Details

Autor(en) / Beteiligte

• Bourgeau-Chavez, L L
• Kasischke, E S
• French, N H
• Riordan, K
• Brunzell, S

Titel

Integrating Satellite Imaging Radar of Alaskan Fire-Disturbed Boreal Forests into Natural Resource Management Applications and Biogeochemical Modeling: the First Fifteen Years

Ist Teil von

• Eos (Washington, D.C.), 2006-12, Vol.87 (52)

Erscheinungsjahr

2006

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Wildfire is a common occurrence in boreal regions and a natural successional process which consumes the deep organic soil layers that build up in the cold boreal climate. Scientists from heritage Environmental Research Institute of Michigan (ERIM) have been studying the use of imaging radar data over boreal Alaska since the first ERS satellite was launched in 1991. Imaging radar is sensitive to the moisture content of the features being imaged including vegetation and soils. Focus has been on recently burned (0-7 years) boreal forests because of their importance to management, ecology and carbon cycling and because they allow moisture in the ground layer to be measured directly from a satellite sensor without interference of a forest canopy. Early research revealed that the C-band (5.7 cm) VV-polarization data at 23 i? incidence angle were favorable for detecting and mapping recently burned forest regions of Alaska during high moisture states (spring and autumn). Early research also revealed relationships between ERS backscatter and in situ surface soil moisture in recently (0-7 years) burned forests. Further research revealed that the surface soil moisture was related to fire weather index codes and thus SAR could potentially be used to predict fuel moisture. Alaskan natural resource management agencies devote considerable resources to fire management and suppression, and mapping of the burn scars is a necessary tool for fire management. The Alaska Fire Service is testing the methods we developed to use C-band SAR for mapping burn scars in an operational sense in fall 2006. Agencies typically rely on cloud-limited Landsat or costly aircraft reconaissance for mapping burn areas. The natural resource managers are also interested in ways to improve the current weather based system of monitoring the potential for wildfire. Currently these agencies rely on the Canadian Forest Fire Danger Rating System's Fire Weather Index (FWI). FWI is based solely on point source weather data collected daily in a sparse network across the state of Alaska and it has limitations, particularly in the determination of the spring start up values. Since FWI codes are key variables used for predicting not only fire danger but also fire behavior and severity, it is important that these variables be as accurate as possible. Our research has resulted in the development and validation of algorithms to predict the FWI Drought Code (DC) from C-band backscatter. This will improve current weather-based estimates by providing a means for calibration of the DC throughout the season, and by providing additional point-sources of fuel moisture estimation. Techniques have also been developed to map spatially varying soil moisture across a burned landscape using a combination of Landsat and C-band imaging radar. This capability has important implications for modeling of post-fire forest regeneration and NPP. Research continues on using SAR to map surface soil moisture in unburned forests. A capability to map surface soil moisture continuously across the burned and unburned landscape will have applications not only for fire managers, but also for modeling of NPP, carbon cycling, and hydrologic cycling.