Nature and Nurture in the Continuum of Carbon, Nitrogen and Phosphorus from Litter to Soil Organic Matter in Canadian Forests

We examine the changes in carbon (C), nitrogen (N) and phosphorus (P) as 10 foliar litters decompose at 21 sites across Canada over 12 years and evaluate the influence of litter quality (nature) and forest floor (nurture) on these changes by applying a stoichiometric approach. Based on all litters and sites, net N loss from the litters occurs at C:N quotients of between 33 and 68, positively correlated with the quotient in the original litter. Net P loss likely occurs at C:P quotients between 800 and 1200. The influence of site on loss of N and P in the litters, relative to C, was evaluated by comparing N and P at 50% original C remaining and showed a weak negative relationship: that is, the higher the soil C:N or C:P quotient in the forest floor, the smaller amount of initial N or P remaining at 50% C remaining. C:N quotients in the original litters ranged from 39 to 83 and show a convergence to an average quotient of 25 when the litters reach 20% original C remaining. When separated into individual litters, those with high initial quotients (cedar and tamarack) showed the most rapid decline in C:N. The differentiation in C:N quotient among the 21 sites is weaker. Initial litter C:P quotients ranged from 369 to 2122 and also showed a convergence, to an average of 427 at 20% original C remaining and there was also a weak differentiation among the sites. Initial N:P quotients ranged from 5 to 26 and converged to an average of 17 at 20% original C remaining. There is a similarity of transformations of C, N and P leading to an average ratio of 427:17:1 when litters have 20% C remaining.