Chapter 6
Assessing Net Ecosystem Exchange of
Carbon Dioxide Between the Terrestrial
Biosphere and the Atmosphere Using
Fluxnet Observations and Remote Sensing
Jingfeng Xiao
Abstract The quantification of net ecosystem exchange (NEE) of carbon dioxide
over regions, continents, or the globe is essential for understanding the feedbacks
between the terrestrial biosphere and the atmosphere in the context of global climate
change. The eddy covariance technique provides continuous NEE measurements for
a variety of ecosystem and climate types. These measurements, however, only
represent the fluxes at the scale of the tower footprint. Here a data-driven approach
and satellite remote sensing are used to upscale NEE observations from eddy
covariance flux towers to the continental scale and to produce gridded flux estimates
for the conterminous U.S. over the period 2000–2009. The resulting 10-year gridded
flux estimates (EC-MOD) have 1 km spatial resolution and 8-day time step, and
provide independent and alternative NEE estimates compared to traditional
approaches. These flux estimates are used to examine the spatial and temporal
dynamics of NEE at seasonal, annual, and interannual scales. On average, the annual
NEE of U.S. natural ecosystems is -0.54 Pg C year
-1 . The EC-MOD estimate of
the U.S. carbon sink agrees with recent estimates from the literature. The dominant
sources of the interannual variability in NEE of the U.S. include drought and
disturbances. EC-MOD is also valuable for evaluating simulations from ecosystem
models and atmospheric inversions.
6.1 Introduction
The quantification of net ecosystem exchange (NEE) of carbon dioxide (CO 2 ) over
regions, continents, or the globe is essential for understanding the feedbacks
between the terrestrial biosphere and the atmosphere in the context of global
J. Xiao (&)
Earth Systems Research Center, Institute for the Study of Earth, Oceans,
and Space, University of New Hampshire, Durham, NH, USA
e-mail: j.xiao@unh.edu
J. M. Hanes (ed.), Biophysical Applications of Satellite Remote Sensing,
Springer Remote Sensing/Photogrammetry, DOI: 10.1007/978-3-642-25047-7_6,
Ó Springer-Verlag Berlin Heidelberg 2014
149
Assessing Net Ecosystem Exchange of
Carbon Dioxide Between the Terrestrial
Biosphere and the Atmosphere Using
Fluxnet Observations and Remote Sensing
Jingfeng Xiao
Abstract The quantification of net ecosystem exchange (NEE) of carbon dioxide
over regions, continents, or the globe is essential for understanding the feedbacks
between the terrestrial biosphere and the atmosphere in the context of global climate
change. The eddy covariance technique provides continuous NEE measurements for
a variety of ecosystem and climate types. These measurements, however, only
represent the fluxes at the scale of the tower footprint. Here a data-driven approach
and satellite remote sensing are used to upscale NEE observations from eddy
covariance flux towers to the continental scale and to produce gridded flux estimates
for the conterminous U.S. over the period 2000–2009. The resulting 10-year gridded
flux estimates (EC-MOD) have 1 km spatial resolution and 8-day time step, and
provide independent and alternative NEE estimates compared to traditional
approaches. These flux estimates are used to examine the spatial and temporal
dynamics of NEE at seasonal, annual, and interannual scales. On average, the annual
NEE of U.S. natural ecosystems is -0.54 Pg C year
-1 . The EC-MOD estimate of
the U.S. carbon sink agrees with recent estimates from the literature. The dominant
sources of the interannual variability in NEE of the U.S. include drought and
disturbances. EC-MOD is also valuable for evaluating simulations from ecosystem
models and atmospheric inversions.
6.1 Introduction
The quantification of net ecosystem exchange (NEE) of carbon dioxide (CO 2 ) over
regions, continents, or the globe is essential for understanding the feedbacks
between the terrestrial biosphere and the atmosphere in the context of global
J. Xiao (&)
Earth Systems Research Center, Institute for the Study of Earth, Oceans,
and Space, University of New Hampshire, Durham, NH, USA
e-mail: j.xiao@unh.edu
J. M. Hanes (ed.), Biophysical Applications of Satellite Remote Sensing,
Springer Remote Sensing/Photogrammetry, DOI: 10.1007/978-3-642-25047-7_6,
Ó Springer-Verlag Berlin Heidelberg 2014
149