Variations in bio-physical and high spectral resolution reflectance properties associated with the light environment in a mature poplar stand (Lirodendron tulipifera L.)
Petya
K. E.
Campbell, JCET/UMBC and, GSFC/NASA, pcampbel@pop900.gsfc.nasa.gov
(Presenting)
Elizabeth
M.
Middleton, GSFC/NASA and, GSFC/NASA, elizabeth.m.middleton@nasa.gov
Lawrence
A.
Corp, SSIA, lawrence.corp@ars.usda.gov
Yen-Ben
Cheng, GSFC/NASA, ybcheng@ucdavis.edu
Gefrey
Parker, SERC, jparker@serc.edu
While the difference in the morphology of sunlit vs. shaded foliage is clearly established, research is needed to determine if the foliar spectral characteristics also differ. The goal of this study is to determine whether bio-physical differences can be inferred using spectral reflectance (R) indicators.
In 2007, a tall crane equipped with man-basket was used to acquire canopy in situ spectral measurements and to collect samples from sun and shade leaves, from the upper (30 m) and lower (20 m) strata of a mature tulip poplar (Lirodendron Tulipifera L., age 60) forest at the SERC, Edgewater, MD. Leaf-level photosynthesis and a suite of bio-physical parameters were measured on the excised samples.
Leaf area was significantly reduced and photosynthetic rates were elevated for sunlit as compared to shaded foliage, while the pigment contents did not significantly differ. The differences in the light environment (sun vs. shade) greatly affected the spectral and photosynthetic parameters, while the upper vs. lower strata location of the foliage within the canopy was of secondary importance. The rate photosynthesis (Amax, μmol CO2 m-2 s-1) and R intensity were positively related in the 450-800 nm region [stronger correlations at 530 nm (r2=0.62), 690 nm (r2=0.75) and 730 nm (r2=0.77)]. Stomatal conductance (mol CO2 m-2 s-1) was also positively correlated to R, at lower levels (maximal correlation at 740 nm, r2=0.57). Pigment content and foliar/canopy structural parameters (FW/DW and foliage location in the canopy) were negatively related to R (450-800 nm). A preliminary analysis indicates that some of the spectral indices strongly associated with the biophysical parameters, such as RE2, G035, Ro and Dmax, significantly differed depending on the light environment. Further analysis of the spectral data and the collected fluorescence and bio-physical variables is currently on the way.
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