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## Nitrogen Allocation

The article outlines the process of nitrogen allocation in the CLM5 land model. The total nitrogen flux to be allocated, referred to as N_supply, is determined by the FUN model. The model then allocates this nitrogen to different plant tissues based on their nitrogen demand.

The nitrogen demand for each tissue is calculated based on the carbon allocated to that tissue and the tissue's carbon-to-nitrogen ratio. The demand is split between current growth and storage.

After calculating the demand for each tissue, the total plant nitrogen demand is summed. The nitrogen allocated to each tissue is then proportional to its fractional demand, with the total allocation equal to the total nitrogen uptake calculated in the FUN model.

The key equations governing this nitrogen allocation process are provided, including the formulas for calculating the nitrogen demand of each plant tissue.