Monday, August 4, 2008
Exhibit Hall CD, Midwest Airlines Center
Background/Question/Methods The NSF-funded Beringia project employs a novel rapid assessment technique to quantify decadal time-scale change in radiative forcing potential (RFP) in the Beringia region. During the 2005, 2006, and 2007 summer seasons, 16 sites throughout the Beringia region were visited. Site locations spanned Chukotka and Wrangel Island in the Russian arctic, the North Slope of Alaska, and the Seward Peninsula. At each site, study plots were established in dominant land cover types (dry, moist, wet, aquatic, tussock, shrub) and the radiative forcing potential (RFP) was determined for each over a three-day sampling period. This report examines the relationship between trace gas exchange (CO2 and CH4), hyperspectral reflectance, surface albedo, soil moisture, species cover, leaf area index (LAI), active layer depth, and above-ground plant biomass for different land cover types studies at each of the study sites.
Results/Conclusions
Gross Ecosystem Productivity (GEP) showed significant correlations with normalized difference vegetation index (NDVI, R2 = 0.42), and leaf area index (LAI, R2 = 0.43). Soil moisture content showed positive correlation with relationship with methane (CH4) efflux, where higher soil water content lead to greater ecosystem CH4 efflux. While wet and aquatic sites were generally the greatest CO2 sinks, they were also the largest sources of CH4 to the atmosphere. These findings underscore the importance of accounting for CH4 exchange when calculating ecosystem RFP. In some cases, the calculated RFP of sites changed from negative to positive when accounting for CH4 in addition to CO2. General trends in the direction of net CO2 and CH4 fluxes appear to be conserved across land cover types at different locations, but the magnitude of the respective fluxes is highly variable across landscapes. Surface albedo is also known to be an important aspect of land cover RFP. While the significance of measurements on tussock dominated land cover are limited by the small number of sites sampled (n=3), initial results show tussock tundra to have a high albedo, and a high ratio of CO2 uptake to CH4 efflux compared to the other tundra land cover types sampled.
Results/Conclusions
Gross Ecosystem Productivity (GEP) showed significant correlations with normalized difference vegetation index (NDVI, R2 = 0.42), and leaf area index (LAI, R2 = 0.43). Soil moisture content showed positive correlation with relationship with methane (CH4) efflux, where higher soil water content lead to greater ecosystem CH4 efflux. While wet and aquatic sites were generally the greatest CO2 sinks, they were also the largest sources of CH4 to the atmosphere. These findings underscore the importance of accounting for CH4 exchange when calculating ecosystem RFP. In some cases, the calculated RFP of sites changed from negative to positive when accounting for CH4 in addition to CO2. General trends in the direction of net CO2 and CH4 fluxes appear to be conserved across land cover types at different locations, but the magnitude of the respective fluxes is highly variable across landscapes. Surface albedo is also known to be an important aspect of land cover RFP. While the significance of measurements on tussock dominated land cover are limited by the small number of sites sampled (n=3), initial results show tussock tundra to have a high albedo, and a high ratio of CO2 uptake to CH4 efflux compared to the other tundra land cover types sampled.
