and enzyme activities in the uppermost horizons of the soil. The strong depth gradient found for all studied parameters was most pronounced in soils under black locust. Microbial‐biomass C and N and enzyme activities were closely related to the amounts of readily mineralizable organic C (HWC and C_org(KCl)). However, the presented results implicate a faster C and N turnover in the top‐soil layers under black locust caused by higher N‐input rates by symbiotic N₂ fixation.