Qwarts - Quantifying Weathering Rates for Sustainable Forestry

Last changed: 04 May 2021
Rain drops on a water surface. Photo.



The project 'Qwarts - Quantifying Weathering Rates for Sustainable Forestry' started in 2012 and finished 2019.

No industrial country has greater hopes than Sweden for forestry's role in its energy future. But official national calculations indicate that the supply of weathering products (e.g. Ca, Mg) is not sufficient to sustain current levels of forest harvest in large areas of the country. This deficit in weathering is of great concern for the supply of both nutrients to the trees and alkalinity to aquatic ecosystems. Compensation for what weathering does not provide might be possible by spreading ash on the soil, but there are major question marks about the feasibility of this.

The processes most in need of improvement in weathering models include quantification of biological influences, aluminium chemistry, and the role of climate. The development of weathering models will occur through the confrontation of models with data from the scales of laboratory, plot and catchment studies to improve the representation of key processes, and then apply the improved models to management scale estimates of the weathering needed to sustain forestry.

The goals of this research consortium were to use that expertise to:

  1. Provide state-of-the-art estimates of weathering at the spatial and temporal scales relevant to sustainable forest management with explicit representation of uncertainty
  2. Predict how changes in climate and forest management affect weathering rates and thus the need for compensation (liming/ash/fertilizers)

The project was financed by FORMAS and had a total budget of 24 MSEK. Out of this, SLU got 10 MSEK.

Participating from the Department were among others Kevin Bishop, Stephan Köhler och Salar Valinia.

External partners were among others Uppsala University, The Royal Institute of Technology (KTH) and Lund University.


QWARTS project and working package leaders


Members of the QWARTS roster in August 2013 with name, work package (WP), position and affiliation:

  • Håkan Wallander, WP A, Professor, Lund University
  • Roger Finlay, WP A, Professor, SLU
  • Shahid Mahmood, WP A, PhD, SLU
  • Zaenab Fahad, WP A, PhD Student, SLU
  • Ingrid Öborn, WP B, Professor, SLU
  • Bengt Olsson, WP B, PhD, SLU
  • Magnus Simonsson, WP , PhD, SLU
  • Sophie Castenou, WP B, PhD Student, SLU
  • Johan Iwald, WP B, PhD Student, SLU
  • Johan Stendahl, WP B, Assoc. , SLU
  • Stephen Köhler, WP C, Professor, Uppsala University
  • Jan Seibert, WP C, Professor, Uppsala University
  • Keith Beven, WP C, Professor, Uppsala University
  • Emil Boulou Bi, WP C, PhD, Uppsala University
  • Martin Erlandsson, WP E, PhD, Uppsala University
  • Nino Amvrosiadi, WP C, PhD Student, Uppsala University
  • Harald Sverdrup, WP D, Professor, Lund University
  • Jon-Petter Gustafsson, WP D, Professor, SLU
  • Nick Rosenstock, WP D, PhD, Lund University
  • Salim Belyazid, WP D, PhD, Lund University
  • Veronika Kronnäs, WP D, PhD Student, Lund University
  • Kevin Bishop, WP E, Professor, Uppsala University
  • Cecilia Akselsson, WP E, Assoc. , Lund University
  • Lars Högbom, WP E, Assoc. , Skogforsk
  • Riitta Hyvönen, WP E, Docent, SLU

Work packages and organisation

The project was built upon the expertise from five departments at three universities. There were eleven original applicants, organized into five work packages (WP). The project is led by the QWARTS Council chaired by the project leaders with representatives from each of the work packages, the chair of the scientific reference and sector liaison committees. Three of the WPs are focusing on specific questions at specific scales. One scales is that of controlled microcosms where the influence of biological feedbacks is a central issue. The next scale is the plot, from detailed long-term studies of different climatic and silvicultural treatments to the thousands of plots visited three times over three decades within the Swedish Forest Soil Inventory. The third scale of study is the headwater catchment, since depleting the store of weathering products in soils will move the acidification “frontier” downstream, further compromising aquatic habitats still recovering from decades of acid deposition that was only controlled in the 1990s.

The fourth WP integrates the insights from each scale of investigation in a unified modeling platform where different conceptualizations can be tested against data. Finally the operationalization WP will take the results to the regional scale where key land management decisions are taken. Throughout all of these work packages, explicit consideration of uncertainty is emphasized, since this been highlighted as a major barrier to defining the sustainability of weathering.

To facilitate the integration of the work packages into a better estimate of weathering than each can achieve individually, funds were reserved for a dedicated “coordinator”. The international experts from the scientific reference committee and the national stakeholders on the sector liaison committee have also been charged with encouraging the project to capitalize on the diversity of approaches being undertaken simultaneously to constrain the estimate of weathering products supplied to trees and aquatic ecosystems.

Work packages A-E

WP A - Laboratory Scale–Quantification of biotic influence


Laboratory (Rosling et al. 2004) and field (Lindahl et al. 2007) experiments conducted in Uppsala and Lund during the last 20 years, strongly suggest that interactions between microorganisms, in particular symbiotic ectomycorrhizal fungi, and minerals take place in forest ecosystems (see Finlay et al. 2009). Indeed, fungal–mineral attachment, biomechanical forcing, and altered interlayer spacing associated with depletion of potassium from biotite by a mycorrhizal fungus has recently been demonstrated (Bonnevilleet al., 2009). However there is still uncertainty about the quantitative significance and how they are regulated (Brantley et al. 2011). Advances in the measurement of surfaces and genomes both open up possibilities for quantifying biological influences, and the environmental controls.


Biological weathering by symbiotic fungi and associated bacteria make a significant contribution to the mineral requirements of forest trees. This biological weathering is regulated by plants in response to changes in environmental conditions.

Research questions:

  1. Quantification of etching through mycorrhizal hyphal contact with different minerals – calculation of mineral volumes solubilized through close contact with hyphae. Scaling up these measurements requires better estimates of mineral-fungal contact area.
  2. Quantification of elements released from different minerals in intact microcosms and the effects of environmental perturbations (regulation), and the effects of changed nutrient regimes and hyphal disruption on rates of mineral release.
  3. Distribution, identity and activity of fungal communities in vertically stratified soil systems (lab and field) will be investigated using metagenomic and metatranscriptomic methods in conjunction with ongoing European and US collaborative projects.

Contact information

Working package A, Professor Roger Finlay

WP B. Plot scale variability in response to mineralogy, vegetation and climate


There is a strong need to validate model estimates over decades against datafrom intensively studied forest ecosystems, at sites with contrasting geological background and in different stand types. Weathering rates can be quantified indirectly from nutrient fluxesin deposition, leaching and biomass accumulation as exemplified by our earlier work on theSkogaby forest fertilization experiment (Simonsson et al in prep), and agricultural soils whereweathering rates are higher (Simonsson et al 2007; Öborn et al 2010). Key processes toinclude are plant uptake, organic matter turnover, Al3+ in soil solution and solubility ofsecondary minerals. Long-term experiments and monitoring will be exploited for this inconcert with determination of quantitative mineralogy and specific surface area. A specialfocus will be on quantifying the uncertainties in the estimated weathering rates (Holmqvist etal, 2003; Yani et al, 2010).


Mass balances over 20-50 years at sites with different mineralogy, climate, management and deposition will challenge and improve the formulation of processes, and help quantify uncertainty in weathering estimates. Quantitative mineralogy and specificsurface area constrain weathering rate estimates.

Research questions:

  1. Utilize differences in geological parent material, stand type, management, depositionhistory, climate, nutrition and acidification status to assess relative weathering rates frommass budgets, and the influences of the different factors on these rates.
  2. Contrast purely chemical models (assuming certain bulk- and/or rhizosphere soil chemicalconditions), with models including dynamic biological control.
  3. Exploit spatial variability in soil weathering between plots to extrapolate such variationbetween stands at regional scales.
  4. Quantify uncertainty in the weathering at the plot scale for estimating uncertainty atregional scales.

Contact Information

Working package B, Professor Ingrid Öborn & Johan Stendahl

WP C. Catchment Weathering for Surface Waters


National weathering estimates for surface water critical loads are based on the MAGIC model which relies solely on mass balances for calibration. No weathering processes are included in the model that could make use of data on soil, mineralogy or texture etc. To improve on this and apply actual soil weathering models such as the ForSAFE platform to catchments, the hydrology needs defined. Addressing this challenge will make better use of biogeochemical process-knowledge and soils data, together with long-term mass balances to predict weathering appropriate to surface waters.


  1. Geochemical weathering models that utilize soils data will provide more robust weathering estimates for surface waters than mass-balance only approaches.
  2. Decadal observations of elemental stoichiometry in catchment outputs and the evolution of water chemistry along hillslopes can constrain catchment scale weathering models.
  3. New geochemical tools such as the use of multiple isotopes (44Ca, 30Si, 11B, 26Mg, 7Li) will allow tracing of both biological activity and different mineral sources and sinks.
  4. Surface waters receive more weathering products than trees, but there are strong differences between catchments which can be predicted from map data.

Research questions:

  1. Integrate the ForSAFE modeling platform with catchment hydrology to predict the amount of weathering products delivered to surface waters in runoff.
  2. Define the contribution of weathering to surface waters that is not captured by plot scale conceptualizations, both at depth blow roots and laterally along the catena.
  3. Generalize the hydrology of catchments and the differences in weathering from map
    information include soils type, geochemistry and topography.
  4. Investigate how spatial variation of weathering rates within catchments at the plot scale influences the aggregate catchment weathering seen in runoff.
  5. Use catchment mass balances, supported by hillslope observations and ratios of both elements and isotopes to constrain model process representation.

Contact Information

Working package C, Dr Stephan Kohler and Professor Keith Beven

WP D. Cross-scale model development


The close interconnectedness between the biota, soil microorganisms, soil chemistry, hydrology and weathering requires integrated biogeochemical modeling to trace effects as well as feedbacks. In this work package, we will develop, test and revise modules that describe drivers for weathering (abiotic and biotic ecosystem factors including climate, soils, vegetation/deposition history and forest management). Implementing these models in the FORSAFE modeling platform (Wallman et al., 2005) will provide an ensemble of realizations that can be used in assessing the structural uncertainty in the models, in addition to the uncertainty in parameter calibration (Beven, 2009). The modules should also be possible to integrate in other weathering models, e.g. the WITCH model (Goddéris et al., 2006). Fundamentally, the dynamic process modules to be enhanced and/or developed should be able to contribute to the ForSAFE platforms ability to simulate biogeochemical processes at point, plot and catchment scales using data from WP A-C.


  1. Descriptions of abiotic factors that affect weathering (e.g. Al speciation, secondary
    minerals, pH, surface area, and hydrology) can be improved.
  2. Biotic processes, including soil microbial activity, have an important effect on weathering rates through their effect on important drivers such as pH and low-molecular-weight organic acids, as well as on the plant-water interface.
  3. Incorporation of hydrology with explicit predictions of vertical and lateral flow paths can scale dynamic biogeochemical models from plot to catchment.
  4. Scaling up plot-scale dynamic models while explicitly addressing internal catchment heterogeneity can link changes in surface water chemistry from the dynamic modeling of ecosystem responses to climate, atmospheric deposition and management.

Research questions:

  1. Do our models adequately reflect the importance of drivers affecting weathering rates,
    including soil temperature, moisture, pH, Al3+, secondary minerals, organic ligands and base cation concentrations, as reported from WP A-C?
  2. Do the models need to explicitly simulate the role of soil microorganisms on weathering rates, particularly in view of a changing climate and relatively elevated nitrogen deposition?
  3. What requirements does large-scale soil heterogeneity within catchments put on
    expanding the modeling from plot to the catchment level?
  4. How can we expand the modeling from the plot scale to catchments and further on to operational regional and national scale models with uncertainty estimates?

Contact Information

Working package D, Dr Salim Belyazid

WP E. Operational Modeling for Sustainable Management


[…] important for policy applications related to sustainable forest management (Akselsson et al., 2006a). When going from site-level to landscape-level, generalizations of some degree are required (Akselsson et al., 2006b). In this WP, we scale up from the improved weathering estimates for well characterized plots and catchments to national predictions using an appropriate ensemble of ForSAFE configurations to predict the variation in weathering rates on a landscape scale and identification of key parameters decisive for the uncertainties in the national estimates. Assessments of uncertainties caused by the up-scaling will be made using the methodologies developed in WP D. This upscaling will consider the influence of both climate and management on weathering rates over a forest rotation period. Different weathering estimates will be made for what is available to trees and what is provided to small lakes and streams that are most sensitive to acidification.

Research Questions:

  1. Identifying and reducing uncertainties in the national weathering assessments: We will use data from the field plots and catchments in WP B and C to analyze spatial variation in different scales, to identify critical input parameters decisive for the uncertainties in the modeled weathering rates and the combinations of process modules to implement in ForSAFE. Together with WP D we will analyze uncertainties on the well-investigated sites and quantify the effect of the uncertainties on the model results, both from parameter
  2. Modeling weathering rates for different forestry and climate scenarios: Weathering rates will be modelled on the 20,000 national forest inventory plots, using the updated ForSAFE platform with an ensemble of process modules and uncertainty estimates arrived at in WP A-C. The results will be compared with earlier PROFILE-based estimates and the implication for nutrient status and surface water chemistry will be investigated in conjunction with WP D. The comparison of model results with measurements of soil chemistry from the sites over three decades will help us evaluate the performance of the weathering predictions. Modelling will be performed for different forestry, climate and deposition scenarios as a basis for assessing the sustainability of different forest management strategies and the need for compensation measures such as forest-ash return and liming.

Contact Information

Working package E, Dr Cecilia Akselsson

Publications during 2012 and 2013 (partially)

QWARTS publications/manuscripts (QWARTS authors highlighted in bold), last updated 10 September 2013

Andrist-Rangel, Y., Simonsson, M., Öborn, I., Hillier, S. (2013) Acid-extractable potassium in agricultural soils: Source minerals assessed by differential and quantitative X-ray diffraction, Journal of Plant Nutrition and Soil Science, 176:407-419.

Berner, C., Johansson, T., Wallander H. (2012) Long-term effect of apatite on ectomycorrhizal growth and community structure. Mycorrhiza 22.8: 615-621.

Davies, J., Beven, K., Rodhe, A., Nyberg, L., Bishop, K. (in press) Integrated modelling of flow and residence times at the catchment scale with multiple interacting pathways. Water Resources Research.

Fahad Z, Mahmood S, Mikusinska A, Ekblad A, Fransson P, Lindahl B, Finlay RD. (201x) Decomposition of ectomycorrhizal mycelium in boreal podzol profiles: a stable isotope probing study. Manuscript.

Futter, M. N., Klaminder, J., Lucas, R.W., Laudon, H., Köhler, S.J. (2012) Uncertainty in silicate mineral weathering rate estimates: source partitioning and policy implications, Environmental Research Letters, 7:024025.

Gamfeldt, L., Snall, T., Bagchi, R., Jonsson, M., Gustafsson, L., Kjellander, P., Ruiz-Jaen, M.C., Froberg, M., Stendahl, J., Philipson, C.D., Mikusinski, G., Andersson, E., Westerlund, B., Andren, H., Moberg, F., Moen, J. and Bengtsson, J. (2013) Higher levels of multiple ecosystem services are found in forests with more tree species. Nat Commun 4, 1340.

Grabs, T., Bishop, K., Laudon, H., Lyon, S.W., Seibert, J. (2012) Riparian zone hydrology and soil water total organic carbon (TOC): implications for spatial variability and upscaling of lateral riparian TOC exports. Biogeosciences 9:3901-3916.

Iwald, J., Löfgren, S., Stendahl, J., E. Karltun (2013) Acidifying effect of removal of tree stumps and logging residues as compared to atmospheric deposition, Forest Ecology and Management, 290(0), 49-58.

Ledesma, J.L.J. Grabs, T., Futter, M.N., Bishop K., Laudon, H., Köhler, S. (2013) Riparian zone controls on base cation concentrations in boreal streams. Biogeosciences. 10:3849–3868, doi:10.5194/bg-10-3849-2013

Mahmood S, Ekblad A, Finlay RD. (201x) Molecular analysis of microbial communities colonising bedrock outcrops in a Swedish forest. ISME Journal

Mahmood S, Martins C, Olofsson M, Bylund D, Finlay, RD. (201x) Does nitrogen affect microbially mediated weathering of primary minerals? Global Change Biology

Mahmood S, Ekblad A, Prosser JI, Finlay RD.(201x) 13C-RNA stable isotope probing reveals patterns of carbon allocation to active microbial communities involved in weathering of minerals in forest soil. Environmental Microbiology / ISME Journal

Mahmood S, Fahad Z, Olofsson M, Bylund D, Finlay RD. (201x) Stable isotope probing analysis of ‘active’ ectomycorrhizal mycelial networks and associated bacterial communities involved in granite weathering under N deposition. ISME Journal / Environmental Microbiology

Mahmood S, Fahad Z, Mikusinska A, Ekblad A, Fransson P, Lindal B, Finlay RD. (201x)R NA stable isotope probing analysis of active microbial communities involved in degradation of ectomycorrhizal mycelium in pine and spruce forest soils. Manuscript

Mahmood S, Jernberg J, Finlay RD. (201x) "Differential response of podzol profile microbial communities to nitrogen addition" or " Microbial communities of boreal podzol horizons respond differently to nitrogen addition". ISME Journal / Environmental Microbiology

Mahmood S, Ekblad A, Finlay RD. (2010) Does nitrogen affect allocation patterns of photosynthetically fixed carbon to different microbial communities in boreal podzol profiles? ISME Journal / Environmental Microbiology

Oni, S. K., Futter, M.N., Bishop, K., Köhler, S. J., Ottosson-Löfvenius, M., Laudon, H. (2013) Long-term patterns in dissolved organic carbon, major elements and trace metals in boreal headwater catchments: trends, mechanisms and heterogeneity, Biogeosciences 10.2315-2330, doi:10.5194/bg-10-2315-2013.

Ortiz, C. A., Liski, J., Gärdenäs, A.I., Lehtonen, A., Lundblad, M., Stendahl, J, Ågren, G.I., Karltun, E. (2013), Soil organic carbon stock changes in Swedish forest soils—A comparison of uncertainties and their sources through a national inventory and two simulation models, Ecological Modelling, 251:221-231.

Schelker, J., Eklöf, K., Bishop, K., Laudon, H. (2012) Effects of Forestry Operations on Dissolved Organic Carbon (DOC) Concentrations and Export in Boreal First-Order Streams. JGR-Biogeosciences 117

Stendahl, J., Akselsson, C., Melkerud, P.-A., S. Belyazid, S. (2013), Pedon-scale silicate weathering: comparison of the PROFILE model and the depletion method at 16 forest sites in Sweden, Geoderma, 211–212: 65-74.

Sverdrup, H., McDonnell, T., Sullivan, T., Nihlgård, B., Belyazid, S., Rihm, B., Porter, E., Bowman, W., Geiser, L., (2012), Testing the Feasibility of Using the ForSAFE-VEG Model to Map the Critical Load of Nitrogen to Protect Plant Biodiversity in the Rocky Mountains Region, USA, Water Air Soil Pollut, 223: 371-387.

Zetterberg, T., Olsson, B.A., Löfgren, S., von Brömssen, C., Brandtberg, P.-O. (2013) The effect of harvest intensity on long-term calcium dynamics in soil and soil solution at three coniferous sites in Sweden, Forest Ecology and Management, 302: 280-294.