Compositional aspects of herbaceous litter decomposition in the freshwater marshes of the Florida Everglades

Authors: Pisani, Oliva; GAO, MIN - Florida International University; MAIE, NAGAMITSU - Kitasato University; MIYOSHI, TOSHIKAZU - University Of Akron; CHILDERS, DANIEL - Arizona State University; JAFFE, RUDOLF - Florida International University

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2017
Publication Date: 11/20/2017
Citation: Pisani, O., Gao, M., Maie, N., Miyoshi, T., Childers, D., Jaffe, R. 2017. Compositional aspects of herbaceous litter decomposition in the freshwater marshes of the Florida Everglades. Plant and Soil. 423(1-2):87-98. https://doi.org.10.1007/s11104-017-3495-3.
DOI: https://doi.org/10.1007/s11104-017-3495-3

Interpretive Summary: Litter decomposition in wetlands controls nutrient cycling, soil accumulation and soil formation. The Florida Everglades is a nutrient poor wetland where litter decomposition processes are dependent on nutrient availability and litter quality. However, not much is known about how the chemical composition of tissues from the two dominant plant species affects decomposition and peat formation in the Florida Everglades. The early stages of litter decomposition from above- and below-ground tissues of sawgrass and spikerush were investigated at two freshwater marsh sites in the Florida Everglades. Litter composition at different stages of decay was compared with fresh plant tissues and soil organic matter to assess both the gradual transformation of plant tissues and their incorporation into wetland soils. Overall, spikerush leaves decayed more quickly than sawgrass leaves, and roots and tubers from both grasses were more resistant to decay. Soil organic matter decay was more advanced compared to the decomposing litter, suggesting that the decay of litter and belowground biomass prior to its incorporation into wetland soils requires longer times than the 12-month duration of this study. Results indicate that litter decay and peat formation in Everglades’ freshwater marshes is driven by a combination of tissue quality and site characteristics such as duration of flooding and nutrient availability.

Technical Abstract: Litter decomposition in wetlands is an important component of ecosystem function in these detrital systems. In oligotrophic wetlands, such as the Florida Everglades, litter decomposition processes are dependent on nutrient availability and litter quality. However, not much is known about how the chemical composition of plant tissues affects early decomposition stages of certain macrophyte species. To understand the chemical changes occurring during the early stages of litter decomposition in wetlands, short-term subaqueous decomposition patterns of above- and belowground tissues from Cladium jamaicense and Eleocharis cellulosa were investigated at two freshwater marsh sites in the Florida Everglades. The composition of litter at different stages of decomposition was compared to that of the two end-members, namely fresh plant tissues and soil organic matter (SOM), in an effort to assess both the gradual transformation of this OM and the incorporation of above- vs. belowground biomass to wetland soils. The chemical composition of the litter and of surface soils was assessed using solid-state 13C nuclear magnetic resonance spectroscopy. Decomposition indices (alkyl/O-alkyl ratio, Aromaticity index) of Cladium and Eleocharis leaves varied during incubation likely reflecting physical leaching processes followed by a shift to microbial decomposition. Overall, Eleocharis leaves were more labile compared to Cladium leaves. Relative to aboveground litter, the belowground biomass of both species was more resistant to degradation, and roots were more resistant than rhizomes. Compared to the observed early diagenetic transformations of the plant litter, the SOM is at a more advanced stage of degradation, suggesting that the decomposition of litter and belowground biomass prior to its incorporation into wetland soils requires longer degradation times than those applied in this study. Litter decomposition in Everglades’ freshwater marshes is driven by a combination of tissue quality and site characteristics such as hydroperiod and nutrient availability, ultimately leading to the accumulation of peat.