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The global carbon cycle is subject to intense research, where sources and sinks for greenhouse gases, carbon dioxide in particular, are estimated for various systems and biomes. Lakes have previously been neglected in carbon balance estimations, but have recently been recognized to be significant net sources of CO2. This thesis estimates emission of carbon dioxide (CO2) from boreal lakes and factors regulating the CO2 saturation from field measurements of CO2 concentration along with a number of chemical, biological and physical parameters. Concentration of dissolved organic carbon (DOC) was found to be the most important factor for CO2 saturation in lake water, whereas climatic parameters such as precipitation, temperature and global radiation were less influential. All lakes were supersaturated with and, thus, sources of CO2. Sediment incubation experiments indicated that in-lake mineralization processes during summer stratification mainly occurred in the pelagial. Approximately 10% of the CO2 emitted from the lake surface was produced in epilimnetic sediments. The mineralization of DOC and emission of CO2 from freshwaters was calculated on a catchment basis for almost 80,000 lakes and 21 major catchments in Sweden, together with rates of sedimentation in lakes and export of organic carbon to the sea. The total export of terrestrial organic carbon to freshwaters could thereby be estimated and consequently also the importance of lakes for the withdrawal of organic carbon export from terrestrial sources to the sea. Lakes removed 30-80% of imported terrestrial organic carbon, and mineralization and CO2 emission were much more important than sedimentation of carbon. The carbon loss was closely related to water retention time, where catchments with short residence times (<1 year) had low carbon retentions, whereas in catchments with long residence times (>3 years) a majority of the imported TOC was removed in the lake systems. The Gulf of Bothnia was also studied in this thesis and found to be a net heterotrophic system, emitting large amounts of CO2 to the atmosphere on an annual basis. The rate of CO2 emission was depending on the balance between primary production and bacterial respiration, and the system was oscillating between being a source and a sink of CO2.

Lau Ka Wah Joyce. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 177-192). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iv / Table of Contents --- p.vi / List of Tables --- p.xi / List of Figures --- p.xiv / List of Plates --- p.xvi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.1.1 --- Environment of Hong Kong --- p.1 / Chapter 1.1.1.1 --- Topography --- p.1 / Chapter 1.1.1.2 --- Climate --- p.1 / Chapter 1.1.1.3 --- Expanding population --- p.3 / Chapter 1.1.2 --- Landslide history in Hong Kong and government action --- p.4 / Chapter 1.1.3 --- Slopes in Hong Kong --- p.6 / Chapter 1.1.4 --- Stabilization means --- p.7 / Chapter 1.2 --- Biotechnical stabilization --- p.8 / Chapter 1.2.1 --- Concept --- p.8 / Chapter 1.2.2 --- History --- p.9 / Chapter 1.2.3 --- Advantages and strengths of vegetation --- p.9 / Chapter 1.2.4 --- Other components in biotechnical stabilization --- p.11 / Chapter 1.3 --- The situation in Hong Kong --- p.12 / Chapter 1.3.1 --- Government policy on control of visual impact of slopes --- p.12 / Chapter 1.3.2 --- Landslip Preventive Measures (LPM) Program --- p.15 / Chapter 1.3.3 --- Slope landscaping proprietary systems --- p.16 / Chapter 1.3.3.1 --- Proprietary systems --- p.16 / Chapter 1.3.3.2 --- Problems and limitations --- p.20 / Chapter 1.4 --- Ecosystem reconstruction on slopes --- p.23 / Chapter 1.4.1 --- Concept --- p.23 / Chapter 1.4.2 --- Plant requirements --- p.24 / Chapter 1.4.3 --- Potential challenges --- p.24 / Chapter 1.4.3.1 --- Steep gradient and related problems --- p.24 / Chapter 1.4.3.2 --- Thin soil --- p.24 / Chapter 1.4.3.3 --- Water supply --- p.26 / Chapter 1.4.3.4 --- Nutrient availability --- p.27 / Chapter 1.5 --- Species selection --- p.28 / Chapter 1.5.1 --- Vegetation types --- p.28 / Chapter 1.5.2 --- Natives or exotics --- p.29 / Chapter 1.5.3 --- Currently employed species and problems --- p.29 / Chapter 1.6 --- The current study --- p.31 / Chapter 1.6.1 --- Objectives --- p.31 / Chapter 1.6.2 --- Significance --- p.31 / Chapter Chapter 2 --- Soil status and vegetation of cutslopes --- p.35 / Chapter 2.1 --- Introduction --- p.35 / Chapter 2.2 --- Materials and methods --- p.42 / Chapter 2.2.1 --- Physical properties of substrates on slopes --- p.43 / Chapter 2.2.1.1 --- Gradient --- p.43 / Chapter 2.2.1.2 --- Aspect --- p.43 / Chapter 2.2.1.3 --- Soil depth --- p.44 / Chapter 2.2.1.4 --- Bulk density --- p.44 / Chapter 2.2.1.5 --- Soil texture --- p.44 / Chapter 2.2.2 --- Chemical properties of substrates on slopes --- p.45 / Chapter 2.2.2.1 --- pH --- p.45 / Chapter 2.2.2.2 --- Conductivity --- p.45 / Chapter 2.2.2.3 --- Organic carbon --- p.46 / Chapter 2.2.2.4 --- Carbon: nitrogen ratio --- p.46 / Chapter 2.2.2.5 --- Total Kjeldahl Nitrogen --- p.46 / Chapter 2.2.2.6 --- Mineral nitrogen (Ammonium and nitrate) --- p.46 / Chapter 2.2.2.7 --- Total phosphorus --- p.47 / Chapter 2.2.2.8 --- Available phosphorus --- p.47 / Chapter 2.2.2.9 --- Major extractable cations --- p.47 / Chapter 2.2.3 --- Statistical analysis --- p.47 / Chapter 2.2.4 --- Other properties on slopes --- p.48 / Chapter 2.2.4.1 --- Green coverage --- p.48 / Chapter 2.2.4.2 --- Invaded species --- p.48 / Chapter 2.3 --- Results --- p.48 / Chapter 2.3.1 --- Physical properties of substrates on slopes --- p.48 / Chapter 2.3.2 --- Chemical properties of substrates on slopes --- p.51 / Chapter 2.3.3 --- Other properties of the slopes --- p.58 / Chapter 2.3.3.1 --- Green coverage --- p.58 / Chapter 2.3.3.2 --- Invaded species --- p.60 / Chapter 2.4 --- Discussion --- p.61 / Chapter 2.4.1 --- The physical properties of substrates on slopes --- p.63 / Chapter 2.4.2 --- Chemical properties of substrates and their seasonal changes on slopes --- p.66 / Chapter 2.4.3 --- Green coverage and its seasonal changes --- p.70 / Chapter 2.4.4 --- Comparison between the standards and results --- p.75 / Chapter 2.4.5 --- Other problems --- p.78 / Chapter 2.5 --- Summary --- p.79 / Chapter Chapter 3 --- Species selection for cutslope revegetation --- p.81 / Chapter 3.1 --- Introduction --- p.81 / Chapter 3.1.1 --- The need to expand species variety for revegetation --- p.81 / Chapter 3.1.2 --- Criteria for plant selection --- p.81 / Chapter 3.1.3 --- Advantages of grasses and herbaceous legumes --- p.83 / Chapter 3.1.4 --- Pot experiment --- p.85 / Chapter 3.2 --- Materials and methods --- p.86 / Chapter 3.2.1 --- Summer grasses --- p.88 / Chapter 3.2.1.1 --- Germination rate --- p.88 / Chapter 3.2.1.2 --- Pot experiment --- p.88 / Chapter 3.2.2 --- Summer legumes --- p.90 / Chapter 3.2.3 --- Winter grasses --- p.90 / Chapter 3.2.4 --- Winter legumes --- p.90 / Chapter 3.3 --- Results --- p.91 / Chapter 3.3.1 --- Soil properties --- p.91 / Chapter 3.3.2 --- Aboveground biomass production --- p.91 / Chapter 3.3.2.1 --- Summer grasses --- p.91 / Chapter 3.3.2.2 --- Summer legumes --- p.98 / Chapter 3.3.2.3 --- Winter grasses --- p.101 / Chapter 3.3.2.4 --- Winter legumes --- p.106 / Chapter 3.3.3 --- Foliar nutrient concentration --- p.111 / Chapter 3.3.3.1 --- Summer grass --- p.111 / Chapter 3.3.3.2 --- Summer legumes --- p.113 / Chapter 3.3.3.3 --- Winter grasses --- p.114 / Chapter 3.3.3.4 --- Winter legumes --- p.115 / Chapter 3.4 --- Discussion --- p.116 / Chapter 3.4.1 --- Aboveground biomass production --- p.119 / Chapter 3.4.1.1 --- Summer grasses --- p.119 / Chapter 3.4.1.2 --- Summer legumes --- p.121 / Chapter 3.4.1.3 --- Winter grasses --- p.122 / Chapter 3.4.1.4 --- Winter legumes --- p.125 / Chapter 3.4.2 --- Foliar nutrient concentration --- p.126 / Chapter 3.4.3 --- Common nutrient application and the plant requirements --- p.128 / Chapter 3.5 --- Summary --- p.129 / Chapter Chapter 4 --- Growth of summer grasses in a combination of stresses --- p.131 / Chapter 4.1 --- Introduction --- p.131 / Chapter 4.2 --- Materials and methods --- p.131 / Chapter 4.2.1 --- Study species --- p.131 / Chapter 4.2.2 --- Pot experiment --- p.132 / Chapter 4.3 --- Results --- p.132 / Chapter 4.3.1 --- Pot experiment --- p.132 / Chapter 4.3.1.1 --- Aboveground biomass --- p.132 / Chapter 4.3.1.2 --- Foliar nutrient concentration --- p.138 / Chapter 4.4 --- Discussion --- p.140 / Chapter 4.4.1 --- Pot experiment --- p.140 / Chapter 4.4.1.1 --- Aboveground biomass --- p.140 / Chapter 4.4.1.2 --- Foliar nutrient concentration --- p.141 / Chapter 4.5 --- Summary --- p.141 / Chapter Chapter 5 --- Growth of summer grasses on simulated slopes --- p.143 / Chapter 5.1 --- Introduction --- p.143 / Chapter 5.2 --- Materials and methods --- p.145 / Chapter 5.2.1 --- Study species --- p.145 / Chapter 5.2.2 --- Artificial panel trial --- p.145 / Chapter 5.2.2.1 --- Experimental setup --- p.145 / Chapter 5.2.2.2 --- Growth pattern and green coverage --- p.147 / Chapter 5.2.2.3 --- Sediment runoff and change in soil thickness --- p.147 / Chapter 5.3 --- Results --- p.148 / Chapter 5.3.1 --- Grass growth on artificial panels --- p.148 / Chapter 5.3.1.1 --- Aboveground biomass and green coverage --- p.148 / Chapter 5.3.2 --- "Relationship between rainfall, runoff and soil loss" --- p.149 / Chapter 5.3.2.1 --- Effect of rainfall on runoff --- p.149 / Chapter 5.3.2.2 --- Effect of runoff on soil loss --- p.151 / Chapter 5.3.2.3 --- Effect of rainfall on soil loss --- p.152 / Chapter 5.3.2.4 --- Effect of aspect --- p.154 / Chapter 5.3.2.5 --- Effect of green coverage on soil loss --- p.154 / Chapter 5.3.3 --- Percentage of greening --- p.155 / Chapter 5.3.4 --- Soil thickness --- p.157 / Chapter 5.4 --- Discussion --- p.159 / Chapter 5.4.1 --- Grass growth on artificial panels --- p.159 / Chapter 5.4.2 --- "Relationship between rainfall, runoff and soil loss" --- p.160 / Chapter 5.4.2.1 --- Effect of rainfall on runoff --- p.160 / Chapter 5.4.2.2 --- Effect of runoff on soil loss --- p.160 / Chapter 5.4.2.3 --- Effect of rainfall on soil loss --- p.161 / Chapter 5.4.2.4 --- Effect of aspect on runoff and soil loss --- p.163 / Chapter 5.4.2.5 --- Effect of green coverage on runoff and soil loss --- p.164 / Chapter 5.4.3 --- Effects of other variables --- p.165 / Chapter 5.4.3.1 --- Effect of green coverage --- p.165 / Chapter 5.4.3.2 --- Effect of aspect --- p.167 / Chapter 5.4.4 --- Soil thickness --- p.168 / Chapter 5.5 --- Summary --- p.168 / Chapter Chapter 6 --- Conclusion --- p.170 / Chapter 6.1 --- Summary of major finding --- p.170 / Chapter 6.2 --- Implications of the study --- p.172 / Chapter 6.2.1 --- Growth medium --- p.172 / Chapter 6.2.2 --- Species selection --- p.174 / Chapter 6.3 --- Limitations of the study --- p.175 / Chapter 6.4 --- Suggestions for further investigation --- p.175 / References --- p.177

<p>The objective of the thesis was to explore the potential of diatoms (<i>Bacillariophyceae</i>) as indicators of Holocene climate and environmental change in northern Sweden (Abisko region, 68°21'N, 18°49'E). A modern surface-sediment calibration set including 100 lakes was developed and lake-water pH, sedimentary organic content (assessed by loss-on-ignition) and temperature were identified as most powerful environmental variables explaining the variance within the diatom assemblages. Transfer functions based on unimodal species response models (WA-PLS) were developed for lake-water pH and mean July air temperature (July T), yielding coefficients of determination of 0.77 and 0.70, and prediction errors based on leave-one-out cross-validation of 0.19 pH units and 0.96 °C for lake-water pH and July T, respectively. The transfer functions were validated with monitoring data covering two open-water seasons (lake-water pH) and meteorological records covering the 20th century (July T). The good agreement between diatom-based inferences and measured monitoring data confirmed the prediction ability of the developed transfer functions. </p><p>Analysing a Holocene sediment core from a lake nearby Abisko (Vuoskkujávri), diatoms infer a linearly decreasing July T trend (1.5 °C) since 6,000 cal. BP, which compares well with inferences based on chironomids and pollen from the same sediment core. The lake-water pH inference shows a pattern of moderate natural acidification (c. 0.5 pH units) since the early Holocene, reaching present-day pH values at c. 5,000 cal. BP. By fitting fossil diatom samples to the modern calibration set by means of residual distance assessment within canonical correspondence analysis (CCA), the early Holocene (between 10,600 and 6,000 cal. BP) was identified as a problematic time-period for diatom-based inferences and, consequently, reconstructions during this period are tentative. Pollen-based inferences also show 'poor' fit between 10,600 and 7,500 cal. BP and chironomids probably provide the most reliable July T reconstruction at Vuoskkujávri, with 'poor' fit only during the initial part of the Holocene (between 10,600 and 10,250 cal. BP). </p><p>Possible factors confounding diatom-based July T inferences were investigated. Using detrended CCA (DCCA), Holocene sediment sequences from five lakes indicate that during the early Holocene, mainly physical factors such as high minerogenic erosion rates, high temperature and low light availability may have regulated diatom assemblages, favouring <i>Fragilaria</i> species. In all five lakes, diatom assemblages developed in a directional manner, but timing and scale of development differed substantially between lakes. The differences are attributed primarily to the geological properties of the lake catchments (with strong effects on lake-water pH), but other factors such as climatic change, vegetation, hydrologic setting and in-lake processes appear to regulate diatom communities in each lake differently. The influence of long-term natural acidification on diatom assemblages progressively declined during the Holocene with corresponding increase of the influence of climatic factors.</p>

<p>This thesis contributes to the understanding of glacier response to climate change by ice dynamical studies on Storglaciären, Sweden, and Bonnevie-Svendsenbreen, Kibergbreen and Plogbreen in Dronning Maud Land, Antarctica. Ice surface velocities, ice geometry and temperature information is fed through a force budget model to calculate ice mass outflux of these glacial systems via three-dimensional stress distributions for a flux-gate. </p><p>Field data were collected through repeated DGPS and GPR observations on Storglaciären between July 2000 to September 2001 and on Kibergbreen and Plobreen during the SWEDARP 2002/03 expedition to Antarctica. The work was strongly supported by remotely-sensed information.</p><p>The results from Storglaciären show a strength in the force budget model to discern both spatial and temporal variability in ice dynamical patterns. It highlights the influence of seasonality and bedrock topography upon glacier flow. A modeling experiment on Bonnevie-Svendsenbreen suggested that ice temperature increases substantially under conditions of high stress (≥0.4 MPa) due to strain-heating. This provides a positive feedback loop, increasing ice deformation, as long as it overcomes the advection of cool ice from the surface. These results explain, to some extent, the mechanism behind fast flowing ice streams. Mass flux caclulations from Bonnevie-Svendsenbreen suggest that the outflux given from force budget calculations can be used as a gauge for influx assuming steady state conditions. Plogbreen receives an influx of 0.48±0.1 km³ a^-1 and expedites a discharge volume of 0.55±0.05 km³ a^-1. This indicative negative mass balance is explained by a falling trend in upstream accumulation and the recent rise in global sea level, as it is likely to induce glacier acceleration due to a reduction in resistive forces at the site of the gate. This result is comparable with other Antarctic studies reporting negative mass balances, e.g. from WAIS, as caused by changes in the global atmospheric circulation pattern.</p>

The objective of the thesis was to explore the potential of diatoms (Bacillariophyceae) as indicators of Holocene climate and environmental change in northern Sweden (Abisko region, 68°21'N, 18°49'E). A modern surface-sediment calibration set including 100 lakes was developed and lake-water pH, sedimentary organic content (assessed by loss-on-ignition) and temperature were identified as most powerful environmental variables explaining the variance within the diatom assemblages. Transfer functions based on unimodal species response models (WA-PLS) were developed for lake-water pH and mean July air temperature (July T), yielding coefficients of determination of 0.77 and 0.70, and prediction errors based on leave-one-out cross-validation of 0.19 pH units and 0.96 °C for lake-water pH and July T, respectively. The transfer functions were validated with monitoring data covering two open-water seasons (lake-water pH) and meteorological records covering the 20th century (July T). The good agreement between diatom-based inferences and measured monitoring data confirmed the prediction ability of the developed transfer functions. Analysing a Holocene sediment core from a lake nearby Abisko (Vuoskkujávri), diatoms infer a linearly decreasing July T trend (1.5 °C) since 6,000 cal. BP, which compares well with inferences based on chironomids and pollen from the same sediment core. The lake-water pH inference shows a pattern of moderate natural acidification (c. 0.5 pH units) since the early Holocene, reaching present-day pH values at c. 5,000 cal. BP. By fitting fossil diatom samples to the modern calibration set by means of residual distance assessment within canonical correspondence analysis (CCA), the early Holocene (between 10,600 and 6,000 cal. BP) was identified as a problematic time-period for diatom-based inferences and, consequently, reconstructions during this period are tentative. Pollen-based inferences also show 'poor' fit between 10,600 and 7,500 cal. BP and chironomids probably provide the most reliable July T reconstruction at Vuoskkujávri, with 'poor' fit only during the initial part of the Holocene (between 10,600 and 10,250 cal. BP). Possible factors confounding diatom-based July T inferences were investigated. Using detrended CCA (DCCA), Holocene sediment sequences from five lakes indicate that during the early Holocene, mainly physical factors such as high minerogenic erosion rates, high temperature and low light availability may have regulated diatom assemblages, favouring Fragilaria species. In all five lakes, diatom assemblages developed in a directional manner, but timing and scale of development differed substantially between lakes. The differences are attributed primarily to the geological properties of the lake catchments (with strong effects on lake-water pH), but other factors such as climatic change, vegetation, hydrologic setting and in-lake processes appear to regulate diatom communities in each lake differently. The influence of long-term natural acidification on diatom assemblages progressively declined during the Holocene with corresponding increase of the influence of climatic factors.

This thesis contributes to the understanding of glacier response to climate change by ice dynamical studies on Storglaciären, Sweden, and Bonnevie-Svendsenbreen, Kibergbreen and Plogbreen in Dronning Maud Land, Antarctica. Ice surface velocities, ice geometry and temperature information is fed through a force budget model to calculate ice mass outflux of these glacial systems via three-dimensional stress distributions for a flux-gate. Field data were collected through repeated DGPS and GPR observations on Storglaciären between July 2000 to September 2001 and on Kibergbreen and Plobreen during the SWEDARP 2002/03 expedition to Antarctica. The work was strongly supported by remotely-sensed information. The results from Storglaciären show a strength in the force budget model to discern both spatial and temporal variability in ice dynamical patterns. It highlights the influence of seasonality and bedrock topography upon glacier flow. A modeling experiment on Bonnevie-Svendsenbreen suggested that ice temperature increases substantially under conditions of high stress (≥0.4 MPa) due to strain-heating. This provides a positive feedback loop, increasing ice deformation, as long as it overcomes the advection of cool ice from the surface. These results explain, to some extent, the mechanism behind fast flowing ice streams. Mass flux caclulations from Bonnevie-Svendsenbreen suggest that the outflux given from force budget calculations can be used as a gauge for influx assuming steady state conditions. Plogbreen receives an influx of 0.48±0.1 km3 a-1 and expedites a discharge volume of 0.55±0.05 km3 a-1. This indicative negative mass balance is explained by a falling trend in upstream accumulation and the recent rise in global sea level, as it is likely to induce glacier acceleration due to a reduction in resistive forces at the site of the gate. This result is comparable with other Antarctic studies reporting negative mass balances, e.g. from WAIS, as caused by changes in the global atmospheric circulation pattern.

Thesis--Bordeaux III, 1977. / Includes bibliographical references (p. 634-660).

Doctor of Philosophy / Department of Geography / Douglas G. Goodin / Hantaviruses are zoonotic, RNA viruses that are harbored by muroid rodents of the families Muridae and Cricetidae. While the virus is endemic, and mostly non-symptomatic in its rodent reservoirs, when humans contact the virus it can result in serious disease. My purpose in this dissertation is to investigate the effect that landscape patterns and land cover condition can have on pathogen prevalence in a hantavirus reservoir species (Akodon montensis) within the Atlantic Forest region of Eastern Paraguay and to investigate ways to analyze those patterns using remotely sensed data. The first component to this research is to test potential improvements to image classifications on land use/land cover classifications useful for the study of small mammal communities. An object-based classification produced the best results with seven classes: Forest, Wet Cerrado, Dry Cerrado, Latifundia, Minifundia, Dry Pasture, and Wet Pasture. The classified imagery was then used to assess landscape effects on the presence of hantaviral antibodies (a 'marker' for exposure to the virus) in populations of A. montensis. In the overall landscape, proximity of similar habitat patches was related to seroprevalence in Akodon. When considering only the forest class, high amount of forest, high number of forest patches, and high diversity in forest patch sizes were all associated with seroprevalence. Next, was an analysis of ways to distinguish understory density variables through the use of satellite imagery. Horizontal and vertical density in the understory has been associated with the presence of hantavirus in A. montensis. Vertical and horizontal density measurements were correlated with NDVI and the Fourth band in the Tasseled Cap transformation. Finally, I consider the relationship between small mammal community diversity and seroprevalence, and their association with NDVI. Diverse small mammal communities are associated with low hantavirus seroprevalence. Low diversity metrics and high hantavirus seroprevalence were associated with high mean NDVI values. Many aspects of landscape patterns are important to hantavirus seroprevalence in small mammal communities in Eastern Paraguay. Several of the landscape patterns important to hantavirus seroprevalence can be studied using satellite-derived data.