Moss growth and decomposition are important processes leading to carbon sequestration in peatlands. The aim of this research was to use a correction for capitulum bulk density to improve the accuracy of productivity measurements made using data on moss growth in length collected 40 years ago from sites in the USA and Canada. Specimens of Sphagnum fuscum collected at the study sites were sectioned into two segments: the capitulum (0.4 to 0.6 cm in length) and a growth increment (0.5 – 1.5 cm) below the capitulum. The relative proportion of mass and volume in each segment were used to partition the bulk density of the live moss layer from cores taken at these sites. Correction for the greater capitulum density provides a more accurate estimate of NPP for comparison to modern values to investigate whether NPP has shifted over time. Results of this research also indicated a difference in moss phenotype between regions. The growth form of specimens from maritime sites is more dense than that for mid-continental sites, thus, the influence of the capitulum correction on productivity estimates varies by region. Correcting for capitulum density decreased NPP estimates by 4% at maritime sites, but by 80% for mid-continental sites. This research has provided baseline estimates of moss growth and productivity from the mid-1980s for comparison to modern and future values, and has documented differences in the growth form of Sphagnum fuscum in maritime vs. midcontinental sites.
