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Carbon Cycle & Ecosystems

Terrestrial ecologists are now called upon to provide regional scale predictions of the delivery of key ecosystem services from complex forest environments that are increasingly subjected to multiple agents of global environmental change. This necessitates the identification of the spatial pattern and fundamental mechanistic linkages among (1) forest functional types (FFT), (2) the magnitude of ecosystem perturbations, and (3) the magnitude of ecosystem responses. We propose to use field and imaging spectroscopic measurements to test an overall hypothesis that for a given perturbation, spatial variability in ecosystem response can be characterized by using spectroscopy to measure a key suite of leaf-based functional traits that define FFT. We will characterize FFT by canopy-based measurement of three key functional traits: cell structure, shade tolerance, and recalcitrance. A synthesis of the literature and our recent research results indicate that these three traits describe fundamental axes of variability in plant physiology. Moreover, they synthetically define a spectrum of FFT ranging from “open” to “closed” patterns of forest nutrient cycling. We will use field spectroscopy, laboratory measurements, and assessments of species composition to directly measure canopy-based values of the biophysical and biochemical properties (i.e. Wm [ratio of leaf water mass to leaf dry mass], chlorophyll, lignin, foliar delta N-15, and leaf mass per area) that are hypothesized to define variation in cell structure, shade tolerance, and recalcitrance. By relating these field measurements to spectra obtained from AVIRIS or Hyperion, we propose to demonstrate the spectroscopic basis and quantify the error and uncertainty in our characterization of FFTs. Moreover, by collecting this field and hyperspectral information across a range of forest ecosystems (15 study sites ranging from boreal to tropical forests), we will identify the degree to which our characterization of FFT may be generalized to all forest ecosystems. Finally, we will test our overall hypothesis by relating characterizations of FFTs to field and remote sensing data describing ecosystem perturbations and ecosystem responses. Our research meets several key NASA programmatic and scientific objectives. First, we will test and validate methods for using imaging spectroscopy to characterize plant physiology and assess ecosystem-relevant FFTs (program sub-element 1). This provides a basis for the development of algorithms suitable for future hyperspectral sensors. Second, we will integrate these assessments of FFTs with our ongoing work utilizing remote sensing information for characterizing disturbance and ecosystem response (program sub-element 2). Finally, our proposed work will generate the data, geographic scope, and synthetic focus that is urgently needed in the ongoing development of a general theory linking plant ecophysiology, ecosystem ecology, and global change science.

Project PI: Philip Townsend/University of Wisconsin-Madison

Russell Labs 1630 Linden Drive Madison, WI 53706

Phone: 608-262-1669

Email: ptownsend@wisc.edu

http://forest.wisc.edu/facstaff/townsend.html

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Started: Aug 09, 2010

Last Activity: Dec 10, 2010

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