Responses of net ecosystem exchanges of carbon dioxide to changes in cloudiness: Results from two North American deciduous forests

Lianhong Gu, Jose D. Fuentes, Herman H. Shugart, Ralf M. Staebler, T. A. Black

Research output: Contribution to journalArticle

173 Scopus citations

Abstract

We analyzed half-hourly tower-based flux measurements of carbon dioxide (CO2) from a boreal aspen forest and a temperate mixed deciduous forest in Canada to examine the influences of clouds on forest carbon uptake. We showed that the presence of clouds consistently and significantly increased the net ecosystem exchanges (NEE) of CO2 of both forests from the level under clear skies. The enhancement varied with cloudiness, solar elevation angles, and differed between the two forests. For the aspen forest the enhancement at the peak ranged from about 30% for the 20°-25° interval of solar elevation angles to about 55% for the 55°-60° interval. For the mixed forest the enhancement at the peak ranged from more than 60% for the 30°-35° interval of solar elevation angles to about 30% for the 65°-70° interval. Averaged over solar elevation angles >20°, the aspen and mixed forests had the maximal NEE at the irradiance equivalent to 78 and 71% of the clear-sky radiation, respectively. The general patterns of current sky conditions at both sites permit further increases in cloudiness to enhance their carbon uptake. We found that both forests can tolerate exceedingly large reductions of solar radiation (53% for the aspen forest and 46% for the mixed forest) caused by increases in cloudiness without lowering their capacities of carbon uptake. We suggest that the enhancement of carbon uptake under cloudy conditions results from the interactions of multiple environmental factors associated with the presence of clouds.

Original languageEnglish (US)
Article number1999JD901068
Pages (from-to)31421-31434
Number of pages14
JournalJournal of Geophysical Research Atmospheres
Volume104
Issue numberD24
DOIs
StatePublished - Dec 27 1999

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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