| 1. |
- Jensen, Anna M
(författare)
-
Effects of facilitation and competition on oak seedlings : using shrubs as nurse-plants to facilitate growth and reduce browsing from large herbivores
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plant–plant interactions have been indicated as a potential means to facilitate oak seedling establishment and reduce herbivory when restoring oak forests. The aim of this thesis was to investigate mechanisms and outcomes of competitive and indirectly facilitative interactions between oak (Quercus robur and Q. petraea) seedlings and neighboring plants, primarily shrubs. The associational resistance of planted oak seedlings to larger herbivores provided by naturally occurring shrubs was tested in ten temperate broadleaved forests across southern Sweden. The results showed that shrubs reduced ungulate browsing frequency and intensity by concealing the oak seedlings and by sharing enemies (i.e. ungulate herbivores) with surrounding and more preferred shrub species, thus providing numeric dilution and associational plant refuges. The occurrence of naturally regenerated oak seedlings, five years after a conservation-oriented thinning, was negatively influenced by the presence of tall ground vegetation and positively influenced by high soil moisture. For oak seedlings planted in an open field, shrubs indirectly facilitated biomass accumulation by reducing competition from herbaceous vegetation. However, shrubs became net competitors three years after planting. The oak seedling response, in terms of biomass accumulation, transpiration and photosynthesis, to competition from shrubs was proportional to resource availability. Aboveground competition for light had a greater effect on oak seedling growth than belowground competition. Nevertheless, oak seedlings were able to produce a second shoot flush, over-topping the shrub canopy. This periodic flushing enabled light-acclimation in a stratified light environment. In conclusion, management of shrubs has the potential to reduce browsing and herbaceous competitors during oak regeneration, particularly during the first years after planting. Although shrubs alone may not replace fences as an effective means of reducing browsing on oaks, they provide a complement to improve the growth of seedlings during the early stages of establishment.
|
|
| 2. |
- Nilsson, Kerstin
(författare)
-
To work or not to work in an extended working life? Factors in working and retirement decisions
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In most of the industrialised world, the proportion of older and retired people in the population is continuously increasing. This will have budgetary implications for maintaining the welfare state, because the active working section of the population must fund the non-active and old population. Aim: The overall aim of this thesis was to obtain knowledge about older workers’ work and life situation in association with their planning and decision to retire from working life. Method: The thesis includes one qualitative and three quantitative studies conducted in Sweden. Result: Self-rated health was found to be a better measure than diagnosed disease of whether older workers believed they could work until 65 years or beyond. Health seems not to be a general impediment to working in old age if older workers are satisfied with their work situation and have enough time and opportunities to recover from fatigue. In one of Sweden’s most hazardous work environments, older workers were not injured significantly more often than younger workers. Good mental and physical work environment, moderate working pace and working time, and the right competence and possibility for skills development were factors determining whether older workers believed they can extend their working life. Attitude to older workers in the organisation, motivation and work satisfaction were factors determining whether older workers want to extend working life. Health, personal economic incentives, family/leisure pursuits and attitude to pension in society affected both whether people believed they can and wanted to extend their working life. In their final retirement decision, older workers considered: i) their possibility to balance and adapt functional ageing and health to a sustainable work situation; ii) their economic situation; iii) possibilities for social inclusion and coherence; and iv) possibilities for meaningful activities. Whether these requirements were best fulfilled in or outside working life determined the decision to continue working or to retire. Conclusion: If it is desirable for society that people will to extend their working life, both the “can work” and the “want to work” factors need to be met. It is important to provide a good fit inside working life. This requires a focus not only on older workers, but also on organisations and managers in order to provide incentives that keep older workers in the work force.
|
|
| 3. |
- Aballay, Erwin
(författare)
-
Rhizobacteria associated to Vitis vinifera and their effect on the control of Xiphinema index, Meloidogyne ethiopica and Vitis growth
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plant-parasitic nematodes are one of the most important pests affecting the growth of vineyards due to the destruction of new roots. Several species are associated with this problem, the most important being the ectoparasite Xiphinema index and the endoparasite Meloidogyne ethiopica. The search for new pest and disease control methods based on bioantagonist microorganisms is an important aspect of modern agriculture and the development of tools based on the use of rhizobacteria is becoming a widely evaluated alternative. The present study on suppressive soils started with a survey undertaken in productive Chilean vineyards to explore the younger roots of grapevines and identify the presence of rhizobacteria. More than 1800 soils were surveyed and a set of 11 vineyards were selected and considered suitable for bacteria isolation, as they showed low densities of plant-parasitic nematodes. A total of 400 bacterial isolates in 25 genera were obtained using tryptic soy broth agar and identified with fatty acid profiling. Two of the most frequently isolated species were Pseudomonas putida (35.1%) and P. fluorescens (6.1%). The effect of these isolates on the parasitism and reproduction of X. index was assessed through assays using potted vine plants (cv. Thompson Seedless) and a bacterial suspension containing 1×106 CFU/mL. Some isolates from Bacillus megaterium, B. brevis, B. mycoides, B. sphaericus, B. thuringiensis, Pseudomonas corrugata, P. putida, P. alcaligenes, P. savastanoi, P. fluorescens, P. pseudoalcaligenes, P. viridiflava, Stenotrophomonas maltophilia, Serratia plymuthica, Cytophaga johnsonae, Rahnella aquatilis, Stenotrophomonas sp., Variovorax paradoxus and Curtobacterium flaccumfaciens reduced root damage and suppressed populations. Isolates of B. brevis, Comamonas acidovorans, B. megaterium, Pantoea agglomerans and P. savastanoi increased plant growth or root weight, but did not control nematodes. Most of the culture filtrates obtained from isolates from four vineyards were effective in killing X. index and decreasing egg hatching, which was not related to damage or population control. It was estimated that 89, 32 and 16% of the isolates were effective against X. index under supernatant conditions, in potted plants growing in sterile substrate and in potted plants growing in field soil, respectively. Sixteen bacterial isolates previously assessed were also evaluated on M. ethiopica in vine cv. Chardonnay. Seven isolates (Serratia marcescens, C. acidovorans, P. agglomerans, Sphingobacterium spiritivorum, B. mycoides, Alcaligenes piechaudii and S. plymuthica) decreased damage or reproduction, showing that different species of nematodes can respond differently to a particular isolate.
|
|
| 4. |
- Abrahamsson, Sara
(författare)
-
Genetic dissection of quantitative traits in Scots pine
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The phenotypic expressions of Scots pine, have been extensively studied over the years, but the gene regulation behind the traits has only just begun to be elucidated. The overall aim of this thesis was to start dissecting the genetics behind a number of adaptive traits in Scots pine and examine how they are influenced by relatedness using different molecular tools. In a full-sib family of Scots pine the genetic variation in autumn frost hardiness and height growth was revelead by measuring open-pollinated offspring. A significant genetic variation for both traits was found, a prerequisite to identify quantitative trait loci (QTL). A conceptual statistical model in the Bayesian framework for identifying QTLs in dynamic traits i.e. traits that vary over time, was developed and applied in a QTL study based on a full-sib family of 250 trees. A set of 160 AFLPs were utilized. QTLs for three latent traits were identified: one for the slope (growth) and two for the quadratic term (growth cessation). As a tool to identify candidate genes for the study of quantitative adaptive traits, gene regulation under continuous red (cR) and far-red (cFR) light was studied in hypocotyls from open-pollinated seeds from a natural population in northern Sweden using microarray technology. The gene expression patterns for the light response pathway in Scots pine under cFR show clear differences from those of angiosperms, wherein we observed up-regulation of cryptochrome1. This gene has, therefore, become a strong candidate gene that deserves further studies to elucidate the genetics behind Scots pine adaptation. Not knowing the genetic relationship and inbreeding of trees, and how it influences the phenotypic expression, can lead to over- or underestimation of additive genetic values resulting in biased heritability estimates. A natural population of Scots pine, earlier identified as being highly inbreed, was used to investigate the influence of inbreeding by the correlation between heterozygosity and propotion of sound seed (PSS), average seed weight and proportion of rare alleles (PRA). Heterozygosity fitness correlation (HFC) was found positive for PSS and negative for PRA most likely due to recessive deleterious alleles purged in homozygotes. The study provided evidence that, as predicted by theory, inbreeding enhances HFC in a species with high outbreeding rate and high number of lethal equivalents as Scots pine.
|
|
| 5. |
- Abro, Rani
(författare)
-
Digestion and metabolism of carbohydrates in fish
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the digestion and metabolism of carbohydrates in Arctic charr, Eurasian perch and tilapia. Two sources of carbohydrates, native starch (wheat) and chitin (zygomycete biomass), were evaluated. Gut tissue of Arctic charr displayed significant chitinase activity, of both endo- and exo-chitinase forms. Moreover, the distribution pattern along the gastrointestinal tract of Arctic charr differed between endo-chitinase and exo-chitinase. The endo-chitinase activity in stomach tissue and in the distal intestine was several hundred-fold higher than the exo-chitinase activity in stomach tissue. The greatest exo-chitinase activity was found in the distal intestine fed a zygomycete-based diet. Disturbed intestinal integrity and increased uptake rate of the amino acid lysine were observed in the distal, but not proximal, intestine of fish fed the zygomycete-based feed. A ¹HNMR metabolomics approach revealed no differences in metabolic profile in liver tissues of Arctic charr fingerlings fed a zygomycete-based diet and a fish-meal based diet. The inclusion of wheat starch did not affect α-amylase activity in gut tissue of Arctic charr and Eurasian perch. Overall, α-amylase activity was correlated with the trends obtained for starch digestibility. The apparent digestibility (AD) of crude protein, starch, crude fat and energy differed between the fish species, with on average higher values for all parameters in Eurasian perch than in Arctic charr. Within fish species, dietary starch level had no effect on AD of dry matter, crude protein, crude fat and energy. Studies of the metabolic response to wheat starch inclusion in Arctic charr and tilapia using ¹HNMR base metabolomics indicated metabolic effects in tilapia, while inclusion of starch in the diet of Arctic charr resulted in partial or negligible metabolism effects. Thus there are species-related differences in the metabolic response to dietary starch inclusion.
|
|
| 6. |
- Abro, Shahid, hussain
(författare)
-
Molecular characterization and detection of infectious bronchitis virus
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the molecular characterization and detection of infectious bronchitis virus (IBV), an important pathogen that causes heavy losses in the poultry populations worldwide. The aim of the research was to better understand the molecular characteristics of the virus and to investigate the factors behind the continuous emergence of new genetic variants and the occurrence of outbreaks. The studies showed that the viral genome is under a continuous evolution, due to mutations, strong selective pressure and recombination events. These forces lead to a wide genetic diversity and the generation of new variants of this virus. The viral genes encoding the spike, envelope and membrane proteins can be considered the main genomic regions, which are indicating the evolution processes of IBV. The various strains contain specific structural and functional motifs in their genes and the alterations in these motifs may affect the infection biology of the virus. The constant emergence of new variants in Sweden is likely due to the introduction of novel IBV strains from other European countries through the import of poultry products, or by the continuous migration of wild birds. The in silico investigations of the spike glycoprotein coding regions of the Massachusetts and QX-like genotypes demonstrated molecular differences between these genotypic variants. It is hypothesized that the genetic diversity in the spike gene of IBV and of other avian coronaviruses, as well as of human, bat, and other animal coronaviruses could be associated with the adaptation and host specificity of these infectious agents. The data obtained by molecular characterization approach was also used for the development of a new molecular method for the improved detection and genotyping of this virus. A microarray platform was developed for the simultaneous detection and rapid typing of IBV variants. This assay provides a practical tool for better diagnosis, for studying the effectiveness of vaccination and for performing large-scale epidemiological studies.
|
|
| 7. |
- Abubaker, Jamal
(författare)
-
Effects of fertilisation with biogas residues on crop yield, soil microbiology and greenhouse gas emissions : recycling of plant nutrients from bioenergy production
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The amount of residues generated by biogas production has increased dramatically due to worldwide interest in using renewable energy. Biogas residues (BRs) originate from anaerobic degradation of different types of rural and urban organic wastes and have been proposed as organic fertilisers because of their high content of ammonium and other valuable macro- and micro-nutrients. However, application of BRs to agricultural soils may be accompanied by environmental risks, since they may contain heavy metals and organic pollutants. Therefore the effects of BRs on crop production and on the soil ecosystem and environment urgently need to be investigated before their wider use. This thesis evaluated and compared different types of BRs against cattle slurry, pig slurry, compost and mineral fertiliser with respect to their (1) ability to provide plants with necessary nutrients, (2) impact on the soil microbial ecosystem and (3) effects on emissions of the greenhouse gas nitrous oxide (N₂O). The results from short-term laboratory experiments and a long-term field trial showed that BRs increased crop yield to the same extent or more than conventional mineral fertiliser and compost, but less than pig slurry. BRs generated from source-separated organic household waste had a tendency to give higher crop yield and soil microbial activities than other BRs. BRs had no general negative effect on soil respiration, but substrate-induced respiration decreased significantly in organic soil on addition of BRs. Although all BRs initially inhibited potential ammonium oxidation and potential denitrification activity, no long-term negative effects were detected. BRs stimulated ammonium assimilation, which can temporarily decrease nitrogen availability to the plant. Furthermore, the bacterial community structure in the sandy soil was altered by BRs and cattle slurry, but no significant change was seen in the community structure of clay and organic soil. Application of BRs and animal slurry increased N₂O emissions, but the total losses and flux patterns were affected by fertiliser type and soil type. In conclusion, the fertiliser value of BRs should be regarded as high and they apparently have no long-term adverse effects on soil microbial functions and structures. Thus the problematic amounts of residues associated with expansion of biogas production could be turned to advantage, as these residues seem to be safe and competitive fertilisers.
|
|
| 8. |
- Adevi, Anna
(författare)
-
Supportive nature - and stress : wellbeing in connection to our inner and outer landscape
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many benefits are claimed for the interplay between humans and nature, such as nature’s potentially positive effect on wellbeing and health. The main aim with the present work was to increase the understanding of how nature nvironments can support and contribute to health improvement from stress related experiences. Different landscape types’ effect on stress was studied in Sweden. Single case-studies focused on factors considered being essential in the recovery process for people diagnosed with exhaustion disorder within a stress rehabilitation-program through garden therapy in Alnarp, Sweden. A simplified conclusion of the thesis would be that the childhood landscape seems to play a significant role affecting the choice of the adult’s recreational setting - and recreational activity when stress is included. People feel more at home in the type of landscape they grew up in and more often chose to settle down in this type of landscape; even if they have moved from their childhood region. People also prefer qualities connected to their childhood landscape, but seem to attach more easily to qualities suggested having innate significance. The stress-recovery process within the garden therapy seems to be supported, hastened and deepened because of a multisensory change in awareness when contact with nature is combined with therapeutic interventions. Different psycho-physiological processes are discussed as well as the importance of self-chosen places in the garden based on present mood and the significance of the interaction between symbolic and concrete activities. The garden, the caregivers, and the group of participants together make up an arena which combines structure with freedom of action, in which the participants get the chance to regulate their needs and desires. Two hypotheses are presented, which might contribute to filling some current gaps in knowledge regarding the potential benefits of human interactions with nature.
|
|
| 9. |
- Adu, George
(författare)
-
Studies on economic growth and inflation : theory and empirics
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of four independent papers. Paper I examines the effect of environmental policy on economic growth in a small open economy in a neoclassical framework with pollution as an input. We show that the effect of environmental policy on growth is stronger in the open economy case relative to the closed economy model if the country has strong aversion to pollution and thus serves as a net exporter of capital in the international capital market. On the other hand, if the agents in the economy have low aversion to pollution and thus import capital, the effect of environmental care on growth is stronger in the closed economy relative to the open economy. Paper II analyses the effect of asymmetry in factor endowments between resource-rich and resource-poor countries on equilibrium bias of technology development and adoption possibilities. First, we show that the bias in equilibrium technology in the resource-poor North is determined by its relative abundance of human capital and physical capital. Secondly, we show that the equilibrium bias in technology in the resource abundant South is dependent positively (negatively) on the relative abundance (scarcity) of skilled (unskilled) labour and the relative abundance (scarcity) of physical (natural) capital in the North. This force is dampened by the relative scarcity of skilled labour and physical capital in the South. These forces drive wage inequality, high cost of capital and skill technology mismatch in the South, all of which are bad for growth. These effects cumulatively, explains part of the observed differences in growth performance between resource -rich and resource-poor countries. Paper III investigated the relationship between long run economic growth in Ghana and natural resource abundance using time series econometric techniques. Using a number of indicators that could proxy for resource abundance in eight alternative specifications, the results rejected the resource curse hypothesis. Paper IV provides an empirical analysis of the factors accounting for inflation dynamics in Ghana using the bounds test and other econometric approaches. We find that real output, nominal exchange rate, broad money supply, nominal interest rate and fiscal deficit play a dominant role in the inflationary process in Ghana.
|
|
| 10. |
- Ahlman, Therese
(författare)
-
Organic dairy production : herd characteristics and genotype by environment interactions
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis was to gain further knowledge about the performance of cows in organic dairy production and their ability to adapt to the organic production environment. Milk production traits, fertility traits, somatic cell count (SCC) and longevity traits were analysed in organic and conventional herds and the reasons for culling in the two systems were investigated. Furthermore, the genetic correlation between traits expressed in organic and conventional production was estimated to assess the occurrence of genotype by environment interaction (GxE). The data contained records from almost all organic and conventional herds in Sweden. This thesis shows that performance of organically managed dairy cows differs from conventionally managed cows. Cows in organic herds had lower production, better fertility and higher SCC than cows in conventional herds. However, the performance of cows in organic production depended to a large extent on the lower milk production level. At a given production level, organically managed cows had slightly worse fertility but equal SCC as cows in conventional herds. Cows stayed longer in organic herds than in conventional herds and the main reason for culling differed between the production systems. The main reason for culling in organic production was poor udder health followed by low fertility. In conventional production the main reason for culling was low fertility followed by poor udder health. The results indicate that organic farmers are more concerned about udder health than conventional farmers are. Genetic correlations for production, fertility, SCC and longevity, estimated in organic and conventional dairy production were in general close to unity. The results indicate that current breeding values for Swedish Red bulls, estimated in conventional production, are adequate for organic production. Weak GxE was found for fertility traits in Swedish Holstein cows, indicating that some cows of this breed are better suited for organic production than others. However, the magnitude of GxE does not justify development of a separate breeding programme for the organic population today.
|
|
