.

Yang, X., et al. (2016). "Seasonal variability of multiple leaf traits captured by leaf spectroscopy at two temperate deciduous forests." Remote Sensing of Environment 179: 1-12. Collection covers all the seasons. Summer is expected to have less variations on the plant's phonology. However, when the model was trained by a season data and then tested to the other seasons, the summer model showed the least RMSE. It means summer was the best season to collect leaves with divers status. It's harsh light must affect various level of stress to sunltis and shaded leaves.

Dechant, B., et al. (2017). "Estimation of photosynthesis traits from leaf reflectance spectra: Correlation to nitrogen content as the dominant mechanism." Remote Sensing of Environment 196: 279-292. Photosynthetic traits has its mechanism by leaf internal components. Comparing the spectroscopic absorption of causing components and their traits, they can be detected and correlation. In the case of Vcmax, N dominantly controls it.