<p>Seasonally dry ecosystems cover large areas over the world, have high potential for carbon sequestration, and harbor high levels of biodiversity. They are characterized by high rainfall variability at timescales ranging from the daily to the seasonal to the interannual, and water availability and timing play key roles in primary productivity, biogeochemical cycles, phenology of growth and reproduction, and agricultural production. In addition, a growing demand for food and other natural resources in these regions renders seasonally dry ecosystems increasingly vulnerable to human interventions. Compounded with changes in rainfall regimes due to climate change, there is a need to better understand the role of climate variabilities in these regions to pave the way for better management of existing infrastructure and investment into future adaptations. </p><p>In this dissertation, the ecohydrological responses of seasonally dry ecosystem to climate variabilities are investigated under a comprehensive framework. This is achieved by first developing diagnostic tools to quantify the degree of rainfall seasonality across different types of seasonal climates, including tropical dry, Mediterranean, and monsoon climates. This global measure of seasonality borrows from information theory and captures the essential contributions from both the magnitude and concentration of the rainy season. By decomposing the rainfall signal from seasonality hotspots, increase in the interannual variability of rainfall seasonality is found, accompanied by concurrent changes in the magnitude, timing, and durations of seasonal rainfall, suggesting that increase in the uncertainty of seasonal rainfall may well extend into the next century. Next, changes in the hydrological partitioning, and the temporal responses of vegetation resulting from these climate variabilities, are analyzed using a set of stochastic models that accounts for the unpredictability rainfall as well as its seasonal trajectories. Soil water storage is found to play a pivotal role in regulating seasonal soil water hysteresis, and the balance between seasonal soil water availability and growth duration is found to induce maximum plant growth for a given amount of annual rainfall. Finally, these methods are applied in the context of biodiversity and the interplay of irrigation and soil salinity, which are prevailing management issues in seasonally dry ecosystems.</p> / Dissertation

The Critical Zone (CZ) is the surficial layer of the planet that sustains life on Earth and extends from the base of the weathered bedrock to the top of the vegetation canopy. Its structure influences water fluxes, biogeochemistry and vegetation. In this dissertation, I explore the relationships between climate, water fluxes, vegetation dynamics, biogeochemistry, and effective energy and mass transfer fluxes (EEMT) in a semi-arid critical zone. This research was carried out in the upper Jemez River Basin in northern New Mexico across gradients of climate and elevation. The main research objectives were to (i) quantify relations among inputs of mass and energy (EEMT), hydrological and biogeochemical processes within the CZ, (ii) determine water fluxes and vegetation dynamics in high elevation mountain catchments with different terrain aspect and solar radiation, and (iii) study temporal variability of climate and its influence on the CZ water availability, forest productivity and energy and mass fluxes. The key findings of this study include (i) significant correlations between EEMT, water transit times (WTT) and mineral weathering products around Redondo Peak. Significant correlations were observed between dissolved weathering products (Na⁺ and DIC) and maximum EEMT. Similarly, ³H concentrations measured at the springs were significantly correlated with maximum EEMT; (ii) terrain aspect strongly controls energy, water distribution, and vegetation productivity in high elevation ecosystems in catchments draining different aspects of Redondo Peak. The predominantly north facing catchment, when compared to the other two eastern catchments, receives less solar radiation, exhibits less forest cover and smaller biomass, has more surface runoff and smaller vegetation water consumption. Furthermore, the north facing catchment showed smaller NDVI values and shorter growing season length as a consequence of energy limitation, and (iii) from 1984 to 2012 a decreasing trend in water availability, increased vegetation water use, a reduction in both forest productivity and EEMT was observed at the upper Jemez River Basin. These changes point towards a hotter, drier and less productive ecosystem which may alter critical zone processes in high elevation semi-arid systems.

Per- and polyfluoroalkyl substances (PFASs) are a group of emerging chemicals which havereceived increasing attention due to their toxicity, persistent properties, and global distribution.In this study, sorption coefficients (Kd and KOC) of PFASs in an industrial site in Sweden wereevaluated. Sorption is a measures of the mobility of a substance in the subsurface, and is a keyfactor in environmental risk assessments. Sorption coefficients were calculated both from fieldsamples processed in laboratory batch tests, and from a simplified approach involving the totalconcentrations in soil and groundwater (field-derived). Soil was sampled from two locations ofthe site; C8 and M6. Field-derived values were calculated based on concentrations which werehistorically measured. The aim was to compare the two methods, and to compare the valueswith literature values as well as guideline sorption values established by the SwedishGeotechnical Institute (SGI). Sorption coefficients for PFHxA, PFHpA, PFOA, PFHxS, PFOS, 6:2 FTS and PFBS could beestablished. Results showed that laboratory-derived sorption coefficients were significantlyhigher than field-derived sorption coefficients. Laboratory-derived sorption values were alsohigher than to SGI’s preliminary sorption values. Comparing C8 and M6 KOC values toliterature values, PFHpA, PFHxA, and PFBS exhibit values above literature values. PFOA,PFHxS, PFOS exhibit KOC values within the range of literature values. According to thesorption coefficients, predictive scenarios of leaching through the unsaturated zone weremodelled, and it was concluded that leaching was higher in M6 compared to C8. The resultsalso showed that an increase in precipitation increased the leaching. / Per- och polyfluorerade alkylsubstanser (PFAS) är en grupp nyligen uppkomna kemikalier somhar fått ökad uppmärksamhet pga. deras toxicitet, ihärdiga egenskaper och globala utbredning.Detta examensarbete har studerat fördelningskoefficienter (Kd och KOC) för PFAS inom ettindustriområde i Sverige. Fördelningskoefficienter är ett mått på mobilitet av en substans iunderjorden, och det är en viktig komponent i riskbedömningar inom förorenad mark.Fördelningskoefficienter beräknades dels utifrån jordprover som tagits i fält och analyserats ilaboratorium med extraktionsmetoder, och dels utifrån ett förenklat tillvägagångssätt därberäkning skett med hjälp av tidigare uppmätta koncentrationer i jord och grundvatten.Jordprover från två områden inom industriområdet; C8 och M6, togs och analyserades.Fältbaserade fördelningskoefficienter beräknades utifrån koncentrationer som tidigare mättsvid brunnsinstallation och vid grundvattenövervakning. Målet med studien var att jämföra detvå metoderna, och dessutom jämföra fördelningskoefficienterna med motsvarande i värdenlitteraturen samt riktvärden för fördelningskoefficienter som Statens Geotekniska Institutet(SGI) arbetet fram. Fördelningskoefficienter för PFHxA, PFHpA, PFOA, PFHxS, PFOS, 6:2 FTS and PFBS kundeberäknas. Resultatet visade att laboratorie-baserade fördelningskoefficienter var betydligthögre än fältbaserade fördelningskoefficienter. Laboratorie-baserade fördelningskoefficientervar även högre än de preliminära riktvärden för fördelningskoefficienter som SGI etablerat. Vidjämförelse av fördelningskoefficienter för C8 och M6 kunde det konstateras att PFHpA,PFHxA, and PFBS hade högre värden än motsvarande i litteraturen. PFOA, PFHxS, PFOSvisade på värden som var inom intervallet av värdena från litteraturen. Med hjälp av deberäknade fördelningskoefficienterna modellerades prediktiva utlaknings-scenarier. Utifrånresultatet sker utlakningen i större grad i M6 jämfört med C8. Utlakningen ökade även vidförhöjd nederbörd.

Freshwater is a vital resource that circulates between the atmosphere, the land and the sea. Understanding and quantifying changes to the partitioning of precipitation into evapotranspiration, runoff and water storage change in the landscape are required for assessing changes to freshwater availability. However, the partitioning processes and their changes are complex due to multiple change drivers and effects. This thesis investigates and aims to identify and separate the effects of atmospheric climate change and various landscape drivers on long-term freshwater change. This is done based on hydroclimatic, land-use and water-use data from the beginning of the twentieth century up to present times and across different regions and scales, from catchment to global. The analyzed landscape drivers include historic developments of irrigated and non-irrigated agriculture and flow regulation. The thesis uses and develops further a data-motivated approach to interpret available hydroclimatic and landscape data for identification of water change drivers and effects, expanding the approach application from local to continental and global scales. Based on this approach development, the thesis identifies hydroclimatic change signals of landscape drivers against the background of multiple coexisting drivers influencing worldwide freshwater change, within and among hydrological basins. Globally, landscape drivers are needed to explain more than 70% of the historic hydroclimatic changes, of which a considerable proportion may be directly human-driven. These landscape- and human-driven water changes need to be considered and accounted for also in modeling and projection of changes to the freshwater system on land. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.</p> / VR, project 2009-3221

<p>The main aim of this thesis was to characterize membrane-solute interactions using artificial membranes in immobilized liposome chromatography or capillary electrophoresis. The partitioning of a solute into a cell membrane is an essential step in diffusion across the membrane. It is a valid parameter in drug research and can be linked to the permeability as well as the absorption of drugs. Immobilized liposome chromatography was also used to study partitioning of lignin precursor models. Lignin precursors are synthesized within plant cells and need to pass the membrane to be incorporated into lignin in the cell wall.</p><p>In immobilized liposome chromatography, liposomes or lipid bilayer disks were immobilized in gel beads and the partitioning of solutes was determined. Capillary electrophoresis using disks as a pseudostationary phase was introduced as a new approach in drug partitioning studies. In addition, octanol/water partitioning was used to determine the hydrophobicity of the lignin precursor models.</p><p>Electrostatic interactions occurred between bilayers and charged drugs, whereas neutral drugs were less affected. However, neutral lignin precursor models exhibited polar interactions. Moreover, upon changing the buffer ionic strength or the buffer ions, the interactions between charged drugs and neutral liposomes were affected. Hydrophobic interactions were also revealed by including a fatty acid or a neutral detergent into the bilayer or by using a buffer with a high salt concentration. The bilayer manipulation had only a moderate effect on drug partitioning, but the high salt concentration had a large impact on partitioning of lignin precursor models.</p><p>Upon comparing the partitioning into liposomes and disks, the latter showed a more pronounced partitioning due to the larger fraction of lipids readily available for interaction. Finally, bilayer disk capillary electrophoresis was successfully introduced for partitioning studies of charged drugs. This application will be evaluated further as an analytical partitioning method and separation technique.</p>

The main aim of this thesis was to characterize membrane-solute interactions using artificial membranes in immobilized liposome chromatography or capillary electrophoresis. The partitioning of a solute into a cell membrane is an essential step in diffusion across the membrane. It is a valid parameter in drug research and can be linked to the permeability as well as the absorption of drugs. Immobilized liposome chromatography was also used to study partitioning of lignin precursor models. Lignin precursors are synthesized within plant cells and need to pass the membrane to be incorporated into lignin in the cell wall. In immobilized liposome chromatography, liposomes or lipid bilayer disks were immobilized in gel beads and the partitioning of solutes was determined. Capillary electrophoresis using disks as a pseudostationary phase was introduced as a new approach in drug partitioning studies. In addition, octanol/water partitioning was used to determine the hydrophobicity of the lignin precursor models. Electrostatic interactions occurred between bilayers and charged drugs, whereas neutral drugs were less affected. However, neutral lignin precursor models exhibited polar interactions. Moreover, upon changing the buffer ionic strength or the buffer ions, the interactions between charged drugs and neutral liposomes were affected. Hydrophobic interactions were also revealed by including a fatty acid or a neutral detergent into the bilayer or by using a buffer with a high salt concentration. The bilayer manipulation had only a moderate effect on drug partitioning, but the high salt concentration had a large impact on partitioning of lignin precursor models. Upon comparing the partitioning into liposomes and disks, the latter showed a more pronounced partitioning due to the larger fraction of lipids readily available for interaction. Finally, bilayer disk capillary electrophoresis was successfully introduced for partitioning studies of charged drugs. This application will be evaluated further as an analytical partitioning method and separation technique.