Cellulose Mass Loss In Ombrotrophic Bogs Of Northeastern North America
Profiles of cellulose mass loss were measured for six Sphagnum bogs in eastern North America as an index of decomposition rates. After 2 years, mass loss rates in the upper 5 cm of the profiles averaged 49% in hummocks, 52% in hollows where the water table was more than 5 cm below the surface, and 21% in hollows where the water table was within 5 cm of the surface. Hummock profiles were of three types: (i) mass loss highest at the surface, gradually decreasing to very low rates below the water table; (ii) mass loss highest at the surface, decreasing for 10 – 20 cm, with a second peak in the region of the water table; and (iii) mass loss low at the surface with a subsurface peak. Mass loss rates for all profiles reached minimum values below the water table, averaging 3% in hummocks and 5% in hollows after 2 years. Cellulose mass loss was quite variable in upper portions of the profiles; within-site variance was almost as great as between-site variance, reflecting similarity among these bogs and heterogeneity within each site. Analysis of variance of mass loss at the hummock surface showed no significant effect of site; however, contrasts among means showed that mass loss rates at the surface of hummocks of the northern (Newfoundland) bogs were significantly lower (p < 0.05) than those from the sites farthest south (in Nova Scotia and Maine). Key words: cellulose mass loss, Sphagnum bog, decomposition.