Papers by Laura Bourgeau-Chavez
Frontiers in Plant Science, Apr 25, 2023
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... The relationship between aboveground biomass and radar backscatter as observed on airborne SA... more ... The relationship between aboveground biomass and radar backscatter as observed on airborne SAR imagery. by Eric S Kasischke, Laura L Bourgeau-Chavez, Norman L Christensen, M ... Firstname. Last name. E-mail address. ...or sign in with Facebook. Readership Statistics. ...
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Imprensa da Universidade de Coimbra eBooks, 2022
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Journal Of Geophysical Research: Biogeosciences, Jun 30, 2022
Northern peatlands play an important role in the global C cycle due to their large C stocks and h... more Northern peatlands play an important role in the global C cycle due to their large C stocks and high potential methane (CH4) emissions. The CH4 and CO2 cycles of these systems are closely linked to hydrology, with water table level regulating the balance of oxic and anoxic conditions and the water content of Sphagnum mosses that dominate primary production. Previous work has demonstrated that hyperspectral indices well‐suited to the detection of altered hydrology in Sphagnum peatlands are also highly correlated with GPP. However, little work has been done to extend these findings to CH4 effluxes. In this study, we evaluate the utility of four hyperspectral indices, two reflecting vegetation photosynthetic function (chlorophyll index (CI); normalized difference vegetation index) and two reflecting water content (wetness index (WI); floating water band index), for detecting effects of altered water table, precipitation, and vegetation community on CH4 and CO2 exchange in two peatland mesocosm studies. We found that CI is a good predictor of net CO2 exchange, and that it captured both drought and vegetation effects consistently across a broad range of vegetation treatments. Further, we demonstrate for the first time that WI combined with CI explained a significant percentage of CH4 efflux (R2 = 0.32–0.57). Our results indicate that CI and WI together may be effective tools for detecting effects of altered hydrology and vegetation on northern Sphagnum‐peatland CH4 and CO2 emissions, with implications for detecting and modeling changes in emissions of greenhouse gases at scales ranging from the ecosystem to the Earth system.
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2014 AGU Fall Meeting, Dec 19, 2014
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Deep Blue (University of Michigan), 1994
The usefulness of ERS-1 SAR imagery in the detection of Alaskan boreal forest fire-scars has been... more The usefulness of ERS-1 SAR imagery in the detection of Alaskan boreal forest fire-scars has been demonstrated in previous studies. These studies have found that recent fire-scars (1-5 years old) have a brighter radar return in the C-VV ERS-1 SAR imagery (3-8 dB brighter) than adjacent unburned forests. However, this signature has been found to vary spatially across a fire-scar as well as temporally throughout a season. The purpose of this study is to analyze this variability and to determine if there is a relationship between severity of burn and radar backscatter
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AGUFM, Dec 1, 2012
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Geophysical Research Letters, Oct 2, 2020
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International Journal of Wildland Fire
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IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium
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ResearchGate, 2020
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Journal of Great Lakes Research, 2021
Abstract A disconnect between scientific research and environmental management communities can be... more Abstract A disconnect between scientific research and environmental management communities can be a detriment to both. In the case of Great Lakes coastal ecosystems, which are inherently complex and subject to uncertain effects of future climatic, environmental, and anthropogenic drivers, greater collaboration could be beneficial to their sustainability. We capture the challenges and opportunities identified by a scientist/decision-maker co-production workshop focused on the future environmental quality of Great Lakes coastal wetlands. We explain our path through the stakeholder workshop process, our challenges in translating meeting outcomes into actionable items, and lessons learned to bridge gaps between scientists and decision-makers. Additionally, we determine topics and directions identified by decision-makers that can be modeled with existing technologies and others that require further research. These topics may be incorporated into future research efforts and could serve as a shortlist of research priorities that were identified by decision-makers working with coastal wetland issues. Based on lessons learned during and after the workshop, we provide suggestions for bridging the gap between researchers and decision-makers, including sustained engagement between these groups and improved interaction through the beginning, duration, and end of research and/or management efforts.
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Previous research in the Arctic has demonstrated changes associated with a warming climate includ... more Previous research in the Arctic has demonstrated changes associated with a warming climate including shrub expansion northward, drying of lakes, increasing active layer depths, and decreasing ice and snow cover. With a warming climate, potential for permafrost thaw, increased evapotranspiration from shrubs, and drying lakes, there have likely been widespread changes in patterns of surface soil moisture across the Arctic landscape over the past 20 to 30 years. We investigated trends in soil moisture in Arctic Alaska using the two-decade long data record of ERS-1 and -2 synthetic aperture radar (SAR) satellite data and ground based measurements of precipitation and soil moisture. SAR data have long been known to be highly sensitive to changes in soil moisture condition, and the C-band SAR (~5.6 cm wavelength) of ERS-1 and 2 are particularly useful for monitoring moisture in the low biomass, open ecosystems of the tundra. Eight sites in Alaska, spanning low to high Arctic and coastal to interior tundra, have been used to develop methodologies and relationships between SAR backscatter and soil moisture in tundra ecosystems. Given the dearth of long-term, in-situ soil moisture data, methods have been investigated using surrogate soil moisture information derived from weather station data and the use of the Fire Weather Index (FWI) subsystem of the Canadian Forest Fire Danger Rating System. Previous SAR work in boreal regions has demonstrated high correlations between SAR backscatter at C-band and the drought code (DC) component of the FWI subsystem. DC is a measure of moisture in the deep organic soil layers of 10-20 cm. This paper will present temporal and spatial trends in soil moisture over the two-decade long observation period among the eight study sites. Differences in soil moisture mapping using SAR data between Arctic and boreal systems will be discussed. Recommendations for the use of ERS-1 and -2 data in longitudinal studies will also be highlighted given calibration and data processing issues encountered in this study
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Traditional electro-optical, satellite-based methods of fire detection and monitoring are severel... more Traditional electro-optical, satellite-based methods of fire detection and monitoring are severely limited in the arctic due to persistent cloud cover and short growing seasons. Radar data can provide an alternative to traditional electro-optical methods due to all-weather imaging capabilities. Previous research in boreal forests and current evaluation in the Alaskan tundra shows that synthetic aperture radar (SAR) data can be used successfully to map burn perimeters and distinguish burned and unburned areas within the perimeter over a longer period of time than optical sensors. Results will be presented on the use of SAR data to measure spatial variations in the microwave signature across a fire scar as well as temporally throughout the growing season and across multiple years. The extensive historical archive of ERS-1 and -2 SAR data has been used to characterize three burned areas in the tundra regions of Alaska. These fires include the 1993 Wainwright fires in the north-western part of the North Slope (Fig 1), the 1999 Uvgoon fire in the Noatak National Preserve and 2007 Anaktuvuk River fire north of the Brooks Range in the central area of the North Slope. The data record includes pre-burn, burn, and post-burn observations until the fire scars are no longer discernible on the landscape. Our results show that burned areas are visible reliably five years post burn and then faintly apparent thereafter up to 12 or more years post-burn. Conversely, our analysis of electro-optical (Landsat) imagery shows near complete obscuration of the fire scar one year post-burn (Loboda et al. 2013). Also presented are results of an analysis of the effects of post-fire soil moisture, as measured in weather and climate datasets, on the SAR signature measured from the available image data archive. Reference: Loboda, T L, N H F French, C Hight-Harf, L Jenkins, M E Miller. 2013. Mapping fire extent and burn severity in Alaskan tussock tundra: An analysis of the spectral response of tundra vegetation to wildland fire. Remote Sens. Enviro. 134:194-209
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Papers by Laura Bourgeau-Chavez