Spectral Reflectance and Spatial Characterization of Arctic Tundra Surface Cover on the Alaskan North Slope PDF Download
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Author: Blake H. Burns
Publisher:
ISBN:
Category : Remote sensing
Languages : en
Pages : 268
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Author: Blake H. Burns
Publisher:
ISBN:
Category : Remote sensing
Languages : en
Pages : 268
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Author: Justin Rich
Publisher:
ISBN:
Category :
Languages : en
Pages : 72
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This investigation examines the current surface conditions of a study area near Toolik Lake, Alaska and seeks to characterize permafrost affected landscapes by using medium resolution multi-spectral imagery and digital elevation models. This study utilized an object-oriented multi-scale segmentation approach, a relatively new technique, which allowed for fuzzy analysis of spatial data and integration of multiple data types (data fusion) within the same project. Construction of a model based on spectral properties of the surface, as well as geometric properties of objects generated through image segmentation, was carried out. This allowed for land surface analysis based on a complex combination of both spectral and geometric properties, along with topological rule sets. This object-based process of classification aided by segmentation has proven a valuable tool for the exploration of surface units within the scene.^It has produced a unique example demonstrating how theoretical interpretations of ground unit characteristics can be applied to image analysis in place of ground truth data. This is shown through the use of more traditional tools, such as NDVI (Normalized Difference Vegetation Index) and simple band ratios (e.g. band 2/3 to identify iron oxides), along with new techniques, such as NDTVI (Normalized Difference Tundra Vegetation Index). The use of geometric attributes (roundness and elongation) of objects has also proven useful in identifying surface features, such as lakes and larger rivers. Previous efforts to derive vegetation maps were based on low resolution images (AVHRR and Landsat MSS) and were validated against low resolution maps (e.g. Muller et al., 1999) or point measurements at sites that were selected to represent zonal vegetation (Walker et al., 2003).^This study is the first to attempt using higher resolution data and vegetation maps in an area of significant local variations in bedrock geology and geomorphology. The results highlight the difficulties of performing vegetation analysis on moderate resolution datasets in arctic ecosystems, a result of very pure separability between classes. Despite its low overall accuracy level of 67.15%, the object-oriented multi-scale segmentation approach still proved more reliable than other, more widely used, methods of classification at 57.76% (Spectral Angle Mapper) and 59.48% (K-Means). It also serves as an example of how delicate an ecosystem can be and how quickly it can display change in response to climate. Landscape units were also studied to look at spatial transitions between acidic and non-acidic ground units, anthropogenic effects on soil chemistry and temporal changes that can effectively be observed within decadal time scales.^It is clear that significant drying can be observed in the southern foothills between 1985 and 1999 as reflected in a shift from high biomass / high moisture (moist acidic tundra) to low biomass / high moisture or dry (dry acidic, dry non-acidic and moist non-acidic tundra), which is characterized by a change in biomass. Interannual variations in climate are likely the major contributing factor for this; however, it is unclear what influence this variation has enacted within the study area, as well as along the acidic-non-acidic boundary to the north.
Author: James F. Reynolds
Publisher: Springer Science & Business Media
ISBN: 366201145X
Category : Science
Languages : en
Pages : 447
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Following the discovery of large petroleum reserves in northern Alaska, the US Department of Energy implemented an integrated field and modeling study to help define potential impacts of energy-related disturbances on tundra ecosystems. This volume presents the major findings from this study, ranging from ecosystem physiology and biogeochemistry to landscape models that quantify the impact of road-building. An important resource for researchers and students interested in arctic ecology, as well as for environmental managers concerned with practical issues of disturbances.
Author: Hyojung Kwon
Publisher:
ISBN:
Category : Arctic regions
Languages : en
Pages : 360
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Temporal and spatial variability in the Arctic introduces considerable uncertainty in estimations of the current carbon and energy budget and Arctic ecosystem response to climate change. Few representative measurements are available for land-surface parameterization of the Arctic tundra in regional and global climate models. Continuous measurements of net ecosystem CO 2 exchange (NEE), water vapor, and energy exchange using the eddy covariance technique were conducted in Alaskan wet sedge tundra and moist tussock tundra during the summer seasons (June 1--August 31) from 1999 to 2003 in order to quantify seasonal and spatial NEE, water vapor, and energy fluxes and to assess primary controlling factors which drive the change in the fluxes for the Arctic tundra ecosystems. At the wet sedge tundra, seasonal variation in energy balance was substantial, indicating ground heat flux (G) was significant during the snow-melt and post-snowmelt periods, whereas sensible heat flux (H) was dominant during the plant growth. During the measurement periods, H was the main energy component comprising 52% of net radiation (R n), followed by latent heat flux (LE) at 26% and G representing 8% of R n . The energy balance and evapotranspiration were strongly influenced by the maritime climate that brought cold, humid air to the site. Warmer and drier conditions prevailed for the moist tussock tundra compared with that of the wet sedge tundra. The wet sedge tundra was a sink for carbon of 46.4 to 70.0 gC m -2 season -1, while the moist tussock tundra either lost carbon of up to 60.8 gC m -2 season -1 or was in balance. The wet sedge tundra showed an acclimation (e.g., over days) to temperature, while the moist tussock tundra illustrated a strong temperature dependence. Warming and drying accentuated ecosystem respiration in the moist tussock tundra causing a net loss of carbon. The contrasting patterns of carbon balance at the two sites demonstrate that spatial variability can be more important in landscape NEE than intra- and inter-seasonal variability due to environmental factors with respect to NEE. Better characterization of spatial variability in NEE and associated environmental controls is required to improve current and future predictions of the Arctic terrestrial carbon balance.
Author:
Publisher:
ISBN: 9781124226262
Category :
Languages : en
Pages : 129
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This research focuses on the spatial and temporal patterns of, and controls on, CO2 in the Alaskan Arctic tundra ecosystem. The sites investigated--wet sedge, moist acidic, and low tussock tundra--represent the dominant land cover types in the Arctic tundra ecosystem, yet none have previously been investigated continuously throughout the year. In the first part of the research presented here, new definitions of season are presented, which will allow better comparisons across sites, seasons, and years in the Arctic tundra, where season length varies among years and locations. The results of this, the first, continuous, yearlong Arctic tundra study in a moist acidic tundra region, show that while summer uptake was detected ( -11 g C m−2 yr−1), the annual carbon signal was overwhelmed by the non-summer seasons, resulting in a net annual carbon release of nearly 38 g C m−2 yr−1. Winter showed low metabolic rates over a long season resulting in a net source of carbon to the atmosphere. The transitional seasons of spring and fall demonstrated active rates over short durations and were also sources of carbon to the atmosphere. In addition to the variable pattern of carbon exchange, the controls on carbon varied by season as well. For example, the effect of increasing soil temperature was negatively related to net ecosystem exchange (NEE) during winter and summer, but positively related to NEE during spring and fall. These results indicate that continuous monitoring of carbon, and related environmental variables, is important in accurate estimation of the current total annual and seasonal carbon budgets. This information, in turn, is critical to our ability to predict, with confidence, future carbon budgets. In the second part of the research, three years of continuous carbon measurements are presented for a low tussock tundra region. This southern site is especially vulnerable to climate change effects because it is at the southern extent of the tundra ecosystem near the graminoid-shrub boundary and increased rates of decomposition, and the region is likely to undergo community compositional changes in the near future. This region is likely to experience deeper active layers in the future, potentially exposing large stocks of carbon. This southern system was a net source of carbon over the three-year period of study, with only two of the three summer seasons acting as net carbon sinks. In one year, drought was so severe that even during the summer season, respiration overwhelmed photosynthesis, leading to a large (87 g C m−2 yr−1) annual efflux compared to the other years of the study (which had 0.04 and 49 g C m−2 yr−1 annual carbon release). In the last part of this research, NEE was measured at three sites located along a latitudinal gradient that spanned the North Slope of Alaska. Only in the northernmost site at Barrow was net annual carbon uptake detected, leading to an average uptake rate of 80 g C m−2 yr−1. Increased temperatures and decreased rainfall led to greater uptake in this, the coldest and least well drained of the sites. The two inland sites were both net sources of carbon to the atmosphere over the three-year period, resulting in an average of 30 and 45 g C m−2 yr−1 at each of the sites. Site differences were the primary controls on carbon variation among the sites, but inter and intra-annual variation were also significant. These data represent the first continuous measurements in the Arctic tundra ecosystem, and highlight the high degree of heterogeneity in the tundra ecosystem. These data may be used to validate and further develop climate and ecosystem models and to more accurately depict the variability, both spatially and temporally, in the Arctic tundra ecosystem.
Author:
Publisher:
ISBN:
Category : Geography
Languages : en
Pages : 564
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Author: Larry L Tieszen
Publisher: Springer
ISBN: 9781461263098
Category : Science
Languages : en
Pages : 686
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This volume on botanical research in tundra represents the culmination of four years of intensive and integrated field research centered at Barrow, Alaska. The volume summarizes the most significant results and interpretations of the pri mary producer projects conducted in the U.S. IBP Tundra Biome Program (1970-1974). Original data reports are available from the authors and can serve as detailed references for interested tundra researchers. Also, the results of most projects have been published in numerous papers in various journals. The introduction provides a brief overview of other ecosystem components. The main body presents the results in three general sections. The summary chapter is an attempt to integrate ideas and information from the previous papers as well as extant literature. In addition, this chapter focuses attention on pro cesses of primary production which should receive increased emphasis. Although this book will not answer all immediate questions, it hopefully will enhance future understanding of the tundra, particularly as we have studied it in Northern Alaska.
Author: Anja N. Kade
Publisher:
ISBN:
Category : Frost heaving
Languages : en
Pages : 490
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"The vegetation and soils in many arctic tundra regions are influenced by the distribution of nonsorted circles, unique patterned-ground features that dot the well-vegetated tundra landscape. They are flat to dome-shaped, bare soil patches 0.5 to 3 m across and lack a border of stones. Localized soil disturbance due to cryogenic processes creates unusual micro-environments with unique plant communities, slow soil development and deep active layers. The contrast between barren nonsorted circles and the well-vegetated stable tundra provides an ideal opportunity to examine the complex linkages among vegetation, soil and disturbance through cryogenic processes, offering insight into how the tundra system operates. The central goal of this thesis is to understand the complex linkages of the nonsorted-circle system along a natural climate gradient on the North Slope in the Alaskan arctic tundra at different scales, ranging from plot level to regional changes. This thesis examines the interactions among vegetation, soil and cryogenic regime by treating the nonsorted circles within the stable tundra as a single complex system. The thesis presents a formal description and analysis of the plant communities on and off nonsorted circles along the climatic gradient using the Braun-Blanquet classification approach. The thesis also studies the physical effects of vegetation, soil organic mat and snow cover on the microclimate of nonsorted circles and the stable tundra along the same climate gradient. The influence of vegetation on cryogenic processes is examined experimentally by manipulating the plant canopy on nonsorted circles. When compared to the stable tundra, nonsorted circles have minimal vegetation cover, resulting in warm soil temperatures and deep thaw depths in summer and allowing for increased ice-lens formation during freeze-up. The resulting frost heave and needle-ice formation at the soil surface maintain the bate surfaces of the circles through soil disturbance. Cryogenic processes dominate the system at the northern sites, while the warmer climate towards the south allows for thick vegetation mats on and off the nonsorted circles, suppressing cryogenic processes. The strength of the interactions among vegetation, soil and cryogenic regime may change under a warming arctic climate, possibly leading to the local disappearance of nonsorted circles"--Leaves iii-iv.
Author: Harry R. Bader
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The Alaska Department of Natural Resources (DNR), Division of Mining, Land, and Water manages cross-country travel, typically associated with hydrocarbon exploration and development, on Alaska's arctic North Slope. This project is intended to provide natural resource managers with objective, quantitative data to assist decision making regarding opening of the tundra to cross-country travel. DNR designed standardized, controlled field trials, with baseline data, to investigate the relationships present between winter exploration vehicle treatments and the independent variables of ground hardness, snow depth, and snow slab thickness, as they relate to the dependent variables of active layer depth, soil moisture, and photosynthetically active radiation (a proxy for plant disturbance). Changes in the dependent variables were used as indicators of tundra disturbance. Two main tundra community types were studied: Coastal Plain (wet graminoid/moist sedge shrub) and Foothills (tussock). DNR constructed four models to address physical soil properties: two models for each main community type, one predicting change in depth of active layer and a second predicting change in soil moisture. DNR also investigated the limited potential management utility in using soil temperature, the amount of photosynthetically active radiation (PAR) absorbed by plants, and changes in microphotography as tools for the identification of disturbance in the field. DNR operated under the assumption that changes in the abiotic factors of active layer depth and soil moisture drive alteration in tundra vegetation structure and composition. Statistically significant differences in depth of active layer, soil moisture at a 15 cm depth, soil temperature at a 15 cm depth, and the absorption of photosynthetically active radiation were found among treatment cells and among treatment types. The models were unable to thoroughly investigate the interacting role between snow depth and disturbance due to a lack of variability in snow depth cover throughout the period of field experimentation. The amount of change in disturbance indicators was greater in the tundra communities of the Foothills than in those of the Coastal Plain. However the overall level of change in both community types was less than expected. In Coastal Plain communities, ground hardness and snow slab thickness were found to play an important role in change in active layer depth and soil moisture as a result of treatment. In the Foothills communities, snow cover had the most influence on active layer depth and soil moisture as a result of treatment. Once certain minimum thresholds for ground hardness, snow slab thickness, and snow depth were attained, it appeared that little or no additive effect was realized regarding increased resistance to disturbance in the tundra communities studied. DNR used the results of this modeling project to set a standard for maximum permissible disturbance of cross-country tundra travel, with the threshold set below the widely accepted standard of Low Disturbance levels (as determined by the U.S. Fish and Wildlife Service). DNR followed the modeling project with a validation study, which seemed to support the field trial conclusions and indicated that the standard set for maximum permissible disturbance exhibits a conservative bias in favor of environmental protection. Finally DNR established a quick and efficient tool for visual estimations of disturbance to determine when investment in field measurements is warranted. This Visual Assessment System (VAS) seemed to support the plot disturbance measurements taking during the modeling and validation phases of this project.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 810
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