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Remote sensing plays an important role within the field of forest inventory. Airborne laser scanning (ALS) has become an effective tool for acquiring forest inventory data. In most ALS-based forest inventories, accurately positioned field plots are used in the process of relating ALS data to field-observed biophysical properties. The geo-referencing of these field plots is typically carried out by means of differential global navigation satellite systems (dGNSS), and often relies on logging times of 15?20 min to ensure adequate accuracy under different forest conditions. Terrestrial laser scanning (TLS) has been proposed as a possible tool for collection of field data in forest inventories and can facilitate rapid...
Trends in the growing season Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) time-series were analyzed for the time period from 2000 to 2010 to understand landscape-level patterns of vegetation change in ecosystems of interior Alaska. The analysis compared data-sets for Alaska vegetation cover types, wetland cover classes, wildfire boundaries since the 1940s, permafrost type, and elevation to identify the most likely combination of factors driving regional changes in habitat quality and ecosystem productivity. Approximately 48% of all ecosystem areas in interior Alaska were detected with significant (p < 0.05) positive or negative MODIS growing season EVI trends from 2000 to...
Forests are an important global resource, playing key roles in both the environment and the economy. The implementation of quality national monitoring programs is required for the generation of robust national statistics, which in turn support global reporting. Conventional monitoring initiatives based on samples of field plots have proven robust but are difficult and costly to implement and maintain, especially for large jurisdictions or where access is difficult. To address this problem, air photo- and satellite-based large area mapping and monitoring programs have been developed; however, these programs also require ground measurements for calibration and validation. To mitigate this need for ground plot data...
Tracking landscape-scale water status in high-latitude boreal systems is indispensible to understanding the fate of stored and sequestered carbon in a climate change scenario. Spaceborne synthetic aperture radar (SAR) imagery provides critical information for water and moisture status in Alaskan boreal environments at the landscape scale. When combined with results from optical sensor analyses, a complementary picture of vegetation, biomass, and water status emerges. Whereas L-band SAR showed better inherent capacity to map water status, C-band had much more temporal coverage in this study. Analysis through the use of L- and C-band SARs combined with Landsat Enhanced Thematic Mapper Plus (ETM+) enables landscape...
A critical part of the National Park Service’s Arctic Network Inventory and Monitoring Programis monitoring the Western Arctic Caribou Herd (WACH). The status, distribution, movementsand trends in the condition of caribou in all five park units are monitored. Accurate and detailedmodels of snow cover within the range of the Western Arctic Caribou Herd will provideimportant context to help understand movement patterns and timing of caribou migrations. Snowdepth influences caribou winter distribution and habitat availability by impacting the costs oflocomotion and cratering for forage plants and lichens. Snow depth patterns on the landscapealso influence plant communities, affecting the distribution of preferred forage...
An interferogram reflecting the motion of Black Rapids Glacier, Alaska, U.S.A., was obtained from two European Remote-sensing Satellite (ERS-1) synthetic-aperture radar (SAR) images, acquired on 22 and 25 January 1992. We investigate whether the interferometric data are quantitatively consistent with terrestrial velocity measurements along three transverse profiles. These terrestrial data are from different years (1987, 1990, 1996) and cover different periods (6-28 April, 23 May-7 July and a whole year) than the SAR interferogram. Terrestrial ice velocity at the date of the SAR imagery is obtained via seasonal and annual corrections that are calculated from other terrestrial velocity measurements available at higher...
Global products of leaf area index (LAI) usually show large uncertainties in sparsely vegetated areas because the understory contribution is not negligible in reflectance modeling for the case of low to intermediate canopy cover. Therefore, many efforts have been made to include understory properties in LAI estimation algorithms. Compared with the conventional data bank method, estimation of forest understory properties from satellite data is superior in studies at a global or continental scale over long periods. However, implementation of the current remote sensing method based on multi-angular observations is complicated. As an alternative, a simple method to retrieve understory NDVI (NDVIu) for sparse boreal...