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Author: Dana Rachel Nossov Brown
Publisher:
ISBN:
Category : Forest fires
Languages : en
Pages : 228
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Book Description
A warming climate is expected to cause widespread thawing of discontinuous permafrost, and the co-occurrence of wildfire may function to exacerbate this process. Here, I examined the vulnerability of permafrost to degradation from fire disturbance as it varies across different landscapes of the Interior Alaskan boreal forest using a combination of observational, modeling, and remote sensing approaches. Across all landscapes, the severity of burning strongly influenced both post-fire vegetation and permafrost degradation. The thickness of the remaining surface organic layer was a key control on permafrost degradation because its low thermal conductivity limits ground heat flux. Thus, variation in burn severity controlled the local distribution of near-surface permafrost. Mineral soil texture and permafrost ice content interacted with climate to influence the response of permafrost to fire. Permafrost was vulnerable to deep thawing after fire in coarse-textured or rocky soils throughout the region; low ice content likely enabled this rapid thawing. After thawing, increased drainage in coarse-textured soils caused reductions in surface soil moisture, which contributed to warmer soil temperatures. By contrast, permafrost in fine-textured soils was resilient to fire disturbance in the silty uplands of the Yukon Flats ecoregion, but was highly vulnerable to thawing in the silty lowlands of the Tanana Flats. The resilience of silty upland permafrost was attributed to higher water content of the active layer and the associated high latent heat content of the ice-rich permafrost, coupled with a relatively cold continental climate and sloping topography that removes surface water. In the Tanana Flats, permafrost in silty lowlands thawed after fire despite high water and ice content of soils. This thawing was associated with significant ground surface subsidence, which resulted in water impoundment on the flat terrain, generating a positive feedback to permafrost degradation and wetland expansion. The response of permafrost to fire, and its ecological effects, thus varied spatially due to complex interactions between climate, topography, vegetation, burn severity, soil properties, and hydrology. The sensitivity of permafrost to fire disturbance has also changed over time due to variation in weather at multi-year to multi-decadal time scales. Simulations of soil thermal dynamics showed that increased air temperature, increased snow accumulation, and their interactive effects, have since the 1970s caused permafrost to become more vulnerable to talik formation and deep thawing from fire disturbance. Wildfire coupled with climate change has become an important driver of permafrost loss and ecological change in the northern boreal forest. With continued climate warming, we expect fire disturbance to accelerate permafrost thawing and reduce the likelihood of permafrost recovery. This regime shift is likely to have strong effects on a suite of ecological characteristics of the boreal forest, including surface energy balance, soil moisture, nutrient cycling, vegetation composition, and ecosystem productivity.
Author: Dana Rachel Nossov Brown
Publisher:
ISBN:
Category : Forest fires
Languages : en
Pages : 228
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Book Description
A warming climate is expected to cause widespread thawing of discontinuous permafrost, and the co-occurrence of wildfire may function to exacerbate this process. Here, I examined the vulnerability of permafrost to degradation from fire disturbance as it varies across different landscapes of the Interior Alaskan boreal forest using a combination of observational, modeling, and remote sensing approaches. Across all landscapes, the severity of burning strongly influenced both post-fire vegetation and permafrost degradation. The thickness of the remaining surface organic layer was a key control on permafrost degradation because its low thermal conductivity limits ground heat flux. Thus, variation in burn severity controlled the local distribution of near-surface permafrost. Mineral soil texture and permafrost ice content interacted with climate to influence the response of permafrost to fire. Permafrost was vulnerable to deep thawing after fire in coarse-textured or rocky soils throughout the region; low ice content likely enabled this rapid thawing. After thawing, increased drainage in coarse-textured soils caused reductions in surface soil moisture, which contributed to warmer soil temperatures. By contrast, permafrost in fine-textured soils was resilient to fire disturbance in the silty uplands of the Yukon Flats ecoregion, but was highly vulnerable to thawing in the silty lowlands of the Tanana Flats. The resilience of silty upland permafrost was attributed to higher water content of the active layer and the associated high latent heat content of the ice-rich permafrost, coupled with a relatively cold continental climate and sloping topography that removes surface water. In the Tanana Flats, permafrost in silty lowlands thawed after fire despite high water and ice content of soils. This thawing was associated with significant ground surface subsidence, which resulted in water impoundment on the flat terrain, generating a positive feedback to permafrost degradation and wetland expansion. The response of permafrost to fire, and its ecological effects, thus varied spatially due to complex interactions between climate, topography, vegetation, burn severity, soil properties, and hydrology. The sensitivity of permafrost to fire disturbance has also changed over time due to variation in weather at multi-year to multi-decadal time scales. Simulations of soil thermal dynamics showed that increased air temperature, increased snow accumulation, and their interactive effects, have since the 1970s caused permafrost to become more vulnerable to talik formation and deep thawing from fire disturbance. Wildfire coupled with climate change has become an important driver of permafrost loss and ecological change in the northern boreal forest. With continued climate warming, we expect fire disturbance to accelerate permafrost thawing and reduce the likelihood of permafrost recovery. This regime shift is likely to have strong effects on a suite of ecological characteristics of the boreal forest, including surface energy balance, soil moisture, nutrient cycling, vegetation composition, and ecosystem productivity.
Author: F. Stuart Chapin
Publisher: Oxford University Press
ISBN: 019028854X
Category : Science
Languages : en
Pages : 368
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Book Description
The boreal forest is the northern-most woodland biome, whose natural history is rooted in the influence of low temperature and high-latitude. Alaska's boreal forest is now warming as rapidly as the rest of Earth, providing an unprecedented look at how this cold-adapted, fire-prone forest adjusts to change. This volume synthesizes current understanding of the ecology of Alaska's boreal forests and describes their unique features in the context of circumpolar and global patterns. It tells how fire and climate contributed to the biome's current dynamics. As climate warms and permafrost (permanently frozen ground) thaws, the boreal forest may be on the cusp of a major change in state. The editors have gathered a remarkable set of contributors to discuss this swift environmental and biotic transformation. Their chapters cover the properties of the forest, the changes it is undergoing, and the challenges these alterations present to boreal forest managers. In the first section, the reader can absorb the geographic and historical context for understanding the boreal forest. The book then delves into the dynamics of plant and animal communities inhabiting this forest, and the biogeochemical processes that link these organisms. In the last section the authors explore landscape phenomena that operate at larger temporal and spatial scales and integrates the processes described in earlier sections. Much of the research on which this book is based results from the Bonanza Creek Long-Term Ecological Research Program. Here is a synthesis of the substantial literature on Alaska's boreal forest that should be accessible to professional ecologists, students, and the interested public.
Author: Abraham Melesse Endalamaw
Publisher:
ISBN:
Category : Biotic communities
Languages : en
Pages : 506
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Book Description
The Interior Alaska boreal forest ecosystem is one of the largest ecosystems on Earth and lies between the warmer southerly temperate and colder Arctic regions. The ecosystem is underlain by discontinuous permafrost. The presence or absence of permafrost primarily controls water pathways and ecosystem composition. As a result, the region hosts two distinct ecotypes that transition over a very short spatial scale - often on the order of meters. Accurate mesoscale hydrological modeling of the region is critical as the region is experiencing unprecedented ecological and hydrological changes that have regional and global implications. However, accurate representation of the landscape heterogeneity and mesoscale hydrological processes has remained a big challenge. This study addressed this challenge by developing a simple landscape model from the hill-slope studies and in situ measurements over the past several decades. The new approach improves the mesoscale prediction of several hydrological processes including streamflow and evapotranspiration (ET). The impact of climate induced landscape change under a changing climate is also investigated. In the projected climate scenario, Interior Alaska is projected to undergo a major landscape shift including transitioning from a coniferous-dominated to deciduous-dominated ecosystem and from discontinuous permafrost to either a sporadic or isolated permafrost region. This major landscape shift is predicted to have a larger and complex impact in the predicted runoff, evapotranspiration, and moisture deficit (precipitation minus evapotranspiration). Overall, a large increase in runoff, evapotranspiration, and moisture deficit is predicted under future climate. Most hydrological climate change impact studies do not usually include the projected change in landscape into the model. In this study, we found that ignoring the projected ecosystem change could lead to an inaccurate conclusion. Hence, climate-induced vegetation and permafrost changes must be considered in order to fully account for the changes in hydrology.
Author: R.B. Spies
Publisher: Elsevier
ISBN: 0080469426
Category : Nature
Languages : en
Pages : 609
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Book Description
This comprehensive text is a major synthesis on ecological change in the Gulf of Alaska. It encompasses the structural and annual changes, forces of change, long-ecological changes in the atmosphere and ocean, plankton, fish, birds and mammals, and the effects of the 1989 Exxon Valdez Oil Spill. With 5 major sections, Long-term Ecological Change in the Northern Gulf of Alaska first describes the physical features, the atmosphere and physical oceanography, the annual production cycle, the forage base for higher animals and trophic transfer, and the adaptations for survival in this changing environment for 9 portal species. Then, the major forces of change are introduced: climate, geophysics, fisheries and harvesting, species interactions, disease and contaminants. Next, the long-term records of change in physical factors and biological populations are presented, as well as the potential reasons for the biological changes. Following is the history of the Exxon Valdez oil spill and its long-term effects. And, finally, the emergent properties of the ecosystem are discussed and an attempt is made to weigh the importance of the major forcing factors in terms of their temporal and spatial scales of influence. * Examines important data on long-term change in the ecosystem and the forcing factors that are responsible for it * Provides an account of the 1989 Exxon Valdez oil spill with emphasis on the long-term effects * Describes the effects of climate change, geophysical change, species interactions, harvesting, disease, the 1989 oil spill, and marine contaminants on key populations of marine organisms
Author: F. Stuart Chapin
Publisher: Oxford University Press
ISBN: 0195154312
Category : Nature
Languages : en
Pages : 369
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Book Description
The Boreal forest is the northern-most forest in the world, whose organisms and dynamics are shaped by low temperature and high latitude. The Alaskan Boreal forest is warming as rapidly as any place on earth, providing an opportunity to examine a biome as it adjusts to change. This book looks at this issue.
Author: Benjamin V. Gaglioti
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 476
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Book Description
The climate is now changing rapidly at high-latitudes, and observing how the Arctic and sub-Arctic environment responded to prehistoric climate changes can hold valuable lessons as we adapt in the future. This dissertation presents four studies that use biogeochemical proxies to reconstruct environmental changes in northern Alaska over the last 40,000 years (40 ka). These records are used to infer how the environment responded to climate changes at different locations and over varying spatial and temporal scales. The first study presents a time series of stable oxygen isotopes contained in radiocarbon-dated (14C) willow wood to quantify the nature and rates of climate change on the North Slope of Alaska over the last 40 ka. The second study examines how past temperature fluctuations affected permafrost thaw and the release of ancient carbon over the last 14.5 ka by compiling 14C-age offsets in the sediment of a small lake in the Brooks Range foothills. In the third study, I document human-caused changes to boreal wildfire frequency near the city of Fairbanks to test whether the primeval forest type and permafrost in the surrounding watershed will be vulnerable to more frequent fires in the future. The fourth study examines how ice age (40-9 ka) climate changes impacted the activity of sand dunes, vegetation productivity, and the dynamics of permafrost recorded in a unique sedimentary exposure located near the Arctic Coastal Plain on Alaska’s North Slope. Overall, I present several new and interesting approaches and findings stemming from this work. Ancient willow isotopes show that between 17 and 8 ka, during the time when ice sheets were in retreat worldwide, temperatures fluctuated widely on the North Slope mostly in concert with those in Greenland. Most notably, rapid changes in temperature and moisture occurred during the initial deglacial warming (ca. 16 ka), and during the Younger Dryas cold period (12.9-11.7 ka). These climate trends were amplified on the North Slope by changes in sea-ice extent in adjacent seas, which also controlled the availability of local precipitation evaporated from these seas. However, these warming and cooling trends were occasionally dampened by the advent of more maritime climate accompanying sea-level rise during the early Holocene, and by the breakdown of the atmospheric circulation patterns created by continental ice sheets in North America during the last glacial maximum. Over the last 7 ka, a gradual, insolation-driven cooling trend ended in ca. AD 1850 when the exceptional rates of recent warming began that continue to today. I found that the vegetation, permafrost and sand dunes in Arctic Alaska were sensitive to external climate forcing, but their responses were moderated by strong, internal feedbacks, including the temperature-buffering effects that thick peat layers have on the underlying permafrost. Prior to peat buildup in the early Holocene, the timing of sedimentary transitions indicate permafrost and aeolian processes were highly responsive to the volatile climate during the last ice age, which included Greenland interstadials. This incessant ice age climate change, coupled with the complex biophysical landscape responses that are particular to the unglaciated Arctic, helped maintain the ecological mosaic of the Mammoth Steppe ecosystem. Prehistoric warming events triggered permafrost thaw and the release of ancient carbon during the Bølling-Allerød (14.5-12.9 ka) and early Holocene warm period (11.7-8.0 ka), and this release is likely to occur again given enough warming. In the boreal forest watershed near Fairbanks, Alaska, the current ecological regime has remained intact despite a three-fold increase in pre-settlement wildfires during the Fairbanks gold rush (1902-1940). Once continued warming surpasses the buffering effects of the current internal feedbacks of the North Slope and boreal forest and the threshold for change is reached, more dynamic aeolian and permafrost processes may again dominate as they did on the more unstable and diverse ice age landscape. Overall, the results of this work will be useful for understanding how climate and landscape change in northern Alaska will respond to global climate forcing in the future.
Author: J. B. Haufler
Publisher: DIANE Publishing
ISBN: 1437933742
Category : Science
Languages : en
Pages : 57
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Book Description
Summarizes potential impacts that are likely from predicted climate change (CC) in Southern Alaska (SA), identifies on-going collaborative efforts directed at climate change, and suggests some possible responses that the Alaska Region (AR) could take to address this challenge. Contents: (1) Intro.; (2) Overview of the AR; (3) Ecosystem Services of the SC and SE Landscapes; (4) CC Threats to Ecosystem Services in Southern Coastal Alaska: Observed Changes in Alaska¿s Climate; Predicted CC in Alaska Climate; (5) Impacts of CC on Ecosystem Services: Changing Sea Levels; Increased Ocean Temp. and Changing Circulation Patterns; Increased Ocean Acidification; Increased Storm Intensities; Changes to Stream Temp. and Flows; Loss of Glaciers; Changes to Wetlands; Forest Temp. and Precipitation Changes; Increases in Invasive Species; (6) Initiatives for CC in Southern Alaska Coastal Landscapes; (7) Strategic Plan for CC. Figures.
Author: Nancy Lord
Publisher: Catapult
ISBN: 1582438684
Category : Nature
Languages : en
Pages : 170
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Book Description
In Shishmaref, Alaska, new seawalls are constructed while residents navigate the many practical and bureaucratic obstacles to moving their entire island village to higher ground. Farther south, inland hunters and fishermen set out to grow more of their own food—and to support the reintroduction of wood bison, an ancient species well suited to expected habitat changes. First Nations people in Canada team with conservationists to protect land for both local use and environmental resilience. In Early Warming, Alaskan Writer Laureate, Nancy Lord, takes a cutting–edge look at how communities in the North—where global warming is amplified and climate–change effects are most immediate—are responding with desperation and creativity. This beautifully written and measured narrative takes us deep into regions where the indigenous people who face life–threatening change also demonstrate impressive conservation ethics and adaptive capacities. Underpinned by a long acquaintance with the North and backed with scientific and political sophistication, Lord's vivid account brings the challenges ahead for us all into ice–water clarity.
Author: Nancy Fresco
Publisher:
ISBN:
Category : Carbon sequestration
Languages : en
Pages : 378
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Book Description
Northern ecosystems and those who rely upon them are facing a time of unprecedented rapid change. Global boreal forests will play an important role in the feedback loop between climate, ecosystems, and society. In this thesis, I examine forest carbon dynamics and the potential for carbon management in Interior boreal Alaska in three distinct frameworks, then analyze my results in the context of social-ecological resilience. In Chapter 1, I analyze comparative historical trends and current regulatory frameworks governing the use and management of boreal forests in Russia, Sweden, Canada, and Alaska, and assess indicators of socio-ecological sustainability in these regions. I conclude that low population density, limited fire suppression, and restricted economic expansion in Interior Alaska have resulted in a 21st-century landscape with less compromised human-ecosystem interactions than other regions. Relative wealth and a strong regulatory framework put Alaska in a position to manage for long-term objectives such as carbon sequestration. In Chapter 2, I model the landscape-level ecological possibilities for sequestration under three different climate scenarios and associated changes in fire and forest growth. My results indicate that Interior Alaska could act as either a weak carbon source or as a weak sink in the next hundred years, and that management for carbon credits via fire suppression would be inadvisable, given the associated uncertainty and risks. In Chapter 3, I perform a social, ecological, and economic analysis of the feasibility of switching from fossil fuels to wood energy in Interior Alaska villages. I demonstrate that this is a viable option with the potential benefits of providing lower-cost power, creating local employment, reducing the risk of catastrophic wildfire near human habitation, and earning marketable carbon credits. Finally, in Chapter 4, I assess how each of the above factors may impact social-ecological resilience. My results show some system characteristics that tend to bolster resilience and others that tend to increase vulnerability. I argue that in order to reduce vulnerability, management goals for Alaska's boreal forest must be long-term, flexible, cooperative, and locally integrated.
Author: Valerie Barber
Publisher: University of Alaska Press
ISBN: 1602233977
Category : Science
Languages : en
Pages : 337
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Book Description
The northwest boreal region (NWB) of North America is a land of extremes. Extending more than 1.3 million square kilometers (330 million acres), it encompasses the entire spectrum between inundated wetlands below sea level to the tallest peak in North America. Permafrost gradients span from nearly continuous to absent. Boreal ecosystems are inherently dynamic and continually change over decades to millennia. The braided rivers that shape the valleys and wetlands continually change course, creating and removing vast wetlands and peatlands. Glacial melt, erosion, fires, permafrost dynamics, and wind-blown loess are among the shaping forces of the landscape. As a result, species interactions and ecosystem processes are shifting across time. The NWB is a data-poor region, and the intention of the NWB Landscape Conservation Cooperative is to determine what data are not available and what data are available. For instance, historical baseline data describing the economic and social relationships in association with the ecological condition of the NWB landscape are often lacking. Likewise, the size and remoteness of this region make it challenging to measure basic biological information, such as species population sizes or trends. The paucity of weather and climate monitoring stations also compound the ability to model future climate trends and impacts, which is part of the nature of working in the north. The purpose of this volume is to create a resource for regional land and resource managers and researchers by synthesizing the latest research on the historical and current status of landscape-scale drivers (including anthropogenic activities) and ecosystem processes, future projected changes of each, and the effects of changes on important resources. Generally, each chapter is coauthored by researchers and land and natural resource managers from the United States and Canada.
