In Situ Decomposition of Roots and Rhizomes of Two Tidal Marsh Plants

In situ decomposition of roots and rhizomes of the marsh plants, Juncus roemerianus and Spartina cynosuroides was investigated using litter bags. The decomposition rate was greatest in the top 10 cm (20% mass loss/yr) of the marsh soil. There was no apparent decomposition below 20 cm depth. Belowground tissues of S. cynosuroides decomposed faster than those of J. roemerianus during the first 4 mo. The rhizome decomposition rate of 27%/yr (mass loss) was faster than the 16%/yr of the roots of J. reomerianus. There was no difference between the composition rate of mixed root and rhizome materials between experiments initiated in winter and those started in the spring. This indicates a relatively constant decomposition rate during the year in the 0—10 cm soil zone. There was no apparent trend in the hydrogen, carbon, phosphorus, nitrogen, or caloric content changes of the decomposing roots and rhizomes during the study.