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  • 1. Berggren Kleja, Dan
    et al.
    Svensson, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Majdi, Hooshang
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Langvall, Ola
    Bergkvist, Bo
    Johansson, Maj-Britt
    Weslien, Per
    Lindroth, Anders
    Pools and fluxes of carbon in three Norway spruce ecosystems along a climatic gradient in Sweden.2008Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 89, nr 1, s. 7-25Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents an integrated analysis of organic carbon (C) pools in soils and vegetation, within-ecosystem fluxes and net ecosystem exchange (NEE) in three 40-year old Norway spruce stands along a north-south climatic gradient in Sweden, measured 2001-2004. A process-orientated ecosystem model (CoupModel), previously parameterised on a regional dataset, was used for the analysis. Pools of soil organic carbon (SOC) and tree growth rates were highest at the southernmost site (1.6 and 2.0-fold, respectively). Tree litter production (litterfall and root litter) was also highest in the south, with about half coming from fine roots (< 1 mm) at all sites. However, when the litter input from the forest floor vegetation was included, the difference in total litter input rate between the sites almost disappeared (190-233 g C m(-2) year(-1)). We propose that a higher N deposition and N availability in the south result in a slower turnover of soil organic matter than in the north. This effect seems to overshadow the effect of temperature. At the southern site, 19% of the total litter input to the O horizon was leached to the mineral soil as dissolved organic carbon, while at the two northern sites the corresponding figure was approx. 9%. The CoupModel accurately described general C cycling behaviour in these ecosystems, reproducing the differences between north and south. The simulated changes in SOC pools during the measurement period were small, ranging from -8 g C m(-2) year(-1) in the north to +9 g C m(-2) year(-1) in the south. In contrast, NEE and tree growth measurements at the northernmost site suggest that the soil lost about 90 g C m(-2) year(-1).

  • 2. Eliasson, Peter
    et al.
    Svensson, Magnus
    Olsson, Mats
    Ågren, Göran .I.
    Forest carbon balances at the landscape scale investigated with the Q model and the CoupModel - Responses to intensified harvests2013Ingår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 290, s. 67-78Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increasing demand for solid biofuels, such as logging residue fuels, has highlighted the importance of considering that, in contrast to fossil fuels, biofuels are produced in dynamic ecosystems. The environmental effects of changes in management policy, whether positive and negative, are not obvious. For example, calculations of the carbon budget in single forest stands show that the carbon balance switches dramatically from uptake to loss at final felling. The time taken to recover the carbon losses after disturbance can span decades to centuries. However, forests are not managed on the single stand level but on the landscape scale. Thus, for example, final felling occurs by definition only once for each rotation period on the whole area considered in a single stand, but within the same time span, it occurs frequently on a fraction of the area in a landscape. The actual frequency and ratio of land area affected each year by final felling depend on the age distribution and rotation age of all stands present in the landscape. In order to reliably evaluate the consequences of new management policies, the aggregated effects of a number of individual stands need to be considered. Here we used two different ecosystem models (the Q model and the CoupModel) to compare the carbon budgets of conventional harvesting of stems on a single-stand level and on the landscape scale under different harvesting intensities. In the calculations, the landscape was assumed to consist of many stands, all of different ages and each representing one year of a given rotation period. The results showed that the aggregated carbon balance in the forest landscape was less dramatic than that of a single stand. Provided that environmental factors and management policy remain unchanged, the aggregated carbon balance remains stable over time in any landscape. However, the carbon gains from harvesting and its effects on soil carbon stock occur on different time scales. While any change in harvesting system takes a long time to be fully implemented, changes in the proportion of increased removals take effect without delay, while components of soil organic carbon have response times longer than centuries. The carbon gain after introducing removal of logging residues starts to increase immediately at the first harvest in a landscape. The quantities of soil carbon lost with the increased removals are always less than the removals in biomass. Soil carbon losses show a declining response over time. © 2012 Elsevier B.V.

  • 3. Fröberg, M.
    et al.
    Grip, H.
    Tipping, E.
    Svensson, Magnus
    Swedish University of Agricultural Sciences, Department of Soil and Environment, P.O. Box 7014, SE-75007 Uppsala, Sweden.
    Strömgren, M.
    Kleja, D. B.
    Long-term effects of experimental fertilization and soil warming on dissolved organic matter leaching from a spruce forest in Northern Sweden2013Ingår i: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 200-201, s. 172-179Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nitrogen deposition and increasing temperature are two of the major large-scale changes projected for coming decades and the effect of this change on dissolved organic matter is largely unknown. We have utilized a long-term fertilization and soil warming experiment in Northern Sweden to study the effects of increased nutrient levels and increased temperature on DOC transport under the O horizon. The site is N limited and mean annual temperature 2. °C. Experimental fertilization with ammonium nitrate and a physiological mixture of other macro- and micro-nutrients has been going on for 22. years and soil warming, 5. °C above ambient soil temperature for 14. years, prior to the study. Experimental plots have been irrigated to avoid drying and we also studied the effect of this long-term irrigation on DOC by establishing control plots receiving no irrigation.DOC concentrations and fluxes under the O horizon were approximately 50% higher in fertilized plots than in non-fertilized control plots. We did not find any statistically significant effect of soil warming. There was a statistically significant effect of long-term irrigation on DOC with higher DOC concentration and fluxes in irrigated plots than in plots without irrigation. There were no major effects on DOC quality measured by specific UV absorbance. Fertilization approximately doubled soil organic matter stocks in the O horizon, whereas there were no such effects of warming or irrigation on soil organic matter amounts. There was no statistically significant treatment effect on DOC collected from the B horizon. We hypothesize that the positive effect of fertilization on DOC is related to increased soil C stocks.

  • 4.
    Gärdenäs, Annemieki
    et al.
    Department of Soil and Environment, Swedish University of Agricultural Sciences.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Biogeofysik.
    Karltun, Erik
    Department of Soil and Environment, Swedish University of Agricultural Sciences.
    Klemendtsson, Leif
    Department of Plant and Environmental Sciences, Gothenburg University.
    Lehtonen, Aleksi
    Finnish Forest Research Institute, Vantaa, Finland.
    Ortiz, Carina
    Department of Soil and Environment, Swedish University of Agricultural Sciences.
    Palosuo, Taru
    MTT Agrifood Research, Helsinki, Finland.
    Svensson, Magnus
    Department of Soil and Environment, Swedish University of Agricultural Sciences.
    Estimating soil carbon stock changes by process-based models and soil inventories: uncertainties and complementarities2011Ingår i: Soil Carbon in Sensitive European Ecosystems: From Science to Land Management / [ed] Robert Jandl, Mirco Rodehiero and Mats Olsson, Oxford: Wiley-Blackwell, 2011Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    In this chapter, four examples of scientific questions and challenges in which process-oriented modelling could provide a useful contribution for accounting soil organic carbon (SOC) stocks and changes are presented. These challenges include cases i) when measurements are either time-consuming and/or expensive or there are methodological limitations; ii) an attempt to verify the national soil inventory estimates through comparison with process-based model estimates; iii) prediction of the potential impact on SOC changes due to land-use change; and iv) a comparison of different scenarios for mitigating GHG-emissions. We found that the use of process-based models offers a complementary way to account SOC change and provides an option for assessing the potential impact of climate and land-use change on SOC stocks. However, uncertainty in model estimates is inherent and needs to be communicated. Progress has been made in the assessment of uncertainty and there is growing awareness of how this uncertainty can be communicated. Suggestions for collaborative approaches are presented in order to reduce the uncertainties.

  • 5. He, H.
    et al.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Svensson, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Meyer, A.
    Klemedtsson, L.
    Kasimir, Å.
    Factors controlling Nitrous Oxide emission from a spruce forest ecosystem on drained organic soil, derived using the CoupModel2016Ingår i: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 321, s. 46-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High Nitrous Oxide (N2O) emissions have been identified in hemiboreal forests in association with draining organic soils. However, the specific controlling factors that regulate the emissions remain unclear. To examine the importance of different factors affecting N2O emissions in a spruce forest on drained organic soil, a process-based model, CoupModel, was calibrated using the generalized likelihood uncertainty estimation (GLUE) method. The calibration also aims to estimate parameter density distributions, the covariance matrix of estimated parameters and the correlation between parameters and variables information, useful when applying the model on other peat soil sites and for further model improvements. The calibrated model reproduced most of the high resolution data (total net radiation, soil temperature, groundwater level, net ecosystem exchange, etc.) very well, as well as cumulative measured N2O emissions (simulated 8.7±1.1kgN2Oha-1year-1 (n=97); measured 8.7±2.7kgN2Oha-1year-1 (n=6)), but did not capture every measured peak. Parameter uncertainties were reduced after calibration, in which 16 out of 20 parameters changed from uniform distributions into normal distributions or log normal distributions. Four parameters describing bypass water flow, oxygen diffusion and soil freezing changed significantly after calibration. Inter-connections and correlations between many calibrated parameters and variables reflect the complex and interrelated nature of pedosphere, biosphere and atmosphere interactions. This also highlights the need to calibrate a number of parameters simultaneously. Model sensitivity analysis indicated that N2O emissions during growing seasons are controlled by competition between plants and microbes for nitrogen, while during the winter season snow melt periods are important. Our results also indicate that N2O is mainly produced in the capillary fringe close to the groundwater table by denitrification in the anaerobic zone. We conclude that, in afforested drained peatlands, the plants and groundwater level have important influences on soil N availability, ultimately controlling N2O emissions.

  • 6. He, Hongxing
    et al.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Svensson, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Bjorklund, Jesper
    Tarvainen, Lasse
    Klemedtsson, Leif
    Kasimir, Asa
    Forests on drained agricultural peatland are potentially large sources of greenhouse gases - insights from a full rotation period simulation2016Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, nr 8, s. 2305-2318Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The CoupModel was used to simulate a Norway spruce forest on fertile drained peat over 60 years, from planting in 1951 until 2011, describing abiotic, biotic and greenhouse gas (GHG) emissions (CO2 and N2O). By calibrating the model against tree ring data a "vegetation fitted" model was obtained by which we were able to describe the fluxes and controlling factors over the 60 years. We discuss some conceptual issues relevant to improving the model in order to better understand peat soil simulations. However, the present model was able to describe the most important ecosystem dynamics such as the plant biomass development and GHG emissions. The GHG fluxes are composed of two important quantities, the spruce forest carbon (C) uptake, 413 g C m(-2) yr(-1) and the decomposition of peat soil, 399 g C m(-2) yr(-1) . N2O emissions contribute to the GHG emissions by up to 0.7 g N m(-2) yr(-1), corresponding to 76 g C m(-2) yr(-1) . The 60-year old spruce forest has an accumulated biomass of 16.0 kg C m(-2) (corresponding to 60 kg CO2 m(-2)). However, over this period, 26.4 kg C m(-2) (97 kg CO2 eq m(-2)) has been added to the atmosphere, as both CO2 and N2O originating from the peat soil and, indirectly, from forest thinning products, which we assume have a short lifetime. We conclude that after harvest at an age of 80 years, most of the stored biomass carbon is liable to be released, the system having captured C only temporarily and with a cost of disappeared peat, adding CO2 to the atmosphere.

  • 7. He, Hongxing
    et al.
    Meyer, Astrid
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Svensson, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Rutting, Tobias
    Klemedtsson, Leif
    Simulating ectomycorrhiza in boreal forests: implementing ectomycorrhizal fungi model MYCOFON in CoupModel (v5)2018Ingår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 11, nr 2, s. 725-751Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The symbiosis between plants and Ectomycorrhizal fungi (ECM) is shown to considerably influence the carbon (C) and nitrogen (N) fluxes between the soil, rhizosphere, and plants in boreal forest ecosystems. However, ECM are either neglected or presented as an implicit, undynamic term in most ecosystem models, which can potentially reduce the predictive power of models. In order to investigate the necessity of an explicit consideration of ECM in ecosystem models, we implement the previously developed MYCOFON model into a detailed process-based, soil-plant-atmosphere model, Coup-MYCOFON, which explicitly describes the C and N fluxes between ECM and roots. This new Coup-MYCOFON model approach (ECM explicit) is compared with two simpler model approaches: one containing ECM implicitly as a dynamic uptake of organic N considering the plant roots to represent the ECM (ECM implicit), and the other a static N approach in which plant growth is limited to a fixed N level (nonlim). Parameter uncertainties are quantified using Bayesian calibration in which the model outputs are constrained to current forest growth and soil C / N ratio for four forest sites along a climate and N deposition gradient in Sweden and simulated over a 100-year period. The "nonlim" approach could not describe the soil C / N ratio due to large overestimation of soil N sequestration but simulate the forest growth reasonably well. The ECM "implicit" and "explicit" approaches both describe the soil C / N ratio well but slightly underestimate the forest growth. The implicit approach simulated lower litter production and soil respiration than the explicit approach. The ECM explicit Coup-MYCOFON model provides a more detailed description of internal ecosystem fluxes and feedbacks of C and N between plants, soil, and ECM. Our modeling highlights the need to incorporate ECM and organic N uptake into ecosystem models, and the nonlim approach is not recommended for future long-term soil C and N predictions. We also provide a key set of posterior fungal parameters that can be further investigated and evaluated in future ECM studies.

  • 8.
    Jansson, Per-Erik
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Svensson, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Berggren Kleja, Dan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Simulated climate change impacts on fluxes of carbon in Norway spruce ecosystems along a climatic transect in Sweden2008Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 89, nr 1, s. 81-94Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simulation study based on recent regional climate scenarios for Sweden investigated possible changes in carbon (C) dynamics and net ecosystem exchange (NEE) of Swedish Norway spruce forest ecosystems. Four sites, representative of well-drained soils in four regions, were included. Stand development was simulated for a 100-year rotation period using a coupled model describing abiotic and biotic processes in the soil-plant-atmosphere system. Two IPCC climate change scenarios, corresponding to a mean annual temperature increase of about 2 degrees C (A2) or 3 degrees C (B2) from the reference period 1961-1990 to a new period 2061-2090, were considered. Annual maximum snow depth decreased with the increase in air temperature, whereas maximum soil frost depth and mean annual soil temperature showed only small changes, especially for the sites in northern Sweden. Simulations suggested that in the warmer climate, gross primary production (GPP) increased by 24-32% in northern Sweden and by 32-43% in the south. In the north, the increase was related to the combined effect of air and soil temperature extending the growing season, whereas in the south it was mainly governed by increased N availability due to increased soil temperature. NEE increased by about 20% (A2) or 25% (B2) at all sites, more or less solely due to increased accumulation of C in the tree biomass (including harvest residues), since changes in soil C were small compared with the current climate. Both light use efficiency and water use efficiency were improved in the future climate scenarios, despite increases in atmospheric CO2 not being considered.

  • 9. Palosuo, T.
    et al.
    Foereid, B.
    Svensson, Magnus
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Shurpali, N.
    Lehtonen, A.
    Herbst, M.
    Linkosalo, T.
    Ortiz, C.
    Rampazzo Todorovic, G.
    Marcinkonis, S.
    Li, C.
    Jandl, R.
    A multi-model comparison of soil carbon assessment of a coniferous forest stand2012Ingår i: Environmental Modelling & Software, ISSN 1364-8152, E-ISSN 1873-6726, Vol. 35, s. 38-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We simulated soil carbon stock dynamics of an Austrian coniferous forest stand with five soil-only models (Q, ROMUL, RothC, SoilCO2/RothC and Yasso07) and three plant-soil models (CENTURY, CoupModel and Forest-DNDC) for an 18-year period and the decomposition of a litter pulse over a 100-year period. The objectives of the study were to assess the consistency in soil carbon estimates applying a multi-model comparison and to present and discuss the sources of uncertainties that create the differences in model results. Additionally, we discuss the applicability of different modelling approaches from the view point of large-scale carbon assessments. Our simulation results showed a wide range in soil carbon stocks and stock change estimates reflecting substantial uncertainties in model estimates. The measured stock change estimate decreased much more than the model predictions. Model results varied not only due to the model structure and applied parameters, but also due to different input information and assumptions applied during the modelling processes. Initialization procedures applied with the models induced large differences among the modelled soil carbon stocks and stock change estimates. Decomposition estimates of the litter pulse driven by model structures and parameters also varied considerably. Our results support the use of relatively simple soil-only models with low data requirements in inventory type of large-scale carbon assessments. It is important that the modelling processes within the national inventories are transparently reported and special emphasis is put on how the models are used, which assumptions are applied and what is the quality of data used both as input and to calibrate the models. © 2012 Elsevier Ltd.

  • 10. Rasmus, S.
    et al.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Koivusalo, H.
    Laurén, A.
    Grelle, A.
    Kauppinen, O. -K
    Lagnvall, O.
    Lindroth, A.
    Rasmus, K.
    Svensson, M.
    Weslien, P.
    Estimation of winter leaf area index and sky view fraction for snow modelling in boreal coniferous forests: Consequences on snow mass and energy balance2013Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 27, nr 20, s. 2876-2891Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Leaf area index (LAI) and canopy coverage are important parameters when modelling snow process in coniferous forests, controlling interception and transmitting radiation. Estimates of LAI and sky view factor show large variability depending on the estimation method used, and it is not clear how this is reflected in the calculated snow processes beneath the canopy. In this study, the winter LAI and sky view fraction were estimated using different optical and biomass-based approximations in several boreal coniferous forest stands in Fennoscandia with different stand density, age and site latitude. The biomass-based estimate of LAI derived from forest inventory data was close to the values derived from the optical measurements at most sites, suggesting that forest inventory data can be used as input to snow hydrological modelling. Heterogeneity of tree species and site fertility, as well as edge effects between different forest compartments, caused differences in the LAI estimates at some sites. A snow energy and mass balance model (SNOWPACK) was applied to detect how the differences in the estimated values of the winter LAI and sky view fraction were reflected in simulated snow processes. In the simulations, an increase in LAI and a decrease in sky view fraction changed the snow surface energy balance by decreasing shortwave radiation input and increasing longwave radiation input. Changes in LAI and sky view fraction affected directly snow accumulation through altered throughfall fraction and indirectly snowmelt through the changed surface energy balance. Changes in LAI and sky view fraction had a greater impact on mean incoming radiation beneath the canopy than on other energy fluxes. Snowmelt was affected more than snow accumulation. The effect of canopy parameters on evaporation loss from intercepted snow was comparable with the effect of variation in governing meteorological variables such as precipitation intensity and air temperature.

  • 11.
    Svensson, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Carbon dynamics in spruce forest ecosystems - modelling pools and trends for Swedish conditions2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Carbon (C) pools and fluxes in northern hemisphere forest ecosystems are attracting increasing attention concerning predicted climate change. This thesis studied C fluxes, particularly soil C dynamics, in spruce forest ecosystems in relation to interactions between physical/biological processes using a process-based ecosystem model (CoupModel) with data for Swedish conditions. The model successfully described general patterns of C and N dynamics in managed spruce forest ecosystems with both tree and field layers. Using regional soil and plant data, the change in current soil C pools was -3 g C m-2 yr-1 in northern Sweden and +24 g C m-2 yr-1 in southern Sweden. Simulated climate change scenarios resulted in increased inflows of 16-38 g C m-2 yr-1 to forest ecosystems throughout Sweden, with the highest increase in the south and the lowest in the north. Along a north-south transect, this increased C sequestration mainly related to increased tree growth, as there were only minor decreases in soil C pools. Measurements at one northern site during 2001-2002 indicated large soil C losses (-96 g C m-2 yr-1), which the model successfully described. However, the discrepancy between these large losses and substantially smaller losses obtained in regional simulations was not explained. A simulation based on Bayesian calibration successfully reproduced measured C, water and energy fluxes, with estimated uncertainties for major components of the simulated C budget. Site-specific measurements indicated a large contribution from field layer fine roots to total litter production, particularly in northern Sweden. Mean annual tree litter production was 66% higher at the most southerly site (240 g C m-2 yr-1 compared with 145 g C m-2 yr-1 in the north), but when field and bottom layers were included the difference decreased to 16% (total litter production 276 g C m-2 yr-1 and 239 g C m-2 yr-1 respectively). Regional simulations showed that decomposition rate for the stable soil C fraction was three times higher in northern regions compared with southern, providing a possible explanation why soil C pools in southern Sweden are roughly twice as large as those in the north.

  • 12.
    Svensson, Magnus
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Modelling soil temperature and carbon storage changes for Swedish boreal forests2004Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    With the use of a process-orientated ecosystem model andmeasurements conducted at different Swedish coniferous forestsites, abiotic and biotic interactions between tree and soilwere identified and related to governing factors. Two differentmodelling approaches to describe soil temperatures at two sitesincluding hydrological transects were tested (I). The approachin which both canopy and soil were considered proved to be amore flexible tool to describe soil temperatures, especiallyduring snow-free winter periods. Five sites along a climatetransect covering Sweden were used to describe soil carbon poolchanges during an 80-year period simulation (II). The dynamicmodelling approach, with a feedback between abiotic and bioticsub-models, was successful in describing simplified patterns offorest stand dynamics and furthermore in differentiatingbetween climate and nitrogen availability factors. The largereffect of nitrogen availability compared to climate on soilcarbon pool changes was clearly shown.

    Keywords:SPAC; soil surface energy balance; Norwayspruce; canopy; LAI; climate; nitrogen; CoupModel

  • 13.
    Svensson, Magnus
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Berggren Kleja, Dan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Modelling soil C sequestration in spruce forest ecosystems along a Swedish transect based on current conditions2008Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 89, nr 1, s. 95-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The change of current pools of soil C in Norway spruce ecosystems in Sweden were studied using a process-based model (CoupModel). Simulations were conducted for four sites representing different regions covering most of the forested area in Sweden and representing annual mean temperatures from 0.7 degrees C to 7.1 degrees C. The development of both tree layer and field layer (understory) was simulated during a 100-year period using data on standing stock volumes from the Swedish Forest Inventory to calibrate tree growth using different assumptions regarding N supply to the plants. The model successfully described the general patterns of forest stand dynamics along the Swedish climatic transect, with decreasing tree growth rates and increasing field layer biomass from south to north. However, the current tree growth pattern for the northern parts of Sweden could not be explained without organic N uptake and/or enhanced mineralisation rates compared to the southern parts. Depending on the assumption made regarding N supply to the tree, different soil C sequestration rates were obtained. The approach to supply trees with both mineralised N and organic N, keeping the soil C:N ratio constant during the simulation period was found to be the most realistic alternative. With this approach the soils in the northern region of Sweden lost 5 g C m(-2) year(-1), the soils in the central region lost 2 g C m(-2) year(-1), and the soils in the two southern regions sequestered 9 and 23 g C m(-2) year(-1), respectively. In addition to climatic effects, the feedback between C and N turnover plays an important role that needs to be more clearly understood to improve estimates of C sequestration in boreal forest ecosystems.

  • 14.
    Svensson, Magnus
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Berggren Kleja, Dan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Langvall, Ola
    Lindroth, Anders
    Bayesian calibration of a model describing carbon, water and heat fluxes for a Swedish boreal forest stand.2008Ingår i: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 213, nr 3-4, s. 331-344Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This study quantified major fluxes of carbon (C), heat and water, including uncertainty estimates, in a boreal forest in northern Sweden, using a process-based model (Coup-Model) and Bayesian calibration methodology. Coupled C, water and heat fluxes were described together with estimated uncertainties for all major components of the simulated C budget. Simulated mean gross primary production was 641 +/- 74 gC m(-2) yr(-1), total ecosystem respiration 570 +/- 55 gC m(-2)yr(-1) and net ecosystem productivity 71 +/- 37gCm(-2)yr(-1). Most high-resolution measurements were well described but some interesting exceptions arose between model and measurements, e.g. latent heat flux was overestimated and field layer (understory) root litter production underestimated. Bayesian calibration reduced the assumed prior parameter ranges in 30 of 33 parameters, thus reducing the uncertainty in the estimates. There was a high degree of couplings between different sub-models and processes in the model, highlighting the importance of considering parameters not as singularities but in clusters

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