Global model for nitrogen release and decay of leaf and root material

A simple model was developed for simulating mass loss and nitrogen release from decomposing leaf and root biomass.  The model was developed using common root and leaf litter decomposition data from ten species decomposing at 27 sites around the world (LIDET experiment).  The variables that control mass loss rate are initial litter lignin to nitrogen ratio, the cellulose to lignin ratio, and the climatic decomposition index (CDI-r²=0.68).  CDI is calculated using monthly minimum and maximum air temperature and precipitation data.  Release of nitrogen from decomposing leaf litter is predicted as a function of initial leaf nitrogen content and the litter mass remaining (r²=0.69).  Nitrogen release from decomposing roots is a simple linear function of root mass remaining with net nitrogen release starting as soon as decomposition starts.  The major discrepancy in the model is that it underestimates mass loss from dry grasslands exposed to high levels of UV radiation.  Results from the dry grasslands also suggest that nitrogen immobilization does not occur for decomposing leaf litter exposed to UV radiation.