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TG-05 Abstract

Modeling Terrestrial Ecosystem Processes, Carbon Fluxes, and Trace Gas Emissions for Land Cover/Use Types of the Amazon Basin

Claudio José Reis de Carvalho — Embrapa Amazônia Oriental (SA-PI)
Christopher S. Potter — NASA/ARC (US-PI)

Objectives





There are few, if any, ecosystem simulation models that have been well validated for

scaling up trace gas fluxes across land use patterns in the tropics. The research we

propose for LBA-ECO is to test a series of fundamental process-level hypotheses

related to specific land use effects on ecosystem biogeochemistry and trace gas fluxes in

the Amazon region. The main tool we will use for these tests is the daily model version of

CASA (Carnegie-Ames-Stanford Approach) developed at NASA Ames Research Center (Potter et

al., 1997), specifically for Amazon land cover/use types. The modeling tests will be

conducted in close collaboration with experimental field studies planned for the LBA

intensive research sites. Our ultimate research goal is to validate our model applications

for different land uses at LBA sites and to scale-up regionally and dynamically the

plant-soil biochemical, hydrologic, and production components of the daily NASA-CASA

Amazon version, so as to more closely simulate and predict the inter-annual ecosystem

observations from LBA. We propose to take a lead role for LBA-ECO in organizing

comparative modeling studies at LBA intensive study sites, and in developing methods to

couple ecosystem models of production and biogeochemistry to simulation models and

assessments of land cover change for the Amazon region.






Research at NASA Ames has been supported for the past two years to refine and

extrapolate the monthly and daily moisture balance and regional plant production

components of our CASA model version for Brazil, through a joint research grant (National

Science Foundation-TECO #9524050) with collaborators (D. Nepstad et al.) at Brazil's

Instituto de Pesquisa Ambiental da Amazon (IPAM) to study moisture relations in forests of

the eastern Amazon. Regional model drivers have been assembled and an Amazon-basin version

(8-km spatial resolution) of the NASA-CASA model has been completed under this grant

(Potter et al., submitted). Under LBA-ECO, we now propose to investigate the effects

of changing land use in more detail, through relatively high resolution (<1 km2) model

applications that focus on ecosystem production, nutrient cycling, and biogenic trace

gases (BTG) exchange along important eco-climatic transects and at intensive LBA study

site locations. A central working hypothesis for our research is that the quality and

supply of decomposing plant material in soil is a major controller of mineralization rates

and trace gas flux during and after land use change. Interacting effects of soil moisture

holding capacity and canopy water relations must also be tested.






As a second new component of the study, we propose to develop and test methods of

scaling up our various cover-type versions of the model to produce regional flux estimates

(at 1-km to 8-km grid cell resolution) primarily of CO2 and N2O (and

secondarily of NO, CH4, CO, and volatile organic compounds (VOC)) for

comparison (validation) with aircraft and tower eddy flux estimates and for input to

transport tracer models of the region. Our fundamental working hypothesis is that

large-scale conversion from primary forest to pasture and recovering forests represents a

substantial and sustained change in the basin-wide emission budgets for trace gases. To

address the LBA priority of scaling up flux estimates of CO2 and N2O

(plus NO, CH4, CO, and isoprene gases), we will conduct spatial model studies

chiefly for upland hydrologic environments. This will require continuous validation of the

model structure to represent major changes in soil moisture status, canopy cover, and

carbon/nutrient content of vegetation and soil with altered land cover/use, including

forest conversion to pasture, selective logging and secondary forest re-growth. We will

test land use effects on BTG flues from soils, nutrient mineralization from litter and

soil organic matter, nitrification rates, and plant nutrient recycling, with increasing

emphasis on phosphorus cycling in degraded areas and feedback to ecosystem production. As

we move closer to full regional scaling of simulations in the various land cover type, our

focus will be on testing model refinements related to broad scale drivers for rainfall,

cloud cover, vegetation types, inundation, and other soil attributes for simulations that

include the most current and detailed LBA results for land cover/use change in the Amazon.








Our modeling research results will identify which factors (ecological and

anthropogenic) significantly influence key processes that control productivity and

biogeochemistry of tropical ecosystems, and have important sources of variability in the

spatial or temporal domains of interest in the LBA. Over the course of the project, we

will deliver to LBA's data information system (DIS) the research products from our Amazon

geographic information system (GIS) analysis, including evaluations of BTG fluxes,

evapotranspiration, soil C and N stocks, and mineralization fluxes at a grid resolution of

1-km to 8-km for the entire Brazilian Amazon basin. In addition, we present plans to

enhance our ongoing cooperative training component in ecosystem modeling for counterpart

scientists and students from Brazil.





Research Team Responsibilities







Principal Investigator:


Christopher Potter -- Overall model development and coordination







Brazilian Collaborator:


Claudio J. Reis de Carvalho --Forest hydrology and radiation balance


EMBRAPA - Amazonia Ocidental


Laboratorio de Ecofisiologia Vegetal


and Instituto de Pesquisa Ambiental da Amazon (IPAM)







Co-Investigators:


Joseph Coughlan -- Forest hydrology and radiation balance model development





Susan Alexander -- Canopy trace gas model development





Steven Klooster -- Ecosystem model programming and scaling







Technicians/Specialists:


Vanessa Brooks (GIS model programming and data assimilation)


Johnson Controls World Services


NASA Ames Research Center





Jennifer Dungan (Geo-statistical model programming and scaling)


Johnson Controls World Services


NASA Ames Research Center





Preferred Sites





Paragominas, Manaus, and Rondônia (TBD)





Activities and Deliverables





Throughout our research period, we will submit (for distribution by the LBA-DIS)

written reports (publishable versions to the peer-reviewed literature) and numerous

associated data products from the modeling efforts described above.







  • Ecosystem Modeling Studies at Intensive Field Sites in the Amazon. Report(s) will

    evaluate the performance of ecosystem model algorithms at various LBA-Amazon study sites

    and land use types, with emphasis on hypothesis testing and identification of critical

    gaps for data input, process calibration, and validation of ecosystem biogeochemistry and

    BTG fluxes.


  • Regional Modeling of Carbon Storage and Trace Gas Fluxes in the Amazon. Report(s) will

    evaluate temporal and spatial aggregation errors related to requisite data sets across the

    Amazon region. The report(s) will identify ecosystem locations and climate regimes most

    strongly affected by temporal-spatial scaling issues and uncertainty. Findings will

    outline future data requirements for improved regional carbon and nutrient budgets.


  • Expected digital products for the Amazon Basin (1- to 8-km) resolution:




            - Soil texture and pH classes a


   
         - Canopy ET fluxes (daily and monthly) b


   
         - Plant and soil CO2 and CO fluxes (monthly) b


   
         - Soil N2O and NO fluxes (monthly) b


   
         - Plant VOC fluxes (monthly) b


   
         - Soil N mineralization rates (monthly) b


   
         - Soil C and N storage (both total a and labile b fractions)





      a Derived from geo-statistical analysis or GIS routines


      b Derived from simulation model output; daily results for transects.









Deliverables from testing the NASA-CASA microclimate framework from a monthly to a

daily and hourly time step include 1) expansion of model microclimatic variables by

simulating cloud cover, short-wave radiation, and dewpoint, 2) optimization of required

model inputs by substitution of observed daily radiation with simulated daily radiation,

3) testing the temporal variability of climate drivers for trace-gas emission algorithms

coupled to the NASA-CASA framework.


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