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Climate Variability & Change

Current ecosystem carbon exchange models are limited by a lack of quantitative information on the spatial and temporal variability of photosynthesis, a critically important physiological and ecological function. The proposed research will establish a robust approach in the use of spectral reflectance to detect vegetation physiological status, and will examine how structural properties of canopies affect the ecosystem responses to stress and their associated reflected signals. We previously found that two of the primary factors that influence the full canopy photosynthetic efficiency are: i) protective responses to environmental stresses, with associated spectral responses that differ for sunlit vs. shaded foliage; and ii) the canopy structure, which influences the sunlit and shaded foliage fractions. We have also demonstrated that the diurnal and seasonal variability in photosynthetic efficiency can be successfully tracked with spectral indicators, without having to acquire extensive ground based information, and that MODIS look-up table fixed biome-scale values misrepresent (over- or under-estimate) efficiencies for the ecosystems we examined. In this successor proposal to the previous terrestrial ecosystem-related study, we will use field data to develop and test models of leaf and canopy level radiative transfer, photosynthesis, and spectral reflectance. From our combined in-situ information of forests and a cornfield (including structural, flux, and micro-meteorological data) and remote sensing (spectral, structural) data, we will determine how the carbon uptake/efficiency is affected by the partitioning of the canopy into sunlit and shaded foliage fractions, as expressed with chlorophyll-related spectral indices and the Photochemical Reflectance Index (PRI). We will verify that the daily and seasonal changes in the sunlit and shaded forest fractions constitute an important ecological factor in carbon balance that affect the GEP as determined for the whole ecosystem. We will extend our investigation of carbon uptake/efficiency for selected ecosystems through models for several IPCC future climate scenarios. This research will support future missions (e.g., HyspIRI) by providing optimal remote sensing strategies and a critical modeling tool for monitoring ecosystem stress (i.e., down-regulation of GEP) and a better understanding of the role of canopy structure in defining ecosystem carbon uptake.

Project PI: Elizabeth Middleton/NASA Goddard Space Flight Center

NASA/GSFC Mail Code 614.4 Greenbelt, MD 20771

Phone: (301)614-6670

Fax: (301) 614-6695

Email: elizabeth.m.middleton@nasa.gov

http://science.gsfc.nasa.gov/sed/index.cfm?fuseAction=people.jumpBio&iPhonebookId;=15953

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Started: Sep 02, 2010

Last Activity: Feb 09, 2011

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