FED/MAC
Background
The Biospheric Sciences Branch (formerly Earth Resources Branch) within the Laboratory
for Terrestrial Physics at NASA's Goddard Space Flight Center and associated University
investigators are involved in a research program entitled Forest Ecosystem Dynamics
(FED) which is fundamentally concerned with vegetation change of forest ecosystems
at local to regional spatial scales (100 to 10,000 meters) and temporal scales
ranging from monthly to decadal periods (10 to 100 years). The nature and extent
of the impacts of these changes, as well as the feedbacks to global climate, may
be addressed through modeling the interactions of the vegetation, soil, and energy
components of the boreal ecosystem.
The FED ecosystem modeling research efforts concentrate on the North American
boreal and northern hardwood transition forests with emphasis on optical and radar
remote sensing technology. This research employs an integrated approach of field
and aircraft studies, theoretical modeling, and satellite image data processing
to infer where landscape pattern and process ecosystem model predictions succeed
or fail at regional spatial scales and interannual temporal scales. We are also
using remote sensing observations as a check on potentially observable forest
ecosystem model predicted attributes (e.g., species composition, tree height distributions,
land use patterns). Conversely, we are investigating the potential of remote sensing
observations for extracting biophysical properties of forest canopies, soils,
and hydrologic parameters used in our forest ecosystem models. On-going work,
in addition to activities discussed here, include modeling, measurement, and data
compilation for a number of boreal zone sites.
The FED model framework (see Levine et al., 1983) integrates existing models of
forest growth and succession (i.e., FORET model of Shugart and West, 1984 and
ZELIG Model of Smith and Urban, 1988), soil processes (Residue model of Bidlake
et al., 1992; Bristow, et al., 1986; TERRA model of Levine, 1984; Levine and Ciolkosz,
1988), and energy dynamics (e.g., Smith et. al., 1981; Kimes and Kirchner, 1982).
Each of the models interact with the others to provide feedback controls on growth,
soil related processes, and energy internal and external to the forest environment.
The forest succession and soil process models require input at the species and
soil characteristics level, respectively. This makes this formulation useful for
examining the effects of changes in climate or anthropogenic factors on the community
composition and structure of the boreal forest.
The results anticipated from this experiment will enable development and validation
of the integrated model to usefully characterize the ecosystem dynamics of the
boreal forest under a variety of conditions. A number of questions pertinent to
the combined experiment may then be considered. For example, how do climatic gradients
determine the spatial distribution of species within the boreal forest? What are
the possible effects of global climate change on the boreal forest? Is the boreal
forest a net source or sink of carbon and methane and will the present state change
if climate changes? Also relevant to the issue of global change are the magnitudes
of the feedbacks between climate and vegetation. The model, as formulated, can
provide insights into the effects of climate change on ecosystem dynamics, but
does not consider the effects of ecosystem changes on climate directly. However,
the model can provide, as outputs, factors that impact climate such as albedo,
evapotranspiration, and trace gas fluxes (i.e., carbon dioxide, methane, and nitrogen).
These questions are also relevant to the BOREAS experiment.
Return
to Multisensor Aircraft Campaigns (FED/MAC)
Return to FED Home Page