Journal
ECOLOGICAL INFORMATICS
Volume 22, Issue -, Pages 58-68Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ecoinf.2014.05.009
Keywords
Phenological observation; RGB; Digital camera; Photograph; Image analysis
Categories
Funding
- KAKENHI (Japan Society for the Promotion of Science [JSPS]) [25281014]
- Environment Research and Technology Development Fund of the Ministry of the Environment of Japan [S-9]
- KAKENHI (JSPS) [4710021]
- Waseda University [2011A-841, 2012B-053, 2013A-6166]
- Grants-in-Aid for Scientific Research [25281014] Funding Source: KAKEN
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Clarification of species-specific year-to-year variations of the timings of the start of leaf-expansion (S-LE) and the end of leaf-fall (E-LF) is an important and challenging task because these timings may alter spatial and temporal variations in ecosystem services such as carbon stock and climate control. Although many previous studies have applied automatically captured digital camera images to observe the timings of S-LE and Em the evaluation of the long-term variation in both timings of each tree species based on image analysis has not yet been sufficiently investigated. In this study, we investigated the year-to-year variation in the timings of S-LE and E-LF for multiple deciduous broad-leaved tree species in a cool-temperate deciduous broad-leaved forest in Japan by using long-term and daily hemispherical (fish-eye) canopy surface images from 2004 to 2013. We found that (1) differences in the characteristics of year-to-year variations in the timing of E-LF among the tree species were more apparent than those of the timing of S-LE among the tree species, (2) the threshold value of the camera-based index (green excess index) for detecting the timing of E-LF varied depending on the spatial and temporal distribution of understories and the visual distortion of the fish-eye images, and (3) the phenological sensitivity of the timing of E-LF to air temperature was lower than that of the timing of S-LE. Our results indicate that it might be helpful for ecologists to use daily continuous canopy surface images for monitoring of species-specific characteristics of spatial and temporal changes in foliage phenology in mixed-species deciduous broad-leaved forests. (C) 2014 Elsevier B.V. All rights reserved.
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