NASA Technologies Predict Stored Carbon in U.S. Forest
Forest ecosystems store enormous amounts of carbon in their standing trees, which until 2000 measured about 54 tons of carbon per every hectare (about two and a half acres) in the United States. As our forest trees grow, mature and die, they contribute to stabilizing the global carbon cycle through photosynthesis, respiration, decomposition and combustion. To monitor and predict the carbon cycle of our new and maturing forests, scientists are working to establish a biomass baseline for the amount of carbon stored in our forests.
By using satellite remote sensing, ecosystems modeling carbon changes and forest inventory data, NASA scientists are making great strides in augmenting the national carbon mapping efforts and developing new modeling approaches using satellite data.
A study led by Christopher Potter and Matthew Fladeland of NASA Ames Research Center, Moffett Field, Calif. and Peggy Gross, Steven Klooster, Vanessa Genovese of Calif. State University Monterey Bay, Seaside, Calif. found that results from state-of-the-art ecosystem models, developed by Ames Research Center, provided original and important information about forest carbon pools and cycles in the United States. They also found that NASA satellite images provided far greater detail about where forests store carbon than any other measurement method known. The study appeared in the April 17, 2008 issue of Climatic Change.
The magnitude of the greenhouse gas emission is why scientists now are examining the amount of carbon stored in forests as a means to offset industrial pollution sources.
According to Potter, scientists are tracking carbon pools because some countries and states, by law, require annual reports of their carbon and greenhouse gas emissions. These reports document the enormous amounts of greenhouse gases released when natural pools change suddenly, such as during a wildfire. Tracking carbon pools also is a reliable way of isolating the natural carbon emissions caused by plants and the oceans from the pollution and greenhouse gas emissions produced by human activities.
Tracking and measuring stored carbon in our forests is not an easy task. Some trees are hardwood, others are softwood, and the amount of carbon stored in the trees depends on the wood type. For instance, western Douglas fir (hardwood) forests store more carbon than eastern hickory-oak (hardwood) forests, which stores more carbon than either the southern loblolly pine (softwood) plantations or the southwestern pinyon-juniper (softwood) woodlands.
In the past, assessments were based on localized inventories, which were costly, time-consuming and based on small sample sizes. Today, forest managers and policy makers require precise information on carbon storage for international reporting as well as forest management plans and forest health assessments, which now requires scientists to look for complementary approaches.
For this study, NASA scientists made region-by-region evaluations using information from the U.S. Forest Service's national Forest Inventory and Analysis data set and the Carbon Online Estimator (COLE). To obtain the standing wood carbon pool, scientists assumed that 50 percent of the woody biomass was carbon. They then updated their ecosystem carbon model, called the NASA- Carnegie Ames Stanford Approaches (CASA) model. Results showed that the new modeling estimates helped map recent changes in forest production and standing biomass.
In summary, forests appear to be accumulating carbon in the United States' Northwest and Southeast areas; due to the regions' abundant annual rainfall and moderate temperature. However, there are still extensive areas of relatively low density forests in the Southeastern U.S. due to frequent forest harvests.
In conclusion, ecosystem models like NASA-CASA coupled with satellite observations enhanced state- and countywide assessments of forest carbon pools.
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Ruth Dasso Marlaire
Ames Research Center, Moffett Field, Calif.