Summary:

## Tissue Stoichiometry

The article discusses the flexible stoichiometry of vegetation tissues in the Community Land Model (CLM5). Key points:

1. Each plant tissue has a target carbon-to-nitrogen (C:N) ratio, which varies by plant functional type (PFT).

2. Nitrogen is allocated at each timestep to allow the plant to match its target stoichiometry. 

3. Insufficient nitrogen availability can lead to nitrogen downregulation of productivity, where the C:N ratio of leaves increases, reducing the availability of nitrogen for photosynthesis and lowering the Vcmax25 and Jmax25 parameters.

4. Table 2.16.1 provides the target leaf C:N ratios for different PFTs, ranging from 20.00 for crops like wheat and soybean to 58.00 for needleleaf evergreen temperate and boreal trees.

The article references further details on the flexible tissue stoichiometry in Chapter 2.19 of the CLM5 technical note.