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- Title
Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China.
- Authors
Zhang, M.; Yu, G.-R.; Zhang, L.-M.; Sun, X.-M.; Wen, X.-F.; Han, S.-J.; Yan, J.-H.
- Abstract
Clouds can significantly affect carbon uptake of forest ecosystems by affecting incoming solar radiation on the ground, temperature and other environmental factors. In this study, we analyzed the effects of cloudiness on the net ecosystem exchange of carbon dioxide (NEE) of a temperate broad-leaved Korean pine mixed forest at Changbaishan (CBS) and a subtropical evergreen broad-leaved forest at Dinghushan (DHS) of ChinaFLUX, based on the flux data obtained during June-August from 2003 to 2006. The results showed that the response of the NEE of forest ecosystem to photosynthetically active radiation (PAR) was different under clear sky and cloudy sky conditions, and this difference was not consistent between CBS and DHS. Compared with clear skies, light-saturated maximum photosynthetic rate (Pec,max) of CBS during mid-growing season (from June to August) was respectively enhanced by 34%, 25%, 4% and 11% on cloudy skies in 2003, 2004, 2005 and 2006; however, Pec,max of DHS was higher under clear skies than under cloudy skies from 2004 to 2006. NEE of forests at CBS 15 reached its maximum when the clearness index (kt) was between 0.4 and 0.6, and the NEE decreased obviously when kt exceeded 0.6. Compare with CBS, although NEE of forest at DHS tended to the maximum when kt varied between 0.4 and 0.6, the NEE did not decrease noticeably when kt exceeded 0.6. The results indicated that cloudy sky conditions were more beneficial to carbon uptake for the temperate forest ecosystem rather than for the subtropical forest ecosystem. This is due to the fact that the non-saturating light conditions and increase of diffuse radiation were more beneficial to photosynthesis, and the reduced temperature was more conducive to decreasing the ecosystem respiration in temperate forest ecosystems under cloudy sky conditions. This phenomenon is important to evaluate carbon uptake of temperate forests under climate change conditions.
- Subjects
CHINA; CLOUDINESS; CARBON dioxide; SOLAR radiation; FOREST ecology; PHOTOSYNTHETICALLY active radiation (PAR); CLIMATE change
- Publication
Biogeosciences Discussions, 2009, Vol 6, Issue 4, p8215
- ISSN
1810-6277
- Publication type
Article
- DOI
10.5194/bgd-6-8215-2009