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

2015 ◽  
Vol 7 (12) ◽  
pp. 16938-16962 ◽  
Author(s):  
Qian Zhang ◽  
Weimin Ju ◽  
Jing Chen ◽  
Huimin Wang ◽  
Fengting Yang ◽  
...  
Keyword(s):  
Coniferous Forest ◽  
Light Use Efficiency ◽  
Photochemical Reflectance Index ◽  
Use Efficiency

scholarly journals Evaluation of Different Methods for Estimating the Fraction of Sunlit Leaves and Its Contribution for Photochemical Reflectance Index Utilization in a Coniferous Forest

2019 ◽  
Vol 11 (14) ◽  
pp. 1643 ◽  
Author(s):  
Huang ◽  
Qiu ◽  
Fan ◽  
Liu ◽  
Zhang
Keyword(s):  
Coniferous Forest ◽  
Weather Conditions ◽  
Short Time Scale ◽  
Canopy Reflectance ◽  
Climate Conditions ◽  
Photochemical Reflectance Index ◽  
Use Efficiency ◽  
Direct Outcome ◽  
Short Time ◽  
Penumbra Region

Proper determinations of light use efficiency (LUE) and absorbed photosynthetically active radiation (APAR) are essential for LUE models to simulate gross primary productivity (GPP). This study intended to apply the photochemical reflectance index (PRI) to track LUE or APAR variations in a subtropical coniferous forest using tower-based PRI and GPP measurements. To improve the ability of using PRI to track LUE or APAR, a two-leaf approach differentiating sunlit and shaded leaves was used to process the remote sensing and flux data. However, penumbra region, the ‘grey region’ between sunlit and shaded leaves, increases the difficulty for quantifying the fractions of sunlit and shaded leaves. Firstly, three methods with different ways on treating the penumbra region were investigated for estimating the fraction of sunlit leaves (PT). After evaluating the correlations between observed PRI (PRIobs) and inversely retrieved PRI (PRIinv) from estimated PT using the three methods, we found that treating a substantial portion of penumbra region as sunlit leaves was reasonable and using the ratio of canopy reflectance to leaf reflectance as PT was accurate and efficient. Based on this, we used the two-leaf approach to estimate the canopy-level PRI, aiming to evaluate the ability of using PRI as a proxy for LUE or APAR. Results showed that PRI was able to capture half-hourly and daily changes in LUE and APAR, and the two-leaf approach could enhance the correlations between PRI and both LUE and APAR at both half-hourly and daily time steps. Strong diurnal correlations (averaged R = 0.82 from 173 days) between two-leaf PRI and APAR were found on more than 80% days and the relationship between them over the whole study period was also very significant (R2>0.5, p<0.0001) regardless of different climate conditions, suggesting that the two-leaf PRI was probably a better proxy for APAR than for LUE at short-term scale as PRI mainly represented the absorbed energy allocated to photoprotection at short time scale and was a direct outcome driven by APAR. However, the scattered relationships of PRI with LUE and APAR indicated there were still many limitations in usage of PRI to accurately estimate physiological parameters affected by changing weather conditions, pigment pool size, etc., which needed further exploration.

Estimating photosynthetic light-use efficiency using the photochemical reflectance index: variations among species

2004 ◽  
Vol 31 (3) ◽  
pp. 255 ◽  
Author(s):  
Jianmin Guo ◽  
Craig M. Trotter
Keyword(s):  
Light Response ◽  
Species Group ◽  
Photosynthetic Parameters ◽  
Co2 Uptake ◽  
Light Use Efficiency ◽  
Photochemical Reflectance Index ◽  
Response Data ◽  
Use Efficiency ◽  
Species Specific ◽  
The Relationship

Recent studies have shown that the photochemical reflectance index (PRI), derived from narrow waveband reflectance at 531 and 570 nm, can be used as a remote measure of photosynthetic light-use efficiency (LUE). However, uncertainty remains as to the consistency of the relationship between PRI and LUE across species. In this study we examined the relationship between the PRI and various photosynthetic parameters for a group of species with varying photosynthetic capacity. At constant irradiance, for the species group as a whole, the PRI was well correlated with LUE (r2=0.58) and with several other photosynthetic parameters, but best correlated with the ratio of carotenoids to chlorophylls contents (Caro / Chl). Despite the interspecific trends observed, determination of light response functions for the PRI in relation to photosynthetic parameters revealed that species-specific relationships were clearly stronger. For example, r2>0.90 for species-level PRI / LUE relationships. Also, the species-specific light-response data show that the magnitude of the PRI can be related to the magnitude of the saturated irradiance and the rate of CO2 uptake. As demonstrated here, a light response function provides a simple yet precise approach for characterising the relationship between the PRI and photosynthetic parameters, which should assist with improved evaluation of the usefulness of the PRI as a generalised measure of LUE.

scholarly journals Potential of Photochemical Reflectance Index for Indicating Photochemistry and Light Use Efficiency in Leaves of European Beech and Norway Spruce Trees

2018 ◽  
Vol 10 (8) ◽  
pp. 1202 ◽  
Author(s):  
Daniel Kováč ◽  
Petra Veselovská ◽  
Karel Klem ◽  
Kristýna Večeřová ◽  
Alexander Ač ◽  
...  
Keyword(s):  
Norway Spruce ◽  
European Beech ◽  
Early Morning ◽  
Photochemical Quenching ◽  
Physiological Status ◽  
Photosynthetic Parameters ◽  
Light Use Efficiency ◽  
Photochemical Reflectance Index ◽  
Temperature Regimes ◽  
Use Efficiency

Hyperspectral reflectance is becoming more frequently used for measuring the functions and productivity of ecosystems. The purpose of this study was to re-evaluate the potential of the photochemical reflectance index (PRI) for evaluating physiological status of plants. This is needed because the reasons for variation in PRI and its relationships to physiological traits remain poorly understood. We examined the relationships between PRI and photosynthetic parameters in evergreen Norway spruce and deciduous European beech grown in controlled conditions during several consecutive periods of 10–12 days between which the irradiance and air temperature were changed stepwise. These regime changes induced significant changes in foliar biochemistry and physiology. The responses of PRI corresponded particularly to alterations in the actual quantum yield of photosystem II photochemistry (ΦPSII). Acclimation responses of both species led to loss of PRI sensitivity to light use efficiency (LUE). The procedure of measuring PRI at multiple irradiance-temperature conditions has been designed also for testing accuracy of ΔPRI in estimating LUE. A correction mechanism of subtracting daily measured PRI from early morning PRI has been performed to account for differences in photosynthetic pigments between irradiance-temperature regimes. Introducing ΔPRI, which provided a better estimate of non-photochemical quenching (NPQ) compared to PRI, also improved the accuracy of LUE estimation. Furthermore, ΔPRI was able to detect the effect of drought, which is poorly observable from PRI.

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