title: Technological Advancement in Tower-Based Canopy Reflectance Monitoring: The AMSPEC-III System.
abstract: Understanding plant photosynthesis, or Gross Primary Production (GPP), is a crucial aspect of quantifying the terrestrial carbon cycle. Remote sensing approaches, in particular multi-angular spectroscopy, have proven successful for studying relationships between canopy-reflectance and plant-physiology processes, thus providing a mechanism to scale up. However, many different instrumentation designs exist and few cross-comparisons have been undertaken. This paper discusses the design evolution of the Automated Multiangular SPectro-radiometer for Estimation of Canopy reflectance (AMSPEC) series of instruments. Specifically, we assess the performance of the PP-Systems Unispec-DC and Ocean Optics JAZ-COMBO spectro-radiometers installed on an updated, tower-based AMSPEC-III system. We demonstrate the interoperability of these spectro-radiometers, and the results obtained suggest that JAZ-COMBO can successfully be used to substitute more expensive measurement units for detecting and investigating photosynthesis and canopy spectra. We demonstrate close correlations between JAZ-COMBO and Unispec-DC measured canopy radiance (0.75 ≤ R² ≤ 0.85) and solar irradiance (0.95 ≤ R² ≤ 0.96) over a three month time span. We also demonstrate close agreement between the bi-directional distribution functions obtained from each instrument. We conclude that cost effective alternatives may allow a network of AMSPEC-III systems to simultaneously monitor various vegetation types in different ecosystems. This will allow to scale and improve our understanding of the interactions between vegetation physiology and spectral characteristics, calibrate broad-scale observations to stand-level measurements, and ultimately lead to improved understanding of changing vegetation spectral features from satellite.
authors.affiliation: Integrated Remote Sensing Studio, Department of Forest Resources Management, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada. riccardo.tortini@ubc.ca.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Tortini
authors.affiliation: College of Forestry, Oregon State University, 231 Peavy Hall, Corvallis, OR 97333, USA. thomas.hilker@oregonstate.edu.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hilker
authors.affiliation: Integrated Remote Sensing Studio, Department of Forest Resources Management, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada. nicholas.coops@ubc.ca.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Coops
authors.affiliation: Faculty of Land and Food Systems, Univeristy of British Columbia, 2357 Main Mall, Vancouver, BC V6T 1Z4, Canada. zoran.nesic@ubc.ca.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Nesic
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D065928:Forests; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology; D058998:Remote Sensing Technology / Q000379:methods*
keywords: PRI; gross primary production; light use efficiency; multi-angle spectroscopy; photosynthesis; remote sensing; spectro-radiometer