Parameter assumptions for analytical simplifications.

Table notes and references: The subscript i refers to nitrogen (N) and phosphorus (P).
1In non-agricultural systems, internal recycling of both N and P (between plants and soils) typically exceeds total inputs and losses (to or from the atmosphere or waterways) many fold, both globally [44], [101] and at individual sites [102]. Consequently, litter decomposition is much greater than litter loss (δiLi >> hiLi), plant uptake is much greater than losses of plant-available nutrients (BνiAi >> kiAi), SOM mineralization is much greater than SOM loss (miDi >> φiDi), and SOM mineralization is much greater than the balance of abiotic inputs and plant-available losses (miDi >> |Ii – kiAi,i|). Exceptions to this pattern will occur where losses are very high (e.g., when ground fires or heavy erosion frequently remove substantial amounts of litter, it is unlikely that δi >> hi), where plant or SOM pools are very small (e.g., at the beginning of primary succession, it is unlikely that miDi >> |Ii – kiAi,i|; see text and analysis), or in heavily polluted regions.
2See ref [51].
3Plants typically have an order of magnitude higher N content than P content [44], [103].
4P is more readily cleaved from organic matter than N (see text).
5For decomposition, we have defined the parameters such that ε controls the relative mineralization of N versus P and δ is the overall litter decomposition rate.
6N and P loss rates via leaching and erosion should be similar because they come from the same organic material. In ecosystems where fire is important, organic N loss rates may be relatively higher than P.