A Study of African Savanna Vegetation Structure, Patterning, and Change

African savannas cover roughly half of the continent, are home to a great diversity of wildlife, and provide ecosystem services to large populations. Savannas showcase a great diversity in vegetation structure, resulting from variation in climatic, edaphic, topographic, and biological factors. Fires play a large role as savannas are the most frequently burned ecosystems on Earth. To study how savanna vegetation structure shifts with environmental factors, it is necessary to gather site data covering the full gradient of climatic and edaphic conditions. Several earlier studies have used coarse resolution satellite remote sensing data to study variation in woody cover. These woody cover estimates have limited accuracy in drylands where the woody component is relatively small, and the data cannot reveal more detailed information on the vegetation structure. We therefore know little about how other structural components, tree densities, crown sizes, and the spatial pattern of woody plants, vary across environmental gradients. This thesis aimed to examine how woody vegetation structure and change in woody cover vary with environmental conditions. The analyses depended on access to very high spatial resolution (\u3c1 \u3em) satellite imagery from sites spread across African savannas. The high resolution data combined with a crown delineation method enabled me to estimate variation in tree densities, mean crown size and the level of aggregation among woody plants. With overlapping older and newer imagery at most of the sites, I was also able to estimate change in woody cover over a 10-year period. I found that higher woody plant aggregation is associated with drier climates, high rainfall variability, and fine-textured soils. These same factors were also indicative of the areas where highly organized periodic vegetation patterns were found. The study also found that observed increases in woody cover across the rainfall gradient is more a result of increasing crown sizes than variation in tree density. The analysis of woody cover change found a mean increase of 0.25 % per year, indicating an ongoing trend of woody encroachment. I could not attribute this trend to any of the investigated environmental factors and it may result from higher atmospheric CO₂ concentrations, which has been proposed in other studies. The most influential predictor of woody cover change in the analysis was the difference between potential woody cover and initial woody cover, which highlights the role of competition for water and density dependent regulation when studying encroachment rates. The second most important predictor was fire frequency. To better understand and explain the dominant ecosystem processes controlling savanna vegetation structure, I constructed a spatially explicit model that simulates the growth of herbaceous and woody vegetation in a landscape. The model reproduced several of the trends in woody vegetation structure earlier found in the remote sensing analysis. These include how tree densities and crowns sizes respond differently to increases in precipitation along the full rainfall range, and the factors controlling the spatial pattern of trees in a landscape

Läkemedelsdistributionen i Norden. En komparativ studie av aktörer, resurser och aktiviteter.

This paper reports on a preliminary studie of the organising of pharmaceutical goods distribution in the Nordic countries. Based on close descriptions of the four national markets, Sweden, Denmark, Norway and Finland, a comparative analysis is made. The chosen comparative dimensions are: activity structures and actor constellations; vertical and horisontal integration; service levels; and pricing system. Despite their apparent similarities the four national markets display many differences in these dimensions. Further, within each national market, there are considerable differences between how the distribution operations are described in principle and how they appear when observed in practice.pharmaceuticals; goods distribution; market re-regulation; pricing

The use of dual-wavelength airborne laser scanning for estimating tree species composition and species-specific stem volumes in a boreal forest

The estimation of species composition and species-specific stem volumes are critical components of many forest inventories. The use of airborne laser scanning with multiple spectral channels may prove instrumental for the cost-efficient retrieval of these forest variables. In this study, we scanned a boreal forest using two channels: 532 nm (green) and 1064 nm (near infrared). The data was used in a two-step methodology to (1) classify species, and (2) estimate species-specific stem volume at the level of individual tree crowns. The classification of pines, spruces and broadleaves involved linear discriminant analysis (LDA) and resulted in an overall accuracy of 91.1 % at the level of individual trees. For the estimation of stem volume, we employed species-specific k-nearest neighbors models and evaluated the performance at the plot level for 256 field plots located in central Sweden. This resulted in root-mean-square errors (RMSE) of 36 m3/ha (16 %) for total volume, 40 m3/ha (27 %) for pine volume, 32 m3/ha (48 %) for spruce volume, and 13 m3/ha (87 %) for broadleaf volume. We also simulated the use of a monospectral near infrared (NIR) scanner by excluding features based on the green channel. This resulted in lower overall accuracy for the species classification (86.8 %) and an RMSE of 41 m3/ha (18 %) for the estimation of total stem volume. The largest difference when only the NIR channel was used was the difficulty to accurately identify broadleaves and estimate broadleaf stem volume. When excluding the green channel, RMSE for broadleaved volume increased from 13 to 26 m3/ha. The study thus demonstrates the added benefit of the green channel for the estimation of both species composition and species-specific stem volumes. In addition, we investigated how tree height influences the results where shorter trees were found to be more difficult to classify correctly

Observational evidence of dissipative photospheres in gamma-ray bursts

The emission from a gamma-ray burst (GRB) photosphere can give rise to a variety of spectral shapes. The spectrum can retain the shape of a Planck function or it can be broadened and have the shape of a Band function. This fact is best illustrated by studying GRB090902B: The main gamma-ray spectral component is initially close to a Planck function, which can only be explained by emission from the jet photosphere. Later, the same component evolves into a broader Band function. This burst thus provides observational evidence that the photosphere can give rise to a non-thermal spectrum. We show that such a broadening is most naturally explained by subphotospheric dissipation in the jet. The broadening mainly depends on the strength and location of the dissipation, on the magnetic field strength, and on the relation between the energy densities of thermal photons and of the electrons. We suggest that the evolution in spectral shape observed in GRB090902B is due to a decrease of the bulk Lorentz factor of the flow, leading to the main dissipation becoming subphotospheric. Such a change in the flow parameters can also explain the correlation observed between the peak energy of the spectrum and low-energy power law slope, alpha, a correlation commonly observed in GRBs. We conclude that photospheric emission could indeed be a ubiquitous feature during the prompt phase in GRBs and play a decisive role in creating the diverse spectral shapes and spectral evolutions that are observed.Comment: Submitted to MNRAS, 14 pages, 7 figure

African Savanna Vegetation Model

The project aimed at creating a model that can simulate the effect of environmental factors on trees and grasses in an African savanna landscape. It enables simulating the growth of woody and herbaceous vegetation in an African savanna landscape, where the user can define the environmental conditions. Input to the model includes: Monthly precipitation Fire regime Grazing pressure Soil type Slope Attributes of the woody species, such as maximum crown size and sensitivity to light conditions, drought, and fire

Digital autenticering - en del av e-demokrati

Dagens samhälle går allt mer mot att vara ett informationssamhälle. Inga viktiga beslut sker idag utan att man först införskaffat tillräckligt med information; den har blivit en hårdvaluta och kritisk resurs. För att våga lita på informationen måste man veta att källan är pålitlig och att informationen är oförvanskad. Ett ökande medium för informations-spridning idag är olika former av digitala dokument. Digitaliseringen av samhället har dock lett till många nya sätt att manipulera informationen i dessa. Syftet med denna uppsats var att utreda vilka tekniker som finns för att autenticera digitala dokument. Frågan vi ställde oss var ”Hur kan man fastställa att ett digitalt dokument är ett original?” För att undersöka detta genomförde vi två skilda litteraturstudier; en inom området e-demokrati, vilken bidrog till en ökad förståelse för problemområdet och en teknisk studie. Den tekniska studien visade på tre tekniker; digitala signaturer, steganografi och digital vattenmärkning, vilka samtliga lämpar sig väl för fastställande av dokumentens autencitet. Vi fann dock att det inte finns någon optimal lösning på problemet, då samtliga lösningar har svagheter. Ytterligare utveckling inom området kommer att krävas

A Study of African Savanna Vegetation Structure, Patterning, and Change

African savannas cover roughly half of the continent, are home to a great diversity of wildlife, and provide ecosystem services to large populations. Savannas showcase a great diversity in vegetation structure, resulting from variation in climatic, edaphic, topographic, and biological factors. Fires play a large role as savannas are the most frequently burned ecosystems on Earth. To study how savanna vegetation structure shifts with environmental factors, it is necessary to gather site data covering the full gradient of climatic and edaphic conditions. Several earlier studies have used coarse resolution satellite remote sensing data to study variation in woody cover. These woody cover estimates have limited accuracy in drylands where the woody component is relatively small, and the data cannot reveal more detailed information on the vegetation structure. We therefore know little about how other structural components, tree densities, crown sizes, and the spatial pattern of woody plants, vary across environmental gradients. This thesis aimed to examine how woody vegetation structure and change in woody cover vary with environmental conditions. The analyses depended on access to very high spatial resolution (<1 m) satellite imagery from sites spread across African savannas. The high resolution data combined with a crown delineation method enabled me to estimate variation in tree densities, mean crown size and the level of aggregation among woody plants. With overlapping older and newer imagery at most of the sites, I was also able to estimate change in woody cover over a 10-year period. I found that higher woody plant aggregation is associated with drier climates, high rainfall variability, and fine-textured soils. These same factors were also indicative of the areas where highly organized periodic vegetation patterns were found. The study also found that observed increases in woody cover across the rainfall gradient is more a result of increasing crown sizes than variation in tree density. The analysis of woody cover change found a mean increase of 0.25 % per year, indicating an ongoing trend of woody encroachment. I could not attribute this trend to any of the investigated environmental factors and it may result from higher atmospheric CO2 concentrations, which has been proposed in other studies. The most influential predictor of woody cover change in the analysis was the difference between potential woody cover and initial woody cover, which highlights the role of competition for water and density dependent regulation when studying encroachment rates. The second most important predictor was fire frequency. To better understand and explain the dominant ecosystem processes controlling savanna vegetation structure, I constructed a spatially explicit model that simulates the growth of herbaceous and woody vegetation in a landscape. The model reproduced several of the trends in woody vegetation structure earlier found in the remote sensing analysis. These include how tree densities and crowns sizes respond differently to increases in precipitation along the full rainfall range, and the factors controlling the spatial pattern of trees in a landscape

Carbon emission during construction phase in multifamily housing projects

Introduction (and aim) – Carbon dioxide emissions have large consequences for nature and humans. If carbon dioxide emissions continue at this rate and the average temperature increases, the tipping point will be reached, and the damage will be too great to repair. Awareness of the climate began to emerge in the late 1980s. As the years went by, awareness increased and protocols for how to stop carbon dioxide emissions was created. In 1997 came the Coyote Protocol and in 2015 came the Paris Agreement. In 2017 Sweden adopted a climate policy framework that has the goal of having net zero emissions by 2045. The goal of this study was to identify what affects carbon dioxide emissions in the construction production phase, how these contribute to carbon dioxide emissions, and how building technology solutions affect carbon dioxide emissions in apartment building projects. Delimitations have been made from earthworks, internal installations and the study relates to the building production stage, A4 and A5. The outline of work is introduction, theoretical framework, method and implementation, results, discussion, conclusions, and suggestions for further research. Method – The research method was a case study with a multiple case design. Data collection methods were a document study of the data provided to the group by Skanska Sverige AB as well as a literature study of doctoral dissertations, handbooks, articles in scientific journals, research reports and conference contributions. A intervju was conducted to complement the document study. Results – Skeppsbron 2 emitted 306.9 kgCO2eq/m2 during A1-A5 construction phase, of which module A4 transportation accounted for 13.9 kgCO2eq/m2 and A5 production for 31.8 kgCO2eq/m2.Slåttertiden had a lower climate footprint and emitted 290.7 kgCO2eq/m2 during the construction phase, where A4 accounted for 16.3 kgCO2eq/m2 and A5 for 44.7 kgCO2eq/m2. Analysis – The construction production phase contributes 9–21% of the carbon dioxide emissions during the construction phase. The construction phase accounts for 25–70% of carbon dioxide emissions during the entire life cycle. What differs the most regarding the building technology solution is the carbon dioxide emissions in module A5.1. Carbon dioxide emissions in module A4 are not affected by the building technology solution but depend on the transport distance. Discussion – When comparing projects, the uncertainty is great, which means that the result can only give an indication of the carbon dioxide emissions