Kurzbeschreibung
(Englisch)
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The main topic of PHENOPHOT is to implement and apply high frequent digital phenological image data of a forest site, to set up observational procedures and quality assurance of phenological monitoring, using digital image analysing methods. Phenolocial and ecological information will be associated with NDVI, derived from MODIS and NOAA-AVHRR data to evaluate possible improvement of subpixel classification of the remotely sensed data, especially its application on vegetation dynamic information like SOS, EOS and GSL, which are widely used in phenological, climatologic and ecological models. Interactions between plant seasonality and annual physical conditions will be evaluated and expressed in a model of budburst and senescence. The implementation in the European Phenological Network is intended for further scientific and public use (one-line public awareness, education).
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Partner und Internationale Organisationen
(Englisch)
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AT, BE, BG, CH, CZ, DE, DK, EE, ES, FI, FR, GR, HU, IE, IT, LT, LU, LV, NL, NO, PL, PT, RO, SE, SI, SK, UK
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Abstract
(Englisch)
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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 FLUX-NET/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. Digital cameras at flux measurement sites do not only provide an objective measure of the physiological state of a forest canopy at high temporal and spatial resolutions but also complement CO2 and water exchange measurements, improving our knowledge of ecosystem processes.
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