Summary:

Model Inputs and Parameter Estimations in LUNA

The LUNA model, used in CLM5, includes four unitless parameters that are estimated by fitting the model to a global dataset of over 800 observations:

1. Jmaxb0 - Baseline proportion of nitrogen allocated for electron transport
2. Jmaxb1 - Response of electron transport rate to light availability 
3. tc,j0 - Baseline ratio of Rubisco-limited rate to light-limited rate
4. H - Response of electron transport rate to relative humidity

These parameter values were estimated to be 0.0311, 0.17, 0.8054, and 6.0999, respectively.

The model inputs include leaf nitrogen content, leaf mass per unit area, and environmental conditions (temperature, CO2, radiation, humidity, daylength). 

In CLM5, the LUNA model is only used for C3 natural vegetation, as the photosynthetic capacity for crops and C4 plants is estimated differently, based on leaf nitrogen and an adjusting factor for daylength. The model simulates both sunlit and shaded leaves, but does not differentiate their photosynthetic capacities.