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Utilizing the spatial information inherent in panchromatic very high spatial resolution (VHSR) imagery, we explored the use of tree crown metrics for identifying leading species over four study sites in the Yukon Territory, Canada. Image segmentation was used to delineate homogeneous forest stands, followed by a tree crown delineation algorithm that identified individual tree crowns within each stand. Leading species in the study area included white spruce, black spruce, lodgepole pine, and trembling aspen. Nonparametric multivariate statistical tests indicated that some tree crown metrics generalized at the stand level have significant utility for discriminating leading species. Based on this result, a classification...
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Carbon emissions from boreal forest fires are projected to increase with continued warming and constitute a potentially significant positive feedback to climate change. The highest consistent combustion levels are reported in interior Alaska and can be highly variable depending on the consumption of soil organic matter. Here we present an approach for quantifying emissions within a fire perimeter using remote sensing of fire severity. Combustion from belowground and aboveground pools was quantified at 22 sites (17 black spruce and five white spruce-aspen) within the 2010 Gilles Creek burn in interior Alaska, constrained by data from eight unburned sites. We applied allometric equations and estimates of consumption...
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Spatial and temporal variability in landscape freeze- thaw (FT) status at higher latitudes and elevations significantly impacts land surface water mobility and surface energy partitioning, with major consequences for regional climate, hydrological, ecological, and biogeochemical processes. With the development of new-generation spaceborne remote sensing instruments, future L-band missions, including the NASA Soil Moisture Active and Passive mission, will provide new operational retrievals of landscape FT state dynamics at moderate (~3 km) spatial resolution. We applied theoretical simulations of L-band radar backscatter using first-order radiative transfer models with two and three-layer modeling schemes to develop...
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The late-Holocene shift from Picea glauca (white spruce) to Picea mariana (black spruce) forests marked the establishment of modern boreal forests in Alaska. To understand the patterns and drivers of this vegetational change and the associated late-Holocene environmental dynamics, we analyzed radiocarbon-dated sediments from Grizzly Lake for chironomids, diatoms, pollen, macrofossils, charcoal, element composition, particle size, and magnetic properties for the period 4100–1800 cal BP. Chironomid assemblages reveal two episodes of decreased July temperature, at ca. 3300–3150 (ca −1 °C) and 2900–2550 cal BP (ca −2 °C). These episodes coincided with climate change elsewhere in the Northern Hemisphere, atmospheric...
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Fire disturbance at high latitudes modifies a broad range of ecosystem properties and processes, thus it is important to monitor the response of vegetation to fire disturbance. This monitoring effort can be aided by lidar remote sensing, which captures information on vegetation structure, particularly canopy height metrics. We used lidar data acquired from the Geoscience Laser Altimetry System (GLAS) on ICESAT to derive canopy information for a wide range of burned areas across Alaska. The GLAS data aided our analysis of postfire disturbance and vegetation recovery by allowing us to derive returned energy height metrics within burned area perimeters. The analysis was augmented with MODIS reflectance data sets, which...
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Plant productivity is a fundamental ecological variable that provides information about the health and status of vegetation communities, but is difficult to obtain. In this study, the normalized difference vegetation index, or NDVI, derived from AVHRR data, was used to estimate NPP. Seven seasonal-based metrics were calculated using the NDVI, and utilized to model NPP over Alaska, U.S.A. They included maximum, mean and summed NDVI for the growing season, total days for the growing season, product of total days and maximum NDVI, an integral estimate of NDVI over the growing season, and a summed product of NDVI and solar radiation for the growing season. Linear relationships between NPP and each NDVI metric were analyzed...
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Over the past fifty years Alaska has experienced an increase in mean annual temperature. This warming may be causing significant changes in hydrology and permafrost dynamics. In recent decades, Native Americans and land managers have reported losses of water bodies and surface water area in interior Alaska. We conducted a study to determine the degree to which these informal observations were representative of a regional trend in surface water area loss. This study examines closed-basin water bodies in nine regions across Alaska: 1) Copper River Basin, 2) Talkeetna, 3) Tetlin National Wildlife Refuge, 4) Denali National Park, 5) Innoko Flats National Wildlife Refuge, 6) Minto Flats State Game Refuge, 7) Stevens...


map background search result map search result map Interim Guidelines for Operational Implementation of SAR Applications for Lake Ice Monitoring and Mapping: Break-up and Freeze-up Stony River MOA earth cover classification Using Remote Sensing to Examine Changes of Closed-basin Surface Water: Area in Interior Alaska from 1950-2002 Standards for mapping ecosystems at risk in British Columbia: An approach to mapping ecosystems at risk and other sensitive ecosystems. Version 1.0 Validation of MODIS FPAR Products in Boreal Forests of Alaska Post-fire evaluation of the effects of fire on the environment using remotely-sensed data Satellite boreal measurements over Alaska and Canada during June-July 2004: Simultaneous measurements of upper tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH3OH, HCOOH, OCS, and SF6 mixing ratios (DOI 10.1029/2006GB002795) Development of a circa 2000 land cover map of northern Canada at 30 m resolution from Landsat Identifying leading species using tree crown metrics derived from very high spatial resolution imagery in a boreal forest environment Quantifying fire-wide carbon emissions in interior Alaska using field measurements and Landsat imagery Late-Holocene climate variability and ecosystem responses in Alaska inferred from high-resolution multiproxy sediment analyses at Grizzly Lake Late-Holocene climate variability and ecosystem responses in Alaska inferred from high-resolution multiproxy sediment analyses at Grizzly Lake Quantifying fire-wide carbon emissions in interior Alaska using field measurements and Landsat imagery Stony River MOA earth cover classification Using Remote Sensing to Examine Changes of Closed-basin Surface Water: Area in Interior Alaska from 1950-2002 Identifying leading species using tree crown metrics derived from very high spatial resolution imagery in a boreal forest environment Validation of MODIS FPAR Products in Boreal Forests of Alaska Post-fire evaluation of the effects of fire on the environment using remotely-sensed data Interim Guidelines for Operational Implementation of SAR Applications for Lake Ice Monitoring and Mapping: Break-up and Freeze-up Standards for mapping ecosystems at risk in British Columbia: An approach to mapping ecosystems at risk and other sensitive ecosystems. Version 1.0 Development of a circa 2000 land cover map of northern Canada at 30 m resolution from Landsat Satellite boreal measurements over Alaska and Canada during June-July 2004: Simultaneous measurements of upper tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH3OH, HCOOH, OCS, and SF6 mixing ratios (DOI 10.1029/2006GB002795)