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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Developing the silviculture of continuous cover forestry : using the data and experience collected from the Glentress Trial Area

MacKintosh, Hamish January 2013 (has links)
Continuous Cover Forestry (CCF) has become increasingly popular since the early 1990s. CCF utilises several silvicultural techniques in order to promote and enhance forest structural diversity and favours natural regeneration. As CCF is relatively new to the UK there are still areas of knowledge regarding management interventions that need to be improved upon. This study utilises simple models, seedling physiology and a hybrid gap model and applies them to the Glentress Trial Area which has been under transformation from even-aged forestry since 1952. These efforts have led to an improved understanding of thinning interventions and the effects they may have on future stand structure. Since the formation of the Forestry Commission in 1919, clearfell-replant forestry has been the main form of management practiced in the UK. CCF management differs in several respects and is commonly practiced using expert knowledge in Continental Europe. In the UK the knowledge-base is still growing and therefore simple models can prove useful for guiding management. This study investigated the use of the idealised reverse-J and the Equilibrium Growing Stock (EGS). This study found that the reverse-J shaped diameter distribution is maintained at the Trial, Block and sub- Block scale indicating that an irregular structure is being approached. In addition, the diminution coefficient, a parameter of the reverse-J distribution, falls within values typical of continental Europe. Comparison of the actual diameter-frequency distribution against an ideal reverse-J distribution can inform both thinning intensity and which diameter classes to target. The EGS, which is a volume–diameter distribution, examines standing volume and how that volume is distributed across three broad diameter classes. Typical distributions from the Swiss Jura indicate that percentage volume should be split 20:30:50 across diameter classes. The EGS analysis showed that standing volume in the Trial Area is much lower than European values at just 174 m3 ha-1. In addition, the classic 20:30:50 percent split was not observed. The 1990 data set showed a 49:43:8 distribution but by 2008 it was 40:41:19. As natural regeneration is favoured in CCF a better understanding of seedling physiology is essential. This study established open (15-35 m2 ha-1) and closed canopy plots (>35 m2 ha-1). Plot characteristics were recorded and then seedlings were selected for physical measurements, chlorophyll fluorescence and gas-exchange measurements. There were clear differences between the physical characteristics with a mean Apical Dominance Ratio (APR) of 1.41 for the open plots and 0.9 for the closed plots which is consistent with previous studies suggesting an APR of 1 is needed for successful regeneration. The chlorophyll fluorescence measurements showed a linear relationship with PAR. However, although the results of the gas-exchange measurements showed an increase in photosynthetic rates with PAR for open plots, there was no obvious relationship in the closed plots. As a result, the study did not find a linear relationship between photosynthetic rate and chlorophyll fluorescence. Finally a complex, hybrid gap model was used to investigate the effects of management on predicted future stand structure. The hybrid gap model, PICUS v1.41, was parameterised for Sitka spruce. The model was used to explore different management scenarios on stand structure over two time periods; 1954-2008 and 1952- 2075. The output from the group selection with underplanting scenario, which resembled the actual management, produced realistic output that was comparable to the stand characteristics measured during the 2008 assessment. The output from the 1952-2075 runs suggested that thinning to a residual basal area suitable to allow natural regeneration (<30 m2 ha-1) or a group selection with underplanting were the best management options for maintaining structural diversity.
2

Carbon Balance Implications of Forest Biomass Production Potential

Poudel, Bishnu Chandra January 2014 (has links)
Forests in boreal and temperate forest-ecosystems have importance for carbonbalance since they sequester large amount of atmospheric carbon by uptake ofcarbon-dioxide during photosynthesis, and transfer and store carbon in the forestecosystem. Forest material can be used for bio-fuel purposes and substitute fossilfuels, and supply wood products, which can replace carbon-and-energy-intensivematerials. Therefore it is vital to consider the role of forests regarding today´s aimto mitigate climate change. This thesis assess (i) how climate change affects futureforest carbon balance, (ii) the importance of different strategies for forestmanagement systems, and biomass production for the carbon balance, (iii) how theuse of forest production affect the total carbon balance in a lifecycle perspective,and (iv) how the Swedish carbon balance is affected from the standpoint of boththe actual use of forest raw material within Sweden and what Swedish forestryexports. The analysis was made mainly in a long-term perspective (60-300 years) toillustrate the importance of temporal and also the spatial perspective, as theanalysis includes stand level, landscape level, and national level. In this thesis, forestry was considered a system. All activities, from forestregeneration to end use of forest products, were entities of this system. In theevaluation, made from a systems perspective, we used life-cycle analysis toestimate carbon stock in different system flows. Different forest managementsystems and forest production were integrated in the analyses. Different forestmanagement scenarios were designed for the Swedish forest management incombination with the effect of future climate change; (i) intensive forest practiceaiming at increased growth, (ii) increased forest set-aside areas, changes in forestmanagement systems for biomass production, and (iii) how the use of forestproducts affect the total carbon balance (construction material, bioenergy and otherdomestic use). The results showed that future climate changes and intensive forest managementwith increased production could increase the biomass production and the potentialuse of forest raw material. This has a positive effect on carbon stock change in theforest biomass, litter production and below ground carbon stock and help reducingcarbon-dioxide emissions. Increased forest set-aside areas can increase the shorttermcarbon stock in forest ecosystems, but will reduce the total long-term carbonbalance. The net carbon balance for clear-cut forestry did not differ significantlyfrom continuous-cover forestry, but was rather a question of level of growth. Mostimportant, in the long term, was according to our analysis, how forest raw materialis used. Present Swedish forestry and use of forest raw material, both withinSweden and abroad, reduce carbon-dioxide emissions and mitigate climate change.The positive effect for the total carbon balance and climate benefit mostly takeplace abroad, due to the Swedish high level of export of wood products and thehigher substitution effects achieved outside Swedish borders. One strategy is toincrease production, harvest and use Swedish forest raw material to replace morecarbon intensive material, which can contribute to significant emission reduction.Carbon-dioxide mitigation, as a result of present Swedish forestry, was shown tobe almost of the same level as the total yearly emission of greenhouse gases. Thetotal carbon benefit would increase if the biomass production and felling increasedand if Swedish wood products replaced carbon intensive materials. This thesis shows also that, by changing forest management, increase thegrowth and the use of forest raw material and export of forest material we cancontribute to even larger climate benefits. In a long-term perspective, thesubstitution effects and replacement of carbon-and energy-intensive materials areof greater significance than carbon storage effects in forests. A more productionoriented forestry needs to make balances and increase the prerequisite forbiological diversity, improve recreation possibilities, and protect sensitive landareas and watersheds. Climate benefits, from Swedish forestry, are highly dependent on policydecision-making and how that can steer the direction for the Swedish forestry.
3

Trakhyggesbruk och hyggesfritt skogsbruk : En jämförelse av värderingar hos medlemmar i olika intresseorganisationer / Clearcutting and continuous-cover forestry : A comparison of values between members of various associations

Johansson, Anna January 2018 (has links)
There is a debate about clearcutting versus continuous-cover forestry in Sweden. In other studies forest owners and the general public have been seen to prefer different values. The aim of this study was to compare how members of various associations value clearcutting and continuous-cover forestry due to its effects on environmental-, social- and economical values. And also to understand the members motives for clearcutting and continuous-cover forestry, respectively. Through a web-based questionnaire this study found that members of all associations valued continuous cover forestry the highest, but members of Södra ranked clearcutting almost as high.  It was also found that Södra-members differed by favoring clearcutting, whilst members of Friluftsfrämjandet and Svenska Naturskyddsföreningen instead preferred continuous-cover forestry. Clearcutting had mostly economical motives and continous-cover forestry had mostly environmental- and social motives. This confirms former studies and points out a need for dialogues and exchange of knowledge when striving for sustainable development.
4

Tillväxtreaktioner efter gallring på försöksytor med olika täthet i Östergötland / Growth reaction after thinning in plots of various density in Östergötland

Hammarstedt, Kaisa January 2018 (has links)
Since the 1950-ies, the dominating silvicultural system in Sweden has included establishment and management of even-aged stands, including final felling. Alternative systems such as continuous cover forestry are increasingly catching interest due the lower impact on stand structure and biodiversity advantages for shade-tolerant species. However it is unknown especially to southern Sweden how trees in a continuous cover forestry system react to common silvicultural measures such as thinning. Therefore the effect of different levels of thinning on the radial growth of larger trees was measured and compared to the ingrowth and proportion of live crown at a site in Östergötland. Unlike previous findings the radial growth was higher in the treatment that had been slightly thinned than in the one that had been heavily thinned. The ability to react with increased radial growth after thinning was not depending on the thinning regime but on the tree’s reaction to a previous thinning. Only trees that had not reacted to the previous thinning increased in radial growth. The radial growth varied more within a treatment than between treatments, which points at the difficulty to allocate growth to specific trees.
5

Lokalt eller hållbart producerat? : Jämförelse mellan koldioxidutsläpp från två alternativa trävirke för brobygge över Skellefteälven. / Locally or sustainably produced? : Comparison between carbon dioxide emissions from two wood source alternatives for bridge construction over Skellefteälven

Berggren, Sally January 2022 (has links)
Emissions of greenhouse gasses, such as carbon dioxide, have been shown to be strongly connected global warming. In 2020 the European Union adopted the goal of reducing emissions of greenhouse gasses to a net of zero before year 2050. This is essential for keeping the average global temperature rise below 1.5 degrees. A large source of carbon dioxide emissions in Sweden is the forestry sector. The carbon balance in ecosystems is usually disturbed due to clear-cutting, which is the main silvicultural system used in Sweden. Introducing more sustainable silvicultural systems, such as continuous cover forestry, is a measure that authorities advocate. This study aimed to examine emissions of carbon dioxide from two timber sources that may be used for a bridge construction in Skellefteå. The timber would either come from a local clear-cut, transported by truck, or from continuous cover forestry in Lithuania, transported to Sweden by ship. The result is based on literature and calculations on data from previous studies. The results showed effects on carbon balance due to different silvicultural systems are complex, though the alternative with continuous cover forestry seemed to contribute to less emissions, despite the timber not being locally produced. The main factor between the systems, and therefore the different levels of emissions, seems to be highly dependent on how much of the harvested trees that is suitable for timber. However, emissions will also depend on local conditions such as timber storage. Therefore, it is important to take this into account when comparing silvicultural systems.
6

Economic analysis of a target diameter harvesting system in radiata pine

Perry, Christopher January 2013 (has links)
Target diameter harvesting (TDH) is a forest management system in which all stems above a set minimum diameter are harvested on a periodic basis. There is evidence in the literature that TDH can achieve a rate of return on a similar scale to a clearfelling regime, with added benefits of regular cash flow from partial harvests, and preservation of non-timber values. Economic analysis was carried out on 12 years of TDH using permanent sample plot (PSP) data from Woodside Forest, a 30ha plantation of radiata pine (Pinus radiata). The Woodside Forest management regime has a target diameter of 60cm, and a harvest cycle of two years. Economic analysis considered the option to partial harvest or clearfell every two years, and compared the outcome of each option in terms of land expectation value (LEV). Comparisons are made between regimes with different numbers of partial harvests, assessing the effect of TDH on stand LEV. Results show that in three of four applicable stands, LEV reached a maximum at ages 30 – 32, (near the time when partial harvesting commenced), and reduced slowy with increased numbers of partial harvests. This shows there is a small opportunity cost associated with choosing TDH over a clearfell system. The effect of revenue from early partial harvesting operations on LEV was small as the majority of stand value is still in the standing crop. This limited the conclusions that can be drawn form this study due to the short time frame analyzed. The study was limited by a small dataset which did not accurately represent average stand values. Because of this, no attempt to quantify the value of the opportunity costs was made. Despite this, the results support the notion that TDH can achieve economic returns similar to clearfelling in radiata pine forests.
7

Hyggesfritt skogsbruk - privata skogsägares metoder, mål och utmaningar / Continuous cover forestry - methods, goals and challenges for private forest owners

Gustavsson, Karina January 2022 (has links)
Hyggesfritt skogsbruk är en övergripande term som innebär att skogen sköts så att marken alltid är trädbevuxen utan att det uppstår några större kalhuggna ytor. Syftet med studien var att få en ökad förståelse för hur hyggesfritt skogsbruk fungerar i praktiken för privata enskilda skogsägare i Sverige. Frågeställningarna berörde vilka metoder som tillämpas, vilka mål som skogsägarna har och vilka utmaningar de ställs inför genom att bruka skogen hyggesfritt. Studien genomfördes med hjälp av en webbenkät. Resultaten visade att den vanligaste hyggesfria metoden för de privata skogsägarna var plockhuggning. De vanligaste målen med det hyggesfria brukandet var bevarad skogskänsla, ökad variation i skogen och ökad biologisk mångfald. Skogsägarnas utmaningar med det hyggesfria brukandet var främst relaterade till maskinparken, brist på kunskap och tillgång till rådgivning. Det finns ett behov av mer forskning om hyggesfritt skogsbruk.
8

Skogsbruksplanläggning i fullskiktad skog / Forestry planning in uneven-aged forest

Blomgren, Andreas January 2021 (has links)
Intresset för olika hyggesfria skogsbruksmetoder ökar men frågan är hur en skogsbruksplan kan anpassas till detta och vilken metod som kan användas. Denna studie inriktade sig på att mäta i fullskiktade skogar med enkla verktyg för att få ut beståndsdata till nytta för skötseln och att användas till en skogsbruksplan. För att få fram diameterspridningen klavades träden. Det krävdes minst 600 m2 för att få tillräcklig kvalitet i diameterspridning. För volymen jämfördes klavning, relaskopmätning och laserdata. Resultatet visade att det är svårt att mäta volym i fullskiktade bestånd beroende på tätheten och ojämnheten. Inte minst gäller detta relaskopmätning som undervärderade volymen. Klavning och laserdata fick ungefär samma precision. Studien visade också att tidsåtgången i fält för klavning jämfört med vanlig planläggning med relaskop endast skiljde några få minuter. Om klavning kombineras med att hämta volymen från laserdata kan till och med denna metod vara mer tidseffektiv.
9

Attitudes, existing support and required incentives to increase Continuous Cover Forestry in Sweden

Lejon, Victoria January 2023 (has links)
An increasing wave of critique against conventional forestry favouring even-aged monoculture plantations and intense ground preparation in Sweden is arising, where some researchers are warning about the negative consequences of the long history of intense forestry and increasing extraction due to the growing demand for bioenergy has caused devastating consequences on ecosystems in forests such as loss of biodiversity. Additionally, reports are revealing that Sweden will not meet its own national environmental goals. Meantime, a growing interest in Continuous Cover Forestry (CCF) has increased due to prioritising biodiversity and conserving ecological and social values in the forests. Therefore, this study aims to explore pathways towards more diverse and varied forest management by examining the attitudes, existing support and required incentives for stakeholders in the Swedish forest sector towards an increase of CCF. This study follows an interpretive approach, where qualitative semi-structured interviews are conducted with different actors within the Swedish forest sector along with a literature review. The empirical data is analysed through a coding procedure and analysed with the multi-level perspective approach. The main findings of this study suggest that the existing attitude and support contribute as well as prevent an increase of CCF to some extent, however, the required incentives are crucial for forest actors’ ability to increase CCF. To conclude, the incentives are discussed to affect the ability to increase CCF, and if implemented, the incentives will in turn influence the attitudes of willingness to increase CCF and the existing support to develop in relation to CCF.
10

Sustainable Forestry? : A Sustainability Analysis of the Swedish Forest Sector Applying 'Backcasting from Sustainability Principles' as the Methodology / Hållbart Skogsbruk? : En hållbarhetsanalys av den svenska skogssektorn med ”backcasting från hållbarhetsprinciper” som metod

Ronge, Victoria January 2017 (has links)
Forests are key providers of terrestrial ecosystem services such as climate regulation, water purification, natural pest control, habitats for biodiversity, as well as different forms of wood based materials and food. Nevertheless forests are dangerously exposed to great pressures from various kinds of societal activities. This report examines the importance of forests for the (i) maintenance of life supporting functions of the biosphere as well as for (ii) providing a flexible resource base for the satisfying of human needs on more and more sustainability-driven markets. How can Swedish forestry be managed such that those two essential roles of forests become mutually supportive? The report also relates the results to three relevant and well-citied protocols for the subject: the Sustainable Development Goals in UN’s Agenda 2030, the Swedish Environmental Quality Objectives, and the Swedish National Forest Program. The approach applied Maxwell’s process design for qualitative research. Data have been collected from literature search and interviews of experts and the analytical instrument for modeling of data was the Framework for Strategic Sustainable Development (FSSD). The report concludes: Sustainable development for forestry relies on a paradigm shift in civilization’s perception of forestry to a practice where planning departures from envisioning a future where natural forest functions to sustain higher life forms and civilization are safeguarded and prioritized before other usages of forestland, and where diversity is enhanced in terms of tree age and species to foster more resilient and high-quality timber forests. When the above points are achieved, the higher diversity of more resilient forests should also have potential to supply markets with various kinds of resources offered to more and more sustainability driven markets. Furthermore, this development of society’s forest use increases the chances for civilization to be sustainable also with relatively smaller forest areas put aside for no forestry at all. In such a situation forestry and society have prioritized forest products and usages with long life spans before such with short. A future sustainable Swedish forest sector has recognized the above, and drawn an essential conclusion from it: the interdependency of forests with society’s overall sustainability performance calls for a cooperative approach that departures from an understanding of basic sustainability principles that are shared across sectors and disciplines. The Sustainable Development Goals, the Swedish Environmental Objectives and the Swedish National Forest Program all fail to take the above broad- systems perspective when it comes to proposing measures for the future, including how to advise further research to explore what the sustainable Swedish forestry could entail. The study arrives at pointing out an overall approach to analyses, planning and further research in those regards, rather than evaluating details on the path towards sustainable forestry. / Skogen är en nyckelresurs i den landbaserade naturen som förser samhället med ekosystemtjänster såsom klimatreglering, vattenrening, naturlig skadedjursbekämpning, habitat för biologisk mångfald, likväl som olika former av träfiberbaserade material och mat. Samtidigt är skogen hotad av kraftigt tryck från olika aktiviteter i samhället. Den här rapporten undersöker skogens betydelse för (i) upprätthållande av biosfärens livsuppehållande funktioner, samt som (ii) flexibel resurs när det gäller att förse mänskliga behov på alltmer hållbarhetsdrivna marknader. Hur bör skogen skötas så att dessa två roller stödjer varandra? Rapporten relaterar också resultaten till tre relevanta och vanligt citerade protokoll: hållbarhetsmålen i FNs Agenda 2030, de svenska miljömålen och det svenska nationella skogsprogrammet. Forskningen har strukturerats med hjälp av Maxwells process-design för kvalitativ forskning. Data har samlats in genom litteraturstudier och från intervjuer med experter. Modellering av data har gjorts genom att använda ramverket för strategisk hållbar utveckling (FSSD) som analysinstrument. Rapporten kommer fram till att: Hållbar utveckling för skogsbruket är beroende av ett paradigmskifte. En skogsskötsel där (i) planering utgår från att föreställa sig en framtid där skogens funktioner för högre liv på jorden är säkrade och satta före annan användning av skogsmark, och (ii) mångfald är främjad gällande trädens ålder och antalet arter så att mer resilienta skogar kan bidra med högkvalitativt timmer. När skogen förvaltas på det sättet så bör de mer diversa och resilienta skogarna ha möjlighet att förse marknader med olika resurser som kan visa sig vara viktiga på alltmer hållbarhetsdrivna marknader. Vidare borde denna utveckling av samhälles skogsanvändning öka chanserna för civilisationen att bli hållbar med relativt mindre ytor reserverade för att skyddas mot skogsbruk. Med en sådan förvaltning har skogsägare och samhället i stort prioriterat produkter och användningsområden med långa livslängder före sådana med korta livslängder. En framtida hållbar svensk skogssektor har insett allt ovanstående och dragit en väsentlig slutsats från det: beroendet mellan skogen och samhällets övergripande hållbarhetsarbete kräver samarbete utgående från grundläggande hållbarhetsprinciper som delas över sektors- och disciplingränser. Hållbarhetsmålen i Agenda 2030, de svenska miljömålen och det svenska nationella skogsprogrammet saknas alla ett tillräckligt brett systemperspektiv när det gäller att föreslå åtgärder för framtiden, inklusive att ge rekommendationer för framtida forskning om hållbart svenskt skogsbruk. Studien pekar snarare ut en övergripande inriktning för analyser, planering och forskning om hållbart svenskt skogsbruk, än utvärderar de exakta stegen på vägen dit.

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