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TG-05 Abstract

Modeling the Effects of Land Use Change and Surface Hydrology on Carbon and Trace Gas Fluxes for the Amazon Region

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

The Amazon region includes the largest remaining tropical forest

ecosystem on Earth.  Despite the Amazon’s potential importance for

climate regulation, the precise pattern of a terrestrial sources and sinks

for CO2 and other “greenhouse gas” compounds like methane remain

uncertain for the region.  These large gaps in our knowledge still

exist to a great degree because many impacts of land cover change and

geochemical controls related to surface hydrology have not been understood

in adequate detail to determine precise regional fluxes for biogenic trace

gases.  Therefore, the fundamental approach we propose for LBA-ECO II

research involves integrated studies and predictive modeling for Amazon

carbon, water, and nutrient cycles using a regional ecosystem model called

NASA-CASA (Carnegie-Ames Stanford Approach), which has been uniquely

developed and applied using satellite data drivers as a component of the

NASA LBA-ECO I program.  Our proposed work thereby builds upon over

four years of coordinated data assimilation and model development, as part

of the LBA Science Team.  The research plan we now propose is designed

to extend the value of new LBA site (tower and small plot flux) data and

remote sensing products by up-scaling with NASA-CASA to the regional level

using a variety of different land cover products available for the Amazon

region.  In this manner, we propose to make new linkages in LBA-ECO

project science between site-based investigation and regional scale modeling

and remote sensing.

A unique aspect of our study approach is to treat land cover

inputs to our ecosystem carbon modeling as variable  according to time,

spatial scale, and spatial resolution.  In the proposed research plan,

the NASA-CASA ecosystem model will make a series of simulation runs using

multiple sequences of land cover change for the entire Amazon regional

extent.  The simulations will include the following land cover/land use

class settings  -- moist primary forest, dry primary forest,

drought-deciduous forest, savanna, disturbed (burned), secondary forest,

pasture, and annual crop.  Nominal spatial resolution for hydro-meteorologic

inputs to our LBA regional simulations will be 8x8 km pixel size.  The

percentage cover-weighted results from these individual model runs for land

cover change sequences will be aggregated to reconstruct a history of

regional heterogeneity in Amazon ecosystem dynamics.  Trace gas fluxes

(e.g., CO2, N2O) will be weighted by land cover change frequency

distributions derived from the highest spatial resolution data available

(e.g., from MODIS and Landsat sensors) for the entire region and for

selected smaller areas around intensive LBA studies.  High resolution

(< 1-km) land cover images for 'footprint' areas of LBA tower sites will

be used to define the proportions of each land cover class with which to

weight ecosystem model estimates and validate against measured tower fluxes

of carbon and water exchange.  Particular emphasis will be placed on

Tapajós National Forest (TNF) tower sites, where our Brazilian

co-investigators are actively making field measurements of energy, water,

and carbon exchange, which are vital to ecosystem model evaluation.

A second integrative aspect of this study will be to extend

NASA-CASA model predictions of carbon and trace gas fluxes to (seasonally)

inundated areas of the region.  Through close collaboration with other

LBA investigator teams whose studies have developed or used radar remote

sensing products or surface water models, we will adapt our CASA model to

include Amazon mainstem and floodplain dynamics, with focus on up-scaling

wetland ecosystem methane and CO2  emission fluxes.  At the

smaller scale of the TNF watershed, we will complete the development of a

new parameterization scheme within the NASA-CASA model for coupling a

surface water routing model called HYDRA (Univ. Wisconsin), and validating

simulations of surface water flow against measured flow and dissolved carbon

chemistry of the Rio Moju discharge network from the TNF.

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