The purpose of this dissertation research was to investigate the spatial patterns of abundance, growth, and stand structure across the geographic ranges of tree species using dendroecological methods. I assessed whether the biogeographic paradigms of the abundant center hypothesis and the principle of ecological amplitude adequately characterize spatial patterns of tree abundance, climate response, and stand composition. The abundant center hypothesis is a longstanding, yet rarely tested assumption that the centers of geographic ranges represent ideal conditions where species can achieve their greatest abundance, and abundance declines with increasing distance from the range center. A corollary to the abundant center hypothesis is the concept of ecological amplitude, which predicts that species will be subject to greater environmental stress near range margins, and thus, will be more sensitive to environmental variability and occupy restricted sites in peripheral locations. To investigate ecological amplitude predictions regarding tree species of North America, I analyzed: (1) the abundance of red fir to directly test the abundant center hypothesis, (2) the response of longleaf pine growth to monthly climate variables at peripheral and interior sites, (3) the spatial pattern of annual growth sensitivity to climate in networks of tree-ring data for two widely-distributed species, and (4) the composition and structure of pine-oak stands at a central and a peripheral location within the ranges of several dominant tree species. The analyses presented here demonstrate that the abundant center hypothesis and ecological amplitude principle do not accurately characterize spatial patterns of abundance, growth, or stand composition among North American tree species. Lack of support for the abundant center/ecological amplitude paradigm suggests that current models of forest change and species’ range dynamics should be reconsidered, and new models should be developed based on empirical analysis of range structure and dynamics.

The Arctic region attracts considerable scientific interest in these years. Some of the Earth's most pronounced signs of the recent climate change are found here. The summer sea-ice cover is shrinking at an alarming rate. At the same time the region warms faster than the rest of the globe. The sea-ice reduction implies an increase of solar-radiation absorption at the surface leading to warming which is expected to be larger at higher than at lower latitudes. It is therefore often assumed that the sea-ice reduction is a major cause of the observed Arctic temperature amplification. However, results presented in this thesis suggest that the snow and ice-albedo feedbacks are a contributing but not dominating mechanism behind the Arctic amplification. A coupled climate-model experiment with a doubling of the atmospheric CO2 concentration reveals a considerable Arctic surface-air-temperature amplification in a world without surface-albedo feedback. The amplification is only 8 % larger when this feedback is included. Instead the greenhouse effect associated with an increase of humidity and cloud cover over the Arctic seems to play a major role for the amplification. Reanalysis data, which are partly based on observations, show Arctic temperature amplification well above the surface in the troposphere. In the summer season, the amplification has its maximum at ~ 2 km height. These trends cannot be explained by the snow- and ice-albedo feedbacks which are expected to induce the largest amplification near the surface. Instead, a considerable part of the trends aloft can be linked to an increase of the atmospheric energy transport into the Arctic. A major topic of this thesis is the linkage between the mid-latitude circulation and the Arctic warming. It is suggested that the atmospheric meridional energy transport is an efficient indicator of this linkage.

This is a thesis regarding a local event that occurred in Babati district in North-Eastern Tanzania during the autumn of 2009. In the district the period between June-November is normally a dry period, but this year the serenity of the drought was considered as harsher than usual. The majority of the workforce in Tanzania and in Babati is within the agricultural sector, and thus are directly dependant on the weather for the cultivation of the crops. A severe drought that wipes out the larger amount of the yield is devastating for the farmer-households, both socially and economical. The drought in question may or may not have been a result of climate changes, but it can be used as a mirror to future and present events that actually happens due to a changed climate. The reactions and consequences that this drought had on the people who got affected can tell us something about how future changes of the climate, or even temporary fluctuations of the weather, may concern people globally. My field study confirms the gendered imbalance in resilience against ecological changes, by illuminating how the women-headed households were the group that had been hardest hit of the farmers that I interviewed. This can be connected to a pandemic structure where poor, rural women constitute the most vulnerable group when it comes to ecological catastrophes and changed patterns in weathers and/or climate. The social impacts that the drought had on the inhabitants of Babati in general, and it’s female inhabitants maintaining on agricultural in particular, works as a general example on how people that already constitute a marginalized group in society, are the least resilient when it comes to endure natural catastrophes.

A large amount of Nile water originates in Ethiopia. However, large uncertainty arises concerning whether land degradation or climate change is the cause for the observed increase in discharge along downstream countries. Previous studies showed increases in discharge at Kessie, Bahir Dar and El Diem over the past four decades with no increase in basin-average rainfall. They cite changes in landscapes or soil coverage as a potential reason for this change. However, the study in this thesis shows that the change in discharge could also be explained in part by spatial changes in precipitation. This thesis investigates trends in rainfall within the Blue Nile River Basin f rom 1963 to 2003. For this study total monthly and daily precipitation data were collected from across the Blue Nile River Basin and analyzed statistically. The results indicate spatial variability in the rainfall observed. The general long-term trends in annual as well as in seasonal precipitation show a general decreasing trend along southwest regions of the study area. However, an increasing  trend was encountered along northeast and southeast region of the Basin (3 of 9 selected stations). Rainfall-runoff modelling was performed to estimate the required precipitation increase to produce the increase in discharge observed in the Blue Nile River Basin. Precipitation needed to increase between 10 % and 25 % to account for the increased discharge. This increase is similar to that observed for some of the precipitation stations showing that increase in discharge seen in the Blue Nile River Basin may in part be due to changes in precipitation.

The urgency of climate change is pressing on the development of different technologies to reduce greenhouse gas emissions among which carbon dioxide (CO2) is the most abundant. A great source of CO2 is the burning of fossil fuels. The installation of carbon capture and storage (CCS) technology could reduce the amount of CO2 released from larger combustion processes by up to 90%. Fossil fuels stand for a great part of the total consumption of energy in the society today. To replace it so rapidly that strict climate change objectives will be reached with only increased energy efficiency and renewable energy would be difficult and would not be the most cost-efficient strategy. To be able to stabilize the atmospheric CO2 level within this decade and in a cost-efficient manner, the development of CCS technologies is clearly needed as a complementary strategy.

The object of this study is a program of government that has, as its immediate objective, the modification and regulation of consumer conduct deemed pertinent to climate change. Drawing from the analytical grid and conceptual tools of governmentality, this study has organized and analyzed an archive of documents related to the One-Tonne Challenge, a ‘public education’ program implemented by the Government of Canada from 2003 to 2006. There are numerous forms of conduct targeted by this program, involving many of the mundane and routine practices of everyday life. Despite their heterogeneity, the targeted forms of conduct can all be measured and evaluated according to the greenhouse gas (GHG) inventory, an ecological technology of government that has had its application extended to the ‘personal’ level. As consumers increasingly engage in practices that are energy efficient, a ‘low intensity GHG emission lifestyle’ will emerge as a new societal norm, which is declared to be the ‘ultimate strategic objective’ of the program. The analysis indentifies and describes two rationalities of government articulated within the archive of the program. Liberal principles and assumptions regarding the market economy are ascendant in practice; they delimit the range of governmental techniques that can be put into operation by the state. Nevertheless, the objectives and technologies of this program belong to an ecological rationality of government. It problematizes the liberal emphasis on ‘voluntary action’ and advances state planning of the market economy through price formation as a necessary governmental technique with which to manipulate the demand for energy and ensure that consumers become energy-efficient. The conclusion interprets and diagnoses the main dangers that could arise from the radical transformation of the market economy that would be brought about by an ecological political reason.

The Arctic is subject to growing economic and political interest. Meanwhile, its water and climate systems are in rapid transformation. Relevant and accessible information about water and climate is therefore vital to detect, understand and adapt to the changes. This thesis investigates hydrological monitoring systems, climate model data, and our understanding of hydro-climatic change, for adaptation to water system changes in the Arctic. Results indicate a lack of harmonized water chemistry data, which may impede efforts to understand transport and origin of key waterborne constituents. Further development of monitoring cannot rely only on a reconciliation of observations and projections on where climate change will be the most severe, as they diverge in this regard. Climate model simulations of drainage basin temperature and precipitation have improved between two recent model generations, but large inaccuracies remain for precipitation projections. Late 20th-century discharge changes in major Arctic rivers generally show excess of water relative to precipitation changes. This indicates a possible contribution of stored water from permafrost or groundwater to sea level rise. The river contribution to the increasing Arctic Ocean freshwater inflow matches that of glaciers, which underlines the importance of considering all sources when assessing change. To provide adequate information for research and policy, Arctic hydrological and hydrochemical monitoring needs to be extended, better integrated and made more accessible. This especially applies to hydrochemistry monitoring, where a more complete set of monitored basins is motivated, including a general extension for the large unmonitored areas close to the Arctic Ocean. Improvements in climate model parameterizations are needed, in particular for precipitation projections. Finally, further water-focused data and modeling efforts are required to resolve the source of excess discharge in Arctic rivers. / <p>At the time of doctoral defence the following papers were unpublished and had a status as follows: Paper 2: Accepted; Paper 4: Manuscript</p>

Climate Change has been related to GHG emissions, of both natural and anthropogenic origin. Agricultural management practices like reduced tillage and intensive cropping systems have a significant impact on the flow of C among its sources and sinks. These management practices involve complex biophysical interactions resulting in a range of impacts on farm income and GHG abatement. The focus of this study was on the impact of alternative annual crop tillage systems on GHG emissions and income to better inform climate change mitigation policy in agriculture. Besides tillage intensity, cropping intensity and crop mix and the interaction of these characteristics with the biological and physical attributes, the emission and income effects are a function of factor inputs, factor costs and commodity prices. Therefpre, the analysis was multi-disciplinary in nature and the tool of choice that depicts impacts on individual indicators is Trade-off Analysis (TOA). A component of risk analysis was also included. The analysis focused on short and long-term performance, the uncertainty of soil N2O emission coefficients as well as changes in weather patterns. As the adoption of reduced till has been a relatively recent development and as such, there is not a lot of long-term biophysical and economic data, which limits the effectiveness of econometric analysis. The different scenarios of uncertainty and long-term impacts were analysed by use of a simulation model. The model was parameterised with Intergovernmental Panel on Climate Change (IPCC) 1996 coefficients, a farmer survey, and cost data from Saskatchewan Agriculture Agri-Food and Rural Revitalization (SAFRR) for 2004. Results indicated that net GHG emissions were relatively lower for reduced tillage management while conventional tillage may be relatively more attractive from an economic perspective. However, results indicated that such economic factors as risk and economies of size may have a significant influence on this latter result. The study also highlighted the need to evaluate the GHG abatement potential of reduced tillage while simultaneously considering the abatement capability of the farm.

Under the current rapid climate change, trees are of critical interest because of diverse ecosystem services that they provide. Although increasing landscape connectivity is though to be crucial in order to maximize their migration capabilities, there are few studies indicating where exactly such increases might best take place. To understand the impact of fragmentation on species climate-change induced migrations and source populations, I calculated migration pathways and source populations under six climate change scenarios in southern Ontario where >70% of forest has been lost through human-use. The results showed that although forest fragmentation increased species required migration rates, the most important migration corridors and source populations were quite similar across all migration models and were concentrated in exiting forest corridors and extensively forested areas, including northeast of Lake Ontario, the Niagara Escarpment, and the Oak Ridges Moraine.

Under the current rapid climate change, trees are of critical interest because of diverse ecosystem services that they provide. Although increasing landscape connectivity is though to be crucial in order to maximize their migration capabilities, there are few studies indicating where exactly such increases might best take place. To understand the impact of fragmentation on species climate-change induced migrations and source populations, I calculated migration pathways and source populations under six climate change scenarios in southern Ontario where >70% of forest has been lost through human-use. The results showed that although forest fragmentation increased species required migration rates, the most important migration corridors and source populations were quite similar across all migration models and were concentrated in exiting forest corridors and extensively forested areas, including northeast of Lake Ontario, the Niagara Escarpment, and the Oak Ridges Moraine.