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  • 1.
    Hansen, Karin
    IVL Svenska Miljöinstitutet.
    Calcium in decomposing foliar litter - A synthesis for boreal and temperate coniferous forests2017Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, nr 403, s. 137–144-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have synthesized available data for calcium (Ca) dynamics in decomposing foliar litter of mainly pine (Pinus), spruce (Picea), and birch (Betula) species to determine patterns of Ca concentration with climate in newly shed litter and its dynamics in decomposing litter as well as a possible role for Ca as regards limit values. Initial Ca concentration was negatively related to mean annual precipitation (MAP) with different relationships among genera. A limited data set showed a positive relationship across species (p < 0.05) to extractable Ca in soil. In paired stands, litter of both Norway spruce (Picea abies) and lodgepole pine (Pinus contorta) had higher Ca concentrations than Scots pine (Pinus silvestris), Norway spruce litter even twice as high. Relationships between initial concentrations of Ca and those of other nutrients appeared to be dominated by the positive ones to potassium (K) and magnesium (Mg) and specifically for deciduous litter there was a negative relationship to nitrogen (N).

    In decomposing litter, Ca concentration followed a negative quadratic (Ca =a + t−t2) function and had a maximum, which was variable. The Ca maximum concentration during decomposition was positively related to initial Ca concentration both within and among species. Separate linear relationships based on species were combined into one, in common for all investigated species and genera (R2 =0.914, n= 63, p < 0.001).

    Limit values for decomposition were positively related to maximum Ca concentration at p < 0.05 with separate functions for pine and spruce litter. Calcium net release started directly after the incubation and was linear to accumulated mass loss of litter, giving a slope coefficient for each study. The net release rates were linear to initial Ca concentration both within and across species/genera. All studies combined gave a negative linear relationship (R2=0.894, n= 67, p < 0.001).

  • 2.
    Hansson, Julia
    IVL Svenska Miljöinstitutet.
    Future demand for forest-based biomass for energy purposes in Sweden2017Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 383, s. 17-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The assessment is based on a review of scenarios and predictions of how the Swedish energy system may develop, taking into account techno-economical conditions. It includes potential changes in district heating, electricity production in combined heat and power plants, industrial process energy, and production of biofuel for road transportation. In addition, the potential demand for forest-based feedstock in the chemical and petrochemical sector, replacing current use of fossil feedstock, is analysed. The assessment suggests that Sweden may see an additional demand for forest fuels at about 30 TW h in 2030 and 35–40 TW h in 2050.

    This can be compared with the current use of biomass for energy in Sweden at 130 TW h per year, and the estimated potential increase of sustainable harvest of logging residues (slash and stumps) at some additional 20 TW h per year, based on current conditions. If also potential demand for forest-based feedstock in the chemical and petrochemical industry is included, another 10–15 and 25–30 TW h of biomass per year may be needed in 2030 and 2050, respectively. The future demand is sensitive to the pace and magnitude of energy efficiency improvements and electrification in the various sectors. If far-reaching energy efficiency improvements and electrification are realised, the total additional demand for biomass as energy and industry feedstock may be about 20 and 30 TW h per year in 2030 and 2050, respectively, thus roughly corresponding to the sustainable harvests of logging residues. If, however, efficiency improvements and electrification are only marginal, then the additional demand for biomass as industry and energy feedstock may reach 70 TW h and 100 TW h per year in 2030 and 2050, respectively.

    In these cases, the use of logging residues will not suffice and additional biomass would be needed. A combination of regulations and incentives is recommended to accelerate the fuel and feedstock switch, especially in the transportation and industrial sectors, and incentives promoting a substantial improvement in energy efficiency and electrification in all sectors.

  • 3.
    Hansson, Julia
    IVL Svenska Miljöinstitutet.
    The potential role of forest management in Swedish scenarios towards climate neutrality by mid century2017Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 383, s. 73-84Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Swedish climate policy targets net zero greenhouse gases (GHG) by mid-century, with road transport independent of fossil fuels by 2030, requiring far-reaching changes in the way energy is used. Forest management is expected to support carbon sequestration and provide biomass for various uses, including energy.

    In this paper, we combine two energy scenarios with four forest scenarios and quantify GHG balances associated with energy-use for heat, electricity, and road transport, and with forest management and production, use, and end-of-life management of various forest products, including products for export. The aggregated GHG balances are evaluated in relation to the 2-degree target and an allocated Swedish CO2 budget. The production of biofuels in the agriculture sector is considered but not analyzed in detail.

    The results suggest that Swedish forestry can make an important contribution by supplying forest fuels and other products while maintaining or enhancing carbon storage in vegetation, soils, and forest products. The GHG neutrality goal is not met in any of the scenarios without factoring in carbon sequestration. Measures to enhance forest productivity can increase output of forest products (including biofuels for export) and also enhance carbon sequestration. The Swedish forest sector can let Sweden reach net negative emissions, and avoid “using up” its allocated CO2 budget, thereby increasing the associated emissions space for the rest of the world.

  • 4.
    Hellsten, Sofie
    IVL Svenska Miljöinstitutet.
    Stump harvesting in Picea abies stands: Soil surface disturbance and biomass distribution of the harvested stumps and roots2018Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 425, s. 27-34Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Finland has a long tradition of utilizing forest-based biomass for energy and industry purposes and the use has steadily increased in the past decade due to changes in international and regional energy policies. Intensive harvesting practices, in which a larger proportion of the woody biomass is removed from the forest stand, are becoming more common.

    The objectives of this study were to evaluate the spatial and temporal extent of soil surface disturbance caused by stump-root system harvesting and to quantify how much biomass and nitrogen is removed from the stand in stump and coarse root harvesting. The extent of surface disturbance was assessed in three clear-cut Norway spruce stands in southern and central Finland, differing in time since harvest. To determine the biomass distribution of the stump-root system, stumps and coarse roots were excavated at one of the experimental stands.

    Across all age classes (time since harvest) less soil surface had remained undisturbed at the stump harvesting sites (52%) than at the sites where only mechanical site preparation (28%) had been carried out. Thus, the findings of this study indicate that soil disturbance caused by stump harvesting can exist on forest soil surface for more than a decade following harvest. The total biomass of the stump-root system in the stand was estimated to 39.3 Mg ha−1 and 79% of this biomass was removed during stump harvesting and consequently, 8.3 Mg ha−1 of stump-root biomass remained in soil. The stump-root system accounted for 17% of the whole-tree biomass, and coarse roots and fine coarse roots represented a significant portion of it (73%). Thus, the stump-root system represents a large biomass component in boreal forest stands. However, forest management utilizing stumps may result in carbon losses from the stand. Download the article here: https://www.sciencedirect.com/science/article/pii/S0378112718304432

  • 5.
    Karlsson, Per Erik
    et al.
    IVL Svenska Miljöinstitutet.
    Etzold, Sophia
    Ferretti, Marco
    Jan Reinds, Gert
    Solberg, Svein
    Gessler, Arthur
    Waldner, Peter
    Schaub, Marcus
    Simpson, David
    Benham, Sue
    Hansen, Karin
    Ingerslev, Morten
    Jonard, Mathieu
    Lindroos, Antti-Jussi
    Marchetto, Aldo
    Manninger, Miklos
    Meesenburg, Hennin
    Merilä, Päivi
    Nöjd, Pekka
    Rautio, Pasi
    GM Sanders, Tanja
    Seidling, Walter
    Skudnik, Mitja
    Thimonier, Anne
    Verstraeten, Arne
    Nitrogen deposition is the most important environmental driver of growth of pure, even-aged and managed European forests.2020Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 458, artikkel-id 117762Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 6.
    Mattsson, Eskil
    et al.
    IVL Svenska Miljöinstitutet.
    Arshad, Ali
    Nissanka, S.P
    Wang, Li-Qiu
    Topmost trees and foremost species underlie tropical forest structure, diversity and biomass through opposing mechanisms2020Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 473, artikkel-id 118299Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tropical forests play a main role in the global carbon cycle due to their higher exchange capacity of carbon dioxide with the atmosphere than any other forest type on the Earth. In this study, we aimed to explore the relative importance of foremost species and topmost trees in shaping forest structure, diversity and biomass in natural tropical forests. We hypothesized that topmost trees promote but foremost species decline tropical forest structure, diversity and biomass in a changing environment (i.e. the ‘tree overtopping hypothesis’). We formulated three questions to address the proposed hypothesis: (1) Are forest structure, diversity and biomass affected by both foremost species and topmost trees, and what is the magnitude and direction of each relative effect? (2) Are foremost species and topmost trees influenced similarly by multiple environmental factors? (3) How do foremost species and topmost trees mediate the feedbacks of forest structure, diversity and biomass to environmental factors? Using 189 plots data from Sri Lanka, we quantified 16 environmental (9 climate and 7 soil) factors, two indices of the topmost trees (i.e. top 1% large-diameter, and tall-stature) and their combination, four indices of foremost species (i.e. top 1% species' importance value index or each of its three components including either relative basal area, relative frequency or relative density), rarefied species richness, and stand density. We used structural equation modeling to test the proposed hypothesis. Strong positive effects of topmost trees whereas negative to negligible positive effects of foremost species shaped tropical forest structure, diversity and biomass through opposing mechanisms, i.e., the promoting part of big trees and suppressing part of dominant species, respectively. Moreover, forest structure promoted biomass directly and indirectly via forest diversity. Environmental factors (i.e. high climatic water and low soil fertility) increased forest structure, diversity and biomass indirectly via topmost trees but decreased via foremost species. The main novelty or contribution of this study determines that the adverse effects of few foremost (i.e. dominant or abundant) species shaped forest structure, diversity and biomass in tropical forests when simultaneously considered the positive effects of topmost trees. Hence, encouraging topmost trees while managing foremost species might necessarily increase complementarity resource-use within a forest community, leading to positive forest diversity – structure – biomass relationships. We argue that both topmost trees and foremost species might have important influences on forest carbon stock in the context of global climate change.

  • 7.
    Pihl-Karlsson, Gunilla
    et al.
    IVL Svenska Miljöinstitutet.
    Hellsten, Sofie
    IVL Svenska Miljöinstitutet.
    Karlsson, Per Erik
    IVL Svenska Miljöinstitutet.
    A bark beetle attack caused elevated nitrate concentrations and acidification of soil water in a Norway spruce stand2018Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, nr 422, s. 338-344Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A bark beetle attack in a Norway spruce forest in southwestern Sweden killed most trees, which however mostly remained standing, and caused elevated nitrate concentrations and subsequent acidification in the soil water. Long-term monitoring showed very low nitrate concentrations in the soil water before the bark beetle attack.

    High nitrate concentrations remained throughout five years after the initiation of the bark beetle attack until the monitoring was terminated. The increased nitrate concentrations in the soil water were accompanied by a decrease in both pH and the acid neutralizing capacity, ANC. The significance for future nitrogen and acidity leakage to ground- and surface waters is discussed in relation to the expected future increase in the frequencies of bark beetle attacks in boreal and northern temperate forests.

  • 8.
    Sahlén Zetterberg, Therese
    IVL Svenska Miljöinstitutet.
    Impact of whole-tree harvest on soil and stream water acidity in southern Sweden based on HD-MINTEQ simulations and pH-sensitivity2016Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The shift in major drivers of acidification from sulfur deposition to biological acidification has put the focus on the impact of biomass harvest for bioenergy on the acid base status of forests soils and surface waters. This paper presents a model-based assessment in which the impact of whole-tree harvest (WTH) is compared with that of no harvest at two different sulfur deposition levels by use of the HD-MINTEQ model. Additionally, the pH-sensitivity of 179 randomly selected boreal headwater streams was assessed. The results indicate that the exchangeable Ca2+ pool in humus and mineral soils (⩽B-horizon) is most affected by harvest. Concerning the pH, the WTH impact is restricted to shallow soils and for a much shorter period of time. The impact of WTH on the soil solution was primarily restricted to the recharge area and much less pronounced in the discharge area.

    Due to high buffering capacity of riparian soils and low pH-sensitivity of many headwater streams, the pH effects of WTH on surface waters will most probably be small, at least over a rotation period of several decades. Over time perspectives of multiple rotations, the pH effects are more uncertain due to a possible slow successive protonation of organic matter in the riparian zone. Another important aspect is the currently restricted availability of mobile anion charge balancing the acidity produced by tree growth. Therefore, the acidity is to a large extent arrested in the soil. At the current low S deposition levels, southwestern Sweden seems to be the least vulnerable region to further acid input due to high buffer capacity at low pH. The streams in central and northern Sweden are much more pH-sensitive, but restricted availability of mobile strong acid anions and large buffer capacity in the soils make them less vulnerable to WTH. The partly diverging results between experimental and model studies indicate that one or more processes (hydrological, chemical or biological) are not fully understood or that available data are lacking for a proper parameterization.

    Thus, the results from long-term WTH experiments are very important for understanding the processes involved as well as for improving and validating model predictions. We therefore encourage societal support of maintaining monitoring and research coupled to such experiments. For the future and for improving our current understanding of biogeochemical dynamics in forest ecosystems subjected to active forestry as well as for policy and management purposes, a mixture of experiments and models ought to be used.

  • 9.
    Sahlén Zetterberg, Therese
    IVL Svenska Miljöinstitutet.
    Long-term soil calcium depletion after conventional and whole-tree harvest2016Inngår i: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 369Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Whole-tree harvest (WTH) may compromise tree productivity and health and lead to soil and surface water acidification. The aim of this study was to assess the long-term change (up to circa 40 years) in soil exchangeable calcium (Ca2+) pools following conventional (CH) and WTH at three Swedish coniferous sites. A second aim was to evaluate how well the results could be reproduced by the dynamic model MAGIC (Model of Acidification of Groundwater in Catchments). Soil Ca2+ pools (down to 20 cm) decreased at all three sites from stand age 15–16 to 37–38 years. The depletion ranged from 2.6 to 8.6 kEq ha−1 (26.5–52.7%) and 0.2 to 5.0 kEq ha−1 (2.3–49.1%) in the CH and WTH treatment, respectively.

    The presence of an interaction effect indicated that the main effect of time was not statistically significant at all three sites. Over the course of time, soil Ca2+ pools have also become more similar between the CH and WTH treatments, but the Ca2+ pools were still significantly lower (p < 0.05) after WTH at stand age 37–38 years. The measured declines in Ca2+ pools were generally greater than what has been found in other studies and were largely explained by high soil Ca2+ availability and high tree Ca2+ uptake, especially in the CH-plots, as indicated by the MAGIC mass balance budgets. Model simulations by MAGIC partly agreed with the measured data. However, the model exaggerated the soil Ca2+ losses between 1990 and 2013 (CH = 3.6–9.9 kEq ha−1; WTH = 3.0–8.3 kEq ha−1), especially at the spruce sites.

    Furthermore, MAGIC could not reproduce the rapid diminishing differences between CH and WTH. Uncertainties in model parameters, underestimated soil Ca2+ pools or biological feed-back mechanisms could explain this discrepancy. Until these have been resolved, interpretations of Ca2+ changes related to CH or WTH using dynamic modelling or mass balance budget calculations should be done with caution

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