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In a future warmer climate, extremely dry, warm summers might become more common. Soil weathering is affected by temperature and precipitation, and climate change and droughts can therefore affect soil chemistry and plant nutrition. In this study, climate change and drought effects on soil weathering rates and release of Ca, Mg, K and Na were studied on seven forest sites across different climates in Sweden, using the dynamical model ForSAFE. Two climate scenarios were run, one medium severity climate change scenario from IPCC (A1B) and one scenario where a future drought period of 5 years was added, while everything else was equal to the first scenario. The model results show a large geographical variation of weathering rates for the sites, without any geographical gradient, despite the strong dependence of temperature on weathering and the strong gradient in temperature in Sweden. This is because soil texture and mineralogy have strong effects on weathering. The weathering rates have a pronounced seasonal dynamic. Weathering rates are low during winters and generally high, but variable, during summers, depending on soil moisture and temperature. According to the model runs, the future yearly average weathering rates will increase by 5 %–17 % per degree of warming. The relative increase is largest in the two southeastern sites, with low total weathering rates. At sites in southern Sweden, future weathering increase occurs throughout the year according to the modelling. In the north, the increase in weathering during winters is almost negligible, despite larger temperature increases than in other regions or seasons (5.9 ∘C increase in winter in Högbränna; the yearly average temperature increase for all sites is 3.7 ∘C), as the winter temperatures still will mostly be below zero. The drought scenario has the strongest effect in southern Sweden, where weathering during the later parts of the drought summers decreases to typical winter weathering rates. Soil texture and amount of gravel also influence how fast the weathering decreases during drought and how fast the soil rewets and reaches normal weathering rates after the drought. The coarsest of the modelled soils dries out and rewets quicker than the less coarse of the modelled soils. In the north, the soils do not dry out as much as in the south, despite the low precipitation, due to lower evapotranspiration, and in the northernmost site, weathering is not much affected. Yearly weathering during the drought years relative to the same years in the A1B scenario are between 78 % and 96 % for the sites. The study shows that it is crucial to take seasonal climate variations and soil texture into account when assessing the effects of a changed climate on weathering rates and plant nutrient availability.

Soil microbes are key players in the cycling of soil organic carbon. In the complex soil system, microbes are faced with multiple stresses and trade-offs. In order to build biomass and proliferate, microbes have to mine accessible substrate and simultaneously have to survive abiotic stresses such as dry conditions. How they allocate carbon to the production of microbial biomass, extracellular enzymes, or biomolecules that help resist abiotic stresses is an important control of soil organic carbon fate. High carbon use efficiency fuels the build-up of microbial necromass, while increased production of exoenzymes might accelerate the breakdown of particulate organic matter. Production of additional biopolymers needed to sustain metabolic activity under stress – e.g., the production of osmolytes for maintaining turgor pressure in drying soils – poses an additional carbon cost that trades-off with the production of biomass and extracellular enzymes. Here we propose a conceptual model of soil carbon cycling with an explicit representation of these microbial allocation trade-offs. The model resolves physical processes such as saturation dependent substrate diffusion and is formulated at steady-state. It is based on the premise that microbes are optimally adapted to the environment they inhabit – meaning that the allocation trade-offs between the production of biomass, extracellular enzymes, and biomolecular stress response are adapted to maximize the microbial growth rate under these conditions. Using this conceptual model, we investigate how microbial allocation traits (fraction of carbon taken up and allocated to new biomass, extracellular enzymes, or osmolytes) might vary over a range of environmental conditions. Optimal allocation of carbon leads to increased investment in extracellular enzymes when carbon is scarce, and to progressively higher investment in osmolytes in drier conditions. While these trends are somewhat expected, the model predicts (rather than prescribing) the sensitivity of these allocation traits to changes in soil moisture and available carbon as a consequence of the optimality assumption. We conclude by exploring what implications these results might have for soil organic carbon fate.

Human activities have dramatically increased nitrogen (N) and sulfur (S) deposition, altering forest ecosystem function and structure. Anticipating how changes in deposition and climate impact forests can inform decisions regarding these environmental stressors. Here, we used a dynamic soil-vegetation model (ForSAFE-Veg) to simulate responses to future scenarios of atmospheric deposition and climate change across 23 Northeastern hardwood stands. Specifically, we simulated soil percent base saturation, acid neutralizing capacity (ANC), nitrate (NO

In a future warmer climate, extremely dry, warm summers might become more common. In Scandinavia, the extreme summer of 2018 was such an event. Soil weathering is affected by temperature and precipitation, and climate change as well as droughts can therefore affect soil chemistry and plant nutrition. In this study, climate change effects on weathering were studied on seven forest sites across widely different climate zones in Sweden, using the dynamical model ForSAFE. Two climate scenarios were run, one climate change base scenario and one drought scenario. The model results show a large geographical variation of weathering rates for the sites. There is, however, no geographical gradient, despite the strong dependence of temperature on weathering, as also soil texture and mineralogy have strong effects on weathering. There is a pronounced seasonal dynamic, with much lower weathering rates during winters than during summers, and with more variable summer weathering rates depending on more variable soil moisture and temperature. According to the climate change base scenario, the weathering rates will increase by 5–17 % per degree of warming. The relative increase is largest in the two south-eastern sites, with low total weathering rates caused by relatively coarse soils and often dry summers. Changes in seasonal dynamics due to climate change differ between regions. At sites in southern Sweden, future weathering increase occurs throughout the year, though generally most in spring and summer. In the north the increase in weathering during winters is almost negligible, even though the temperature increase during winter is high, as the winter temperatures still will mostly be below zero. The drought scenario has the strongest effect in southern Sweden and here weathering can temporally become as low as winter weathering during drought summers. Soil texture also has an effect on how fast the weathering decrease during drought occurs, as well as how fast the soil rewets and resume normal weathering rates after the drought, where coarse soils respond quicker. Yearly weathering during the drought years in the most affected site is only 78 % of the weathering of the base scenario. In the north, the soils do not dry out as much despite the low precipitation, and in the northernmost site weathering is not much affected. The study shows that it is crucial to take seasonal climate variations and soil texture into account when assessing the effects of a changed climate on weathering rates and plant nutrient availability.

Climate change will bring about a consistent increase in temperatures. Annual precipitation rates are also expected to increase in boreal countries, but the seasonal distribution will be uneven, and several areas in the boreal zone will experience wetter winters and drier summers. This study uses the dynamic forest ecosystem model ForSAFE to estimate the combined effect of changes in temperature and precipitation on forest carbon stocks in Sweden. The model is used to simulate carbon stock changes in 544 productive forest sites from the Swedish National Forest Inventory. Forest carbon stocks under two alternative climate scenarios are compared to stocks under a hypothetical scenario of no climate change (baseline). Results show that lower water availability in the future can cause a significant reduction in tree carbon compared to a baseline scenario, particularly expressed in the southern and eastern parts of Sweden. In contrast, the north-western parts will experience an increase in tree carbon stocks. Results show also that summer precipitation is a better predictor of tree carbon reduction than annual precipitation. Finally, the change in soil carbon stock is less conspicuous than in tree carbon stock, showing no significant change in the north and a relatively small but consistent decline in the south. The study indicates that the prospect of higher water deficit caused by climate change cannot be ignored in future forest management planning.

Weathering rates are of considerable importance in estimating the acidification sensitivity and recovery capacity of soil and are thus important in the assessment of the sustainability of forestry in a time of changing climate and growing demands for forestry products. In this study, we modelled rates of weathering in mineral soil at two forested sites in southern Sweden included in a monitoring network, using two models. The aims were to determine whether the dynamic model ForSAFE gives comparable weathering rates to the steady-state model PROFILE and whether the ForSAFE model provided believable and useful extra information on the response of weathering to changes in acidification load, climate change and land use. The average weathering rates calculated with ForSAFE were very similar to those calculated with PROFILE for the two modelled sites. The differences between the models regarding the weathering of certain soil layers seemed to be due mainly to differences in calculated soil moisture. The weathering rates provided by ForSAFE vary seasonally with temperature and soil moisture, as well as on longer timescales, depending on environmental changes. Long-term variations due to environmental changes can be seen in the ForSAFE results, for example, the weathering of silicate minerals is suppressed under acidified conditions due to elevated aluminium concentration in the soil, whereas the weathering of apatite is accelerated by acidification. The weathering of both silicates and apatite is predicted to be enhanced by increasing temperature during the 21st century. In this part of southern Sweden, yearly precipitation is assumed to be similar to today's level during the next forest rotation, but with more precipitation in winter and spring and less in summer, which leads to somewhat drier soils in summer but still with increased weathering. In parts of Sweden with a bigger projected decrease in soil moisture, weathering might not increase despite increasing temperature. These results show that the dynamic ForSAFE model can be used for weathering rate calculations and that it gives average results comparable to those from the PROFILE model. However, dynamic modelling provides extra information on the variation in weathering rates with time and offers much better possibilities for scenario modelling.

The demand of renewable energy has increased the interest in whole-tree harvesting. The sustainability of whole-tree harvesting after clear-cutting, from an acidification point of view, depends on two factors: the present acidification status and the further loss of buffering capacity at harvesting. The aims of this study were to investigate the relationship between these two factors at 26 sites along an acidification gradient in Sweden, to divide the sites into risk classes, and to examine the geographical distribution of them in order to provide policy-relevant insights. The present status was represented by the acid neutralizing capacity (ANC) in soil solution, and the loss of buffering capacity was represented by the estimated exceedance of critical biomass harvesting (CBH). The sites were divided into three risk classes combining ANC and exceedance of CBH. ANC and exceedance of CBH were negatively correlated, and most sites had either ANC &lt, 0 and exceedance (high risk) or ANC &gt, 0 and no exceedance (low risk). There was a geographical pattern, with the high risk class concentrated to southern Sweden, which was mainly explained by higher historical sulfur deposition and site productivity in the south. The risk classes can be used in the formulation of policies on whole-tree harvesting and wood ash recycling.

Although the PROFILE and ForSAFE model can accurately reproduce the chemical and mineralogical evolution of the soil unsaturated zone, it overestimates weathering rates in deeper soil layers and in groundwater systems. This overestimation has been corrected by improving the kinetic expression describing mineral dissolution by adding or upgrading braking functions. The base cation and aluminium brakes have been strengthened, and an additional silicate brake has been developed, improving the ability to describe mineral- water reactions in deeper soils. These brakes are developed from a molecular-level model of the dissolution mechanisms. Equations, parameters and constants describing mineral dissolution kinetics have now been obtained for 113 minerals from 12 major structural groups, comprising all types of minerals encountered in most soils. The PROFILE and ForSAFE weathering sub-model was extended to cover two-dimensional catchments, both in the vertical and the horizontal direction, including the hydrology. Comparisons between this improved model and field observations are available in Erlandsson Lampa et al. (2019, This special issue). The results showed that the incorporation of a braking effect of silica concentrations was necessary and helps obtain more accurate descriptions of soil evolution rates at greater depths and within the saturated zone.

In a world of climate change we need to minimize and stop greenhouse gas (GHG) emissions and instead accumulate carbon in ecosystems - we call this ‘negative emissions’. Drained peatlands are in many cases large sources of GHGs to the atmosphere but rewetting of a peatland can mitigate these emissions and possibly reach a net uptake. However, carbon accumulation in peatlands is a dynamic and complex balance between uptake and release, which is mainly driven by the groundwater table (WT) depth. Our new project funded by the Swedish Research Council FORMAS (2020-2022) aims to produce a handbook with guidance on how to change management of drained organic soil in order to convert them into low or negative emission peatlands. Researchers from Gothenburg, Stockholm, Lund and York Universities will collaborate with landowners, public authorities and NGO’s to assemble the most relevant knowledge.We will compare GHG fluxes from organic soils under different traditional and newly suggested land uses in the Swedish landscape, by collected field data, which will be the input for upscaling in time and space by using state-of-the-art process models (CoupModel and ForSAFE). For modelling purposes, extensive abiotic and GHG datasets will be available from the research station ‘Skogaryd’ in Västra Götaland, Sweden (https://gvc.gu.se/english/research/skogaryd), from a drained peat with spruce forest, before and after the clear-cut in 2019. This clear-cut area will now be partly rewetted by building a dam, and GHG flux measurements will be collected in response to different soil WT and vegetation types. Other available data are from a variety of drained and rewetted peat soils in neighboring countries. In addition, GHG measurements in Sweden on restored bogs are starting during summer 2020. Models will allow us to assess and examine the influence of 1) WT fluctuations, 2) soil fertility, and 3) management on both carbon storage and GHG fluxes for rewetted cases with moss vegetation, meadow or swamp forest.

The integrated character of the sustainable development goals in Agenda 2030, as well as research in environmental security, flag that sustainable peace requires sustainable and conflict-sensitive natural resource use. The precise relationship between the risk for violent conflict and natural resources remains contested because of the interplay with socio-economic variables. This paper aims to improve the understanding of natural resources&rsquo, role in the risk of violent conflicts by accounting for complex interactions with socio-economic conditions. Conflict data was analysed with machine learning techniques, which can account for complex patterns, such as variable interactions. More commonly used logistic regression models are compared with neural network models and random forest models. The results indicate that a country&rsquo, s natural resource features are important predictors of its risk for violent conflict and that they interact with socio-economic conditions. Based on these empirical results and the existing literature, we interpret that natural resources can be root causes of violent intrastate conflict, and that signals from natural resources leading to conflict risk are reflected in and influenced by interacting socio-economic conditions. More specifically, the results show that variables such as access to water and food security are important predictors of conflict, while resource rents and oil and ore exports are relatively less important than other natural resource variables, contrasting what prior research has suggested. Given the potential of natural resource features to act as an early warning for violent conflict, we argue that natural resources should be included in conflict risk models for conflict prevention.

Soil and water acidification was internationally recognised as a severe environmental problem in the late 1960s. The interest in establishing “critical loads” led to a peak in weathering research in the 1980s and 1990s, since base cation weathering is the long-term counterbalance to acidification pressure. Assessments of weathering rates and associated uncertainties have recently become an area of renewed research interest, this time due to demand for forest residues to provide renewable bioenergy. Increased demand for forest fuels increases the risk of depleting the soils of base cations produced in situ by weathering. This is the background to the research programme Quantifying Weathering Rates for Sustainable Forestry (QWARTS), which ran from 2012 to 2019. The programme involved research groups working at different scales, from laboratory experiments to modelling. The aims of this study were to (1) investigate the variation in published weathering rates of base cations from different approaches in Sweden, with consideration of the key uncertainties for each method; (2) assess the robustness of the results in relation to sustainable forestry; and (3) discuss the results in relation to new insights from the QWARTS programme and propose ways to further reduce uncertainties. In the study we found that the variation in estimated weathering rates at single-site level was large, but still most sites could be placed reliably in broader classes of weathering rates. At the regional level, the results from the different approaches were in general agreement. Comparisons with base cation losses after stem-only and whole-tree harvesting showed sites where whole-tree harvesting was clearly not sustainable and other sites where variation in weathering rates from different approaches obscured the overall balance. Clear imbalances appeared mainly after whole-tree harvesting in spruce forests in southern and central Sweden. Based on the research findings in the QWARTS programme, it was concluded that the PROFILE/ForSAFE family of models provides the most important fundamental understanding of the contribution of weathering to long-term availability of base cations to support forest growth. However, these approaches should be continually assessed against other approaches. Uncertainties in the model approaches can be further reduced, mainly by finding ways to reduce uncertainties in input data on soil texture and associated hydrological parameters but also by developing the models, e.g. to better represent biological feedbacks under the influence of climate change.

Ecological effects of atmospheric nitrogen (N) and sulfur (S) deposition on two hardwood forest sites in the eastern United States were simulated in the context of a changing climate using the dynamic coupled biogeochemical/ecological model chain ForSAFE-Veg. The sites are a mixed oak forest in Shenandoah National Park, Virginia (Piney River) and a mixed oak-sugar maple forest in Great Smoky Mountains National Park, Tennessee (Cosby Creek). The sites have received relatively high levels of both S and N deposition and the climate has warmed over the past half century or longer. The model was used to evaluate the composition of the understory plant communities, the alignment between plant species niche preferences and ambient conditions, and estimate changes in relative species abundances as reflected by plant cover under various scenarios of future atmospheric N and S deposition and climate change. The main driver of ecological effects was soil solution N concentration. Results of this research suggested that future climate change might compromise the capacity for the forests to sustain habitat suitability. However, vegetation results should be considered preliminary until further model validation can be performed. With expected future climate change, preliminary estimates suggest that sustained future N deposition above 7.4 and 5.0 kg N/ha/yr is expected to decrease contemporary habitat suitability for indicator plant species located at Piney River and Cosby Creek, respectively.

Cation release rates to catchment runoff from chemical weathering were assessed using an integrated catchment model that included the soil's unsaturated, saturated and riparian zones. In-situ mineral dissolution rates were calculated in these zones as a function of pH, aluminum and dissolved organic carbon (DOC) concentrations along a hillslope in Northern Sweden where soil water was monitored over nine years. Three independent sets of mineral dissolution equations of varying complexity were used: PROFILE, Transition-State Theory (TST), and the Palandri & Kharaka database. Normalization of the rate-coefficients was necessary to compare the equations, as published rate-coefficients gave base cation release rates differing by several orders of magnitude. After normalizing the TST- and Palandri & Kharaka-rate coefficients to match the base cation release rates calculated from the PROFILE-equations, calculated Ca2 + and Mg2 + release rates are consistent with mass balance calculations, whereas those of Na+ and K+ are overestimated. Our calculations further indicate that a significant proportion of base cations are released from the organic soils in the near-stream zone, in part due to its finer texture. Of the three sets of rate equations, the base cation release rates calculated from the normalized TST-equations were more variable than those calculated using the other two sets of equations, both spatially and temporally, due to its higher sensitivity to pH. In contrast, the normalized Palandri & Kharaka-equations were more sensitive to variations in soil temperature.

Publisher's version (útgefin grein), The integrated forest ecosystem model ForSAFE-Veg was used to simulate soil processes and understory vegetation composition at three—sugar maple, beech, yellow birch—hardwood forest sites in the Northeastern United States (one at Hubbard Brook, NH, and two at Bear Brook, ME). Input data were pooled from a variety of sources and proved coherent and consistent. While the biogeochemical component ForSAFE was used with limited calibration, the ground vegetation composition module Veg was calibrated to field relevés. Evaluating different simulated ecosystem indicators (soil solution chemistry, tree biomass, ground vegetation composition) showed that the model performed comparably well regardless of the site’s soil condition, climate, and amounts of nitrogen (N) and sulfur (S) deposition, with the exception of failing to capture tree biomass decline at Hubbard Brook. The model performed better when compared with annual observation than monthly data. The results support the assumption that the biogeochemical model ForSAFE can be used with limited calibration and provide reasonable confidence, while the vegetation community composition module Veg requires calibration if the individual plant species are of interest. The study welcomes recent advances in empirically explaining the responses of hardwood forests to nutrient imbalances and points to the need for more research., Funding for this study was provided by the U.S. Environmental Protection Agency (EPA) (contract EP-C-11-036). Data for Hubbard Brook Experimental Forest (HBEF) were largely derived from the datasets of the cooperative Hubbard Brook Ecosystem Study, which is operated and maintained by the U.S. Department of Agriculture (USDA) Forest Service (USFS). Data for Bear Brook Watershed in Maine (BBWM) were derived from datasets from the BBWM research program and publications. BBWM data have been collected since 1986 with support from the U.S. EPA, U.S. National Science Foundation, U.S. Geological Survey, USFS, The Maine Agricultural and Forest Experiment Station, the Senator George Mitchell Center for Environmental and Watershed Research, and the University of Maine. The project principal investigators are I.J. Fernandez, J.S. Kahl, S.A. Norton, L.E. Rustad, and G.B. Wiersma. The University of Maine has a long-term lease with International Paper Corporation, the landowner. The authors appreciate access to these data and would like to specifically acknowledge the extra efforts of Cheryl Spencer for providing EB soil samples and Farrah Fatemi for providing BBWM soil solution data.

Climate change is generally expected to have a positive effect on weathering rates, due to the strong temperature dependence of the weathering process. There are, however, a number of feedback effects, both positive and negative, that can affect the weathering response to climate change, but that have not been fully taken into account in previous estimates. Important feedback mechanisms are the direct effect of changes in soil moisture, and the indirect effects through tree growth and decomposition on weathering rates. In this study, the dynamic forest ecosystem model ForSAFE, with mechanistic descriptions of tree growth, decomposition, weathering, hydrology and ion exchange processes, is used to investigate the effects of future climate scenarios on weathering rates in a more holistic way than has been done before. 544 productive coniferous forest sites, part of the Swedish National Forest Inventory, are modelled, and differences in weathering responses to changes in climate from two Global Climate Models are investigated. The study shows that weathering rates are likely to increase, but not to the extent predicted by a direct response to elevated air temperatures. The simulations show that increases in soil temperatures are less evident than those in air temperature, thereby dampening the effect of warming on weathering. Most importantly, the study shows that soil moisture availability has a strong potential to limit the expected response to increased temperature. While changes in annual precipitation may not indicate further risk for more severe water deficits, seasonal differences show a clear difference between winters and summers. Taking into account the seasonal variation, the study shows that reduced soil water availability in the summer seasons will strongly limit the expected gain in weathering associated with higher temperatures.

The PROFILE model, now incorporated in the ForSAFE model can accurately reproduce the chemical and mineralogical evolution of the soil unsaturated zone. However, in deeper soil layers and in groundwater systems, it appears to overestimate weathering rates. This overestimation has been corrected by improving the kinetic expression describing mineral dissolution by adding or upgrading breaking functions. The base cation and aluminium brakes have been strengthened, and an additional silicate brake has been developed, improving the ability to describe mineral-water reactions in deeper soils. These brakes are developed from a molecular-level model of the dissolution mechanisms. Equations, parameters and constants describing mineral dissolution kinetics have now been obtained for 102 different minerals from 12 major structural groups, comprising all types of minerals encountered in most soils. The PROFILE and ForSAFE weathering sub-model was extended to cover two-dimensional catchments, both in the vertical and the horizontal direction, including the hydrology. Comparisons between this improved model and field observations is available in Erlandsson Lampa et al. (2019, This special issue). The results showed that the incorporation of a braking effect of silica concentrations was necessary and helps obtain more accurate descriptions of soil evolution rates at greater depths and within the saturated zone.

The study evaluates the biogeochemical model ForSAFE-2D, designed to simulate water and chemical transport from the forest to the stream, by simulating the hydrology and the transport of the chemical tracer chloride (Cl−) along a forest hillslope in Northern Sweden. The simulated Cl− exports were in balance with the simulated inputs but measurements suggested a net release of Cl− from the catchment. Underestimated deposition inputs (deposition peaks and possibly dry deposition) were probably and partially responsible for this mismatch. However, we could not exclude that other soil biogeochemical processes omitted in ForSAFE-2D could also contribute to Cl− exports from the catchment. The study showed that ForSAFE-2D is a promising tool to better understand the factors that regulate the chemical export from the forest to the stream. The results also confirmed that there are limitations in using Cl− as a tracer in forest ecosystems.

Policy-makers face the challenge of assessing and implementing sustainability measures, while also dealing with parallel and sometimes conflicting policy agendas, long-term policy impacts, and contested interpretations of sustainability. To support evidence-based decision-making in this context, this paper presents the results from an integrated assessment of sustainability goal interactions. Links between the bio-based economy, the 2030 Agenda, and the so-called strong sustainability paradigm were explored in a regional-scale case. The analysis focused primarily on developments in the forestry and energy sectors. Direct trade-offs and synergies as well as broader systemic impacts were identified. The results show how goals from the bio-based economy, 2030 Agenda and strong sustainability paradigm are mutually interacting. Positive interactions were found within two clusters of goals, offering coherent and synergetic transition pathways within these. The first cluster encompasses developments toward intensified forestry, renewable energy, and closed-loop production systems. The second pathway supports diversified forestry and protection of critical natural capital. However, while internally coherent, trade-offs were identified between these goal clusters, demonstrating the difficulty in simultaneously making progress on goals belonging to different sustainability agendas. The results also stress the need for disaggregation and long-term assessments to identify trade-offs and synergies. Finally, the analysis highlights the theoretical potential but practical challenges of implementing the bio-based economy and 2030 Agenda in a way that adheres to strong sustainability. The analytical framework used in the present study may be adapted and applied to other decision-making contexts. It is particularly useful in settings characterized by uncertainty and unstructured problem spaces.

Research directions from the 27th conference for Specialists in Air Pollution and Climate Change Effects on Forest Ecosystems (2015) reflect knowledge advancements about (i) Mechanistic bases of tree responses to multiple climate and pollution stressors, in particular the interaction of ozone (O3) with nitrogen (N) deposition and drought; (ii) Linking genetic control with physiological whole-tree activity; (iii) Epigenetic responses to climate change and air pollution; (iv) Embedding individual tree performance into the multi-factorial stand-level interaction network; (v) Interactions of biogenic and anthropogenic volatile compounds (molecular, functional and ecological bases); (vi) Estimating the potential for carbon/pollution mitigation and cost effectiveness of urban and peri-urban forests; (vii) Selection of trees adapted to the urban environment; (viii) Trophic, competitive and host/parasite relationships under changing pollution and climate; (ix) Atmosphere-biosphere-pedosphere interactions as affected by anthropospheric changes; (x) Statistical analyses for epidemiological investigations; (xi) Use of monitoring for the validation of models; (xii) Holistic view for linking the climate, carbon, N and O3 modelling; (xiii) Inclusion of multiple environmental stresses (biotic and abiotic) in critical load determinations; (xiv) Ecological impacts of N deposition in the under-investigated areas; (xv) Empirical models for mechanistic effects at the local scale; (xvi) Broad-scale N and sulphur deposition input and their effects on forest ecosystem services; (xvii) Measurements of dry deposition of N; (xviii) Assessment of evapotranspiration; (xix) Remote sensing assessment of hydrological parameters; and (xx) Forest management for maximizing water provision and overall forest ecosystem services. Ground-level O3 is still the phytotoxic air pollutant of major concern to forest health. Specific issues about O3 are: (xxi) Developing dose-response relationships and stomatal O3 flux parameterizations for risk assessment, especially, in under-investigated regions; (xxii) Defining biologically based O3 standards for protection thresholds and critical levels; (xxiii) Use of free-air exposure facilities; (xxiv) Assessing O3 impacts on forest ecosystem services.

Whole-tree harvesting, i.e. harvesting of stems, branches and tops, has become increasingly common during recent decades due to the increased demand for renewable energy. Whole-tree harvesting leads to an increase in base cation losses from the ecosystem, which can counteract recovery from acidification. An increase in weathering rates due to higher temperatures is sometimes suggested as a process that may counteract the acidifying effect of whole-tree harvesting. In this study the potential effect of increasing temperature on weathering rates was compared with the increase in base cation losses following whole-tree harvesting in spruce forests, along a temperature gradient in Sweden. The mechanistic model PROFILE was used to estimate weathering rates at National Forest Inventory sites at today’s temperature and the temperature in 2050, as estimated by two different climate projections. The same dataset was used to calculate base cation losses following stem-only and whole-tree harvesting. The calculations showed that the increase in temperature until 2050 would result in an increase in the base cation weathering rate of 20–33 %, and that whole-tree harvesting would lead to an increase in base cation losses of 66 % on average, compared to stem-only harvesting. A sensitivity analysis showed that moisture changes are important for future weathering rates, but the effect of the temperature change was dominating even when the most extreme moisture changes were applied. It was concluded that an increase in weathering rates resulting from higher temperatures would not compensate for the increase in base cation losses following whole-tree harvesting, except in the northernmost part of Sweden.

Whole tree harvesting (WTH) following final felling of productive forests is increasingly promoted as a method to extract biomass for energy purposes. Despite its importance, there is a limited number of experimental studies investigating the impacts of WTH on forest ecosystem sustainability. Modelling studies have previously been carried out to complement and explain empirical observations from four long-term WTH experiments in Sweden. The literature shows a significant discrepancy between these studies, and open questions remain as to the fate of the base cations that are not removed in the absence of WTH. This study uses the integrated ecosystem model ForSAFE, which simulate a forest ecosystem’s biogeochemical processes and the feedbacks between these processes, to trace the fate of base cations for the said four long-term WTH experiments. The study shows that the model generally captures the observed effects of WTH on the stocks of base cations in the biomass and in the soil. The modelled results were also used to map how the base cations removed through WTH would otherwise (if left at the site) have been distributed in the ecosystem. The results indicate that the soil organic pool may be more important to the long-term base cation balance than the exchangeable pool, and should receive more attention in future research.

Weathering rates are of considerable importance in estimating the acidification sensitivity and recovery capacity of soil, and are thus important in the assessment of the sustainability of forestry in a time of changing climate and growing demands for forestry products. In this study, we modelled rates of weathering in mineral soil at two forested sites in southern Sweden included in the SWETHRO monitoring network using two models. The aims were to determine whether the dynamic model ForSAFE gives comparable weathering rates as the steady-state model PROFILE, and whether the ForSAFE model provided useful extra information on weathering behaviour. The average weathering rates calculated with ForSAFE were very similar to those calculated with PROFILE for the two modelled sites. The differences between the models regarding the weathering of certain soil layers seemed to be due mainly to differences in calculated soil moisture. The weathering rates provided by ForSAFE vary seasonally with temperature and soil moisture, as well as on longer time scales, depending on environmental changes. Long-term variations due to environmental changes can be seen in the ForSAFE results, for example: the weathering of silicate minerals is suppressed under acidified conditions due to elevated aluminium concentration in the soil, whereas the weathering of apatite is accelerated by acidification. The weathering of both silicates and apatite is predicted to be enhanced by increasing temperature during the 21st century. In this part of southern Sweden, precipitation is assumed to be similar to today’s level during the next forest rotation. However, in parts of Sweden with projected decreasing soil moisture, weathering might not increase despite increasing temperature. These results show that the dynamic ForSAFE model can be used for weathering rate calculations and that it gives average results comparable to those from the PROFILE model. However, dynamic modelling provides extra information on the variation in weathering rates with time, and offers much better possibilities for scenario modelling.

There is a growing interest in the bio-based economy, evident in the policy domain as well as in the academic literature. Its proponents consider it an opportunity to address multiple societal challenges, and the concept has broad reach across different sectors of society. However, a potential transition process is also linked to areas of risk and uncertainty, and the need for interdisciplinary research and for the identification of potential trade-offs and synergies between parallel visions of the bio-based economy have been emphasized. The aim of this paper is to contribute to addressing this gap by using an approach combining tools for systems analysis with expert interviews. Focusing specifically on dynamics in the agricultural sector in Sweden, an integrated understanding of the social and ecological processes contributing to or hindering a transition in this area is developed, high order leverage points are identified, and potential impacts of proposed interventions explored. The paper also considers cross-sectoral linkages between the forestry and agricultural sectors.

A transition to a bio-based economy would entail change in coupled social–ecological systems. These systems are characterised by complexity, giving rise to potential unintended consequences and trade-offs caused by actions aiming to facilitate a transition process. Yet, many of the analyses to date have been focusing on single and predominantly technological aspects of the bio-based economy. The main contribution of our work is to the development of an integrated understanding of potential future transition pathways, with the present paper focusing specifically on terrestrial biological resources derived from the forestry sector in Sweden. Desired change processes identified include a transition to diversified forest management, a structural change in the forestry industry to enable high-value added production, and increased political support for the bio-based economy concept. Hindrances identified include the ability to demonstrate added values for end consumers of novel biomass applications, and uncertainty linked to a perceived high level of polarisation in the forestry debate. The results outline how these different processes are interrelated, allowing for the identification of high order leverage points and interventions to facilitate a transition to a bio-based economy.

In this study, a phosphorus (P) module containing the biogeochemical P cycle has been developed and integrated into the forest ecosystem model ForSAFE. The model was able to adequately reproduce the measured soil water chemistry, tree biomass (wood and foliage), and the biomass nutrient concentrations at a spruce site in southern Sweden. Both model and measurements indicated that the site showed signs of P limitation at the time of the study, but the model predicted that it may return to an N-limited state in the future if N deposition declines strongly. It is implied by the model that at present time, the plant takes up 0.50 g P m−2 y−1, of which 80% comes from mineralization and the remainder comes from net inputs, i.e. deposition and weathering. The sorption/desorption equilibrium of P contributed marginally to the supply of bioavailable P, but acted as a buffer, particularly during disturbances.

The contribution of forest harvesting to base cation losses and soil acidification has increased in recent years in Sweden, as the demand for bioenergy has increased and the sulphur deposition has decreased. Thus, new policy tools are required to evaluate the progress of the recovery from acidification, and as a basis for forest management recommendations. In this study we introduce and test a concept, “Critical biomass harvesting”. The concept builds on the concept “Critical loads”, which has been used world-wide for several decades as a bridge between science and policies related to transboundary air pollution and acidification. The basis for the concept is an acidity mass balance, with sources and sinks of acidity. A critical limit defines the highest acceptable acidification status of the water leaving the root zone. Based on the critical limit, the highest allowed biomass harvesting can be calculated, keeping the other parameters constant. In this study the critical limit was set to ANC (Acid Neutralizing Capacity) = 0. Nitrogen was assumed to be affecting acidity only if it leaches from the root zone. The critical biomass harvesting was calculated for almost 12 000 National Forest Inventory sites with spruce and pine forest, using the best available data on deposition, weathering and nitrogen leaching. The exceedance of critical biomass harvesting was calculated as the difference between the estimated harvest losses and the critical biomass harvesting. The results were presented as median values in merged catchments in a catchment database, with totally 2079 merged catchments in Sweden. According to the calculations, critical biomass harvesting was exceeded in the southern half of Sweden already at stem harvesting in spruce forests. Whole-tree harvesting expanded the exceedance area, and increased the exceedance levels in southern Sweden. The exceedance in pine forest was lower and affected smaller areas. It was concluded that the concept of critical biomass harvesting can be successfully applied on the same database that has been used for critical load calculations in Sweden, using basically the same approach as has been extensively applied, evaluated and discussed in a critical load context. The results from the calculations in Sweden indicate that whole-tree harvesting, without wood ash recycling, can be expected to further slow down recovery, especially in the most acidified parts of the country, in the southwest.

National audience

The Convention on Long-Range Transboundary Air Pollution was signed by different European countries to reduce the emissionsand the atmospheric deposition of pollutants, and particularly to limit the noticeable impact of atmospheric nitrogen deposition onterrestrial ecosystems. The MODYCRIN project describes a modelling approach, which couples biogeochemical and ecologicalmodels. The objective is to predict the atmospheric deposition effects under climate change on forest ecosystems, particularly usingthe modifications observed at the understorey vegetation scale. These changes are used to calculate nitrogen critical loads thatreflect ecosystems sensitivity to nitrogen atmospheric deposition. Following previous investigations, the first steps of the project aimat doing an important work to calibrate and validate the biogeochemical – ecological coupled model ForSAFE for Frenchenvironmental conditions. For that purpose, data from some well-documented forest sites belonging to the French forest ICP networkRENECOFOR, are used. This work was done in partnership with Swedish modellers and French ecologists.The MODYCRIN project has a main objective to enlarge the modelling approach to the country scale using the whole RENECOFORnetwork – i.e. 102 sites previously classified according to their EUNIS habitat class. To reach this aim, the project was focussed onending the construction of the Table VEG for France by combining with the measured phytoecological datas from the ecologicaldatabase EcoPlant (Gegout et al. 2005)), as well as the calibration of the ForSAFE model on 12 reference RENECOFOR sites,before extrapolation to the whole set of RENECOFOR sites. The parametrisation of the vegetation table was set up to performlogistic regression models, in order to predict the evolutions of a hundred of vegetation species for the French territory, under theinfluence of a decade of main environmental factorsThe calibration of the ForSAFE model on the whole set of RENECOFOR sites was performed using a large set of parameters whichvariations were known (measured) on a long period of time, and which are representative of the environmental conditions of theforest stations usually found on the forest network (RENECOFOR). Taking into account of these parameters allow a reliablecalibration of the model for a large environmental gradient in France.; Dans le cadre de la convention de Genève sur la pollution atmosphérique transfrontalière à longue distance, les pays européenss’engagent à réduire leurs émissions et dépôts atmosphériques, notamment azotés. Pour la France, il apparaît en effet primordial depouvoir prédire l’effet de ces dépôts atmosphériques sur les écosystèmes forestiers, notamment du fait de leur impact sur lefonctionnement des sols, sur la santé des forêts et sur la biodiversité végétale du sous-bois. Pour ce faire, des modèles couplésbiogéochimiques – écologiques, tels que ForSAFE-VEG, sont développés. Ils permettent de simuler sur le long terme l’impact desdépôts atmosphériques et du changement climatique sur la biodiversité forestière et donc d’estimer les charges critiques, outilpermettant d’apprécier la sensibilité d’un écosystème aux dépôts d’azote. Au cours de précédents projets, le modèle ForSAFE-VEG aété calibré et validé pour la France sur certains sites forestiers appartenant au réseau national RENECOFOR (décrits au niveau 3).L’étude MODYCRIN vise à élargir l’utilisation de cette approche à l’ensemble des 102 placettes du réseau RENECOFOR afin d’estimerles charges critiques azotées à l’échelle du territoire et d’en faire la cartographie, en rattachant chacune d’elles à une classe d’habitatEUNIS, et en utilisant la notion de groupes fonctionnels pour les prévisions de changement de biodiversité. L’accent est mis sur lafinalisation de la construction d’une table de végétation pour la France, basée sur des données mesurées issues d’une grande basede données phytoécologiques (base de données EcoPlant, (Gegout et al. 2005), ainsi que sur la fin de la calibration du modèleForSAFE (grâce notamment à l’ utilisation de cette base de données finalisée) sur une douzaine de placettes de référence dans unpremier temps, puis sur l’ensemble des placettes du réseau RENECOFOR.La paramétrisation de la table de végétation est réalisée pour élaborer des modèles de régression logistique permettant de prédirel’évolution de plusieurs centaines d’espèces végétales forestières métropolitaines, en réponse à des modifications d’une dizaine defacteurs environnementaux majeurs. Par ailleurs, en collaboration étroite avec des modélisateurs Suédois, la calibration du modèleForSAFE sur l’ensemble des placettes étudiées s’effectue notamment par une prise en compte stricte d’un grand nombre deparamètres dont les variations sont connues (mesurées) au cours du temps, et qui sont représentatifs des conditions stationnellesrencontrées sur l’ensemble des placettes du réseau RENECOFOR. La prise en compte de ces paramètres a donc permis unecalibration du modèle qui intègre l’ensemble des gradients environnementaux présents sur la France.

The study presents a method to evaluate the response of forest ecosystems to increased biomass extraction based on the integrated ecosystem model ForSAFE. It evaluates the effects of residue removal, intensification of thinnings and a shorter rotation period on a forest site in Southern Sweden. The evaluation includes multiple ecosystem indicators for productivity, carbon storage, wood production, water use and water quality. Such integrated assessments can contribute to identify negative or positive impacts affecting ecosystem services provided by forests. Results show that increased biomass extraction reduces the carbon stored in the forests, but at the same time reduces the loss of nitrogen and carbon through leaching. Within one rotation, residue removal affects the carbon stock in the soil, but it does not affect forest productivity and therefore tree carbon stock. Contrarily, the intensification of thinnings and shorter rotation periods reduce carbon stored in trees. In all cases, the amount of wood available for products increases, but the additional harvest from increased thinnings and earlier clear cutting does not compensate for the loss of carbon in trees. A positive consequence of removing the decomposing material from the site is the reduced amount of nutrients lost with runoff. Both leached nitrogen and dissolved organic carbon decrease with intensification. In addition, a positive effect of increased thinnings and a shorter rotation period is a reduced evapotranspiration, i.e. reduced water use. The effect on acidification differed depending on the time frame considered and the applied management scenario, due to different dominating processes regulating acidity. To avoid acidification, management intensification should include measures to prevent loss of base cations in the soil. Overall, under the studied conditions, the risk for negative effects seems to be smaller for residue extraction than for management changes including additional tree harvest. (C) 2014 Elsevier B.V. All rights reserved.

Weathering of soil minerals is important for the recovery from acidification and for the sustainability of forestry. However, there is still substantial uncertainty about its absolute rate. This study presents a harmonized comparison of field weathering rates estimated with the mechanistic model PROFILE and the depletion method for 16 intensively sampled soil profiles across Sweden representing different site conditions. In general, a correspondence in total weathering rates was found between the two methods except in rare cases where either method yielded deviating results. The weathering rate was higher according to the depletion method than according to PROFILE for Mg, while PROFILE produced higher weathering rates for the other base cations. The Spearman rank correlation (rho) between the two methods indicated significant correlation for Ca (rho = 0.44, p = 0.04) and non-significant correlation for Mg (rho = 0.51, p = 0.09), Na (rho = 0.25, p = 0.34), K (rho = 0.07, p = 0.80), and the sum of the base cations (rho = 0.11, p = 0.67). The variation in weathering rates with depth showed opposite gradients in the upper 50 cm, which reflects the conceptual differences between the methods. This study shows the potential of using multiple methods to identify a probable weathering rate, if harmonized input data are used. Furthermore, it highlights the importance of making comparisons for individual elements in order to interpret differences between methods. Regardless of the method used, weathering rates were below or at the same level as the losses caused by whole-tree harvesting, particularly in southern Sweden, indicating a risk of negative effects on soils and waters. (C) 2013 Elsevier B.V. All rights reserved. (Less)

International audience

The study presents a hydrology concept developed to include lateral water flow in the biogeochemical model ForSAFE. The hydrology concept was evaluated against data collected at Svartberget in the Vindeln Research Forest in Northern Sweden. The results show that the new concept allows simulation of a saturated and an unsaturated zone in the soil as well as water flow that reaches the stream comparable to measurements. The most relevant differences compared to streamflow measurements are that the model simulates a higher base flow in winter and lower flow peaks after snowmelt. These differences are mainly caused by the assumptions made to regulate the percolation at the bottom of the simulated soil columns. The capability for simulating lateral flows and a saturated zone in ForSAFE can greatly improve the simulation of chemical exchange in the soil and export of elements from the soil to watercourses. Such a model can help improve the understanding of how environmental changes in the forest landscape will influence chemical loads to surface waters.

Historical deposition of nitrogen (N) and sulfur (S) over the Eastern United States has impacted ecosystem structure and function. The potential for recovery of ecosystems is relatively uncertain, with deposition paired with future climate change contributing to this uncertainty. The impacts of N and S deposition and climate change (from 1900 to 2100) on two sugar maple–beech–yellow birch sites in the Northeastern United States were evaluated using the paired biogeochemical–vegetation response model ForSAFE-Veg at two research sites, Hubbard Brook Experimental Forest and Bear Brook Watershed. Deposition was found to be the dominant stressor, causing changes in soil acid–base chemistry, N enrichment, and shifts in understory species composition. Responses of the two sites varied due primarily to differences in buffering capacity and levels of deposition. However, at both sites, recovery of soil and plant community properties to 1900 conditions was approached only when future deposition to 2100 was returned to pre-industrial levels. Policy-based reductions in deposition generally halted further damage to soils and plants and resulted in no or only partial recovery. Increased temperatures and precipitation according to Intergovernmental Panel on Climate Change (IPCC) climate futures stimulated soil and plant response, thereby accelerating changes in plant communities and N enrichment and counteracting the acidifying impacts of N and S deposition on soil acid–base chemistry.

A Norway spruce (Picea abies Karst) forest site in southwest Sweden was chosen to study the effects of storm disturbances over the period 1997-2009, during which two storms, 'Lothar' (December 1999) and 'Gudrun' (January 2005), affected the area. Monitored deposition data, soil water chemistry data and forest inventory data were compared with the predictions of an integrated ecosystem model, ForSAFE, in an effort to reveal and understand the effects of storms on acidification/recovery in forest soils. Both storms caused windthrow loss leading to increased nitrate and sulphate concentrations in soil water as a result of stimulated mineralization. Lothar led to increased concentrations of Na+, Mg2+, and Cl- in soil water due to sea-salt episode. No general sea-salt episode was seen following Gudrun, but small sea-salt episodes were observed in 2007 and 2008. Each sea-salt episode caused a temporary decrease of pH, and a subsequent recovery, but overall, the soil water pH decreased from 4.54 to 3.86 after Lothar. Modelling suggested that the site was recovering from acidification from 1990s, and would continue to recover in future. Both modelled and monitored data showed that storm caused disturbances in the recovery; monitored data even suggested that soil acidification happened due to storm disturbances. Sea-salt episode does not increase soil acidity in the long term, and will probably decrease the soil acidity by replenishing the base saturation. The modelled data also suggested that storms with only windthrow would not have effects on soil acidification recovery in the long term, but they may influence the soil fertility by losses of base cations. (C) 2015 Elsevier B.V. All rights reserved.

The ForSAFE-VEG model was used to estimate atmospheric nitrogen deposition and climate effects on soil chemistry and ground vegetation in alpine and subalpine zones of the northern and central Rocky Mountains region in the USA from 1750 to 2500. Model simulations for a generalized site illustrated how the critical load of atmospheric nitrogen deposition could be estimated to protect plant biodiversity. The results appear reasonable compared with past model applications in northern Europe. Atmospheric N deposition critical loads estimated to protect plant biodiversity were 1 to 2 kg N/ha/year. This range could be greater, depending on the values selected for critical site-specific parameters (precipitation, temperature, soil chemistry, plant nutrient uptake, and any eventual harvest of biomass) and the amount of biodiversity change allowed.

A dynamic model of forest ecosystems was used to investigate the effects of climate change, atmospheric deposition and harvest intensity on 48 forest sites in Sweden (n = 16) and Switzerland (n = 32). The model was used to investigate the feasibility of deriving critical loads for nitrogen (N) deposition based on changes in plant community composition. The simulations show that climate and atmospheric deposition have comparably important effects on N mobilization in the soil, as climate triggers the release of organically bound nitrogen stored in the soil during the elevated deposition period. Climate has the most important effect on plant community composition, underlining the fact that this cannot be ignored in future simulations of vegetation dynamics. Harvest intensity has comparatively little effect on the plant community in the long term, while it may be detrimental in the short term following cutting. This study shows: that critical loads of N deposition can be estimated using the plant community as an indicator; that future climatic changes must be taken into account; and that the definition of the reference deposition is critical for the outcome of this estimate.

The ForSAFE-VEG model was used to investigate the impacts of climate change and air pollution scenarios on soil chemistry and ground vegetations composition. In particular, the model involves a ground vegetation model incorporating plant changes to ambient site conditions in terms of climate and chemistry, but the model also incorporate competition between the different plant groups. The model was validated against observed values and reproduced observations of tree growth, soil chemistry, and ground vegetation compositions to satisfaction. The results show that the ground vegetation reacts strongly to changes in air pollution, in particular nitrogen as well as to climate change with major shifts in plant composition. A procedure for estimating critical loads for nitrogen, using ground vegetation biodiversity as criterion, was tested and the method seems operable. It suggests that if we want to protect the present biodiversity of the ground vegetation, this will face significant difficulties because of permanent climate change that induced changes in the ecosystem. We conclude that the reference state for ground vegetation biodiversity is rather to be sought for in the future, hopefully using models, than in the past or present.

Field observations and experimental data of effects of nitrogen (N) deposition on plant species diversity have been used to derive empirical critical N loads for various ecosystems. The great advantage of such an approach is the inclusion of field evidence, but there are also restrictions, such as the absence of explicit criteria regarding significant effects on the vegetation, and the impossibility to predict future impacts when N deposition changes. Model approaches can account for this. In this paper, we review the possibilities of static and dynamic multispecies models in combination with dynamic soil–vegetation models to (1) predict plant species composition as a function of atmospheric N deposition and (2) calculate critical N loads in relation to a prescribed protection level of the species composition. The similarities between the models are presented, but also several important differences, including the use of different indicators for N and acidity and the prediction of individual plant species vs. plant communities. A summary of the strengths and weaknesses of the various models, including their validation status, is given. Furthermore, examples are given of critical load calculations with the model chains and their comparison with empirical critical N loads. We show that linked biogeochemistry–biodiversity models for N have potential for applications to support European policy to reduce N input, but the definition of damage thresholds for terrestrial biodiversity represents a major challenge. There is also a clear need for further testing and validation of the models against long-term monitoring or long-term experimental data sets and against large-scale survey data. This requires a focused data collection in Europe, combing vegetation descriptions with variables affecting the species diversity, such as soil acidity, nutrient status and water availability. Finally, there is a need for adaptation and upscaling of the models beyond the regions for which dose–response relationships have been parameterized, to make them generally applicable.