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Carbon Refixation in Photosynthetic Bark of Western White Pine Branches Item Info

I conducted a methodological experiment related to measuring gas exchange in woody tissues using removable cuvettes. The question addressed was whether the volume of respiring tissues should be measured between the midpoints of gaskets used to attach the cuvettes to tissue sections, or between the gasket interior edges. The simple experiment suggested that the gasket midpoints were the correct position for determining the tissue volume actually contributing to a respiration measurement. I investigated the functional controls over light-dependent refixation of respired CO2 in photosynthetic bark of western white pine (Pinus monticola Dougl. Ex D. Don) branches. Gross photosynthesis increased with increasing intensity of photo synthetically active radiation (PAR) to >2000µmol m-2 s -1 and with increasing bark surface temperature from 15 to >45˚ C. Maximum observed refixation rates were 76±3% (mean ± SE) of dark respiration. At a given temperature and irradiance, dark respiration rate was the physiological parameter that correlated most strongly with gross photosynthesis (R=0.89, p<0.0001, n=43). Dark respiration rates varied 20-fold among branches. Over this range, refixation averaged 55±2% of dark respiration at 25˚C and 1000 µmol PAR m-2 s -1. However, refixation was not correlated with internal CO2 concentrations in illuminated branches; these concentrations remained fairly constant. Specific bark area, bark conductance to water vapor, bark chlorophyll a/b ratio, and bark nitrogen concentration varied pronouncedly with canopy depth in mature trees. Results are summarized in a simple model of refixation driven by light, temperature, and dark respiration rate.

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Title:
Carbon Refixation in Photosynthetic Bark of Western White Pine Branches
Creator:
Cernusak, Lucas A.
Date Created:
1999-12
Description:
I conducted a methodological experiment related to measuring gas exchange in woody tissues using removable cuvettes. The question addressed was whether the volume of respiring tissues should be measured between the midpoints of gaskets used to attach the cuvettes to tissue sections, or between the gasket interior edges. The simple experiment suggested that the gasket midpoints were the correct position for determining the tissue volume actually contributing to a respiration measurement. I investigated the functional controls over light-dependent refixation of respired CO2 in photosynthetic bark of western white pine (Pinus monticola Dougl. Ex D. Don) branches. Gross photosynthesis increased with increasing intensity of photo synthetically active radiation (PAR) to >2000µmol m-2 s -1 and with increasing bark surface temperature from 15 to >45˚ C. Maximum observed refixation rates were 76±3% (mean ± SE) of dark respiration. At a given temperature and irradiance, dark respiration rate was the physiological parameter that correlated most strongly with gross photosynthesis (R=0.89, p<0.0001, n=43). Dark respiration rates varied 20-fold among branches. Over this range, refixation averaged 55±2% of dark respiration at 25˚C and 1000 µmol PAR m-2 s -1. However, refixation was not correlated with internal CO2 concentrations in illuminated branches; these concentrations remained fairly constant. Specific bark area, bark conductance to water vapor, bark chlorophyll a/b ratio, and bark nitrogen concentration varied pronouncedly with canopy depth in mature trees. Results are summarized in a simple model of refixation driven by light, temperature, and dark respiration rate.
Document Type:
Thesis
Library Call Number:
QK882.C47 1999
Subjects:
Flat Creek western white pine pinus monticola carbon refixation gas exchange forest ecology
UIEF Unit:
Flat Creek
Location:
UIEF; Flat Creek
Latitude:
46.851013
Longitude:
-116.724478
Department:
Department of Forest Resources
Type:
text
Format:
application/pdf

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Preferred Citation:
"Carbon Refixation in Photosynthetic Bark of Western White Pine Branches", UIEF Research Exchange, University of Idaho Library Digital Collections, https://www.lib.uidaho.edu/digital/uief/items/uief_0030.html
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