P.I.(s): Elizabeth A. Walter-Shea -- University of Nebraska
Co-I(s): Tim J. Arkebauer - -University of Nebraska
Objectives: Coordinated research program emphasizing measurements of radiation and gas exchange characteristic of canopy elements and resulting interactions of radiation and gas exchange within canopy environments in a boreal forest ecosystem with the following components:
Objectives:
The goal of our coordinated research program is to gain an understanding of radiation and gas exchanges of canopy elements within a boreal forest and the coupling between radiation and gas exchange. The three objectives identified to achieve our goal are:
Group | Data Type | Equipment |
---|---|---|
I | Optical properties | SE-590, integrating sphere, |
Leaf and conifer | imaging system | |
Twig | - | |
Substrate leaf and bark | - | |
Leaf and conifer shoot geometry | Digital calipers, balance | |
Shoot water potential | Pressure chamber | |
II | Leaf and conifer shoot geometry & needle surface area | Digital calipers, balance |
light response | LI 6200 photosynthesis system, screens | |
A/Ci | LI 6200 | |
Ambient photosynthesis | LI 6200 | |
respiration | LI 6200, film developing bag | |
III | Substrate reflectance | Exotech, calibrated reference, camera |
Places and Times of Measurements:
Problems and Caveats:
Calculations of needle transmittance in the visible portion of the spectrum occasionally yield negative numbers. The equation used in the calculation requires a measure of the non-intercepted fraction of the illumination beam (i.e., the fraction of light which passes between the mounted needle samples). The calculated transmittance is sensitive to any error in the fraction; our methods yield a fraction within 5% of the
true value.
Accurate determination of conifer needle surface area by the volume displacement method required image analysis of needle cross sections to quantify the ratio of the perimeter to the square root of the cross sectional area.
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Last Updated: March 5, 1999