Periodic monitoring of contaminant levels in fish from the Yukon Territory indicated that organochlorine (OC) contaminants had rapidly declined since the early 1990s. This study examined OC concentrations, including chlordane (sigma-CHL), sigma-DDT, hexachlorocyclohexane (sigma-HCH), toxaphene (sigma-CHB), sigma-PCB and chlorinated benzenes (sigma-CBz) in sentinel fish (species of consistent annual observation and collection) from two Yukon lakes (Kusawa, Quiet), and from the aquatic food web of a focus lake (Lake Laberge) across several temporal points between 1993 and 2003. OC analysis and phytoplankton counts from dated sediment cores as well as climate data were also collected. Population, morphological (length, weight, age), biochemical (lipid content, delta-13C, delta-15N) and OC contaminant data for fish and invertebrates (zooplankton, snails, clams) were reviewed to elucidate the primary causes for these OC declines. Although some spatial differences in contaminant levels exist between the Yukon lakes, OC concentrations were declining for lake trout in all three lakes, with declines also noted for burbot from Lake Laberge. Several other fish species as well as zooplankton from Lake Laberge exhibited decreases in contaminant levels except northern pike, which registered consistently higher levels from 1993 to 2001. There was no evidence to support the hypotheses of changes in fish trophic levels or food sources with the exception of burbot, which marginally decreased, and northern pike, which climbed a half trophic level. Through OC flux analysis in dated sediments, the hypothesis that declines in abiotic deposition affected the contaminant levels in the food web was also negated. The closure of the Lake Laberge commercial fishery resulted in faster fish growth and larger fish populations, which are contributing to biomass dilution of OC concentrations, higher OC biomagnification factors for some species and likely changes in predator-prey interactions as resource competition increases. The large ratio of OC decreases in the lower vs. higher trophic levels of Lake Laberge have increased food web magnification factors (FWMF) for all six OC groups. It is also suspected that above-average temperatures and below-average precipitation in the lower Yukon region over the 1990s may have contributed towards an increase in lake primary production resulting in biomass dilution of contaminants in zooplankton for all three study lakes. Concurrently, shifts in the Lake Laberge zooplankton community, from climate fluctuations or increased fish predation, have gone from an abundance of Cyclops scutifer in 1993 to dominance by Diaptomus pribilofensis in 2001, although sample sites were limited. Characteristics specific to each species (e.g. body size, composition and metabolism) likely play a role in the significant OC declines measured in zooplankton. Fluctuations in population dynamics, species characteristics and OC contaminant concentrations in the Lake Laberge ecosystem may continue for several years to come. Sentinel species such as lake trout, burbot, whitefish, cisco and plankton should continue to be monitored in all three Yukon lakes for future temporal correlations with contaminants or climate change.

The tundra ecosystem, with its frost-molded landscape and large peat reserves, is vulnerable to climate change. Thus, any increase in temperature due to global warming will cause changes in above-and belowground biota. Understanding the linkage between these biotas will help make prediction of the biodiversity and ecosystem functioning when global change phenomena occur, and consequently aid in making management strategies. The role of nematodes in nutrient cycling and decomposition, among many other attributes, make them useful organisms to study soil processes. Associations between plant and nematode communities, from six sites (Berm Face, Berm Crest, Tundra Heath, Polygon, Hummock and Forest) and from within a young, visually homogeneous tundra heath field site, were examined in the subarctic environment of Churchill, Manitoba. The study also provided nematofaunal information, which is very limited in this region. Multivariate analyses of nematode taxa abundance revealed four distinct groupings: Berm Face, Berm Crest, heaths (Tundra Heath, Polygon and Hummock) and Forest. The result showed a parallel relationship between nematode and vegetation assemblages, and thus, a seeming interdependency between above-ground and below-ground biota. Conversely, association between nematode and plant assemblages within a visually homogeneous tundra site was not as obvious. At this fine scale, the heterogeneous nature of edaphic factors and not plant assemblages is hypothesized to influence within-site nematode communities. The thesis also provided results to improve nematofaunal analysis to enhance their utility as bioindicators of soil food webs.

This thesis characterizes the cycling of carbon, nitrogen and silicon by marine polar diatoms through the aid of a field study and a laboratory study. Field studies were conducted along a transect from Victoria, Canada to Barrow, Alaska and particulate carbon, nitrogen and silicon, chlorophyll a, nitrate, phosphate, silicic acid, and carbon and nitrogen incorporation, along with biogenic silica net incorporation were measured. Total primary production was lowest in the NE Pacific (0.3 to 1.0 mmol m-3 day-1), with new production contributing 17 to 38% of total production. Biogenic silica net incorporation in the upper 250 m of the water column in the NE Pacific was relatively low (0 to 0.12 mmol m-3 day-1), but positive, indicating the opportunity for export from the euphotic zone. Total primary, new production and production by siliceous plankton was highest in the Chukchi Sea, due to the influence of nutrient influx from the Anadyr Stream. Total primary production ranged from 1.0 to 3.2 mmol m-3 day-1, new production contributed as much as 56% of total production, and the production by siliceous phytoplankton was as high as 5.6 mmol m-3 day-1. Siliceous biomass was usually recycled in the upper water column of the Bering and the Chukchi Seas, in contrast to the NE Pacific. The interference of lithogenic material on the measurement of biogenic silica was explored using data from the Bering and Chukchi Seas. Results show that lithogenic interference is location specific. Sediment clay composition data should be considered when high concentrations of lithogenic silica are present. The laboratory study examined the effects of different irradiance and temperature conditions on two polar diatom species: Thalassiosira antarctica and Porosira glacialis. Temperature and irradiance had species-specific effects on the cellular content of carbon, nitrogen and silicon. The relationship between growth rate and silicon content for T. antarctica showed that silicon content increased as growth rate decreased, which is in agreement with previous studies. However, this relationship did not hold for P. glacialis at low temperatures. These species-specific effects complicate the understanding of how environmental change will influence phytoplankton populations in Arctic and sub-Arctic marine areas. In general, primary production was lower in the Bering and Chukchi Seas when compared to previous studies, however it is unknown whether differences are due to interannual variability or a trend of decreasing production. Data from both the field and laboratory component indicate a high amount of biological silicon cycling in polar environments. This study represents the first time net silicon incorporation has been measured as far north as the Chukchi Sea.

The Western James Bay region of northern Ontario (the Mushkegowuk Territory) is home to some of Canada’s largest wetlands and most pristine ecosystems. This region is also home to approximately 10,000 Omushekgo Cree who inhabit four First Nation communities. Environmental change due to climate change and major resource development are a reality to the people of this sub-arctic region. Furthermore, it is predicted that climate change will have amplified impacts in northern climates. Climate change has and will continue to have impacts on the distribution of species in arctic and sub-arctic ecosystems. To date, it is not clear to what extent these distributional changes in species due to climate change will have on First Nations’ place-based relationship with the land and what measures the Cree will take to adapt to these changes. The University of Waterloo’s Computer Systems Group has developed an approach and toolkit for the development of web-based, spatial data and information management systems referred to as collaborative geomatics. This system allows for place-based information, environmental and traditional environmental knowledge (TEK) storage and sharing between First Nation communities. And allows for the development of adaptive strategies and plans for future land use activities in the face of further resource development. This collaborative geomatic system has been designed with First Nation input and has been demonstrated to Chiefs and Councils of the Mushkegowuk Territory. Collaborative geomatics is an interactive, web-based, informatics tool that has been designed to store data, in a secure and culturally-appropriate framework on high-resolution satellite imagery. High-resolution imagery will become the backdrop to placed-based and TEK data. Community members will have the ability to input locations (e.g., significant sites, such as, seasonal camps and hunting locations) on the map in addition to uploading tabular and media data. This allows for the generation of dynamic and robust spatially-relevant information and knowledge-base. Beginning in August of 2009, formal and informal meetings were held with personnel from the Lands and Resources unit of Mushkegowuk Council, First Nations Chiefs and Councils (the elected local government), and other community members of MooseCree First Nation, Fort Albany First Nation, Kashechewan First Nation, Attawapiskat First Nation, and Weenusk First Nation to gather their assessment (i.e., viability) of the Mushkegowuk collaborative geomatics tool. Together with this formative assessment process, 16 semi-directive interviews (from October 2010 to February 2011) were conducted with community members of Fort Albany First Nations. Interview participants were purposively sampled and included: Chief & Council members, First Nation office personnel, education personnel, health services personnel, elders (≥60 years of age), and young adults. Each interview was audio recorded and transcribed verbatim. Following an adapted grounded theory methodological approach, the transcripts of each interview were coded and categorized according to themes. Throughout the assessment process, the research team received constructive feedback on the system. Each participant noted the utility of the tool to be used in the education of younger generations. Furthermore, participants felt that they would be able to use the tool to store TEK and help monitor environmental change. The greatest strength of the system was seen to be the visualization of information in numerous media forms (pictures and videos), while the greatest perceived weakness of the system was the security of the information. However, once user accessibility (usernames and passwords) was explained the concern over security of information was greatly reduced. This collaborative geomatic system has the potential to enhance the Mushkegowuk First Nations’ adaptive capacity to address environmental change by allowing them to make informed decisions, utilizing the knowledge stored in the collaborative geomatics tool.

Periodic monitoring of contaminant levels in fish from the Yukon Territory indicated that organochlorine (OC) contaminants had rapidly declined since the early 1990s. This study examined OC concentrations, including chlordane (sigma-CHL), sigma-DDT, hexachlorocyclohexane (sigma-HCH), toxaphene (sigma-CHB), sigma-PCB and chlorinated benzenes (sigma-CBz) in sentinel fish (species of consistent annual observation and collection) from two Yukon lakes (Kusawa, Quiet), and from the aquatic food web of a focus lake (Lake Laberge) across several temporal points between 1993 and 2003. OC analysis and phytoplankton counts from dated sediment cores as well as climate data were also collected. Population, morphological (length, weight, age), biochemical (lipid content, delta-13C, delta-15N) and OC contaminant data for fish and invertebrates (zooplankton, snails, clams) were reviewed to elucidate the primary causes for these OC declines. Although some spatial differences in contaminant levels exist between the Yukon lakes, OC concentrations were declining for lake trout in all three lakes, with declines also noted for burbot from Lake Laberge. Several other fish species as well as zooplankton from Lake Laberge exhibited decreases in contaminant levels except northern pike, which registered consistently higher levels from 1993 to 2001. There was no evidence to support the hypotheses of changes in fish trophic levels or food sources with the exception of burbot, which marginally decreased, and northern pike, which climbed a half trophic level. Through OC flux analysis in dated sediments, the hypothesis that declines in abiotic deposition affected the contaminant levels in the food web was also negated. The closure of the Lake Laberge commercial fishery resulted in faster fish growth and larger fish populations, which are contributing to biomass dilution of OC concentrations, higher OC biomagnification factors for some species and likely changes in predator-prey interactions as resource competition increases. The large ratio of OC decreases in the lower vs. higher trophic levels of Lake Laberge have increased food web magnification factors (FWMF) for all six OC groups. It is also suspected that above-average temperatures and below-average precipitation in the lower Yukon region over the 1990s may have contributed towards an increase in lake primary production resulting in biomass dilution of contaminants in zooplankton for all three study lakes. Concurrently, shifts in the Lake Laberge zooplankton community, from climate fluctuations or increased fish predation, have gone from an abundance of Cyclops scutifer in 1993 to dominance by Diaptomus pribilofensis in 2001, although sample sites were limited. Characteristics specific to each species (e.g. body size, composition and metabolism) likely play a role in the significant OC declines measured in zooplankton. Fluctuations in population dynamics, species characteristics and OC contaminant concentrations in the Lake Laberge ecosystem may continue for several years to come. Sentinel species such as lake trout, burbot, whitefish, cisco and plankton should continue to be monitored in all three Yukon lakes for future temporal correlations with contaminants or climate change.

Abstract The elongation response of Scots pine (Pinus sylvestris L.) seedlings to the removal of blue light (400–500 nm) was studied in field experiments in northern Finland. The seedlings were grown in orange or transparent plexiglass chambers or in ambient control plots. The orange plexiglass removed the blue wavelengths from sunlight, while the others served as controls. The experiment was conducted at sub-arctic (69°N) and mid-boreal (64°N) latitudes with three- and two-year-old seedlings originating from 67°N latitude. The response to blue light depletion was also investigated at the 69°N latitude in the following plant subjects: one-year-old Scots pine seedlings of northern (67°N) and southern (62°N) provenances, deciduous Betula pubescens ssp. czerepanovii and Betula pubescens f. rubra seedlings and herbaceous Epilobium angustifolium and Glechoma hederacea plants. Additionally, diurnal change in light quality at the 69°N latitude during the summer was measured. The elongation of Scots pine seedlings was increased by the removal of blue wavelengths. The increase was more pronounced at the 69°N latitude, while at the 64°N latitude the response was smaller or absent. This is due to increased amount of scattered growth-inhibiting blue light during the nights at the high latitude. The removal of blue light increased stem elongation in northern origin Scots pine seedlings much more compared to the southern origin seedlings, which suggests that the northern provenance is more sensitive to blue light. Irrespective of that, southern origins also suffer from reduced elongation in the north as they migrate according to climatic change scenarios. However, it is obvious that they grow longer than local origins in the north. Morphological variables and photosynthetic pigments confirm that the increased elongation of Scots pine seedlings under blue light depletion is not a result of etiolation or it is only a marginal factor. Also, it was neither dependent on temperature nor photosynthesis and growth resources. Instead, the increased elongation is probably a photomorphogenic regulation response of metabolism. In addition, shade intolerant Scots pine, Betula seedlings and herbaceous Epilobium angustifolium responded stronger to blue light removal compared to the more shade-tolerant herbaceous Glechoma hederacea.

This report studies a subarctic greenhouse located in Nikkala, Sweden called Nikkala handelsträdgård. Through a visit to the greenhouse coupled with the creation of two simulation models this study investigates the differences in energy demand with water-carried and air-carried heating systems, high pressure sodium lights and Light emitting diode lights and insulation in parts of the greenhouse without a active cultivation. With the purpose of comparing the alternatives to the existing system at Nikkala handelsträdgård. This, to evaluate if an investment in insulation for the non cultivating parts or changing to a water-carried heating system with Light emitting diode lights could be considered profitable. Operating a greenhouse in a subarctic climate is a hard task and especially if the operation is year round. Efficient heating systems, thermal screens, dehumidifying measures and Lighting systems are crucial to ensure a profitable business. At Nikkala handelsträdgård they are currently using a pellets burner in combination with a air-carried heating system and HPS lamps in the majority of the greenhouse.  The simulations of the main greenhouse were made in Ansys fluent where the crop section was simulated by implementing source terms to a macro porous medium. The parts of the greenhouse which did not host an active cultivation were simulated in IDA ICE.  It was found that saving of just under 14 800 SEK monthly or 18 % could be made by implementing a water-carried heating system in combination with state of the art lighting. Given this a payback-time of 3-9 years could be expected given different scenarios. An implementation of insulation in the non cultivation greenhouse parts would save up to 25 300 SEK annually or 46 % of the heat demand and the investment would give a payback-time of 1-2 years given different scenarios. Given this a reduction of CO2 equivalents of just under 1,9 tonnes could be achieved yearly. It was concluded that relatively inexpensive investments could have a great impact on the energy demand and thereby the economical performance of a subarctic greenhouse. New operations should be built with a LED light system and water-carried heating system and all parts of the greenhouse which is not housing an active cultivation needs to be insulated.

Understanding the drivers of climate change requires knowledge about the global carbon (C) cycle. Although inland waters play an important role in the C cycle by emitting and burying C, streams and lakes are in general overlooked in bottom-up approached C budgets. In this thesis I estimated emissions of carbon dioxide (CO2) and methane (CH4) from all lakes and streams in a 15 km2 subarctic catchment in northern Sweden, and put it in relation to the total catchment C exchange. I show that high-latitude aquatic systems in general and streams in particular are hotspots for C emission to the atmosphere. Annually, the aquatic systems surveyed in this study emitted about 10.8 ± 4.9 g C m-2 yr-1 (ca. 98 % as CO2) which is more than double the amount of the C laterally exported from the catchment. Although the streams only covered about 4% of the total aquatic area they emitted ca. 95% of the total aquatic C emission. For lake emissions, the ice break-ups were the most important annual events, counting for ca. 45% of the emissions. Overall, streams dominated the aquatic CO2 emission in the catchment while lakes dominated CH4 emission, 96 % and 62 % of the totals, respectively. When summing terrestrial and aquatic C fluxes together it showed that the aquatic emissions alone account for approximately two thirds of the total annual catchment C loss. The consequence of not including inland waters in bottom-up derived C budgets is therefore a risk of overestimating the sink capacity of the subarctic landscape. However, aquatic systems can also act as C sinks, by accumulating C in sediment and thereby storing C over geological time frames. Sediment C burial rates were estimated in six lakes from a chronology based on 210Pb dating of multiple sediment cores. The burial rate ranged between 5 - 25 g C m-2 yr-1, which is of the same magnitude as lake C emissions. I show that the emission:burial ratio is about ten times higher in boreal compared to in subarctic-arctic lakes. These results indicate that the balance between lakes C emission and burial is both directly and indirectly dependent on climate. This process will likely result in a future increase of C emissions from high-latitude lakes, while the C burial capacity of these same lakes sediments weaken.

In recent years, concern has grown over the consequences of global warming. The arctic region is thought to be particularly vulnerable to increasing temperatures, and warming is occurring here substantially more rapidly than at lower latitudes. Consequently, assessments of the state of the Arctic are a focus of international efforts. For the terrestrial Arctic, large datasets are generated by remote sensing of above-ground variables, with an emphasis on vegetation properties, and, by association, carbon fluxes. However, the terrestrial component of the carbon (C) cycle remains poorly quantified and the below-ground distribution and stocks of soil C can not be quantified directly by remote sensing. Large areas of the Arctic are also difficult to access, limiting field surveys. The scientific community does know, however, that this region stores a massive proportion (although poorly quantified, soil C stocks for tundra soils vary from 96 to 192 Gt C) of the global reservoir of soil carbon, much of it in permafrost (900 Gt C), and these stocks may be very vulnerable to increased rates of decomposition due to rising temperatures. The consequences of this could be increasing source strength of the radiatively forcing gases carbon dioxide (CO2) and methane (CH4). The principal objective of this project is to provide a critical evaluation of methods used to link soil C stocks and fluxes at the usual scales spanned by the field surveys (centimetre to kilometre) and remote sensing surveys (kilometre to hundreds of kilometres). The soil C distribution of two sub-arctic sites in contrasting climatic, landscape/geomorphologic and vegetation settings has been described and analysed. The transition between birch forest and tundra heath in the Abisko (Swedish Lapland) field site, and the transition between mire and birch forest in the Kevo (Finnish Lapland) field site span several vegetation categories and landscape contexts. The natural variability of below-ground C stocks (excluding coarse roots > 2 mm diameter), at scales from the centimetre to the kilometre scale, is high: 0.01 to 18.8 kg C m-2 for the 0 - 4 cm depth in a 2.5 km2 area of Abisko. The depths of the soil profiles and the soil C stocks are not directly linked to either vegetation categories or Leaf Area Index (LAI), thus vegetation properties are not a straightforward proxy for soil C distribution. When mapping soil or vegetation categories over large areas, it is usually necessary to aggregate several vegetation or soil categories to simplify the output (both for mapping and for modelling). Using this approach, an average value of 2.3 kg C m-2 was derived both for soils beneath treeless areas and forest understorey. This aggregated value is potentially misleading, however, because there is significant skew resulting from the inclusion of exposed ridges (with very low soil C stocks) in the ‘treeless’ category. Furthermore, if birch trees colonise tundra heath and other ‘open’ plant communities in the coming decades, there will likely be substantial shifts in soil C stocks. This will be both due to direct climate effects on decomposition, but also due to changes in above- and below-ground C inputs (both in quantity and quality) and possibly changes in so-called root ‘priming’ effects on the decomposition of existing organic matter. A model of soil respiration using parameters from field surveys shows that soils of the birch forest are more sensitive to increases in mean annual temperature than soils under tundra heath. The heterogeneity of soil properties, moisture and temperature regimes and vegetation cover in ecotone areas means that responses to climate change will differ across these landscapes. Any exercise in upscaling results from field surveys has to indicate the heterogeneity of vegetation and soil categories to guide soil sampling and modelling of C cycle processes in the Arctic.

Abstract Plants and soil organisms are closely linked. Plants are the sole source of carbon in the soil and soil organisms are responsible for recycling of nutrients, making them available for plant growth. To understand the function of a system, it is important to understand the interactions between the soil and plants. These interactions have mainly been studied in temperate areas, with few studies in the arctic and subarctic. The aim of this thesis was to investigate the effect of ecological disturbances in sub- and low-arctic grasslands on soil organisms and plant-soil feedback relationships. The effect of removal of vegetation, replanting of a local plant species, and different components of grazing (trampling, defoliation and return of nutrients) on soil decomposer organisms were studied. Whether short term effects of defoliation depended on plant species community was also studied, as well as whether defoliation in the field could create changes in the soil system systems that affect the growth of seedlings. Experiments were conducted under both controlled greenhouse conditions and in field sites. The results showed that physical disturbance (removal of vegetation and trampling) reduced the abundance and diversity of soil biota. Defoliation increased soil decomposer abundance in the short term. Plant species composition did not affect soil biota and only in a few cases did it changes their responses to defoliation. In the long-term, effects of fertilization and defoliation on the soil biota were context-dependent. However, defoliation did create changes in the soil that reduced the growth of seedlings planted into the soil. Furthermore, plant species community and spatial heterogeneity (revealed by blocking) had important effects on the soil communities.