Quantitative phenological observations of a mixed beech forest in northern Switzerland with digital photography
Article first published online: 9 OCT 2008
Copyright 2008 by the American Geophysical Union.
Journal of Geophysical Research: Biogeosciences (2005–2012)
Volume 113, Issue G4, December 2008
How to Cite
2008), Quantitative phenological observations of a mixed beech forest in northern Switzerland with digital photography, J. Geophys. Res., 113, G04004, doi:10.1029/2007JG000650., , , , , , , and (
- Issue published online: 9 OCT 2008
- Article first published online: 9 OCT 2008
- Manuscript Accepted: 23 JUL 2008
- Manuscript Revised: 2 APR 2008
- Manuscript Received: 12 NOV 2007
- digital camera;
- image analysis;
- flux tower
 Vegetation phenology has a strong influence on the timing and phase of global terrestrial carbon and water exchanges and is an important indicator of climate change and variability. In this study we tested the application of inexpensive digital visible-light cameras in monitoring phenology. A standard digital camera was mounted on a 45 m tall flux tower at the Lägeren FLUXNET/CarboEuropeIP site (Switzerland), providing hourly images of a mixed beech forest. Image analysis was conducted separately on a set of regions of interest representing two different tree species during spring in 2005 and 2006. We estimated the date of leaf emergence based on the levels of the extracted red, green and blue colors. Comparisons with validation data were in accordance with the phenology of the observed trees. The mean error of observed leaf unfolding dates compared with validation data was 3 days in 2005 and 3.6 days in 2006. An uncertainty analysis was performed and demonstrated moderate impacts on color values of changing illumination conditions due to clouds and illumination angles. We conclude that digital visible-light cameras could provide inexpensive, spatially representative and objective information with the required temporal resolution for phenological studies.