| 1. |
- Belyazid, Salim
(författare)
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DYNAMIC MODELLING OF BIOGEOCHEMICAL PROCESSES IN FOREST ECOSYSTEMS
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Forests in Sweden are undergoing rapid and considerable changes regarding both management methods and environmental conditions. To understand the effects of these changes and to be able to predict impending changes in forest ecosystems, a holistic understanding of the processes governing the ecosystem is needed. To gain such an understanding, the ForSAFE model of the biogeochemical cycles in a forest ecosystem has been developed. ForSAFE is a dynamic model which closes the physical cycles between the living biomass, the soil organic matter, the soil hydrology and the soil chemistry. The model was complemented with a supplementary module, called VEG, to include the response of the composition of the ground vegetation to the conditions at the sites. This thesis describes ForSAFE-VEG and its application to forest ecosystems in Sweden. The model was applied to a number of coniferous Swedish sites with a wide geographical distribution to investigate the responses of the forest ecosystems to changes in atmospheric deposition and harvest methods. The model output was validated on different levels, including the biomass, the soil organic matter and the soil chemistry. The results of the simulations show that there is a high risk of nitrogen leaching, particularly in the south and centre of Sweden. The leaching of nitrogen is found to be triggered by harvesting, but the magnitude of the leaching depends on the historical accumulation of N from deposition. The simulations also predict an increase in the number of sites with acidified soils in the future, contrary to what has been predicted by previous models. The reason behind this increase was found to be the high uptake rates of base cations associated with high biomass growth rates, which in turn are the result of the high nitrogen deposition. Finally, the results of the ForSAFE-VEG were used to differentiate between the different causes of change in the ground vegetation diversity. The results indicate that the changes in the composition of the ground vegetation are triggered by clear-cutting, but that the direction of these changes is governed by the histories of the sites and the intensity of atmospheric deposition.
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| 2. |
- Belyazid, Salim, et al.
(författare)
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Modelling changes in forest soil chemistry at 16 Swedish coniferous forest sites following deposition reduction
- 2006
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 144:2, s. 596-609
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic forest ecosystem model ForSAFE was applied at 16 coniferous forest sites in Sweden to investigate past and future changes in soil chemistry following changes in atmospheric deposition. The simulation shows a considerable historical soil acidification. Acidification in the southwest, where deposition has been greatest, was more expressed in the deepest soil layers, while it was more evenly distributed through the soil profile in central Sweden, and was greater in the upper soil layers in the north. The simulation also shows that a slight recovery took place after the reduction in emissions, but was counteracted by the effect of harvesting. The simulation predicts an increase in the number of acidified sites in the future. The results also suggest that future acidification will be mainly due to the enhanced tree growth resulting from the chronic high deposition of nitrogen and the removal of soil base cations through harvesting. (c) 2006 Elsevier Ltd. All rights reserved.
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| 3. |
- Belyazid, Salim, et al.
(författare)
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Using ForSAFE-Veg to investigate the feasibility and requirements of setting critical loads for N based on vegetation change - pilot study at Gårdsjön
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The dynamic integrated ecosystem model ForSAFE-Veg was applied at the intensively monitored experimental catchment Gårdsjön, with the aim to investigate the performance of the model and the feasibility of using the composition of the ground vegetation community as an indicator of potential change due to N deposition. The quality, long term, and integrity of the measured data provided an ideal testing opportunity for evaluating the performance of the model, which proved satisfactory. The study shows that it is feasible to use the composition of the ground vegetation community as a biological indicator of ecosystem change. Yet, to be used in estimating critical loads of nitrogen (N) deposition, the biological indicator has to be simplified into a single-dimensional variable referred to as the average yearly exceedance (of change in the composition of the ground vegetation). The study shows that setting conditions to protect the dominant segment of the plant community, and thereby protecting ecosystem services, will also result in protecting the marginal plants proportion at the site. However, the choice of the segment of the plant community to be protected and the acceptable level of change remain bound to social preferences
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| 4. |
- Haraldsson, Hördur, et al.
(författare)
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The tyranny of small steps: A reoccurring behaviour in management
- 2008
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Ingår i: Systems Research and Behavioral Science. - : Wiley. - 1099-1743 .- 1092-7026. ; 25:1, s. 25-43
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Tidskriftsartikel (refereegranskat)abstract
- The Tyranny of Small Steps (TYST) behaviour has been investigated. Explained through a systemic perspective, the behaviour TYST is an unwanted change to a system through a series of small activities that may be independent from one another. These activities are small enough not to be detected by the 'surveillance' within the system, but significant enough to encroach upon the 'tolerance zone' of the system and compromise integrity of the system. TYST is an unintentional process that is experienced within the system and made possible by the lack of transparency between an overarching level and a local level where the encroachment is taking place. The Orby case study illustrates a real life manifestation of the TYST behaviour in management and planning. The TYST illustrates the necessity for total transparency in any systems in order to avoid unintended consequence. The TYST process may be regarded as a part of wide range of complex systems but depending on the conditions, it can remain dormant, and only become active when the conditions for lack of transparency are fulfilled.
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| 5. |
- Haraldsson, Hördur V., et al.
(författare)
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Causal Loop Diagrams – Promoting Deep Learning of Complex Systems in Engineering Education (rev 2007-05-11)
- 2006
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Ingår i: [Host publication title missing].
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Konferensbidrag (refereegranskat)abstract
- The use of systems analysis involving tools like Causal loop diagrams and stock and flow diagrams can be shown in practical tests to greatly enhance systems insight and understanding of the dynamic behaviour of complex systems. Whereas many students may have difficulty understanding what a coupled system of differential equations really do, systems analysis creates such insights even to those with differentiofobia. Within the systems analysis course given at LUMES, we have extensive experience in teaching systems analysis and the use of CLD and SFDs to people of different backgrounds, and also seen how technical problems in engineering have a great help in using CLD and SFDs to explain and communicate insight into complex systems to non-technical people
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| 6. |
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| 7. |
- Hellsten, Sofie, et al.
(författare)
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Effekter av skogsbränsleuttag på markförsurning, näringsbalanser och tillväxt - Uppskalning baserat på experimentella data och modellberäkningar som grund för kartläggning av behov av askåterföring
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna studie har tre olika verktyg använts för att studera effekten på näringsbalanser (N, P, Ca, Mg, K och Na) och försurning samt tillväxt vid skogsbränsleuttag; i) utvärdering av långliggande helträdsförsök, ii) beräkningar med en näringsbalansmodell med hög geografisk upplösning, samt iii) dynamisk modellering. Tre olika scenarier har studerats; stamuttag, GROT-uttag och stubbskörd. Stor vikt har lagts vid att göra en känslighetsanalys för näringshalter i olika träddelar, som är en viktig indata-parameter i näringsbalansberäkningarna, samt att undersöka möjligheterna att minska osäkerheten i näringshalter samt biomassa. Tre långliggande försök visade på en minskning i biomassa, vid tidpunkten för första gallringen, på omkring 15% efter GROT-uttag. Även halterna i träddelar av olika ämnen minskade efter GROT-uttag med upp till 10 %. De långliggande försöken visar på en minskning av basmättnaden i humuslagret och den övre delen av mineraljorden, oftast mellan 10 och 30 %, 15 och 26 år efter GROT-uttag. Samband hittades både för tall och gran mellan C/N i humuslagret och kvävehalt i barr. Denna studie visar att det finns stor potential i att använda näringsbalansberäkningar och beräkningar av överskottsaciditet på Riksskogstaxeringens punkter för att bedöma utarmningstakten för baskatjoner samt behovet av askåterföring. Känslighetsanalysen visade att osäkerheten i näringshalter har relativt stor påverkan på resultatet för N, Ca och K. Vidare arbete med den dynamiska modelleringen (fler lokaler, fler scenarier och fler omloppstider) kan öka förståelsen för effekter av GROT-uttag. Det är även viktigt att utveckla och förfina stubb-beräkningarna, och att tillsammans med representanter från det praktiska skogbruket jobba vidare med att utveckla realistiska scenarier för uttag av stam, GROT och stubbar.
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| 8. |
- Sahlén Zetterberg, Therese, et al.
(författare)
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Regionala förutsättningar och miljörisker till följd av kväveupplagring i skogsmarken vid olika scenarier för skogsskötsel och kvävedeposition
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport beskriver regionala förutsättningar och miljörisker av ett förändrat kvävegödslingsprogram, inom en rotationsperiod, på regional nivå. Möjligheterna och miljöriskerna beskrivs med utgångspunkt från regionala scenarioberäkningar av kvävebalanser i skogsmark samt dynamiska modellberäkningar av framtida förändringar i biomassa, markkemi och vegetation. Kväveupplagring har i denna rapport använts som en indikator på risken för en förhöjd kväveutlakning tillsammans med nuvarande och historisk kvävedeposition samt C/N-kvoten i skogsmark. Massbalansberäkningarna visade att balansen mellan till- och bortförseln av kväve i skogsmark varierar starkt, inte bara i olika regioner utan även mellan olika skötselmetoder och trädslag. För närvarande sker en kväveupplagring i marken i hela Sverige enligt nuvarande deposition, men ett ökat uttag av biomassa och/eller en minskad kvävedeposition kan leda till negativa kvävebalanser, särskilt i granbestånd. Vidare indikerar modellberäkningarna att kvävegödsling leder till en ökad kväveupplagring vid normalt stamvedsuttag, trots att upplagringen delvis motverkas av den ökade tillväxten. Kväveupplagringen ökar med ökad gödselgiva. Vid ett ökat uttag av biomassa uppstår negativa eller svagt positiva kvävebalanser i stora delar av Sverige, oavsett om beståndet gödslas eller ej. Detta gäller framför allt granbestånden. Vidare leder kvävegödsling till kraftiga vegetationsförändringar jämfört med dagens vegetationssammansättning i norra Sverige men inte i södra eller mellersta Sverige, där betydande förändringar troligtvis redan har ägt rum till följd av ett högt kvävenedfall. Under den första rotationsperioden är effekterna av gödslingen relativt kortlivade, men under den andra rotationsperioden orsakar gödslingen sannolikt kroniska förändringar av vegetationssammansättningen i näringsfattiga bestånd.
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| 9. |
- Sverdrup, Harald, et al.
(författare)
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Modelling Change in Ground Vegetation Response to Acid and Nitrogen Pollution, Climate Change and Forest Management in Sweden 1500--2100 a.d.
- 2007
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Ingår i: Water, Air, & Soil Pollution: Focus. - : Springer Science and Business Media LLC. - 1573-2940 .- 1567-7230. ; 7:1, s. 163-179
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Tidskriftsartikel (refereegranskat)abstract
- The ForSAFE model, designed for modelling biogeochemical cycles (water, acidity, base cation, nitrogen and carbon) in terrestrial ecosystems, was modified with a vegetation response module (VEG), incorporating the effects of: nitrogen pollution, acidification, soil moisture, temperature, wind chill exposure, light and shading by trees, grazing by animals, competition between plants, above ground for light and below ground for water and nutrients. The model calculates the response of number ground vegetation plant groups. The integrated model was tested and validated at integrated level II forest monitoring sites across Sweden, four have been shown here, and used to assess the effect of acidification and nitrogen pollution in relation to factors such as climate change, forest management and changing grazing pressure. The response functions have been derived from single-factor experiments and integrated through the model structure for use on whole systems. The tests with the model suggest that the ground vegetation composition is reasonably well predicted, that much research remains before the model is fully tested and operational, and that the model may serve as a tool for assessing impacts of climate change, acid rain and forest management on plant biodiversity in forested areas.
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| 10. |
- Wallman, Patrik, et al.
(författare)
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DECOMP - A semi-mechanistic model of litter decomposition
- 2006
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Ingår i: Environmental Modelling & Software. - : Elsevier BV. - 1364-8152. ; 21:1, s. 33-44
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Tidskriftsartikel (refereegranskat)abstract
- The decomposition of organic matter in a forest ecosystem is simulated by DECOMP, a process-based, semi-mechanistic model built on system dynamic principles. The model divides a litter into four different substrate quality classes with different decomposition rates which are differently influenced by temperature, soil moisture content, pH and aluminum concentration in the soil solution. The model is presented with its core equations and parameter values, but also presented from a system dynamics perspective in its context as a cornerstone in a forest-soil-atmosphere model. DECOMP is aimed at simulating long-term dynamics of decomposition over several forest management rotations, and to function in concert with other model components used in forest modeling. The model is evaluated against empirical data and shows good resemblance when simulating decomposition of Scots pine needle litter with data from a four-year litter bag field experiment.
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