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2.18.4. Nitrogen Retranslocation¶
The retranslocation uses an iterative algorithm to remove Nitrogen from each piece of falling litter. There are two pathways for this, ‘free’ uptake which removes the labile N pool, and ‘paid-for’ uptake which uses C to extract N from increasingly more recalcitrant pools.
At each timestep, the pool of carbon in falling leaves (\(C_{fallingleaf}\), g m-2) is generated from the quantity of litterfall on that day (see Phenology chapter for details). The amount of N in the litter pool (\(N_{fallingleaf}\), g m-2) is calculated as the total leaf N multiplied by the fraction of the leaf pool passed to litter that timestep.
\[N_{fallingleaf} = N_{leaf}.C_{fallingleaf}/C_{leaf}\]
The carbon available at the beginning of the iterative retranslocation calculation is equal to the \(C_{avail}\) input into FUN.
\[C_{avail,retrans,0} = C_{avail}\]