Performance of Linear and Nonlinear Two-Leaf Light Use Efficiency Models at Different Temporal Scales

Abstract

Abstract:The reliable simulation of gross primary productivity (GPP) at various spatial and temporal scales is of significance to quantifying the net exchange of carbon between terrestrial ecosystems and the atmosphere. This study aimed to verify the ability of a nonlinear two-leaf model (TL-LUEn), a linear two-leaf model (TL-LUE), and a big-leaf light use efficiency model (MOD17) to simulate GPP at half-hourly, daily and 8-day scales using GPP derived from 58 eddy-covariance flux sites in Asia, Europe and North America as benchmarks. Model evaluation showed that the overall performance of TL-LUEn was slightly but not significantly better than TL-LUE at half-hourly and daily scale, while the overall performance of both TL-LUEn and TL-LUE were significantly better (p < 0.0001) than MOD17 at the two temporal scales. The improvement of TL-LUEn over TL-LUE was relatively small in comparison with the improvement of TL-LUE over MOD17. However, the differences between TL-LUEn and MOD17, and TL-LUE and MOD17 became less distinct at the 8-day scale. As for different vegetation types, TL-LUEn and TL-LUE performed better than MOD17 for all vegetation types except crops at the half-hourly scale. Remote Sens. 2015, 7 2240At the daily and 8-day scales, both TL-LUEn and TL-LUE outperformed MOD17 for forests. However, TL-LUEn had a mixed performance for the three non-forest types while TL-LUE outperformed MOD17 slightly for all these non-forest types at daily and 8-day scales. The better performance of TL-LUEn and TL-LUE for forests was mainly achieved by the correction of the underestimation/overestimation of GPP simulated by MOD17 under low/high solar radiation and sky clearness conditions. TL-LUEn is more applicable at individual sites at the half-hourly scale while TL-LUE could be regionally used at half-hourly, daily and 8-day scales. MOD17 is also an applicable option regionally at the 8-day scale.

Ability of the Photochemical Reflectance Index to Track Light Use Efficiency for a Sub-Tropical Planted Coniferous Forest

“…To capture this difference, another method for calculating LUE was performed as APAR was calculated using the algorithm in a TL-LUE model developed by He et al [21,61]. The specific description of this method was presented in Appendix B.…”

“…Sunlit leaves can absorb both direct and diffuse radiation, while shaded leaves can only absorb diffuse radiation. The APAR on per unit leaf area was calculated separately for sunlit (APAR sun ) and shaded leaves (APAR sh ) [21,[59][60][61], and the total canopy APAR calculated using this algorithm was termed as TL_APAR:…”

Annual balances and extended seasonal modelling of carbon fluxes from a temperate fen cropped to festulolium and tall fescue under two‐cut and three‐cut harvesting regimes

“…The GPP model was improved by including a temperature dependence function (Ft) of photosynthesis to account for photosynthetic constraints imposed by low air temperature (e.g. Wu et al ., ): …”

Description and validation of the Simple, Efficient, Dynamic, Global, Ecological Simulator (SEDGES v.1.0)

“…5.1, with negative productivity biases occurring in regions with reduced downwelling surface SW radiation for their latitude (in the reanalysis), especially in the equatorial tropics. Recent studies show that including a sunlit/shade leaf distinction reduces errors in the simulation of GPP (Yuan et al, 2014;Wu et al, 2015) (but cf. Schaefer et al, 2012).…”