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Forest models are instrumental for understanding and projecting the impact of climate change on forests. A considerable number of forest models have been developed in the last decades. However, few systematic and comprehensive model comparisons have been performed in Europe that combine an evaluation of modelled carbon and water fluxes and forest structure. We evaluate 13 widely used, state-of-the-art, stand-scale forest models against field measurements of forest structure and eddy-covariance data of carbon and water fluxes over multiple decades across an environmental gradient at nine typical European forest stands. We test the models' performance in three dimensions: accuracy of local predictions (agreement of modelled and observed annual data), realism of environmental responses (agreement of modelled and observed responses of daily gross primary productivity to temperature, radiation and vapour pressure deficit) and general applicability (proportion of European tree species covered). We find that multiple models are available that excel according to our three dimensions of model performance. For the accuracy of local predictions, variables related to forest structure have lower random and systematic errors than annual carbon and water flux variables. Moreover, the multi-model ensemble mean provided overall more realistic daily productivity responses to environmental drivers across all sites than any single individual model. The general applicability of the models is high, as almost all models are currently able to cover Europe's common tree species. We show that forest models complement each other in their response to environmental drivers and that there are several cases in which individual models outperform the model ensemble. Our framework provides a first step to capturing essential differences between forest models that go beyond the most commonly used accuracy of predictions. Overall, this study provides a point of reference for future model work aimed at predicting climate impacts and supporting climate mitigation and adaptation measures in forests., Global Change Biology, 28 (23), ISSN:1354-1013, ISSN:1365-2486

Atmospheric deposition of nitrogen (N) has exceeded its demand for plant increment in forest ecosystems in Germany. High N inputs increased plant growth, the internal N cycling within the ecosystem, the retention of N in soil and plant compartments, and the N output by seepage water. But the processes involved are not fully understood, notably the effect of fructification in European beech (Fagus sylvatica L.) on N fluxes. The frequency of fructification has increased together with air temperature and N deposition, but its impact on N fluxes and the sequestration of carbon (C) and N in soils have been hardly studied. A field experiment using 15 N-labeled leaf litter exchange was carried out over a 5.5-year period at seven long-term European beech (Fagus sylvatica L.) monitoring sites to study the impact of current mast frequency on N cycling. Mean annual leaf litterfall contained 35 kg N ha −1 , but about one-half of that was recovered in the soil 5.5 years after the establishment of the leaf litter 15 N exchange experiment. In these forests, fructification occurred commonly at intervals of 5 to 10 years, which has now changed to every 2 years as observed during this study period. Seed cupules contributed 51 % to the additional litterfall in mast years, which creates a high nutrient demand during their decomposition due to the very high ratios of C to N and C to phosphorus (P). Retention of leaf litter 15 N in the soil was more closely related to the production of total litterfall than to the leaf litterfall, indicating the role of seed cupules in the amount of leaf N retained in the soil. Higher mast frequency increased the mass of mean annual litterfall by about 0.5 Mg ha −1 and of litterfall N by 8.7 kg ha −1 . Mean net primary production (NPP) increased by about 4 %. Mean total N retention in soils calculated by input and output fluxes was unrelated to total litterfall, indicating that mast events were not the primary factor controlling total N retention in soils. Despite reduced N deposition since the 1990s, about 5.7 out of 20.7 kg N ha −1 deposited annually between 1994 and 2008 was retained in soils, notably at acid sites with high N / P and C / P ratios in the organic layers and mineral soils, indicating P limitation for litter decomposition. Trees retained twice as much N compared to soils by biomass increment, particularly in less acidic stands where the mineral soils had low C / N ratios. These results have major implications for our understanding of the C and N cycling and N retention in forest ecosystems. In particular the role of mast products in N retention needs more research in the future.

Most trees form symbioses with ectomycorrhizal fungi (EMF) which influence access to growth-limiting soil resources. Mesocosm experiments repeatedly show that EMF species differentially affect plant development, yet whether these effects ripple up to influence the growth of entire forests remains unknown. Here we tested the effects of EMF composition and functional genes relative to variation in well-known drivers of tree growth by combining paired molecular EMF surveys with high-resolution forest inventory data across 15 European countries. We show that EMF composition was linked to a three-fold difference in tree growth rate even when controlling for the primary abiotic drivers of tree growth. Fast tree growth was associated with EMF communities harboring high inorganic but low organic nitrogen acquisition gene proportions and EMF which form contact versus medium-distance fringe exploration types. These findings suggest that EMF composition is a strong bio-indicator of underlying drivers of tree growth and/or that variation of forest EMF communities causes differences in tree growth. While it may be too early to assign causality or directionality, our study is one of the first to link fine-scale variation within a key component of the forest microbiome to ecosystem functioning at a continental scale., The ISME Journal, 16 (5), ISSN:1751-7362, ISSN:1751-7370

Este artículo contiene 11 páginas, 2 tablas, 4 figuras., Local biodiversity trends over time are likely to be decoupled from global trends, as local processes may compensate or counteract global change. We analyze 161 long-term biological time series (15–91 years) collected across Europe, using a comprehensive dataset comprising ~6,200 marine, freshwater and terrestrial taxa. We test whether (i) local long-term biodiversity trends are consistent among biogeoregions, realms and taxonomic groups, and (ii) changes in biodiversity correlate with regional climate and local conditions. Our results reveal that local trends of abundance, richness and diversity differ among biogeoregions, realms and taxonomic groups, demonstrating that biodiversity changes at local scale are often complex and cannot be easily generalized. However, we find increases in richness and abundance with increasing temperature and naturalness as well as a clear spatial pattern in changes in community composition (i.e. temporal taxonomic turnover) in most biogeoregions of Northern and Eastern Europe., We are grateful to the ILTER network and the eLTER PLUS project (Grand Agreement No. 871128) for financial support. We acknowledge the E-OBS dataset from the EUFP6 project ENSEMBLES (http://ensembles-eu.metoffice.com) and the data providers in the ECA&D project (http://www.ecad.eu). The evaluation of forest plant diversity was based on data collected by partners of the official UNECE ICP Forests Network (http://icp-forests.net/contributors); part of the data were co-financed by the European Commission, project LIFE 07 ENV/D/000218 “Further Development and Implementation of an EU-level Forest monitoring Systeme (FutMon)”. Data on wintering water birds in Bulgaria were provided by the national Executive Environment Agency with the Ministry of Environment and Waters. Data from the Finnish moth monitoring scheme were supported by the Finnish Ministry of the Environment. Data from the Swedish ICP Integrated Monitoring sites were financed by the Swedish Environmental Protection Agency. Data collection at Esthwaite Water and a subset of UK ECN sites was supported by Natural Environment Research Council award number NE/ R016429/1 as part of the UK-SCaPE programme delivering National Capability. Sponsorship of other UK ECN sites contributing data was provided by Agri-Food and Biosciences Institute, Biotechnology and Biological Sciences Research Council, Department of Environment Food and Rural Affairs, Natural Resources Wales, Defense Science Technology Laboratory, Environment Agency, Forestry Commission, Forest Research, the James Hutton Institute (The Rural & Environment Science & Analytical Services Division of the Scottish Government), Natural England, Rothamsted Research, Scottish Government, Scottish Natural Heritage and the Welsh Government. Data from the Mondego estuary (Portugal) were supported by the Centre for Functional Ecology Strategic Project (UID/BIA/04004/2019) within the PT2020 Partnership Agreement and COMPETE 2020, and by FEDER through the project ReNATURE (Centro 2020, Centro-01-765-0145-FEDER-000007). We would like to thank Limburgse Koepel voor Natuurstudie (LiKoNa) for the data related to the National Park Hoge Kempen (BE). We would like to acknowledge the support for the long-term monitoring program MONEOS in the Scheldt estuary (BE) by ‘De Vlaamse Waterweg’ and ‘Maritieme Toegang’ (Flemish government). We are grateful to the board of the National Park “De Hoge Veluwe” for the permission to conduct our research on their property. We thank Ian J. Winfield and Terje Bongard for contributing data for the sites: Bassenthwaite Lake, Derwent Water (UK) and Atna River (Norway, freshwater invertebrate time series). Open access funding provided by Umeå University.

In the Bramke valley (western Harz mountains, North Germany), three forested headwater catchments have been monitored since decades. A broad range of observables relevant to forestry, hydrology, hydrochemistry and ecosystem research allows to compare different approaches to environmental monitoring; each of them has its own set of relevant observables. The basic temporal resolution is daily for hydrometeorology and bi-weekly for streamwater chemistry; standing biomass of the Norway spruce stands is measured every couple of years.Tree growth (site index) has changed between and within rotation periods (of up to 129 years); changes in soil nutrient pools are typical variables used to explain this nonstationary forest growth when the spatial-temporal scales match. In hydrology, transport mechanisms of water and solutes through catchment soils are used to model and predict runoff and its chemistry. Given the homogeneity of the area in terms of geology, soils and topography as well as climate, differences between the catchments in the Bramke valley are mostly related to forestry variables. The catchments exhibit long-term changes and spatial gradients related to atmospheric deposition, management and changing climate. After providing a short multivariate summary of the dataset, we present several nonlinear metrics suitable to detect and quantify subtle changes and to describe different behavior, both between different variables from the same catchment, as well as for the same variable across catchments.Soil water potential and solution chemistry are further links between forestry and hydrology. However, at Lange Bramke, similar to other catchment studies, the evaluation of these data sets has not converged to a consistent, realistic model at the catchment scale. We hypothesize that this lack of model integration is due to theoretical rather than technical limits. A possible representation of these limits might be phrased in a category theory approach.

Atmospheric deposition of nitrogen (N) has exceeded its demand for plant increment in forest ecosystems in Germany. High N inputs increased plant growth, the internal N cycling within the ecosystem, the retention of N in soil and plant compartments, and the N output by seepage water. But the processes involved are not fully understood, notably the effect of fructification in European beech (Fagus sylvatica L.) on N fluxes. The frequency of fructification has increased together with air temperature and N deposition, but its impact on N fluxes and the sequestration of carbon (C) and N in soils have been hardly studied. A field experiment using 15N-labeled leaf litter exchange was carried out over a 5.5-year period at seven long-term European beech (Fagus sylvatica L.) monitoring sites to study the impact of current mast frequency on N cycling. Mean annual leaf litterfall contained 35 kg N ha−1, but about one-half of that was recovered in the soil 5.5 years after the establishment of the leaf litter 15N exchange experiment. In these forests, fructification occurred commonly at intervals of 5 to 10 years, which has now changed to every 2 years as observed during this study period. Seed cupules contributed 51 % to the additional litterfall in mast years, which creates a high nutrient demand during their decomposition due to the very high ratios of C to N and C to phosphorus (P). Retention of leaf litter 15N in the soil was more closely related to the production of total litterfall than to the leaf litterfall, indicating the role of seed cupules in the amount of leaf N retained in the soil. Higher mast frequency increased the mass of mean annual litterfall by about 0.5 Mg ha−1 and of litterfall N by 8.7 kg ha−1. Mean net primary production (NPP) increased by about 4 %. Mean total N retention in soils calculated by input and output fluxes was unrelated to total litterfall, indicating that mast events were not the primary factor controlling total N retention in soils. Despite reduced N deposition since the 1990s, about 5.7 out of 20.7 kg N ha−1 deposited annually between 1994 and 2008 was retained in soils, notably at acid sites with high N/P and C/P ratios in the organic layers and mineral soils, indicating P limitation for litter decomposition. Trees retained twice as much N compared to soils by biomass increment, particularly in less acidic stands where the mineral soils had low C/N ratios. These results have major implications for our understanding of the C and N cycling and N retention in forest ecosystems. In particular the role of mast products in N retention needs more research in the future.

We analyze time series from several forested headwater catchments located adjacent to each other in the Bramke valley, Harz mountains (Germany) which are monitored since decades for hydrology, hydrochemistry and forest growth. The data sets include meteorological variables, runoff rates, streamwater chemical concentrations, and others. The basic temporal resolution is daily for hydrometeorology and two-weekly for streamwater chemistry (in addition, standing biomass of a Norway spruce stand is measured every couple of years).A model was calibrated and run for the streamflow from one of the catchments, based on precipitation, temperature and (simulated) evapotranspiration of the growing trees, to elucidate the effect of forest growth on catchment hydrology.The catchments exhibit long-term changes and spatial gradients related to atmospheric deposition, management and changing climate. After providing a short multivariate summary of the dataset, we present several nonlinear metrics suitable to detect and quantify subtle changes and to describe different behavior, both between different variables from the same catchment, as well as for the same variable across catchments. The methods include, but are not limited to: Tarnopolski analysis, permutation entropy and complexity, q- and α-complexities, and Horizontal Visibility Graphs.The detection of these changes is remarkable, because linear trends have already been removed prior to analysis. Hence, their presence reflects intrinsic changes in the patterns of the time series. The metrics also allow for a detailed model evaluation from a nonlinear perspective.An important methodological aspect is the temporal resolution of the time series. We investigate the scaling behavior of the nonlinear metrics through aggregation or decimation to coarser resolutions and conclude on what the scaling behavior may imply for inverse (hydrological) modelling tasks.

Forests face considerable pressure from climate change, while demand of provided ecosystem services is high. Managing and planting forests need well informed decisions by practitioners, to fulfill the goal of sustainability. In Germany, informed decisions are derived from forest site evaluation maps, integrating biogeoecolocigal conditions (climate, soil water, nutrients). Here, we focus on mapping of nutrients in the federal state Hesse, Germany. For Hesse, a forest site map exists, which indicates a soil nutrient regime (SNR) index (classes very poor, poor, medium, rich, very rich). Site mapping was done in the field by experts, considering ground vegetation and soil morphology. Guidelines exist for choosing management options (i.e. suitable species composition, harvest restrictions, etc.), but if spatial information is not accurate, management decisions will be misguided.Three major challenges regarding the currently available site information exist: (1) the spatial proportion of “medium” sites is exceptionally high (65% of mapped forest area) and while there is differentiation between parent materials, topography is neglected. (2) Whereas 80% of Hesse’s forests were mapped, there is need to fill the gaps. (3) The existing SNR index does not take analytical measurements of soil nutrients into account. Objectives were (1) to refine and expand the existing map of SNR by (2) including soil chemical properties from the second National Forest Soil Inventory (NFSI), (3) which have to be regionalised beforehand.Stocks of Ca, Mg and K, base saturation, effective cation exchange capacity (90cm depth and organic layer), and C/N ratio (organic layer or 0-5 cm) of 380 profiles from the NFSI were chosen to characterise the SNR. Regionalisation was performed with generalised additive models (GAM) by using environmental relationships of the target variables with variables of climate, vegetation, parent material and soil properties (soil map 1:50,000). Ten-fold cross validation revealed R² values from 0.54 to 0.79, with low relative root mean square deviation (5 to 17%) and slopes not significantly different from 1. From the six successfully modelled target variables, we inferred a single SNR for each soil map polygon. This was challenging, because variables provided contrasting information regarding the SNR. We addressed this by using the Soil Inference Engine (SIE), which bases on fuzzy logic. Each variable received an optimality value for each SNR class. Using an expert-driven weighting system a SNR membership was inferred, whereas highest membership defined the SNR class. The result was highly sensitive towards parent material and topography. For instance, acidic parent material had lower SNR classes compared to base rich parent material. Within a given parent material, ridges where judged less nutrient rich compared to planes and topographic positions, where material is accumulated.The results provide a much more differentiated and complete map for SNR, which mirror actual expectations of nutrient distribution across Hesse’s landscape units. The approach is transparent and inter-subjectively reproducible. The new map will be used to guide reforestation activities in Hesse after the severe forest disturbances by recent climatic extremes (e.g. drought, storms) and the approach can be transferred to other regions.

Changing environmental conditions may substantially interact with site quality and forest stand characteristics, and impact forest growth and carbon sequestration. Understanding the impact of the various drivers of forest growth is therefore critical to predict how forest ecosystems can respond to climate change. We conducted a continental-scale analysis of recent (1995–2010) forest volume increment data (ΔVol, m3 ha−1 yr−1), obtained from ca. 100,000 coniferous and broadleaved trees in 442 even-aged, single-species stands across 23 European countries. We used multivariate statistical approaches, such as mixed effects models and structural equation modelling to investigate how European forest growth respond to changes in 11 predictors, including stand characteristics, climate conditions, air and site quality, as well as their interactions. We found that, despite the large environmental gradients encompassed by the forests examined, stand density and age were key drivers of forest growth. We further detected a positive, in some cases non-linear effect of N deposition, most pronounced for beech forests, with a tipping point at ca. 30 kg N ha−1 yr−1. With the exception of a consistent temperature signal on Norway spruce, climate-related predictors and ground-level ozone showed much less generalized relationships with ΔVol. Our results show that, together with the driving forces exerted by stand density and age, N deposition is at least as important as climate to modulate forest growth at continental scale in Europe, with a potential negative effect at sites with high N deposition.

Questions The understorey vegetation of temperate forests may serve as an indicator of long-term change in site conditions. We investigated vegetation change of the herb and moss layers during the last 50 years in managed European beech (Fagus sylvatica) and Sessile oak (Quercus petraea) forests under chronic nitrogen (N) deposition. We tested the hypotheses that (i) the species richness of the understorey vegetation has increased in intensively managed forests because species gains due to increased light and nutrient supply are greater than species losses, and (ii) shifts in species richness and community composition differ between beech and oak stands due to contrasting light regimes. Location Forests of the Solling Mountains, Central Germany. Methods We re-sampled 95 releves of the herb and moss layers after 46/47 years (1966/67 vs. 2013) to analyse change in cover and species composition. In the beech forests, two widespread types of production forest (selection cutting vs. shelterwood management) were compared with unmanaged forest reserves. Trends in vegetation change were related to a long-term record of N deposition and soil chemistry, shifts in Ellenberg Indicator Values (EIV), and changes in canopy structure. Results A decrease in the cover of the uppermost tree layer and emerging lower tree and shrub layers have increased the heterogeneity of canopy structure and indicate a more heterogeneous light distribution on the forest floor of the beech and oak forests. Plot-level species richness has increased in both forest types (except for beech stands under shelterwood management). Under chronic N deposition (~40 kg N ha−1 yr−1 before 1990, 20-25 kg ha−1 yr−1 since 1990), the organic layer N pool more than doubled between 1966 and 1993 with a decrease thereafter, and the EIV-nitrogen scores have increased. The N score increase was not related to changes in the canopy. Conclusions This study presents evidence of an N deposition effect on the understorey vegetation, which acts independently from the recorded changes in canopy structure. We conclude that altered nutrient supply due to atmospheric N deposition, together with changes in light regimes and management-related disturbance, are the main drivers of vegetation change in the studied stands. This article is protected by copyright. All rights reserved.

Many forest soils are sensitive to acidification due to input of acids from the atmosphere. As acidic deposition was strongly reduced during the last decades, the question arises, if indications of recovery from soil acidification are detectable in German forest soils. The comparison of the National Forest Soil Inventory II (NFSI II) with the NFSI I showed a recovery of the organic layers and mineral topsoils, but further acidification of deeper soil layers at acid-sensitive substrates. Changes of the acid-base status of forest soils are indicated by pH value and base saturation. Where increases of pH were detected, these are higher for pH(H2O) as compared to pH(KCl). Limed soils experienced a stronger recovery from acidification than unlimed soils, especially if they are stocked with deciduous trees. In parts of northeastern Germany, extensive deposition of basic dust prior to NFSI I was leached from the soils between NFSI II and NFSI I resulting in strong acidification. The comparison with long-term studies of soil acidification suggests that acidification ceased in the period between the two inventories.

The availability of water to roots is a central property for the growth and productivity of forests. Because nearly all plant nutrients are taken up from the soil solution, there is a close connection between forest nutrition and the water budget. Furthermore, seepage water transports substances between the atmosphere, the soil, and the hydrosphere and determines the soils’ filter function. Information on the water budget is therefore an important basis for the assessment of forest sites. Through processing and combination of data on soil, root and forest stand parameters in the NFSI data set, it was possible to reliably estimate the factors that control the soil water budget. Soil hydraulic properties such as water retention and water conductivity were derived from measured and estimated soil properties using pedotransfer functions. Additionally, the depth profiles of fine roots for each of the NFSI profiles were estimated in a correlation analysis between fine root density and soil properties (Hartmann and Wilpert 2014). Based on the processed NFSI data, the soil water budget model LWF-Brook90 was parameterized, and the dynamic water budget for all NFSI profiles was modelled. The aim was to identify in what way water flow and availability are affected by the variability of soil properties. All simulations were carried out in daily resolution, and model output, such as seepage water rates, soil water storage and evapotranspiration, was derived in daily resolution. This chapter gives an overview on (1) the soil water budget model LWF-Brook90, (2) the methodologies used to derive the input parameters for the soil water budget modelling (specifically the soil hydraulic and rooting properties) and (3) the results of the soil water modelling. The discussion of results focusses on the assessment of drought indices. It is shown that the plant-available soil water storage and other drought indices display similar trends. According to the model results, the intensity of water shortage has increased since 1990 and years with above-average soil water supply.

The management of forests needs well informed decisions by stakeholders to fulfil the goals of sustainability, stability, and productivity. Decisions are guided by forest site maps. The forest site map of Hesse, Germany, consists of six soil nutrient index (SNI) classes (poor, moderate-weak, moderate, moderate-good, rich, carbonatic). Three major challenges regarding the currently available site information exist: (i) the spatial proportion of “moderate” sites is exceptionally high (65% of mapped forest area) and while there is differentiation between parent materials, topography is neglected. (ii) As 80% of Hesse's forests were mapped, there is demand to fill the gaps without site information. (iii) The existing SNI does not take soil analysis into account, which is required to detect finer differences in morphologically similar soil profiles. Objectives were to regionalize soil chemical variables and derive a more differentiated SNI for Hesse's forest soils with complete forest coverage. Stocks of intermediately available Ca, Mg, and K, base saturation, effective cation exchange capacity, and C/N ratio of 380 profiles from the National Forest Soil Inventory were used to characterize the SNI. Regionalization of soil chemical variables was successfully performed (R2 values from 0.54 to 0.79, root mean square deviation 5 to 17%) using generalized additive models. SNI classes were inferred by fuzzy logic for dealing with soil chemical variables. The results were highly sensitive towards parent material and topography. The modelled SNI map provides a much more differentiated and complete map for Hesse, Germany, which mirror actual expectations across landscape units. The approach is transparent and inter-subjectively reproducible. The new map will be used to guide the management and reforestation of sites, which were damaged by biotic or abiotic threats due to recent climatic extreme events.

Long-term estimates of the water balance of forests are essential for forest ecosystem analysis. Such estimates can be achieved by using numerical modelling approaches for water balance calculations. These modelling approaches require data, e.g., for the description of the hydraulic properties of forest soils using soil water retention or hydraulic conductivity functions. However, these functions are usually valid only for fine-earth conditions. However, many forest soils, especially those located in mountainous regions, contain larger fractions of gravel and rock fragments in the soil profiles. In our study, the impact of stoniness correction of soil hydraulic functions on the performance of a numerical water balance modelling approach was evaluated by using continuously measured time series of daily throughfall, soil water contents and pressure heads provided from three different ICP Forests Level II plots with high stoniness in the soil profiles. These measured data were compared with the corresponding model outputs. The application of stoniness correction of the soil hydraulic functions improved the model performance in terms of the Nash-Sutcliffe Index NS and the coefficient of determination R2. This indicated the need for such a correction.

International audience; Published by Copernicus Publications on behalf of the European Geosciences Union. 5568 M. Camino-Serrano et al.: Trends in soil solution dissolved organic carbon Abstract. Dissolved organic carbon (DOC) in surface waters is connected to DOC in soil solution through hydrological pathways. Therefore, it is expected that long-term dynamics of DOC in surface waters reflect DOC trends in soil solution. However, a multitude of site studies have failed so far to establish consistent trends in soil solution DOC, whereas increasing concentrations in European surface waters over the past decades appear to be the norm, possibly as a result of recovery from acidification. The objectives of this study were therefore to understand the long-term trends of soil solution DOC from a large number of European forests (ICP Forests Level II plots) and determine their main physico-chemical and biological controls. We applied trend analysis at two levels: (1) to the entire European dataset and (2) to the individual time series and related trends with plot characteristics , i.e., soil and vegetation properties, soil solution chemistry and atmospheric deposition loads. Analyses of the entire dataset showed an overall increasing trend in DOC concentrations in the organic layers, but, at individual plots and depths, there was no clear overall trend in soil solution DOC. The rate change in soil solution DOC ranged between −16.8 and +23 % yr −1 (median = +0.4 % yr −1) across Eu-rope. The non-significant trends (40 %) outnumbered the increasing (35 %) and decreasing trends (25 %) across the 97 ICP Forests Level II sites. By means of multivariate statistics , we found increasing trends in DOC concentrations with increasing mean nitrate (NO − 3) deposition and increasing trends in DOC concentrations with decreasing mean sulfate (SO 2− 4) deposition, with the magnitude of these relationships depending on plot deposition history. While the attribution of increasing trends in DOC to the reduction of SO 2− 4 deposi-tion could be confirmed in low to medium N deposition areas, in agreement with observations in surface waters, this was not the case in high N deposition areas. In conclusion, long-term trends of soil solution DOC reflected the interactions between controls acting at local (soil and vegetation properties) and regional (atmospheric deposition of SO 2− 4 and inorganic N) scales.

In this paper the concept of resilience is discussed on the base of 13 case studies from the German branch of the International Long-Term Ecological Research Program. In the introduction the resilience approach is presented as one possibility to describe ecosystem dynamics. The relations with the concepts of adaptability and ecological integrity are discussed and the research questions are formulated. The focal research objectives are related to the conditions of resilient behaviour of ecosystems, the role of spatio-temporal scales, the differences between short- or long-term dynamics, the basic methodological requirements to exactly define resilience, the role of the reference state and indicators and the suitability of resilience as a management concept. The main part of the paper consists of 13 small case study descriptions, which demonstrate phase transitions and resilient dynamics of several terrestrial and aquatic ecosystems at different time scales. In the discussion, some problems arising from the interpretation of the time series are highlighted and discussed. The topics of discussion are the conceptual challenges of the resilience approach, methodological problems, the role of indicator selection, the complex interactions between different disturbances, the significance of time scales and a comparison of the case studies. The article ends with a conclusion which focuses on the demand to link resilience with adaptability, in order to support the long-term dynamics of ecosystem development. published

Time series of values of ingenious parameters indicating ecosystem services from European beech and Norway spruce ecosystems at Solling, Germany, were evaluated with respect to resilient or adaptive behaviour. Studied indicators comprise the use of monitoring data with up to more than 40 years of observation on deposition of potential acidity, sulphate (SO 4 2− ) budgets, exchangeable base cation pools, Bc/Al ratio in soil solution, nitrogen (N) budgets, foliar nutrition as indicated by the foliar Bc/N ratio, and defoliation. Deposition of potential acidity decreased considerably at both ecosystems. SO 4 2− budgets reveal retention of sulphur in the soils affecting acid/base budgets. Exchangeable base cation pools decreased at both ecosystems by about 60%. Bc/Al ratio in soil solution in the mineral soil was mostly below critical limits indicating potential toxic stress to tree roots. N retention in the soils decreased from about 40 kg ha −1 yr −1 in the 1970s to currently very low rates of 0–20 kg ha −1 yr −1 indicating increasing N saturation. Foliar Bc/N ratio decreased at the spruce ecosystem indicating possible nutrient imbalances. Defoliation at both Solling ecosystems is on a high level compared to other forests in Germany, but reveals no distinct relation to soil acidification or N saturation. From the selected indicators, SO 4 2− and N budgets reveal resilient behaviour, whereas indicators related to the acid/base status tend to adaptive behaviour.

Soil vegetation atmosphere transport (SVAT) models are important for the quantification of water fluxes, soil water availability, drought stress and their uncertainties under climate change. We present LWFBrook90R , an enhanced implementation of the well-established, process-based SVAT model LWF-Brook90 for the R environment for statistical computing. The package provides new functions and sub-models for model parameterization, and facilitates parallel computing, sensitivity analysis and inverse calibration of the model. A case study comprising i) basic forward water balance simulations for temperate grassland vegetation, deciduous and evergreen forest, ii) a parallelized sensitivity analysis, and iii) Bayesian calibrations based on soil water storage observed in a poplar (Populus nigra × P. maximowiczii) Short Rotation Forest (SRF) demonstrates the utility of the R package. The sensitivity analysis revealed parameters affecting plant-available soil water storage capacity and the vegetation's timing and level of water demand to be most important for the annual course of simulated soil water storage, with seasonal and interannual differences in parameter importance rankings. The subsequent calibration yielded a very high agreement between daily simulated and observed soil water storage (0-200 cm soil depth) for the calibration and validation datasets, with Nash-Sutcliffe efficiencies of 0.97 and 0.95, respectively. The final model predicted high though realistic rates of annual evapotranspiration (2011: 844 ± 3.8 mm y-1, 2012: 733 ± 4.5 mm y-1) for the poplar SRF, regularly exceeding grass reference evaporation (ET0) by 20-47% during the months of the growing season. However, basing calibrations solely on observed soil water storage probably resulted in biased partitioning of evapotranspiration towards interception losses. The integration of the LWF-Brook90 hydrological model into R with its wide variety of extensions was successfully tested and may provide efficient, reliable and reproducible water balance predictions by facilitating complex statistical analyses and large-scale applications of the model.

The reversal of freshwater acidification in the low mountain ranges of Germany is of public, political and scientific concern, because these regions are near natural ecosystems and function as an important drinking water supply. The aim of this study was to evaluate the status and trends of acidification reversal after two decades of reduced anthropogenic deposition in selected freshwaters of the low mountain ranges in the Harz, the Fichtelgebirge, the Bavarian Forest, the Spessart and the Black Forest. In response to decreased sulphate deposition, seven out of nine streams investigated had significantly decreasing sulphate concentrations (all trends were calculated with the Seasonal Kendall Test). The decrease in sulphate concentration was only minor, however, due to the release of previously stored soil sulphur. No increase was found in pH and acid neutralising capacity (defined by Reuss and Johnson, 1986). Aluminum concentrations in the streams did not decrease. Thus, no major acidification reversal can currently be noted in spite of two decades of decreased acid deposition. Nevertheless, the first signs of improvement in water quality were detected as there was a decrease in the level and frequency of extreme values of pH, acid neutralising capacity and aluminium concentrations in streams. With respect to nitrogen, no change was determined for either nitrate or ammonium concentrations in precipitation or stream water. Base cation fluxes indicate increasing net loss of base cations from all ecosystems investigated, which could be interpreted as an increase in soil acidification. The latter was due to a combination of continued high anion leaching and significant reduction of base cation deposition. No major improvement was noted in biological recovery, however, initial signs of recovery were detectable as there was re-occurrence of some single macroinvertebrate species which were formerly extinct. The results of this study have important implications for water authorities, forest managers and policy makers: the delay in acidification reversal suggests a need for ongoing intensive amelioration of waters, a careful selection of management tools to guarantee sustainable management of forests and the reduction of nitrogen deposition to prevent further acidification of soils and waters. Keywords: freshwater, acidification reversal, drinking water supply, forested catchments, Germany

Following the decline in sulphur deposition in Europe, sulphate dynamics of catchments and the reversibility of anthropogenic acidification of soils and freshwaters became of major interest. Long-term trends in sulphate concentrations and fluxes in precipitation/throughfall and freshwaters of 20 European catchments were analysed to evaluate catchment response to decreasing sulphate deposition. Sulphate deposition in the catchments studied declined by 38-82% during the last decade. Sulphate concentrations in all freshwaters decreased significantly, but acidification reversal was clearly delayed in the German streams. In Scandinavian streams and Czech/Slovakian lakes sulphate concentrations responded quickly to decreased input. Sulphate fluxes in run-off showed no clear trend in Germany and Italy but decreased in Scandinavia, the Czech Republic and Slovakia. The decrease, however, was less than the decline in input fluxes. While long-term sulphate output fluxes from catchments were generally correlated to input fluxes, most catchments started a net release of sulphate during the early 1990s. Release of stored sulphate leads to a delay of acidification reversal and can be caused by four major processes. Desorption and excess mineralisation were regarded as the most important for the catchments investigated, while oxidation and weathering were of lesser importance for the long-term release of sulphate. Input from weathering has to be considered for the Italian catchments. Sulphate fluxes in German catchments, with deeply weathered soils and high soil storage capacity, responded more slowly to decreased deposition than catchments in Scandinavia and the Czech Republic/Slovakia, which have thin soils and relatively small sulphate storage. For predictions of acidification reversal, soil characteristics, sulphur pools and their dynamics have to be evaluated in future research. Keywords: acidification reversal, sulphur, sulphate release, Europe, catchments, deposition, lake, stream

Explaining the large-scale diversity of soil organisms that drive biogeochemical processes—and their responses to environmental change—is critical. However, identifying consistent drivers of belowground diversity and abundance for some soil organisms at large spatial scales remains problematic. Here we investigate a major guild, the ectomycorrhizal fungi, across European forests at a spatial scale and resolution that is—to our knowledge—unprecedented, to explore key biotic and abiotic predictors of ectomycorrhizal diversity and to identify dominant responses and thresholds for change across complex environmental gradients. We show the effect of 38 host, environment, climate and geographical variables on ectomycorrhizal diversity, and define thresholds of community change for key variables. We quantify host specificity and reveal plasticity in functional traits involved in soil foraging across gradients. We conclude that environmental and host factors explain most of the variation in ectomycorrhizal diversity, that the environmental thresholds used as major ecosystem assessment tools need adjustment and that the importance of belowground specificity and plasticity has previously been underappreciated.

The type and intensity of forest management directly influences regional catchment hydrology. Future forest management must optimise the effects of its practices to achieve sustainable management. With scenario analysis of forestry practices, the effects of different forest utilisation strategies on the hydrology of forested catchments can be temporally and spatially quantified. The approach adopted in this study necessitated the development of an interactive system for the spatially distributed modelling of hydrology in relation to forest stand development. Consequently, a forest growth model was used to simulate stand development assuming various forest management activities. Selected simulated forest growth parameters were entered into the hydrological model to simulate water fluxes under different conditions of forest structure. The approach enables the spatially differentiated quantification of changes in the water regime (e.g. increased evapotranspiration). The results of hydrological simulations in the study area, the Oker catchment (northern Harz Mountains), show that forests contribute to the protection of water systems because they have a balancing effect on the hydrological regime. As scenario simulations also suggest, however, forestry practices can also lead to substantial changes in water budgets of forested catchments. The preservation of the hydrological services of forests requires a sustainable and long-term forest conversion on the basis of current management directives for near natural silviculture. Management strategies on basis of moderate harvesting regimes are preferred because of their limited impact on the water budget.

Through litter decomposition enormous amounts of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to understand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litter and methodologies, adding major uncertainty to syntheses, comparisons and meta-analyses across different experiments and sites. In the TeaComposition initiative, the potential litter decomposition is investigated by using standardized substrates (Rooibos and Green tea) for comparison of litter mass loss at 336 sites (ranging from -9 to +26 °C MAT and from 60 to 3113 mm MAP) across different ecosystems. In this study we tested the effect of climate (temperature and moisture), litter type and land-use on early stage decomposition (3 months) across nine biomes. We show that litter quality was the predominant controlling factor in early stage litter decomposition, which explained about 65% of the variability in litter decomposition at a global scale. The effect of climate, on the other hand, was not litter specific and explained

Phosphorus availability may shape plant–microorganism–soil interactions in forest ecosystems. Our aim was to quantify the interactions between soil P availability and P nutrition strategies of European beech (Fagus sylvatica) forests. We assumed that plants and microorganisms of P-rich forests carry over mineral-bound P into the biogeochemical P cycle (acquiring strategy). In contrast, P-poor ecosystems establish tight P cycles to sustain their P demand (recycling strategy). We tested if this conceptual model on supply-controlled P nutrition strategies was consistent with data from five European beech forest ecosystems with different parent materials (geosequence), covering a wide range of total soil P stocks (160–900 g P m−2

Atmospheric deposition to forests has been monitored within the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) with sampling and analyses of bulk precipitation and throughfall at several hundred forested plots for more than 15 years. The current deposition of inorganic nitrogen (nitrate and ammonium) and sulphate is highest in central Europe as well as in some southern regions. We compared linear regression and Mann-Kendall trend analysis techniques often used to detect temporal trends in atmospheric deposition. The choice of method influenced the number of significant trends. Detection of trends was more powerful using monthly data compared to annual data. The slope of a trend needed to exceed a certain minimum in order to be detected despite the short-term variability of deposition. This variability could to a large extent be explained by meteorological processes, and the minimum slope of detectable trends was thus similar across sites and many ions. The overall decreasing trends for inorganic nitrogen and sulphate in the decade to 2010 were about 2% and 6%, respectively. Time series of about 10 and 6 years were required to detect significant trends in inorganic nitrogen and sulphate on a single plot. The strongest decreasing trends were observed in western central Europe in regions with relatively high deposition fluxes, whereas stable or slightly increasing deposition during the last 5 years was found east of the Alpine region as well as in northern Europe. Past reductions in anthropogenic emissions of both acidifying and eutrophying compounds can be confirmed due to the availability of long-term data series but further reductions are required to reduce deposition to European forests to levels below which significant harmful effects do not occur according to present knowledge. © 2014 The Authors.

Change history: In the HTML version of this Article, author 'Filipa Cox' had no affiliation in the author list, although she was correctly associated with affiliation 3 in the PDF. In addition, the blue circles for 'oak' were missing from Extended Data Fig. 1. These errors have been corrected online.

Dissolved organic carbon (DOC) concentrations have risen in upland waters across large areas of Europe and North America. Two proposed drivers of these increases are (1) deposition of atmospheric pollutant nitrogen (N) with consequent effects on plant and decomposer carbon dynamics, and (2) soil recovery from acidification associated with decreasing sulphur deposition. Examination of 12 European and North American field N addition experiments showed inconsistent (positive, neutral, and negative) responses of DOC to N addition. However, responses were linked to the form of N added and to resulting changes in soil acidity. Sodium nitrate additions consistently increased DOC, whereas ammonium salts additions usually decreased DOC. Leachate chemistry was used to calculate an index of “ANC forcing” of the effect of fertilization on the acid-base balance, which showed that DOC increased in response to all de-acidifying N additions, and decreased in response to all but three acidifying N additions. Exceptions occurred at two sites where N additions caused tree mortality, and one experiment located on an older, unglaciated soil with high anion adsorption capacity. We conclude that collectively these experiments do not provide clear support for the role of N deposition as the sole driver of rising DOC, but are largely consistent with an acidity-change mechanism. It is however possible that the unintended effect of acidity change on DOC mobility masks genuine effects of experimental N enrichment on DOC production and degradation. We suggest that there is a need, more generally, for interpretation of N manipulation experiments to take account of the effects that experimentally-induced changes in acidity, rather than elevated N per se, may have on ecosystem biogeochemistry.

Key message Exceedance of critical limits in soil solution samples was more frequent in intensively monitored forest plots across Europe with critical loads for acidity and eutrophication exceeded compared to other plots from the same network. Elevated inorganic nitrogen concentrations in soil solution tended to be related to less favourable nutritional status. Context Forests have been exposed to elevated atmospheric deposition of acidifying and eutrophying sulphur and nitrogen compounds for decades. Critical loads have been identified, below which damage due to acidification and eutrophication are not expected to occur. Aims We explored the relationship between the exceedance of critical loads and inorganic nitrogen concentration, the base cation to aluminium ratio in soil solutions, as well as the nutritional status of trees. Methods We used recent data describing deposition, elemental concentrations in soil solution and foliage, as well as the level of damage to foliage recorded at forest plots of the ICP Forests intensive monitoring network across Europe. Results Critical loads for inorganic nitrogen deposition were exceeded on about a third to half of the forest plots. Elevated inorganic nitrogen concentrations in soil solution occurred more frequently among these plots. Indications of nutrient imbalances, such as low magnesium concentration in foliage or discolouration of needles and leaves, were seldom but appeared more frequently on plots where the critical limits for soil solution were exceeded. Conclusion The findings support the hypothesis that elevated nitrogen and sulphur deposition can lead to imbalances in tree nutrition.

Fine root distribution and turnover were investigated in ca. 40-year-old pure Norway spruce (Picea abies Karst.) stands in Germany, growing on four sites that differed in soil acidity (Ebergotzen < Barbis < Fichtelgebirge = Harz). The density of fine root biomass and necromass in different soil horizons differed among the sites. At one of the most acidic sites (Harz), fine root density in the humus layer was more than twice that at the least acidic site (Ebergotzen). At the two most acidic sites, Fichtelgebirge and Harz, the ratio of biomass to necromass was significantly lower than at Ebergotzen and Barbis, particularly in the subsoil layer. In each stand, clear vertical gradients in fine root length density and root tip density were observed. Most of the roots and the root tips were in the humus layer and in the first mineral soil horizon (0-10 cm). There was a significantly different decrease in specific root length (cm gDM (-1)) and specific root tip density (root tips gDM (-1)) in the more acidified stands Fichtelgebirge and Harz compared with Ebergotzen and Barbis. Fine root production estimated by ingrowth cores and a net method was approximately twice as high in the more acidic stands Fichtelgebirge and Harz compared with Ebergotzen and Barbis. Rates of living fine root biomass turnover were higher at the Fichtelgebirge and Harz sites than at the Ebergotzen site. Rates of necromass turnover were similar at all sites. The results suggest that the accumulation of necromass was not due to a slower disappearance at the more acid sites, but to earlier root death. Roots contributed 46% to root + needle litter and 32% to root + total aboveground litter at the Harz site in 1997.

The North German Lowland is a region with locally high nitrate (NO3−) concentrations in seepage water, inducing an increased susceptibility to the effects of climate change. The future risk of rising NO3− concentrations in seepage water from forests was quantified for four regions in the North German Lowland using climate projections and a modelling system comprising submodels for forest stand development (WaldPlaner), water budgets (WaSiM-ETH), and biogeochemical element cycles (VSD+). The simulations for the period from 1990 to 2070 included three different forest management scenarios (reference, biodiversity, and climate protection) and showed a general decrease in groundwater recharge which could hardly be influenced by any of the management options. The simulated soil organic matter stocks adequately represented their past increase as expected from the National Forest Soil Inventory (NFSI), but also showed a future decline under climate change conditions which leads to higher organic matter decomposition and a long-lasting increase of NO3− leaching from forest soils. While the climate protection oriented scenario shows the highest increase in NO3− concentrations during the projection period until 2070, the biodiversity scenario kept NO3− concentrations in seepage water below the legal thresholds in three of four selected model regions.

The quantitative mineralogical composition which determines considerably the acid buffering capacity of soils can either be analyzed directly (modal) using mineralogical methods or can be calculated (normative) from the chemical total analysis of the soil considering previous knowledge of its qualitative mineralogical composition. In this study the normative mineralogical composition of loess-derived soils in Northern Germany is compared with their modal mineralogical composition determined by X-ray diffractometry and infrared spectroscopy. The CIPW norm (acronym for Cross, Iddings, Pirsson and Washington; Cross et al., 1902) has been used to calculate the mineralogical composition. For the application to soils the CIPW norm had to be modified with respect to pedogenic minerals. The differences between the normative (n) mineral contents and the respective modal (m) data [(n-m) × m−1 × 100] are for quartz −10% ± 4% (mean ± standard deviation), for orthoclase −8% ± 24%, for albite 26% ± 17%, for illite/mica −9% ± 24%, for calcite 14% ± 2%, and for dolomite 11% ± 19%. The chemical composition of illite/mica has been defined horizon-specific. The differences between normative and modal data are in the range of the error of mineralogical methods such as X-ray and optical techniques. Therefore the modified CIPW norm proves to be useful to estimate quantitatively the mineralogical composition of loess-derived soils. Normative Mineralberechnung in norddeutschen Lossboden nach der modifizierten CIPW-Norm Die mineralogische Zusammensetzung von Boden, die masgeblich das Saurepuffervermogen bestimmt, kann entweder direkt mittels mineralogischer Verfahren (modal) analysiert oder aus der chemischen Gesamtanalyse von Bodenproben (normativ) berechnet werden. Fur letzteren Weg ist Vorwissen uber die qualitative mineralogische Zusammensetzung erforderlich. In der vorliegenden Arbeit werden mittels rontgenographischer und infrarotspektroskopischer Verfahren ermittelte (modale) Daten mit dem normativ berechneten Mineralbestand von Lossboden aus Norddeutschland verglichen. Die normative Berechnung erfolgte mit der CIPW-Norm (Akronym fur Cross, Iddings, Pirsson and Washington; Cross et al., 1902), die fur diese Anwendung auf Boden bezuglich pedogener Minerale modifiziert wurde. Die Abweichungen der normativen (n) mineralogischen Zusammensetzung gegenuber der modal (m) bestimmten [(n-m) × m−1 × 100] liegen fur Quarz bei −10% ± 4% (Mittelwert ± Standardabweichung), fur Orthoklas bei −8% ± 24%, fur Albit bei 26% ± 17% und fur Illit/Glimmer bei −9% ± 24%. Bei Illit/Glimmer wurde von einer horizontspezifischen Stochiometrie ausgegangen. Bei den Carbonaten betragt die Abweichung fur Calcit 14% ± 2% und fur Dolomit 11% ± 19%. Die Abweichungen zwischen modalem und normativem Mineralbestand liegen im Fehlerbereich von modalen Mineralanalysen, die mittels rontgenographischer und optischer Verfahren durchgefuhrt werden. Die Anwendung der modifizierten CIPW-Norm kann daher als ein geeignetes Verfahren zur Schatzung des quantitativen Mineralbestandes in Lossboden betrachtet werden.

Meteorological variables affect composition, structure, growth, health, and dynamics of forest ecosystems. The measurement of meteorological data at forest monitoring plots is essential for the interpretation of climate change effects. Within an ecological monitoring network, standard meteorological variables such as precipitation, air temperature, relative humidity, solar radiation, wind velocity, and direction should be measured. These variables are essential for the calculation of total deposition of air pollutants, for the interpretation of biological processes or for the derivation of water budgets and percolation from the rooting zone. Additional variables of interest are soil temperature, stand precipitation, and soil moisture. The magnitude and changes in time of the meteorological variables can be assessed as explanatory factors for other observations made in forest ecological monitoring. A detailed description of different methods is given. As an example for an integrated analysis, the application of meteorological data in water budget modeling is described and results of a pilot study are shown.

Chemical content of soil solution is varying in time and space and is dependent on the sampling and measurement techniques in use. It is a valuable indicator for effects of stress factors on both forests and the surrounding water ecosystems. A continuous standardized methodology for soil solution collection and analysis is of ultimate importance. Methods for harmonized collection and analysis of soil solution on a Europe-wide scale are presented with a special emphasis on sampling and measurement techniques, Quality Assurance, and laboratory analyses. Results based on data produced by the harmonized soil solution monitoring under ICP Forests are presented. They show regular exceedances of critical limits for nitrogen concentrations in soil solution on the majority of the examined sites.

Long term trends of element fluxes in atmospheric deposition and of concentrations in seepage output of seven coniferous and deciduous forest stands in northwestern Germany have been evaluated for the period 1981 – 1994. Decreasing deposition rates of SO4 (50 – 70%) and H+ (60 – 80%) occured at all sites concomitant with the decline of SO2 emission rates in the former Federal Republic of Germany. Deposition of Ca, Mg, and K decreased at the Soiling and Gottinger Wald stands. During this period no consistent trends in the flux rates of NH4 and NO3 were apparent. Sulfate concentrations in soil solution decreased at the Soiling and Gottinger Wald stands, whereas an increase occured at Lange Bramke south slope. As a consequence of reduced deposition and mobile anion concentrations a decrease of Ca, Mg, K, Al, and Mn in soil solution has been observed at the Soiling stands. At the other stands trends of cations in soil solution are not consistent. Nitrate concentrations in soil solution decreased at the Gottinger Wald. A rising tendency with great fluctuations of NO3 concentrations occured at the Soiling spruce stand.

Atmospheric deposition of acidifying compounds (e.g. S), nitrogen (N) as a nutrient and base cations (e.g. Ca) to forests is a major driver for many processes in forests. In Europe, various measures have been taken to reduce S and N deposition since the late 1980ties. Trend analyses are regularly performed based on measurement in open field by EMEP and in forests by ICPForests. However, various trend analyses techniques are in use. In this study the trends of bulk and throughfall N and S deposition on ICP-Forests level II sites have been investigated. Sulphur deposition showed a decreasing trend from 2001 to 2010 that has been identified to be significant for the majority of the about 50 sites with continuous data (linear regression, 95% sign. Level). The mean thoughfall of theses sites decreased from about 12 kg S ha-1 a-1 in 2001 to about 6 kg S ha-1 a-1 (about 6% a-1). For N this value decreased from about 15 kg N ha-1 a-1 to about 12 kg N ha-1 a-1 (about 2.5% a-1), however, decreasing trends were identified to be significant for much fewer sites. In order to estimate the minimal detectable trend, p-values were plotted against the relative slope. Most p-values were in a similar bell-shaped band for time series with the same length for most ions. For time series with 10 years S deposition data, the band falls below 0.05 at relative slope larger than about 3% a-1. With 6 years of data, relative slopes need to be larger to reliably attain p

Various dynamic soil chemistry models have been developed to gain insight into impacts of atmospheric deposition of sulphur, nitrogen and other elements on soil and soil solution chemistry. Sorption parameters for anions and cations are generally calibrated for each site, which hampers extrapolation in space and time. On the other hand, recently developed surface complexation models (SCMs) have been successful in predicting ion sorption for static systems using generic parameter sets. This study reports the inclusion of an assemblage of these SCMs in the dynamic soil chemistry model SMARTml and applies this model to a spruce forest site in Solling Germany. Parameters for SCMs were taken from generic datasets and not calibrated. Nevertheless, modelling results for major elements matched observations well. Further, trace metals were included in the model, also using the existing framework of SCMs. The model predicted sorption for most trace elements well.

Element inputs by atmospheric deposition form a major contribution to a number of element fluxes of forest ecosystems. During the last few decades, inputs from the atmosphere have significantly altered the geochemical cycles of forest ecosystems especially in heavily polluted areas of Central Europe where forests have remained major sinks for air pollution. The deposition of acids such as sulphuric and nitric acids was a major environmental concern during recent decades (Galloway 1995). Acid deposition has caused the acidification of soils and freshwaters in large areas of North America and Europe (Johnson et al. 1991). The effects of soil acidification are the leaching of base cations from the soil (Matzner and Murach 1995), the release of aluminium (Al) ions and heavy metals into soil solution (Tyler 1983), reduced decomposition of soil organic matter, and reduced growth of fine roots (Godbold et al. 2003). The release of acid soil solutions to the hydrosphere is detrimental to aquatic ecosystems. During the last two decades, deposition of acids has decreased substantially in Central Europe due to improved emission controls and the closing down of industry in eastern Germany after the reunion (Meesenburg et al. 1995). However, the deposition of nitrogen (N) compounds has decreased only slightly and has become an increasingly important fraction of the total deposition of acids (Wright et al. 1995). Despite reduced deposition of free acidity, the acid load to soils is still high because of high deposition of ammonium (NH 4 + ). The fate of elevated N-input on forest ecosystem remains partly unknown, but besides the impact on the acid/base balance of ecosystems there are some indications of increased tree growth, reduced root/shoot ratio, nutrient imbalances, reduced frost hardiness and elevated foliage consumption by insects (Binkley and Hogberg 1997; Aber et al. 1998; Meiwes et al. 1999). In N-saturated ecosystems, soils have increased susceptibility for losses of nitrate (NO 3 − ) to the hydrosphere and of trace gases to the atmosphere (Aber 2002).

Climate is one of the major factors controlling the growth and functioning of plant ecosystems in general and of beech forests in particular. In the present Chapter climatic conditions at three experimental beech forest sites are described. The territory of Germany extends for about 8° (55°–47°N) from the coastal line of the North and Baltic Seas to the Alps, within the range of maritime temperate climate sub-zones Cfb and Cwb according to Koeppen classification (e.g. McKnight and Hess 2000). It is described as a transition zone between the maritime climate of western Europe and the continental one of eastern Europe. Major agents of the general atmospheric circulation pattern contributing to the maritime character of the climate are the Icelandic low-pressure system, the Azores high-pressure system and often the Asian (or Siberian) high-pressure system. The first two of them furnish western Europe with moisture-loaded air masses propelled by dominant westerly winds. Other major factors are: (1) the maritime influence of the Atlantic Ocean adding to climate ‘oceanicity’; (2) the mountain ranges hindering the southward advance of maritime air masses and, thus, adding to climate ‘continentality’, and (3) the altitude effects in highland regions. Therefore, in general, the oceanicity of climate increases to the north and the west whereas the continentality increases to the south and east. During winter time, the air temperature isotherms run from north to south with values increasing westward, and in summer the isotherms run generally parallel to latitudes (from west to east) with temperatures increasing southward. The mean annual temperature thus decreases generally from north-west to south-east and the annual precipitation from west to east (Fig. 2.1) Table 2.1 summarises the mean climatic conditions over the area of Germany based on data from the German Weather Service (Deutsche Wetterdienst – DWD) for the standard climatological period of 1961–1990. Mean annual air temperature for Germany is +8.4°C with July being the warmest month and January – the coldest. DWD data indicate a gentle increase of annual temperatures after 1988 when compared to the 30-year mean value. Mean annual precipitation for Germany is 700 mm with the pronounced seasonal peak in summer (June–August) with 31.4% of annual precipitation. Seasonal relative minimum value was observed for December–February – 21.5% of annual precipitation. Based on these climatic characteristics most of the land area in Germany could be considered as almost optimal for beech (Fagus silvatica L.) growth as beech prefers oceanic climates with at least 600 mm per year precipitation, with annual mean temperature of about +8° (though wide temperature variations are tolerated) and a growing season of at least 5 months (Mayer 1992). The climatic conditions in Germany fall around these mean values and are classified into four major climatic regions (Schuepp and Schirmer 1977), namely: (1) Northern Lowlands, (2) German Highlands, (3) The German Alpine Foreland and (4) The German Alps. Since the investigated sites are located within the German Highlands, a brief description of climatic conditions of this area is provided below.