The decomposition of standing and fallen litter of Typha glauca and Scirpus fluviatilis

Abstract

Changes in dry weight and N, P, K, Na, Ca, Mg, Al, and Fe content were studied over a 525-day period in decomposing Typha glauca and Scirpus fluviatilis shoots. Submerged Typha litter decomposed more rapidly than submerged Scirpus litter, losing 50% of its original dry weight in 325 days while Scirpus litter still retained 62% of its original dry weight after 525 days. Major pathways of mineral flow from standing litter were (1) leaching during the first few weeks after shoot death and (2) fragmentation and litter fall during the rest of the study. Mineral losses from fallen litter were mainly due to leaching or to excretion by microbial populations associated with the litter. Microbial uptake (N, P) and adsorption (Ca, Al, Fe) were important processes in the fallen litter. After 525 days, as a result of the combined action of mineral uptake and release, Typha litter had net releases of N (71 kg/ha), P(10 kg/ha), K (123 kg/ha), Na (94 kg/ha), Ca (41 kg/ha), and Mg (25 kg/ha) and net accumulations of Al (21 kg/ha) and Fe (20 kg/ha). Scirpus litter, during this same period, had net releases of N (10 kg/ha), K (9 kg/ha), and Na (11 kg/ha). All other minerals increased in decomposing Scirpus litter: P (8 kg/ha), Ca (55 kg/ha), Mg (5 kg/ha), Al (13 kg/ha), and Fe (11 kg/ha). At the end of the study, the calculated combined dry weight of undecomposed standing and fallen litter had decreased by only 20% in Typha litter and 14% in Scirpus litter. Most of the biomass and minerals were in the fallen litter.