The relationship between incident light intensity and net ecosystem CO2 exchange (NEE) was examined at a low-shrub bog located near Ottawa, Canada. Shrub height was 0.25 m and maximum leaf area index was 1.3 at the peatland. Light intensity was expressed as a clearness index (CI), where values approaching zero indicate heavy overcast conditions and values approaching unity represent cloudless conditions. Light saturation with respect to net CO2 uptake at the canopy scale occurred at low CI, near 0.3. Contrary to reports from some forest ecosystems, in which peak NEE occurred with CI in the range 0.4–0.7, at the peatland there were no differences in NEE across all ranges of CI above 0.3. At the same time, CI in the range of 0.4–0.7 was infrequent and of short duration relative to clear skies and thick overcast conditions. Finally, we show that the use of half-hourly average radiation measurements to determine CI can lead to significant overestimation of the CI index in the range between 0.4–0.7.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 12 • No. 1