Understanding Change in the Biosphere
Approach: The degree to which primary production, soil carbon, and trace gas fluxes in tropical forests of the Amazon are limited by moisture availability and other environmental factors has been examined using an ecosystem modeling application for the country of Brazil. A regional geographic information system (GIS) serves as the data source of climate drivers, satellite "greenness" images, land cover, and soil properties for input to the NASA-CASA model over a 8-km grid resolution.
Major findings:
More more information see Amazon Ecology from Space
Net primary production estimated at 8-km cell resolution by the NASA-CASA model for Brazil, circa 1990.
FIGURE CAPTION Net Primary Production
References:
Potter, C. S., E. A. Davidson, S. A. Klooster, D. C. Nepstad, G. H. de Negreiros, and V. Brooks. 1998. Regional application of an ecosystem production model for studies of biogeochemistry in Brazilian Amazonia. Global Change Biology. 4(3):315-334.
Reference Global Change Biology Home Page
Produced in collaboration with D. Nepstad and E. Davidson (Woods Hole Research Center), with grant support from the National Science Foundation
Support for computing resources provided by the High Performance Computing and Communications (HPPC) Program by granting access to their testbed computers.
To view monthly animation of Net primary production download 4.2Mb mpeg amazon.mpeg
Approach:
Monthly NASA-CASA model estimates of NO emissions from soils were simulated for a nine-state region of the southeastern USA, as part of the Southern Oxidants Study (SOS). Simulations used a regional geographic information system (GIS) as the data source for climate drivers, satellite images, land cover, and soil properties over a 8-km grid resolution. The simulated emissions are used to place the relative magnitude of soil NO emissions into perspective with other regional sources of NOx, and to examine spatial and temporal patterns of soil NO emissions across the region.
Major findings:
References: Davidson, E. A., C. S. Potter, P. Schlesinger, and S. A. Klooster. 1997. A regional model of NO emission from soils. Ecological Applications. (Submitted).
Soil NO emission estimated at 8-km cell resolution by the NASA-CASA model for the nine-state SOS region of the southeastern USA.
FIGURE CAPTION Soil NO emission
Produced in collaboration with E. Davidson (Woods Hole Research Center), with grant support from the Southern Oxidants Study
Approach: The objective of this project was to estimate NH3 emissions from a variety of major crop-fertilizer combinations and from native soils in California.
Phase one of this was to:
Evaluate an active sampler for monitoring NH3 emissions from fertilized fields and background soil emission levels.
Major findings:
Time series plots showed peak emissions shortly after fertilizer application Emission factors are highly consistent among most fertilizer application forms and methods.
Estimated annual emissions of N-NH3 from native soils in California are 14 X 10^6 kg from cropland and 16 x 10^6 kg from non-cropland (mainly coniferous forest) areas.
Estimated annual emissions of N-NH3 from chemical fertilizer are 23 x 10^6 kg.
More more information see california
References:
Potter, C., S. Klooster, C. Krauter, M. Benjamin, V. Brooks Genovese, and A. Torregrosa. 2000. Development of Statewide Inventory Estimates of Ammonia Emissions from Native Soils and Crop Fertilizers in California. EOS, Transactions, AGU.
This work is funded by the California Air Resources Board & NASA Ames Research Center.
Approach:
The Boreal Ecosystem-Atmosphere Study (BOREAS) project has addressed fundamental questions concerning moisture and carbon in the boreal forest biome.
See Boreal Ecosystem-Atmosphere Study (BOREAS) project
What are the primary mechanisms controlling variability in water and carbon fluxes within each of the major boreal ecosystem types?
What measured modeling parameters are most important in terms of scaling up the seasonal patterns of water and carbon cycling across diverse ecosystem types within the boreal forest region?
Main objectives:
Evaluate the performance of the NASA-CASA (Carnegie-Ames-Stanford Approach) simulation model against water and carbon fluxes measured independently at BOREAS field sites.
Refine the concepts and algorithms upon which this generalized scheme for soil trace gas emissions can be built.
Evaluate requirements to scale-up model results and extrapolate interannual trace gas flux estimates over the entire North America boreal forest region, relying on satellite data to characterize properties of the land surface.
Major findings:
Model-measurement and model-model discrepancies were observed among all the BOREAS carbon models (with respect to eddy covariance and/or other site measurements), although more detail (physiology, physics) in a subset of models did tend to improve accuracy, as evaluated by RMSE analysis with measured daily CO2 and ET fluxes.
model sensitivity comparisons imply that past conditions of the ecosystem (e.g., historical climate patterns and time since last major disturbance), as represented in the models' initial standing wood and soil carbon pools, can be as important as potential future climate changes in predicting the annual model response for a net ecosystem carbon sink in the boreal spruce forest.
More more information see
References:
Potter, C. S., J. C. Coughlan, and V. Brooks. 1999. Investigations of BOREAS spatial data in support of regional ecosystem modeling. J. Geophys. Res. 104: 27,771-27,788.
Potter, C. S., J. Bubier, P. Crill, and P. LaFleur. 2001. Ecosystem modeling of methane and carbon dioxide fluxes for boreal forest sites. Can. J. For. Res. 31: 208-223.
Amthor, J. S., J. M. Chen, J. S. Clein, S. E. Frolking, M. L. Goulden, R. F. Grant, J. S. Kimball, A. W. King, A. D. McGuire, N. T. Nikolov, C. S. Potter, S. Wang, and S. C. Wofsy, Boreal forest CO2 exchange and evapotranspiration predicted by nine ecosystem process models: Inter-model comparisons and relations to field measurements. J. Geophys. Res., (In Press).
Next topic NASA Landsurface Hydrology program
NASA Landsurface Hydrology program
