3. Element Cycling Model
Cycling of elements was assessed using a model developed by Nihlgård (1972) (Figure 3). The analysis was limited
to the above-ground parts, as root production and the release of nutrients from the root litter and leaching
of elements from the soil were not estimated. However, root biomass was measured. In determining the dynamics
of organic matter in a forest, the above-ground yearly net primary production (P) the yearly litterfall (L) and
the decomposition rate (k) are the most important factors. Understanding element cycling requires information
on the amounts of elements in the primary plant production, the biomass increase (ΔB), yearly litterfall (L), surface
litter (SL) and the canopy-leached fraction (CL = the difference between total through fall and incoming
rainfall).