Using MODIS derived fPAR with ground based flux tower measurements to derive the light use efficiency for two Canadian peatlands

Abstract. We used satellite remote sensing data; fraction of photosynthetically active radiation absorbed by vegetation (fPAR) from the Moderate Resolution Imaging Spectroradiometer (MODIS) in combination with tower eddy covariance and meteorological measurements to characterise the Light Use Efficiency parameter (ε) variability and the maximum ε (ε_max) for two contrasting Canadian peatlands. Eight-day MODIS fPAR data were acquired for the Mer Bleue (2000 to 2003) and Western Peatland (2004). Flux tower eddy covariance and meteorological measurements were integrated to the same eight-day time stamps as the MODIS fPAR data. A light use efficiency model: GPP = ε×APAR (where GPP is Gross Primary Productivity and APAR is absorbed photosynthetically active radiation) was used to calculate ε. The ε_max value for each year (2000 to 2003) at the Mer Bleue bog ranged from 0.58 g C MJ⁻¹ to 0.78 g C MJ⁻¹ and was 0.91 g C MJ⁻¹ in 2004, for the Western Peatland. The average growing season ε for the Mer Bleue bog for the four year period was 0.35 g C MJ⁻¹ and for the Western Peatland in 2004 was 0.57 g C MJ⁻¹. The average snow free period for the Mer Bleue bog over the four years was 0.27 g C MJ⁻¹ and for the Western Peatland in 2004 was 0.39 g C MJ⁻¹. Using the light use efficiency method we calculated the ε_max and the annual variability in ε for two Canadian peatlands. We determined that temperature was a growth-limiting factor at both sites Vapour Pressure Deficit (VPD) however was not. MODIS fPAR is a useful tool for the characterization of ε at flux tower sites.