Using near-infrared-enabled digital repeat photography to track structural and physiological phenology in Mediterranean tree-grass ecosystems

Yunpeng Luo, Tarek S. El-Madany, Gianluca Filippa, Xuanlong Ma, Bernhard Ahrens, Arnaud Carrara, Rosario Gonzalez-Cascon, Edoardo Cremonese, Marta Galvagno, Tiana W. Hammer, Javier Pacheco-Labrador, M. Pilar Martín, Gerardo Moreno, Oscar Perez-Priego, Markus Reichstein, Andrew D. Richardson, Christine Römermann, Mirco Migliavacca

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

Tree-grass ecosystems are widely distributed. However, their phenology has not yet been fully characterized. The technique of repeated digital photographs for plant phenology monitoring (hereafter referred as PhenoCam) provide opportunities for long-term monitoring of plant phenology, and extracting phenological transition dates (PTDs, e.g., start of the growing season). Here, we aim to evaluate the utility of near-infrared-enabled PhenoCam for monitoring the phenology of structure (i.e., greenness) and physiology (i.e., gross primary productivity-GPP) at four tree-grass Mediterranean sites. We computed four vegetation indexes (VIs) from PhenoCams: (1) green chromatic coordinates (GCC), (2) normalized difference vegetation index (CamNDVI), (3) near-infrared reflectance of vegetation index (CamNIRv), and (4) ratio vegetation index (CamRVI). GPP is derived from eddy covariance flux tower measurement. Then, we extracted PTDs and their uncertainty from different VIs and GPP. The consistency between structural (VIs) and physiological (GPP) phenology was then evaluated. CamNIRv is best at representing the PTDs of GPP during the Green-up period, while CamNDVI is best during the Dry-down period. Moreover, CamNIRv outperforms the other VIs in tracking growing season length of GPP. In summary, the results show it is promising to track structural and physiology phenology of seasonally dry Mediterranean ecosystem using near-infrared-enabled PhenoCam. We suggest using multiple VIs to better represent the variation of GPP.

Original languageEnglish (US)
Article number1293
JournalRemote Sensing
Volume10
Issue number8
DOIs
StatePublished - Aug 1 2018

Keywords

  • Dehesa
  • Growing season length (GSL)
  • Near-infrared-enabled digital repeat photography
  • PhenoCam
  • Phenological transition date (PTD)
  • Phenology
  • Tree-grass ecosystem

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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