Journal ArticleDOI
Use of digital webcam images to track spring green-up in a deciduous broadleaf forest.
Andrew D. Richardson,J. P. Jenkins,Bobby H. Braswell,David Y. Hollinger,Scott V. Ollinger,Marie-Louise Smith +5 more
TLDR
It is concluded that webcams offer an inexpensive means by which phenological changes in the canopy state can be quantified and a network of cameras could offer a novel opportunity to implement a regional or national phenology monitoring program.Abstract:
Understanding relationships between canopy structure and the seasonal dynamics of photosynthetic uptake of CO2 by forest canopies requires improved knowledge of canopy phenology at eddy covariance flux tower sites. We investigated whether digital webcam images could be used to monitor the trajectory of spring green-up in a deciduous northern hardwood forest. A standard, commercially available webcam was mounted at the top of the eddy covariance tower at the Bartlett AmeriFlux site. Images were collected each day around midday. Red, green, and blue color channel brightness data for a 640 × 100-pixel region-of-interest were extracted from each image. We evaluated the green-up signal extracted from webcam images against changes in the fraction of incident photosynthetically active radiation that is absorbed by the canopy (f
APAR), a broadband normalized difference vegetation index (NDVI), and the light-saturated rate of canopy photosynthesis (A
max), inferred from eddy flux measurements. The relative brightness of the green channel (green %) was relatively stable through the winter months. A steady rising trend in green % began around day 120 and continued through day 160, at which point a stable plateau was reached. The relative brightness of the blue channel (blue %) also responded to spring green-up, although there was more day-to-day variation in the signal because blue % was more sensitive to changes in the quality (spectral distribution) of incident radiation. Seasonal changes in blue % were most similar to those in f
APAR and broadband NDVI, whereas changes in green % proceeded more slowly, and were drawn out over a longer period of time. Changes in A
max lagged green-up by at least a week. We conclude that webcams offer an inexpensive means by which phenological changes in the canopy state can be quantified. A network of cameras could offer a novel opportunity to implement a regional or national phenology monitoring program.read more
Citations
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Journal ArticleDOI
Terrestrial biosphere models need better representation of vegetation phenology: results from the North American Carbon Program Site Synthesis
Andrew D. Richardson,Ryan S. Anderson,M. Altaf Arain,Alan G. Barr,Gil Bohrer,Guangsheng Chen,Jing M. Chen,Philippe Ciais,Kenneth J. Davis,Ankur R. Desai,Michael Dietze,Danilo Dragoni,S. R. Garrity,Christopher M. Gough,Robert F. Grant,David Y. Hollinger,Hank A. Margolis,Harry McCaughey,Mirco Migliavacca,Russell K. Monson,J. William Munger,Benjamin Poulter,Brett Raczka,Daniel M. Ricciuto,A. K. Sahoo,Kevin Schaefer,Hanqin Tian,Rodrigo Vargas,Hans Verbeeck,Jingfeng Xiao,Yongkang Xue +30 more
TL;DR: In this article, the authors evaluate the representation of phenology, and the associated seasonality of ecosystem-scale CO2 exchange, in 14 models participating in the North American Carbon Program Site Synthesis.
Journal ArticleDOI
Tracking the rhythm of the seasons in the face of global change: phenological research in the 21st century.
Jeffrey T. Morisette,Andrew D. Richardson,Alan K. Knapp,Jeremy I. Fisher,Eric Graham,John T. Abatzoglou,Bruce E. Wilson,David D. Breshears,Geoffrey M. Henebry,Jonathan M. Hanes,Liang Liang +10 more
TL;DR: Phenology is the study of recurring life-cycle events, classic examples being the flowering of plants and animal migration as mentioned in this paper, which are increasingly relevant for addressing applied environmental issues.
Journal ArticleDOI
Digital repeat photography for phenological research in forest ecosystems
Oliver Sonnentag,Oliver Sonnentag,Koen Hufkens,Cory Teshera-Sterne,Adam M. Young,Mark A. Friedl,Bobby H. Braswell,Tom Milliman,John O'Keefe,Andrew D. Richardson +9 more
TL;DR: The results indicate that gcc from different digital cameras can be used for comparing the timing of key phenological events across sites, and advocate the use of gcc for phenological research.
Journal ArticleDOI
Leaf‐out phenology of temperate woody plants: from trees to ecosystems
TL;DR: For most species, onset of leaf-out will continue to advance, although advancement may be slowed for some species because of unmet chilling requirements, and more information is needed to reduce the uncertainty in predicting the timing of future spring onset.
Journal ArticleDOI
Near-surface remote sensing of spatial and temporal variation in canopy phenology
TL;DR: It is shown how inexpensive, networked digital cameras ("webcams") can be used to document spatial and temporal variation in the spring and autumn phenology of forest canopies, and lays the foundation for regional- to continental-scale camera-based monitoring of phenology at network observatory sites, e.g., National Ecological Observatory Network (NEON) or AmeriFlux.
References
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TL;DR: In this paper, the authors evaluated the performance and validity of the MODIS vegetation indices (VI), the normalized difference vegetation index (NDVI) and enhanced vegetation index(EVI), produced at 1-km and 500-m resolutions and 16-day compositing periods.
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Journal ArticleDOI
FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities
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TL;DR: The FLUXNET project as mentioned in this paper is a global network of micrometeorological flux measurement sites that measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere.
Journal ArticleDOI
Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999
Ramakrishna R. Nemani,Charles D. Keeling,Hirofumi Hashimoto,Hirofumi Hashimoto,William M. Jolly,Stephen C. Piper,Compton J. Tucker,Ranga B. Myneni,Steven W. Running +8 more
TL;DR: It is indicated that global changes in climate have eased several critical climatic constraints to plant growth, such that net primary production increased 6% (3.4 petagrams of carbon over 18 years) globally.
FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities
Dennis D. Baldocchi,Eva Falge,Lianhong Gu,Richard J. Olson,David Y. Hollinger,Steven W. Running,P. M. Anthoni,Christian Bernhofer,Kenneth J. Davis,Robert G. Evans +9 more