In smooth-cordgrass (Spartina alterniflora) saltmarshes, fungi are nitrogen-limited during growth within standing-decaying leaf blades. It may be that this is not true in at least some freshwater-grass systems. Note in the figure below that the percentage of nitrogen that is present in living-fungal mass in cordgrass and sedge (Carex walteriana) is considerably lower in older decaying sedge blades than it is in cordgrass blades. Maximum mean living-fungal contents of standing-decaying sedge blades has been found to be substantially lower than that of smooth-cordgrass blades (about 200 ug g^-1 organic mass of decay system for sedge; for smooth cordgrass, about 500-600 ug g^-1). Some of the nitrogen of older decayed sedge blades is present in dead-fungal mass (empty hyphal tubes), as indicated by high contents of glucosamine and mannose. See: Newell SY, MA Moran, R Wicks, RE Hodson. 1995. Productivities of microbial decomposers during early stages of decomposition of leaves of a freshwater sedge. Freshwater Biology 34:135-148; Newell SY, VD Wall. 1998. Response of saltmarsh fungi to the presence of mercury and polychlorinated biphenyls at a Superfund site. Mycologia 90:777-784.

Legend: Calculated capture percentages of decaying-system nitrogen by fungi for decaying leaf blades of smooth cordgrass (Spartina) and a sedge (Carex). Cordgrass leaves were tagged at the time of leaf senescence (yellow/green striped), and sampled at various times thereafter. Extra nitrogen was added to some plots of shoots, as fertilizer to the roots (Newell, Chapter 7 of Advances in Microbial Ecology 13, 1993). Sedge leaves were sampled at two time points, over a spectrum of progression of leaf decay (C = 1/3 green, 2/3 yellow-brown; D = mostly brown; E = entirely brown on living stems; F = entirely brown, on dead stems; G = broken on peat surface). Nitrogen capture is that portion of decaying-system nitrogen estimated to be in living-fungal mass, and was calculated based on ergosterol- fungal mass, assuming 4% nitrogen of living-fungal mass.