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  • 1. Christiansen, J. R.
    et al.
    Elberling, B.
    Jansson, Per-Erik.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Modelling water balance and nitrate leaching in temperate Norway spruce and beech forests located on the same soil type with the CoupModel2006In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 237, no 03-jan, p. 545-556Article in journal (Refereed)
    Abstract [en]

    Two contrasting forest ecosystems located in close proximity to each other were selected for evaluating the importance of tree species and afforestation in relation to the water balance and the quality of the water leaving the forest root zone. Measurements included soil water content and the collection of precipitation, canopy throughfall, stem flow and soil solution on a weekly basis during 15 months (1999-2000). Soil solutions were extracted using suction probes installed at all major horizons within the upper 120 cm of a Norway spruce (N. spruce) stand (Picea Abies [L.] Karst.) and a European beech stand (Fagus Sylvatica L.) located on the same soil type. Soil solutions were analyzed for the content of all major ions, including nitrate. A water balance model (CoupModel) was used to estimate percolation rates beneath the root zone. Percolation at the beech stand was 292 mm and only 41 rnm at the N. spruce stand mainly due to differences in the interception loss. The highest annual leaching of Mg, K, Na, Al, Cl, SO4-S was noted in the N. spruce stand while leaching of NO3-N was highest in the beech stand, corresponding to 39 kg ha(-1) year(-1). By contrast, the annual leaching of NO3-N in the N. spruce stand was only 0.5 kg ha(-1) year(-1). The larger amount of NO3-N was leaving the beech forest soil despite the fact that the N. spruce stand had the highest atmospheric N-deposition. Thus, differences in NO3-N leaching between the stands must be related to differences in uptake and accumulation of N in the vegetation and within the upper 120 cm of the soil. Differences in the water balance and NO3-N leaching between beech and N. spruce stands call for further attention to the selection of tree-species on a soil type basis when planning future afforestation projects, particularly when such projects aim to improve the quality of water infiltrating to the groundwater zone.

  • 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 harvests2013In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 290, p. 67-78Article in journal (Refereed)
    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. Engelmark, O.
    et al.
    Sjoberg, K.
    Andersson, B.
    Rosvall, O.
    Agren, G. I.
    Baker, W. L.
    Barklund, P.
    Bjorkman, C.
    Despain, D. G.
    Elfving, B.
    Ennos, R. A.
    Karlman, M.
    Knecht, M. F.
    Knight, D. H.
    Ledgard, N. J.
    Lindelow, A.
    Nilsson, C.
    Peterken, G. F.
    Sörlin, Sverker
    Sykes, M. T.
    Ecological effects and management aspects of an exotic tree species: the case of lodgepole pine in Sweden2001In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 141, no 02-jan, p. 3-13Article in journal (Refereed)
    Abstract [en]

    The North American tree Pinus contorta var, latifolia was experimentally introduced in Sweden already in the 1920s, and has been used in Swedish forestry on a large scale since the 1970s. These plantations now cover 565,000 ha, mainly in the northern area. In this paper we summarize and discuss existing ecological knowledge of this species introduction. With regard to longterm sustainability we suggest management means to minimize harmful effects of the introduction on ecosystems. These include aspects of self dispersal, pests, ecosystem and landscape structures, and also ecological processes and biodiversity. We also focus on observed and possible interactions in the ecosystems. As Pinus contorta seeds are disseminated and trees regenerated outside initial plantations, this may have future bearings on biodiversity. We suggest a strategy which takes account of the uncertainty in predicting future ecological effects. The strategy includes areal restrictions and zones without Pinus contorta, but also to set up a monitoring program. Observations of adverse effects from the plantations would then give the possibility to adjust P. contorta management.

  • 4.
    Jacks, Gunnar
    et al.
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Norrström, Ann-Catrine
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Hydrochemistry and hydrology of forest riparian wetlands2004In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 196, no 03-feb, p. 187-197Article in journal (Refereed)
    Abstract [en]

    Forest stream riparian wetlands have a number of important features. This investigation treats one aspect, the nitrogen retention after upland clear-cutting which leads to elevated nitrate leaching, and the importance of the flow pathways in this connection. The runoff occurs mainly via the upper permeable section of the peat while the lower peat act as an aquitard, restricting the flow from the underlying till. The till groundwater is progressively artesian towards the discharging stream. Water analyses from piezometers show that the water chemistry in the peat is rather variable, indicating the presence of channelling. Channelling is also indicated by spring discharges from the peat that have elevated nitrate contents pointing to bypass flow. Redox bars indicating sulphate reduction display the same picture of irregular distribution. However, a general observation is that volumes with sulphate reduction increase towards the stream and that sulphate reduction occurs preferably in the surface peat, indicating the importance of a degradable substrate for the sulphate reducers. Nitrate reduction during the growth season occurs predominantly close to the upland till areas. The riparian tree stand is dominated by spruces which are likely to be disfavoured by the rising groundwater level after clear-cutting. The riparian tree stand does not extend far enough towards the upland to be benefited by the elevated nitrate flux. Buffer stands should be broader, extending into the till upland where they can utilise the leached nitrate and, more important, thanks to their deeper rooting depth protect the peatland trees against wind felling.

  • 5. Rappe George, M. O.
    et al.
    Hansson, L. J.
    Ring, E.
    Jansson, Per Erik
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Gärdenäs, A. I.
    Nitrogen leaching following clear-cutting and soil scarification at a Scots pine site – A modelling study of a fertilization experiment2017In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 385, p. 281-294Article in journal (Refereed)
    Abstract [en]

    Boreal forest stands fertilized with nitrogen (N) might be susceptible to elevated N leaching following clear-cutting, with consequences for water quality and soil acidification. Here, we studied a forest fertilization experiment with N, 165 Hagfors, in Sweden during the first six years (2006–2011) following clear-cutting. The N fertilization treatments were 0 kg ha−1 (0 N) and 450 kg ha−1 of N (450 N), supplied during 1981–1992 to a Scots pine (Pinus sylvestris L.) stand: the stand was harvested in March 2006. Following clear-cutting, disc trenching was performed and furrows (F), ridges (R) and areas in-between two furrows (IB) were created. We calculated the N leaching fluxes and ecosystem N budget during 2006–2011 as affected by previous N fertilization, disc trenching and interactions thereof, at Hagfors by the use of a process-based biogeophysical ecosystem model (CoupModel). The model was calibrated against measurements of soil water and temperature dynamics and previously reported measurements of N in soil solution, soil organic matter and vegetation biomass. Criteria for acceptance of model estimates were based on the range enclosed by the 95% confidence intervals of the mean of the field data used in calibration sampled at low frequency (1–2 occasions) and a combination of the mean error and the coefficient of the determination for variables sampled at a higher frequency (28–1921 occasions). The accepted model estimates of the mean annual leaching rates of N were 3.1 (range 1.4–22.7) and 2.4 (range 0.8–7.0) kg ha−1 of N year−1 in the treatments 0 N and 450 N, respectively, without disc trenching. Disc trenching increased N leaching during the regeneration phase, more so in the 450 N treatment (mean 6.1, range 1.9–16.7 kg ha−1 of N year−1) than in the 0 N treatment (mean 4.6, range 1.9–12.9 kg ha−1 of N year−1). Overall, differences in the posterior model parameter estimates between N treatments and disc trenched treatments F, R and IB were related to the soil physical component: the differences resulted in enhanced drainage in the disc trenched treatments. We conclude that vegetation biomass N accumulation controlled soil water N leaching, and disc trenching increased N leaching from the previously N fertilized plots at Hagfors by its effects on water drainage flow and vegetation N uptake. This finding warrants more research since N fertilization followed by soil scarification in boreal forests is a practice which may increase in the future.

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