Fungal biomass and productivity in standing-decaying leaves of black needlerush (Juncus roemerianus)

Abstract

Ascomycetous fungal decomposers generate the major part of the microbial biomass on and in standing naturally decaying shoots for one (smooth cordgrass, Spartina alterniflora ) of the two major ramet-forming marsh plants of the south-eastern USA. Evidence from frequency of occurrence of sexual structures (ascomata) in the second major ramet-forming marsh plant (black needlerush, Juncus roemerianus ) suggests that fungi are major secondary producers in the needlerush decomposition system also. To test this, samples of needlerush blades at three stages of decay were collected seasonally for three years. Average living-fungal standing crop (as ergosterol) of needlerush blades (254 µ g g ^{– 1} organic mass of decay system) was ~65%of a comparable average for smooth cordgrass, but fungal mass was equally active between the two species (near 30 pmol acetate incorporated into ergosterol µ g ^{– 1} ergosterol h ^–1 ). Although maximum living-fungal crop for needlerush was found in winter, and in winter and spring for smooth cordgrass, in many other respects, patterns of change in needlerush fungal variables were quite different from those for smooth cordgrass. For example, living-fungal standing crop rose 1.5-fold with decay stage for needlerush, but was constant for cordgrass, perhaps because of lesser mycophagous activity and lesser competition from bacterioplankton associated with tidal flooding in the high-marsh, needlerush zones.