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Geoscientific Instrumentation, Methods and Data Systems An interactive open-access journal of the European Geosciences Union

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Geosci. Instrum. Method. Data Syst., 5, 417-426, 2016
https://doi.org/10.5194/gi-5-417-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
12 Sep 2016
Digital photography for assessing the link between vegetation phenology and CO2 exchange in two contrasting northern ecosystems
Maiju Linkosalmi1, Mika Aurela1, Juha-Pekka Tuovinen1, Mikko Peltoniemi2, Cemal M. Tanis1, Ali N. Arslan1, Pasi Kolari3, Kristin Böttcher4, Tuula Aalto1, Juuso Rainne1, Juha Hatakka1, and Tuomas Laurila1 1Finnish Meteorological Institute, Helsinki, Finland
2Natural Resources Institute Finland (LUKE), Vantaa, Finland
3Faculty of Biosciences, University of Helsinki, Helsinki, Finland
4Finnish Environment Institute (SYKE), Helsinki, Finland
Abstract. Digital repeat photography has become a widely used tool for assessing the annual course of vegetation phenology of different ecosystems. By using the green chromatic coordinate (GCC) as a greenness measure, we examined the feasibility of digital repeat photography for assessing the vegetation phenology in two contrasting high-latitude ecosystems. Ecosystem–atmosphere CO2 fluxes and various meteorological variables were continuously measured at both sites. While the seasonal changes in GCC were more obvious for the ecosystem that is dominated by annual plants (open wetland), clear seasonal patterns were also observed for the evergreen ecosystem (coniferous forest). Daily and seasonal time periods with sufficient solar radiation were determined based on images of a grey reference plate. The variability in cloudiness had only a minor effect on GCC, and GCC did not depend on the sun angle and direction either. The daily GCC of wetland correlated well with the daily photosynthetic capacity estimated from the CO2 flux measurements. At the forest site, the correlation was high in 2015 but there were discernible deviations during the course of the summer of 2014. The year-to-year differences were most likely generated by meteorological conditions, with higher temperatures coinciding with higher GCCs. In addition to depicting the seasonal course of ecosystem functioning, GCC was shown to respond to environmental changes on a timescale of days. Overall, monitoring of phenological variations with digital images provides a powerful tool for linking gross primary production and phenology.

Citation: Linkosalmi, M., Aurela, M., Tuovinen, J.-P., Peltoniemi, M., Tanis, C. M., Arslan, A. N., Kolari, P., Böttcher, K., Aalto, T., Rainne, J., Hatakka, J., and Laurila, T.: Digital photography for assessing the link between vegetation phenology and CO2 exchange in two contrasting northern ecosystems, Geosci. Instrum. Method. Data Syst., 5, 417-426, https://doi.org/10.5194/gi-5-417-2016, 2016.
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Short summary
Digital photography has become a widely used tool for monitoring the vegetation phenology. The seasonal cycle of the greenness index obtained from photographs correlated well with the CO2 exchange of the plants at our wetland and Scots pine forest sites. While the seasonal changes in the greenness were more obvious for the ecosystem dominated by annual plants, clear seasonal patterns were also observed for the evergreen forest.
Digital photography has become a widely used tool for monitoring the vegetation phenology. The...
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