Comparison of decomposition of belowground and aboveground plant litters in peatlands of boreal Alberta, Canada

Abstract

Studies examining the decomposition rates of belowground plant tissues in peatlands are scarce despite the significant contribution these tissues make to total plant production. Therefore, we measured mass losses of Carex aquatilis Wahlenb. leaves and rhizomes and Salix planifolia Pursh leaves and roots in a rich, sedge-dominated fen and Sphagnum fuscum (Schimp.) Klinggr. plants in a forested bog using the litter bag technique over a 2-year period in southern boreal Alberta. After 2 years, mass losses of C. aquatilis rhizomes (75%) were significantly higher than those of C. aquatilis leaves and Salix planifolia leaves, which were similar to each other (54 and 48%, respectively). Sphagnum fuscum and Salix planifolia root mass losses also were similar to each other (21 and 29%, respectively), but they were significantly lower than those of the other three litter types. Different tissue nutrient concentrations as well as alkalinity- and phosphorus-related surface water chemistry variables correlated significantly with mass losses of different litter types; however, they alone did not explain all of the mass loss trends. The majority of sedge peat and carbon in the fen originates from C. aquatilis leaves (188 and 86 g·m-2, respectively), with the remainder originating from C. aquatilis rhizomes (102 and 47 g·m-2, respectively) after the first 2 years of decomposition. Conversely, the majority of Salix planifolia peat and carbon originates from its roots (33 and 16 g·m-2, respectively) and the remainder from its leaves (24 and 11 g·m-2, respectively) over the same period. After the first 2 years of decomposition, 150 g·m-2of peat and 71 g·m-2of carbon remained from the decomposing Sphagnum fuscum in the bog.Key words: bog, fen, mass losses, Carex aquatilis, Salix planifolia, Sphagnum fuscum.