The light-use efficiency (LUE) of vegetation is one of the essential parameters in production estimation models for terrestrial ecosystems. LUE generally expressed as the ratio of GPP to APAR. Due to the characteristic of the photochemical reflectance index (PRI), which is sensitive to changes in carotenoid pigments in live foliage. We recorded the canopy spectral reflectance data to calculate the PRI and sorted and analysed the diurnal, seasonal, and inter-annual changes of PRI. We measured and documented the CO2 flux data and micrometeorological data since 2014. We also made use of the digital camera since 2016 to monitor the canopy phenology changes and calculated the greenness indices.
Our findings demonstrated that LUE has a good relationship with the PRI. Correlation coefficient calculated results shows that LUE and PRI significantly associated in 297 fine days (R＞0.75). Apparent seasonal and diurnal change of the PRI was observed. Furthermore, the PRI reaches the peak in September and the valley in February. Distinct phenology changes patterns indicate the greenness index showed similar seasonal changes with that of PRI. When the redness index reaches the peak, the PRI reaches the valley. It suggested that leaf redding causes the decline of PRI and LUE.