Snow depth effects on vegetation dynamics and development of near-remote sensing techniques in high-Arctic tundra

Snow exerts key controls on many aspects of plant ecology in the Arctic, including community composition. With climate predictions forecasting dramatic changes in winter climate and snow cover in the Arctic in the near future, it is important to improve our understanding of snow effects on plant communities in these regions. This study used a snow depth manipulation experiment established in 2006 in Adventdalen, Svalbard, Norway (78°10’N, 16°04’E) to investigate long-term effects of deepened snow on plant community composition. Two common tundra vegetation types were studied (Cassiope heath and mesic meadow) using data from three years (2015, 2020, and 2021). The study further used ‘near-remotely’ sensed vegetation indices (VIs; RGB-based indices, image based, and non-image based NDVI) to describe differences between snow regimes, years, and vegetation types. Green Chromatic Coordinate as well as image and non-image based NDVI were compared with cover of major plant groups in an initial step towards understanding the relationships between VIs and plant cover over several years and in different vegetation types. This study documented general decreases in the cover of live vascular plants, especially shrubs, and simultaneous increases in bryophytes and the forb Bistorta vivipara under deepened snow. Community changes were similar between the Heath and the Meadow vegetation types but changes were more pronounced in Heath. Near-remotely sensed VIs showed differences between snow regimes, possibly reflecting the documented vegetation change. However, relationships between VIs and plant cover were ambiguous when compared between years, vegetation types and snow regimes. The relationships generally differed in magnitude, but sometimes also direction, and were likely confounded by phenology and variations in maximum VI values between years. These findings highlight remaining challenges in the use of near-remote sensing as a tool for vegetation monitoring. Further studies should investigate the relationships between VIs and plant cover in a context of annual variations in maximum VI values, and phenological stages, as this may improve the usefulness of near-remote sensing in the future

Price Coordination and Consumer Behavior : Evidence from Retail Fuel

This thesis consists of an introduction and three essays on price coordination and consumer behavior in the retail fuel market. Each essay includes one of the research articles that compose the principle part of the thesis. The essays use microeconometric methods and data from the Norwegian retail fuel market to investigate how firms use price leadership to coordinate more frequent price increases, the costs and benefits of price leadership, and long-run dynamics in consumers’ response to changes in the intertemporal price pattern. The introduction summarizes the essays, discusses the merits of studying firm and consumer behavior in the retail fuel market, and elaborates on policy implications of the research in the thesis. Price leadership—a practice involving sequential price changes whereby a leader changes price first and rivals quickly follow—is commonly observed in many retail markets. The first chapter use a unique dataset spanning 14 years with the exact timing of price changes for most Norwegian gasoline stations to study price leadership and coordination in the Norwegian retail gasoline market. The market features asymmetric price cycles where prices slowly fall for several days before being restored to a high level within a few hours. The main contribution is to show how large retail chains use price leadership to both agree on and sustain a new equilibrium with more frequent price hikes. I argue that faster price changes due to a lack of price regulations in Norway can explain why the chains in Norway end up coordinating on a different equilibrium than in other countries. By combining the price data with data on volumes and costs, I estimate that the transition to more frequent price hikes has a substantial positive effect on volume-weighted retail margins. Price leadership can bring about higher prices for all firms in the market, but can also be costly for the leader because it loses volume to rivals in the interim period when it is the sole firm with a high price. The second chapter of my thesis studies the costs and benefits of price leadership in the Norwegian retail gasoline market. The dataset with high-frequency price and volume data coupled with a particular pricing pattern allows the estimation of the costs and benefits of leading price hikes. The main result is that the leader’s volume loss from being the sole firm to raise its price until the other firms match that price increase is small compared with the large margin increases and profit gains resulting from the price jumps. Furthermore, I find that the leader is not worse off than the non-leading firms. The results can assist in explaining why firms are willing to act as regular price leaders. Many retail markets feature intertemporal price variation caused by promotional sales, short-run wholesale price variation, or price cycles where prices fall for several days before quickly being restored to a high level. The third chapter uses 11 years of high-frequency prices and volumes for Norwegian gas stations to study the short- and long-run consumer response to price cycles with a regular low-price period at the same time every week (the sale period). I show that diesel and gasoline consumers over time increasingly fill their tanks during the sale period. Before the transition to the new price pattern, about 21% of the weekly gasoline and diesel volumes are sold in that part of the week. In the first quarter after the transition, the sale-period volume shares increase by 1–2 percentage points. In the subsequent years, the sale-period rebates remain stable while the sale-period volume shares keep rising, to total increases of 6–9 percentage points five years later. The intertemporal price elasticity increases from about -2 immediately after the transition to -6 five years later. These findings emphasize the importance of accounting for dynamics when studying consumer responses to intertemporal price variation and suggest that non-volume-weighted prices may be a poor proxy for the prices consumers pay.Doktorgradsavhandlin