Patterns of Carbon, Nitrogen and Phosphorus Dynamics in Decomposing Foliar Litter in Canadian Forests T. R. Moore, 1 * J. A. Trofymow, 2 C. E. Prescott, 3 J. Fyles, 4 B. D. Titus 2 , and CIDET Working Group 1 Department of Geography and Centre for Climate and Global Change Research, McGill University, Montre ´ al, Quebec, Canada; 2 Pacific Forestry Centre, Canadian Forest Service, Victoria, British Columbia, Canada; 3 Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada; 4 Department of Natural Resource Science, McGill University, Montre ´ al, Quebec, Canada ABSTRACT We examined the patterns of nitrogen (N) and phosphorus (P) gain, retention or loss in ten foliar tissues in a litterbag experiment over 6 years at 18 upland forest sites in Canada, ranging from sub- arctic to cool temperate. N was usually retained in the decomposing litter until about 50% of the original C remained. The peak N content in the litter was observed at between 72 and 99% of the original C remaining, with C:N mass quotients between 37 and 71 (mean 55). The rate of N re- lease from the litters was not related to the original N concentration, which may be associated with the generally narrow range (0.59–1.28% N) in the litters. P was immediately lost from all litters, ex- cept beech leaves, with critical litter C:P mass quotients for P release being in the range 700–900. The rate of P loss was inversely correlated with the original litter P concentration, which ranged from 0.02 to 0.13%. The soil underlying the litterbags influenced the pattern of N and P dynamics in the litters; there were weak correlations between the N and P remaining at 60% C remaining in the litters and the C:N and C:P quotients of the surface layer of the soil. There was a trend for higher N and P retention in the litter at sites with lower soil C:N and N:P quotients, respectively. Although there was a large variation in C:N, C:P and N:P quotients in the original litters (29–83, 369–2122 and 5–26, respectively), and some variation in the retention or loss of N and P in the early stages of decompo- sition, litters converged on C:N, C:P and N:P quo- tients of 30, 450 and 16, when the C remaining fell below 30%. These quotients are similar to that found in the surface organic matter of these eco- systems. Key words: litter; forests; decomposition; carbon; nitrogen; phosphorus; lignin. INTRODUCTION The continual, long-term input of fresh litter to the surface of the forest floor through litterfall and its ensuing progressive decomposition as it is broken down physically and chemically into smaller units leads to the formation of more recalcitrant soil or- ganic material (humus) that accumulates and forms the different horizons in the forest floor. As fresh litter decays along this continuum that leads to the formation of soil organic matter (Melillo and Received 5 March 2004; accepted 5 November 2004; published online 30 January 2006 *Corresponding author; e-mail: tim.moore@mcgill.ca Ecosystems (2006) 9: 46–62 DOI: 10.1007/s10021-004-0026-x 46