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## Nitrogen Retranslocation

The article describes the process of nitrogen retranslocation, where nitrogen is removed from falling litter using an iterative algorithm. There are two pathways for this:

1. "Free" uptake, which removes the labile nitrogen pool.
2. "Paid-for" uptake, which uses carbon to extract nitrogen from increasingly more recalcitrant pools.

The amount of nitrogen in the falling leaf litter pool (Nfallingleaf) is calculated as the total leaf nitrogen multiplied by the fraction of the leaf pool that is passed to litter in that timestep.

The carbon available at the beginning of the iterative retranslocation calculation (Cavail,retrans,0) is equal to the Cavail input into the FUN model.

The summary captures the main points of the text, including the two pathways for nitrogen retranslocation, the calculation of the nitrogen in the falling leaf litter pool, and the starting point for the carbon available in the retranslocation calculation.