Here is a concise summary of the article on seasonal-deciduous phenology:

## Seasonal-Deciduous Phenology

The seasonal-deciduous phenology algorithm is based on the Biome-BGC v. 4.1.2 offline model and the parameterizations from White et al. (1997) for temperate deciduous broadleaf forests.

Key points:

- Leaf onset is triggered when a degree-day summation exceeds a critical value.
- Leaf litterfall is initiated when daylength is shorter than a critical value.
- This algorithm is only valid for latitudes outside the tropical zone (|latitude| > 19.5°).
- It uses the winter and summer solstices as coordination signals to identify the onset and offset periods.
- The algorithm calculates daylength using the latitude and solar declination.
- It allows a maximum of one onset period and one offset period per year.

In summary, the seasonal-deciduous phenology algorithm models the leaf onset and litterfall processes for temperate deciduous forests, using environmental cues like degree-days and daylength.