Fungal contributions to carbon flow and nutrient cycling during decomposition of standing Typha domingensis leaves in a subtropical freshwater marsh

Abstract

Summary Despite the well‐known occurrence of ‘standing‐dead’ emergent plant litter in freshwater marshes, the role of fungi in its decomposition is poorly known. Here, we quantified the growth and biomass dynamics of fungi associated with standing‐dead Typha domingensis leaves, estimated the contribution of fungi to carbon flow during decomposition and assessed their contribution to nutrient (nitrogen and phosphorus) cycling. In a subtropical freshwater marsh, standing leaves of T. domingensis were sampled in August while living (green) and then monthly during leaf senescence and standing‐dead decomposition for 1 year. Leaf samples were analysed for mass loss, fungal biomass (ergosterol), rates of fungal production (14C‐acetate incorporation) and microbial respiration (CO2 evolution), and for litter chitin (glucosamine), carbon, N and P concentrations. Losses in T. domingensis leaf carbon (37%) occurred during senescence and standing decomposition. During this time, increases in ergosterol and chitin concentrations were observed in the standing litter, indicating the rapid colonisation of decaying Typha leaves by fungi. Estimated fungal biomass (from ergosterol) reached a maximum of 37 mg C g−1 detrital C. Over the entire study period, estimated cumulative fungal production in standing Typha litter was 39 mg C g−1 initial detrital C, indicating that 11% of leaf C was converted to fungal C. The corresponding estimate of cumulative microbial respiration was 136 mg C g−1 initial detrital C, indicating that 37% of Typha leaf litter C was mineralised by microorganisms (bacteria and fungi) during decomposition. Fungi also immobilised up to c.27% and c.55% of the total detrital N and P, respectively. Fungi play an important role in the cycling of C and nutrients in freshwater marshes, and this should be integrated into current models that describe major biogeochemical pathways.

Long‐term responses of leaf litter decomposition to temperature, litter quality and litter mixing in plateau wetlands

“…Litter quality, defined by C and nitrogen (N) concentrations (Yavitt & Fahey, 1986), C:N ratio (Edmonds, 1980), lignin concentrations (Gholz, Fisher & Prichett, 1985) and lignin:N ratio (Waring & Schlesinger, 1985;Aerts, 1997), also has important implications for the rates of mass loss. However, there is still no universally accepted litter-quality variable for aquatic ecosystems (Kuehn et al, 2011;Su, Kuehn & Phipps, 2015) because the process of litter mass loss depends on complex interactions between soil properties, water properties, climatic factors and litter types (Meentemeyer, 1978;Fierer et al, 2005;Xu et al, 2010;Handa et al, 2014).…”

Lentic and lotic habitats as templets for fungal communities: traits, adaptations, and their significance to litter decomposition within freshwater ecosystems

“…This discussion will specifically focus on fungal dynamics occurring on plant litter in forested headwater streams and emergent freshwater marshes, since published data concerning their role in these systems is considerably more abundant in comparison to other freshwater habitats, such as ponds and lake pelagic habitats. Although much less studied, recent research and reviews by Wurzbacher and colleagues (Wurzbacher et al, 2010;2014) provide an excellent synthesis of our current knowledge of fungi and fungal-like organisms in lake pelagic zones.…”

“…While aquatic hyphomycetes do not appear to be overly sensitive to low pH (Krauss et al, 2011), the presence of acidic conditions in combination with other dissolved constituents, such as metal ions (e.g., Al, Zn), appear to have combined effects that inhibit the decay activities of fungi in streams. Anthropogenic acidification of headwater streams is well documented (e.g., Mullholland et al, 1987) and known to severely impact aquatic biota (e.g., shredders, fungi) and leaf litter processing through a reduction in pH, increases in stream water metal concentrations, and decrease in base cation availability (Niyogi et al, 2001;Dangles et al, 2004;Cornut et al, 2012;Clivot et al, 2013;2014). Increasing concentrations of Al are known to negatively alter aquatic hyphomycete activities on decaying leaf litter (Dangles et al, 2004;Clivot et al, 2014;Pacioglu et al, 2015).…”

“…Increasing concentrations of Al are known to negatively alter aquatic hyphomycete activities on decaying leaf litter (Dangles et al, 2004;Clivot et al, 2014;Pacioglu et al, 2015). Furthermore, recent studies have provided evidence that elevated Al concentrations may also alter the phosphorus cycle in acidified streams, which could induce P limitation of microbial (fungal) decomposers and affect their litter decay activities (Clivot et al, 2013;2014).…”

Distinct microbial communities alter litter decomposition rates in a fertilized coastal plain wetland

“…Specifically, we question how changes in internal C:N:P plant litter stoichiometry and external C:N:P additions affect soil microbiomes and carbon cycling. The rate of heterotrophic decomposition is limited by N and P availability (Su et al, 2015;Van Der Heijden et al, 2008); therefore, plant and soil C:N:P composition affects rates of biogeochemical processes such as decomposition. Changes in the nutrient stoichiometry of both plants and surrounding soils are expected to affect microbial community composition and function, leading to changes in elemental cycling.…”