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Acidic deposition has been well studied for its impacts on forest soils and plants and is thought to detrimentally affect sugar maple (Acer saccharum) in northeastern North America. The physiological mechanism driving reduced tree growth on acid impaired sites is not well understood, but has been suggested to involve increased autotrophic respiration rates. We measured foliar respiration and leaf elemental composition on two species with contrasting acid tolerances (sugar maple and American beech, Fagus grandifolia) across a naturally occurring soil base saturation (BS) gradient in the Adirondack Mountains of New York. Foliar chemistry varied strongly as anticipated across the BS gradient, with decreases in base cations and increases in phytotoxic metals (e.g., Mn) on sites with highly acidified soils. However, foliar respiration rates were not correlated with most measures of acidity (e.g., BS, foliar concentrations of Ca, Mg, Al content). Respiration rates did correlate with other leaf traits (N content, leaf mass per unit area) reflective of leaf morphological variation in response to variable light availability. After accounting for multivariate trait covariation, mass-based respiration rates were associated with foliar Mn content, suggesting a positive relationship between the concentration of this phytotoxic metal and foliar respiration rates. Soluble foliar Ca, Mg, and Mn were closely correlated with total foliar concentrations of these elements. Overall these results demonstrate that soil acidification and loss of base cations is largely unrelated to foliar respiration rates, although the accumulation of foliar Mn on acidified soils may contribute to the metabolic burden of both sugar maple and American beech trees. [ABSTRACT FROM AUTHOR]

Atmospheric acid deposition has increased sharply since the beginning of industrialization but has decreased considerably since the 1980s owing to clean-air policies. Soil acidification induced by an input of acidity has been demonstrated in numerous studies using repeated forest-soil inventories. So far, relatively few data have been sampled to analyze long-term soil trends and only a few studies show the recovery of forest soils from acidification, whereas the recovery of surface waters following declining acid deposition is a widespread phenomenon. To assess a possible recovery from acid deposition, soil resampling data from 21 forested permanent soil-monitoring sites in Lower Saxony (Germany) were evaluated. For most sites, at least three repetitions of inventories from a period of 30 to 50 years were available. Trend analyses of indicators for the acid-base status of unlimed forest soils using generalized additive mixed models (GAMM) show either a trend reversal or a stagnation of the acid-base status at a strong acidification level. The recovery, if indicated by an increase of soil pH and base saturation, of soils from plots with deciduous trees appears to have occurred faster than in coniferous forest stands. This observation may be attributed to a larger amount of temporarily stored sulfur in the soil because of the higher atmospheric input into coniferous forests. As indicators for the acid-base status still show considerable soil acidification, mitigation measures such as forest liming still appear to be necessary for accelerating the regeneration process. [ABSTRACT FROM AUTHOR]

Questions: Vegetation in forest understories is determined by a complex interplay of many different environmental factors, including light, water and nutrient availability. Changes in these conditions, especially changes in nitrogen (N) availability, have been widely discussed to cause shifts in species composition and loss of oligotrophic species. We examined whether nitrogen is the most important factor for the decline of nitrogen-sensitive species in understorey communities, as measured by average Ellenberg N values and the share and number of nitrogen-sensitive character species. Location: Nine different oligo-mesotrophic types of temperate forest in southwest Germany. Methods: We combined understorey vegetation and soil data from 135 forest stands. To study the importance of variables in explaining the vegetation gradients, we used random forest analyses and non-metric multidimensional scaling (NMDS) ordinations combined with fitting of environmental vectors. Results: We detected strong differences between three examined forest type groups: eutrophication in the understorey vegetation of broad-leaved forests on carbonate soils was strongly related to high canopy closure and low soil carbon/phosphorus (C/P) ratio. In broad-leaved forests on acidic soil, base saturation played a major role, but the vegetation was also influenced by the C/N and C/P ratios. In coniferous forests on acidic soil, soil pH and organic layer depth were important, as were the C/N, C/P and N/P ratios. Conclusion: Our results show that eutrophication in understorey forest vegetation is not monocausal. Rather, oligotrophic species of forest communities are reduced at sites with higher N or P availability and/or higher base saturation and soil pH. These conditions favor fast-growing ubiquitous species in the competition for light and other limiting factors. Since these factors were of varying importance between the forest types examined, differences shaping the forest communities need to be regarded when evaluating the impact of environmental changes, for example through atmospheric nitrogen deposition. [ABSTRACT FROM AUTHOR]

In recent years, the importance of the forest soils started to gain an increasing attention both among forest specialists, policy makers and other stakeholders. This is mainly due to their importance for humanity, being the base for assuring several forest products and services. Since the 1980s, the Romanian soil specialists developed several soil taxonomy systems, based on the developments and data acquired at a certain moment. Knowing the type of the soil and its characteristics is crucial also for the foresters, for a sustainable forest management point of view. The aim of this study was to highlight the main characteristics of the forest soils across Getic Piedmont. Data from the forest management plans of twelve forest district that are responsible for managing the forests across the region were taken into account. The main representatives of Luvisols Class accounted for three quarters of the forest soils. In general, the characteristics of the forest soils are favorable for mixed-oak forest stands. In the future, special attention should be given to preserving the forests composed by autochthonous species, in order to maintain the fertility of the forest soils. [ABSTRACT FROM AUTHOR]

Key message : Aggregated, consolidated, and derived soil physicochemical data of 286 ICP Forests Level II plots were completed with soil hydraulic properties for integrated use with forest monitoring data. Database access should be requested at . Metadata associated available at Context : The ICP Forests database is one of the most comprehensive forest ecosystem datasets in Europe and contains the accumulated results of more than two decades of harmonised forest monitoring all over Europe. Aims : The aim of this paper is to share knowledge on the ICP Forests Level II soil data for broader use among forest scientists. Methods : After standard analysis, quality checks, aggregation, and calculation of derived variables (e.g. nutrient stocks, base saturation, C:N ratio, and water retention parameters), data have been gathered into a static database (AFSCDB.LII.2.2), which will be updated to new versions as soon as new measurements become available. Results : The database provides a basis for the combined evaluation of up to 130 unique soil variables of 286 plots with dynamic data on tree growth, ground vegetation, foliar chemistry, crown condition, tree phenology, leaf area index, ozone injury, litterfall, soil solution chemistry, deposition, ambient air quality, and meteorological data assessed on the same plots. Conclusion : The unprecedented comprehensiveness and level of detail in this newly aggregated database may overcome existing restrictions so far impeding the realisation of large-scale forest ecosystem studies in Europe. [ABSTRACT FROM AUTHOR]

This study, aiming to unravel whether topsoil conditions under tree species with nutrient-poor leaf litter can be altered by admixing a shrub layer, was performed in 12 pine (mainly Pinus sylvestris ) and 12 oak ( Quercus robur ) stands on sandy podzolic soils in north-east Belgium. We examined the effects of presence of a shrub layer on forest floor mass and topsoil chemical properties related to soil acidification. The shrub species included were European rowan ( Sorbus aucuparia ), alder buckthorn ( Rhamnus frangula ) and black cherry ( Prunus serotina ). For each tree species, 60–90 years old stands were selected containing shrubs present in varying cover classes: sparse (<20%), intermediate (20–70%) and dense (>70%). The oak stands were characterized by less but ‘nutrient-richer’ litterfall, compared to the pine stands. This was reflected in less humus build-up (FH-horizon) and higher pH, CEC, BS and lower C/N in the topsoil in the oak stands compared to the pine stands. However, despite the fact that the shrubs produced litter with significantly higher base cation and N concentrations than that of the studied tree species, we did not find any significant changes in topsoil conditions in the pine and oak stands under study, even under dense shrub layers (87–91% cover). [ABSTRACT FROM AUTHOR]

Abstract: In this paper we provide support for the hypothesis that trees and fungi modify their physical environment in acidic forest soils by actively translocating metal cations from the mineral to the organic horizon. We suggest that pH buffering and soil organic matter (SOM) turnover in organic horizons are regulated by Ca and Mg cycling via the tree canopy and litter fall and by fungal translocation of Al from mineral soil. Fungi in addition translocate Fe from mineral to organic horizons to enhance the degradation of aromatic structures in SOM. Together these processes are in control of N bioavailability, including new inputs via N fixation. Cycling of Ca and Mg via tree canopy typically increase the base saturation and pH towards the surface of organic forest soil horizons. This process is most clearly depicted at sites with laterally moving groundwater. An up-transport of Al from mineral to the organic horizon is most important as a pH buffering process in less productive, acid soils having a pH below approximately 4.5. At this pH, the non-acidic properties of organically complexed Al keep pH at a level sufficiently high for maintained microbial activity. Furthermore, the formation of bridging bonds between major organic functional groups (carboxyls and phenols) and di- and trivalent metal cations of Ca, Al and Fe possesses a strong influence on the tertiary structure of SOM and its persistence to degradation and delivery of N. [Copyright &y& Elsevier]

In May 31, 2000, the Government of the Czech Republic, has adopted the Decision No. 532, assigning the minister of agriculture to realize liming and fertilizing in the Krušné hory Mts. and Orlické hory Mts. Based on the decision, in 2000-2003, liming of forest stands was done, at the area of 34,000 ha. Changes of soil and leaf chemistry two years after liming were studied in the Western Krušné hory Mts., Forest administration Horní Blatná. Slight pH increase layer was stated both in the humus layer, and in upper horizons of mineral soil. Increased contents of calcium and magnesium, same as nitrogen and potassium were also recorded. Content of basic cations, mainly of magnesium and calcium, in the sorption complex was increased, aluminium content was decreased. C/N ratio in the humus layer did not change, ratio of basic cations and aluminium in the humus layer was increased significantly. Analyses of the assimilation organs of spruce have proved increase of magnesium and calcium content. The increase was higher in the stands of originally lower values of these elements. While before liming, in about a half of the samples of second needle year class, magnesium was under the deficiency level, two years after liming no deficient values were recorded.

Abstract: To monitor the effects of liming on forest ecosystems, experimental plots were installed in forests in mid-western Germany. In addition to soil chemical indices, earthworm communities were investigated on these plots about 15years after first lime applications took place. As a “natural reference”, communities were compared to earthworm records that derived from a beech forest on limestone. In the non-acidified plots that had never been limed only epigeic earthworms were detected in small numbers and low species richness. Forest liming caused higher pH and a higher base saturation in the mineral topsoils. To a large extent, epigeic earthworm species seemed to benefit from this and had increased in number and biomass at all three different locations selected for the investigations. The epigeic dominated communities were completed by anecic Lumbricus terrestris that was rarely found in some of the samples from one location and a number of endogeic species that showed a very patchy distribution in limed plots. In contrast to this, the soil of the beech forest on limestone showed a different community composition. It was dominated by endogeic species in abundance and by anecic species in biomass. On limestone the total biomass of earthworms clearly exceeded the biomass values from all other plots. In conclusion, a long-term support of forest earthworm fauna due to liming was detected. This support was mainly effective for epigeic species, but in some cases for endogeic and anecic species, too. [Copyright &y& Elsevier]

The role of soil and bedrock in acid neutralizing processes has been difficult to quantify because of hydrological and biogeochemical uncertainties. To quantify those roles, hydrochemical observations were conducted at two hydrologically well-defined, steep granitic hillslopes in the Tanakami Mountains of Japan. These paired hillslopes are similar except for their soils; Fudoji is leached of base cations (base saturation <6%), while Rachidani is covered with fresh soil (base saturation >30%), because the erosion rate is 100–1000 times greater. The results showed that (1) soil solution pH at the soil–bedrock interface at Fudoji (4.3) was significantly lower than that of Rachidani (5.5), (2) the hillslope discharge pH in both hillslopes was similar (6.7–6.8), and (3) at Fudoji, 60% of the base cations leaching from the hillslope were derived from bedrock, whereas only 20% were derived from bedrock in Rachidani. Further, previously published results showed that the stream pH could not be predicted from the acid deposition rate and soil base saturation status. These results demonstrate that bedrock plays an especially important role when the overlying soil has been leached of base cations. These results indicate that while the status of soil acidification is a first-order control on vulnerability to surface water acidification, in some cases such as at Fudoji, subsurface interaction with the bedrock determines the sensitivity of surface water to acidic deposition. [Copyright &y& Elsevier]

We reviewed the current methods for calculating critical loads of acidity for forest soils. The consequences of four sets of assumptions concerning the soil model structure, parameter values and the critical loads criterion were explored by comparing the values of the average accumulated exceedance (AAE) calculated for Finland with deposition values for the year 1995. The AAE index is given in the unit of deposition and is a measure of how far a region is from being protected in terms of fulfilling a certain criterion, taking into account the size of the ecosystem areas. Using a critical limit for the molar ratio of the concentrations of base cations to aluminium in soil solution gave the lowest average accumulated exceedance. Assuming organo-aluminium complexes and leaching of organic anions gave AAE = 4 eq ha-1 a-1, which was close to the value obtained with the standard approach used in Finland, assuming gibbsite equilibrium and no leaching of organic anions, yielding AAE = 5 eq ha-1 a-1. With a critical base saturation limit, instead of the concentrations criterion, the AAE index was 17 eq ha-1 a-1. The highest average accumulated exceedance (AAE = 25 eq ha-1 a-1), corresponding to the lowest critical load, was obtained when the effects-based criterion (critical concentration or critical base saturation) was substituted with one restricting the deterioration of the neutralizing capacity of the soil, ANCle(crit) = 0. These tests illustrate the variability of the critical load values for acidity that can be introduced by changing the criterion or by varying the calculation method, without, however, representing the extreme values of critical loads that could be derived. [ABSTRACT FROM AUTHOR]

Between 1993 and 1995 a system of six intensive monitoring stations in representative stands of Norway spruce (Picea abies), sessile oak (Quercus robur) and Scots pine (Pinus sylvestris) were installed in forests of Saxony (Germany), they are integrated in the European Level II - Programme. As a complementary system, and in addition to the annual nation-wide forest decline survey, 280 sites within the forest soil condition survey (European Level I - Programme) have been examined since 1992. The results of deposition monitoring show that until 1997 the acidity in precipitation and troughfall still was very high, despite of strong reductions in industrial emissions between 1989 and 1992. The annual fluxes (hydrological year 1996) of sulphur in throughfall ranged between 16 and 77 kg-ha-1, whereas the fluxes of total inorganic N varied between 17 and 46 kg-ha-1. The forest soils show high degrees of acidification with only low base saturation. In most cases the nutrient status of the soils has to be improved in the course of a regeneration programme in order to rebuild more natural forest ecosystems. [ABSTRACT FROM AUTHOR]