Summary:

## Background Litterfall

The article discusses two types of phenology algorithms used in models: evergreen and stress-deciduous. Both algorithms can specify a "background litterfall" flux, which represents a slow, continuous litterfall process not associated with specific offset periods.

For evergreen types, the background litterfall is the only litterfall flux. For stress-deciduous types, either the offset period litterfall or the background litterfall mechanism may be active, but not both at once.

The article provides the equations to calculate the carbon and nitrogen fluxes associated with the background litterfall:

1. Leaf and fine root carbon litterfall fluxes:
   - CF_leaf,litter = r_bglf * CS_leaf
   - CF_froot,litter = r_bglf * CS_froot

2. Leaf and fine root nitrogen litterfall fluxes:
   - NF_leaf,litter = CF_leaf,litter / CN_leaf_litter
   - NF_froot,litter = CF_froot,litter / CN_froot

3. Leaf nitrogen retranslocation flux:
   - NF_leaf,retrans = (CF_leaf,litter / CN_leaf) - NF_leaf,litter

The key parameters in these equations are the background litterfall rate (r_bglf) and the carbon-to-nitrogen ratios of the leaf and fine root litter.