Digital photography for assessing the link between vegetation phenology and CO2 exchange in two contrasting northern ecosystems

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Linkosalmi , M , Aurela , M , Tuovinen , J-P , Peltoniemi , M , Tanis , C M , Arslan , A N , Kolari , P , Bottcher , K , Aalto , T , Rainne , J , Hatakka , J & Laurila , T 2016 , ' Digital photography for assessing the link between vegetation phenology and CO2 exchange in two contrasting northern ecosystems ' Geoscientific Instrumentation, Methods and Data Systems , vol. 5 , no. 2 , pp. 417-426 . DOI: 10.5194/gi-5-417-2016

Title: Digital photography for assessing the link between vegetation phenology and CO2 exchange in two contrasting northern ecosystems
Author: Linkosalmi, Maiju; Aurela, Mika; Tuovinen, Juha-Pekka; Peltoniemi, Mikko; Tanis, Cemal M.; Arslan, Ali N.; Kolari, Pasi; Bottcher, Kristin; Aalto, Tuula; Rainne, Juuso; Hatakka, Juha; Laurila, Tuomas
Contributor: University of Helsinki, Ecosystem processes/ Jaana Bäck
Date: 2016-09-12
Language: eng
Number of pages: 10
Belongs to series: Geoscientific Instrumentation, Methods and Data Systems
ISSN: 2193-0856
URI: http://hdl.handle.net/10138/182584
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.
Subject: CARBON-DIOXIDE EXCHANGE
REPEAT PHOTOGRAPHY
EDDY COVARIANCE
CLIMATE-CHANGE
SEASONAL DYNAMICS
SPRING PHENOLOGY
BUD BURST
FOREST
TEMPERATURE
TRENDS
1171 Geosciences
1172 Environmental sciences
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