| 1. |
- Akselsson, Cecilia, et al.
(författare)
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Weathering rates in Swedish forest soils
- 2019
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 16:22, s. 4429-4450
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Forskningsöversikt (refereegranskat)abstract
- 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.
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| 2. |
- Erlandsson Lampa, Martin, et al.
(författare)
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Catchment export of base cations : improved mineral dissolution kinetics influence the role of water transit time
- 2020
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Ingår i: SOIL. - : Copernicus GmbH. - 2199-3971 .- 2199-398X. ; 6:1, s. 231-244
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Tidskriftsartikel (refereegranskat)abstract
- Soil mineral weathering is one of the major sources of base cations (BC), which play a dual role in forest ecosystems: they function as plant nutrients and buffer against the acidification of catchment runoff. On a long-term basis, soil weathering rates determine the highest sustainable forest productivity that does not cause acidification. It is believed that the hydrologic residence time plays a key role in determining the weathering rates at the landscape scale. The PROFILE weathering model has been used for almost 30 years to calculate weathering rates in the rooting zone of forest soils. However, the mineral dissolution equations in PROFILE are not adapted for the saturated zone, and employing these equations at the catchment scale results in a significant overprediction of base cation release rates to surface waters. In this study, we use a revised set of PROFILE equations which, among other features, include retardation due to silica concentrations. Relationships between the water transit time (WTT) and soil water concentrations were derived for each base cation, by simulating the soil water chemistry along a one-dimensional flow path, using the mineralogy from a glacial till soil. We show how the revised PROFILE equations are able to reproduce patterns in BC and silica concentrations as well as BC ratios (Ca2+/BC, Mg2+/BC and Na+/BC) that are observed in the soil water profiles and catchment runoff. In contrast to the original set of PROFILE equations, the revised set of equations could reproduce the fact that increasing WTT led to a decreasing Na+/BC ratio and increasing Ca2+/BC and Mg2+/BC ratios. Furthermore, the total release of base cations from a hillslope was calculated using a mixing model, where water with different WTTs was mixed according to an externally modeled WTT distribution. The revised set of equations gave a 50% lower base cation release (0.23 eqm 2 yr 1) than the original PROFILE equations and are in better agreement with mass balance calculations of weathering rates. Thus, the results from this study demonstrate that the revised mineral dissolution equations for PROFILE are a major step forward in modeling weathering rates at the catchment scale.
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| 3. |
- Erlandsson Lampa, Martin, et al.
(författare)
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Effects of whole-tree harvesting on soil, soil water and tree growth - A dynamic modelling exercise in four long-term experiments
- 2019
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 414
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Zanchi, Giuliana, et al.
(författare)
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Modelling the effects of forest management intensification on base cation concentrations in soil water and on tree growth in spruce forests in Sweden
- 2021
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Ingår i: European Journal of Forest Research. - : Springer Science and Business Media LLC. - 1612-4669 .- 1612-4677.
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Tidskriftsartikel (refereegranskat)abstract
- The study investigated the effects of forest residue extraction on tree growth and base cations concentrations in soil waterunder different climatic conditions in Sweden. For this purpose, the dynamic model ForSAFE was used to compare theeffects of whole-tree harvesting and stem harvesting on tree biomass and the soil solution over time at 6 different forestsites. The study confirmed the results from experimental sites showing a temporary reduction of base cation concentrationin the soil solution for a period of 20–30 years after whole-tree harvesting. The model showed that this was mainly causedby the reduced inputs of organic material after residue extraction and thereby reduced nutrient mineralisation in the soil. Themodel results also showed that whole-tree harvesting can affect tree growth at nitrogen-poor forest sites, such as the ones innorthern Sweden, due to the decrease of nitrogen availability after residue removal. Possible ways of reducing this impactcould be to compensate the losses with fertilisation or extract residue without foliage in areas of Sweden with low nitrogendeposition. The study highlighted the need to better understand the medium- and long-term effects of whole-tree harvestingon tree growth, since the results suggested that reduced tree growth after whole-tree harvesting could be only temporary.However, these results do not account for prolonged extraction of forest residues that could progressively deplete nutrientpools and lead to permanent effects on tree growth.
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