Evidence of Recent Treeline Dynamics in Southwest Yukon from Aerial Photographs

Small-scale vertical aerial photographs taken in 1947 and 1948 covering 200 km2 of the Kluane Ranges, southwest Yukon, were compared with corresponding photographs taken in 1989 for the purpose of characterizing changes in the distribution and abundance of white spruce (Picea glauca (Moench) Voss) at the alpine treeline. Digital photogrammetry, including orthorectification and on-screen interpretation, was supplemented by stereoscopic inspection of the original prints. Qualitative assessment of change across nine image pairs was accompanied by quantitative analysis of changes in spruce density and elevation using 1 hectare plots and 100 m wide elevational belt transects, respectively, superimposed on the orthorectified images. Significant changes were observed over the 41 years, but the degree of change varied throughout the study area. The most common changes were an increase in canopy size of individual trees and an increase in stand density resulting from the establishment of new individuals. Several instances of treeline advance were also observed. An absence of major natural disturbances or widespread land use change indicates that treeline change is attributable to climate. Results from concurrent dendroecological studies indicate that these dynamics represent only part of the total extent of change to occur during the 20th century.Des photographies aériennes verticales à petite échelle prises en 1947 et 1948 sur une aire de 200 km2 de la chaîne de montagnes Kluane, dans le sud-ouest du Yukon, ont été comparées à des photos correspondantes prises en 1989 dans le but de caractériser les changements en matière de répartition et d’abondance de l’épinette blanche (Picea glauca (Moench) Voss) à la hauteur de la limite alpine des arbres. La photogrammétrie numérique, dont les techniques de redressement différentiel et d’interprétation à l’écran, a été supplémentée par l’inspection stéréoscopique des épreuves photographiques originales. L’évaluation qualitative du changement par rapport à neuf paires d’images s’est accompagnée de l’analyse quantitative des changements en matière de densité des épinettes et d’élévation à l’aide de parcelles de 1 hectare et de transects d’élévation en bandes de 100 m de large, respectivement, superposés sur les images ayant fait l’objet du redressement différentiel. D’importants changements ont été observés au cours de la période de 41 ans, mais le degré de changement variait d’un endroit à l’autre visé par l’étude. Les changements les plus courants consistaient en l’augmentation de la taille du couvert des arbres individuels ainsi qu’en l’augmentation de la densité de peuplement découlant de l’établissement de nouveaux individus. Plusieurs occurrences d’avancement de la limite des arbres ont également été observées. L’absence de perturbations naturelles majeures ou d’importants changements sur le plan de l’utilisation des terres laisse croire que le changement de la limite des arbres est attribuable au climat. Les résultats découlant d’études dendroécologiques concurrentes indiquent que ces dynamiques ne représentent qu’une partie de l’ampleur totale du changement s’étant produit au cours du XXe siècle

Compendium of Yukon climate change science: 2003-2011

This compendium is intended to provide an overview of recent (2003-2011) climate change work involving Yukon. It is comprised of various types of documents including scientific journal articles, government publications, workshop reports, and conference proceedings.-- i

Compendium of Yukon Climate Change science: 2002 - 2013

"The Compendium is intended to provide an overview of recent (2003-2013) climate change work involving Yukon. It is comprised of various types of documents, including scientific journal articles, government publications, workshop reports, and conference proceedings."--from Foreword

Compendium of Yukon climate change science 2003 - 2013

"The Compendium is intended to provide an overview of recent (2003-2013) climate change work involving Yukon. It is comprised of various types of documents, including scientific journal articles, government publications, workshop reports, and conference proceedings."--from Foreword

Effects of observed and experimental climate change on terrestrial ecosystems in northern Canada: results from the Canadian IPY program

Published VersionTundra and taiga ecosystems comprise nearly 40 % of the terrestrial landscapes of Canada. These permafrost ecosystems have supported humans for more than 4500 years, and are currently home to ca. 115,000 people, the majority of whom are First Nations, Inuit and Métis. The responses of these ecosystems to the regional warming over the past 30–50 years were the focus of four Canadian IPY projects. Northern residents and researchers reported changes in climate and weather patterns and noted shifts in vegetation and other environmental variables. In forest-tundra areas tree growth and reproductive effort correlated with temperature, but seedling establishment was often hindered by other factors resulting in sitespecific responses. Increased shrub cover has occurred in sites across the Arctic at the plot and landscape scale, and this was supported by results from experimental warming. Experimental warming increased vegetation cover and nutrient availability in most tundra soils; however, resistance to warming was also found. Soil microbial diversity in tundra was no different than in other biomes, although there were shifts in mycorrhizal diversity in warming experiments. All sites measured were sinks for carbon during the growing season with expected seasonal and latitudinal patterns. Modeled responses of a mesic tundra system to climate change showed that the sink status will likely continue for the next 50–100 years, after which these tundra systems will likely become a net source of carbon dioxide to the atmosphere. These IPY studies were the first comprehensive assessment of the state and change in Canadian northern terrestrial ecosystems and showed that the inherent variability in these systems is reflected in their site-specific responses to changes in climate. They also showed the importance of using local traditional knowledge and science, and provided extensive data sets, sites and researchers needed to study and manage the inevitable changes in the Canadian North

Land cover change on the Seward Peninsula: the use of remote sensing to evaluate the potential influences of climate change on historical vegetation dynamics

Thesis (M.S.) University of Alaska Fairbanks, 2000Vegetation on the Seward Peninsula, Alaska, which is characterized by transitions from tundra to boreal forest, may be sensitive to the influences of climate change on disturbance and species composition. To determine the ability to detect decadal-scale structural changes in vegetation, Change Vector Analysis (CVA) techniques were evaluated for Landsat TM imagery of the Seward Peninsula. Scenes were geographically corrected to sub-pixel accuracy and then radiometrically rectified. The CVA results suggest that shrubbiness is increasing on the Seward Peninsula. The CVA detected vegetation change on more than 50% of the burned region on TM imagery for up to nine years following fire. The use of both CVA and unsupervised classification together provided a more powerful interpretation of change than either method alone. This study indicates that CVA may be a valuable tool for the detection of land-cover change in transitional regions between tundra and boreal forest.Abstract -- List of figures -- List of tables -- Acknowledgements -- Introduction -- Methods -- Results -- Radiometric rectification -- Fire disturbance -- Land cover change on the Seward Peninsula -- Potential false change -- Discussion -- CVA vs. unsupervised classification -- Fire disturbance -- Land cover change on the Seward Peninsula -- Challenges and limitations -- Improvements and future directions -- Literature cited

30 years of change : visualizing hotter drought at upper treeline along the Colorado Trail

Over the last 30 years, the Southern Rocky Mountains (SRM) have experienced an unprecedented period of warming and aridity. The consequences of this hotter and drier climate are becoming increasingly evident across Rocky Mountain forests, where megadisturbances are resulting in state shifts from forested to non-forested ecosystems. This research, which revisits twelve photographs taken along the Colorado Trail in 1992, has revealed alarming new findings. It shows that some of the highest treeline ecotones along the spine of the Rockies have been devastated by spruce beetle-induced mortality and that spruce seed production will be increasingly constrained by threshold high temperatures. The repeat photos also reveal that a dramatic vegetation composition shift is occurring in the SRM with the accelerated proliferation of willow into alpine tundra, thriving under warmer conditions amid spruce beetle devastation. Furthermore, this study highlights that projected declines in forest cover in western North America must now take into account the loss of Engelmann spruce from upper treeline ecotones and that the trend of expansion of the mountain forest belt via treeline advance appears to be particularly unlikely and is instead likely to be one of forest contraction. Ultimately, the results of this regional-scale repeat photography study point to a future of spruce at treeline that is not promising because of (1) beetle-induced mortality, (2) rising temperature stressing seed production, (3) the need for moisture, (4) challenges to natural seed dispersal, and (5) willow encroachment throughout the alpine tundra.Includes bibliographical references

Burwash Landing and Destruction Bay Landscape Hazards: Geological mapping for climate change adaptation planning

This project investigates contemporary landscape hazards related to permafrost degradation in Burwash Landing and Destruction Bay, Yukon. It also considers potential impacts of a changing climate on the local landscape. The work is accomplished by conducting surficial geological mapping and gathering geoscience data, including landscape metrics, permafrost conditions and hydrology. Projections of future climate variability (e.g., temperature and precipitation) for the region are used to identify potential future trajectories of change. Based on these data, landscape hazards are ranked in four categories, varying from no risk to high risk, and are represented graphically (in stoplight colours) on maps covering the study area. By incorporating projections of future climate variability, landscape hazards classification reflects both contemporary and potential future conditions.Peer reviewe