Assessment of canopy photosynthetic capacity and estimation of GPP by using spectral vegetation indices and the light-response function in a larch forest

作者：Ide Reiko^*; Nakaji Tatsuro; Oguma Hiroyuki

来源：Agricultural and Forest Meteorology, 2010, 150(3): 389-398.

DOI：10.1016/j.agrformet.2009.12.009

• GPP
• Light-response curve
• Maximum photosynthesis (P(max))
• Initial slope (phi)
• Spectral vegetation index
• Vapor pressure deficit (VPD)
• Relative solar radiation
• Eddy covariance

Integration of CO(2) flux observations with remote sensing technique and ecosystem modeling is expected to be useful for estimation of gross primary production (GPP). We focused on the changes in the two main parameters for the canopy-scale light-response curve-P(max) (maximum GPP at light saturation) and phi (initial slope) as indicators to represent canopy photosynthetic capacity. We hypothesized that P(max) and phi could be evaluated by using spectral reflectance related to the changes in the levels of canopy nitrogen and chlorophyll. We analyzed the relationships between P(max) and phi, derived from tower-based CO(2) flux observations, and ground-based spectral vegetation indices (VIs) in a temperate deciduous coniferous forest.
The canopy-scale P(max) and phi showed clear seasonal changes accompanying phenological stages. Both the variations in P(max) and phi were strongly correlated with VIs, especially with the ratio vegetation index (RVI) and enhanced vegetation index (EVI), independent of the growth stages. Moreover, day-to-day short-term variations of P(max) and phi were affected by meteorological conditions such as vapor pressure deficit (VPD) and relative solar radiation which was calculated as the ratio of monitored radiation per theoretical maximum radiation.
Thus, seasonal changes of P(max) and phi were effectively assessed by RVI or EVI, and their short-term variations were evaluated by the empirical relationships with VPD and relative solar radiation. We propose a new simple method for estimating GPP with good precision; by fitting the light-response function with the evaluated parameters, the estimated GPP reflects 3 types of temporal variation: diurnal, day-to-day, and seasonal.

• 出版日期2010-3-15