Annual production of leaf-decaying fungi in 2 streams

Abstract

We determined fungal biomass and production associated with decaying leaves over an annual cycle in 2 streams that differed in water chemistry to obtain an indication of the variability of these parameters. Basin Creek is a softwater stream with a pH of 6.3 and relatively low concentrations of inorganic N (94 μg N/L) and P (3 μg P/L), whereas Hendrick Mill Branch is a hardwater stream with a pH of 8.2 and somewhat higher concentrations of inorganic N (139 μg N/L) and P (6 μg P/L). Both streams received similar annual leaf litter fall (379–422 g/m2), but the mean annual standing crop of leaf detritus was higher in Basin Creek (41.6 g/m2) than in Hendrick Mill Branch (20.0 g/m2). Concentrations of fungal spores in the water of both streams peaked in September and December. Leaves sampled in Hendrick Mill Branch generally contained higher concentrations of fungal biomass and fungi had higher rates of production/g leaf than in Basin Creek. This observation agreed with results from litter bags of red maple (Acer rubrum L.) leaves placed in the 2 streams. However, fungal biomass and production associated with leaves sampled, expressed on an areal basis, were higher in Basin Creek because of the higher standing crop of leaves in that stream than in Hendrick Mill Branch. Mean annual fungal biomass was 2.4 g/m2 in Basin Creek and 1.4 g/m2 in Hendrick Mill Branch. Annual fungal production was 31.7 g/m2 in Basin Creek and 26.6 g/m2 in Hendrick Mill Branch, with maximum production/m2 in both streams occurring in the autumn. Turnover time of fungi based on annual production to biomass ratios was shorter in Hendrick Mill Branch (18 d) than in Basin Creek (27 d). Differences in the streams (water chemistry, temperature) favored greater fungal activity in Hendrick Mill Branch, but the higher standing crop of leaf litter in Basin Creek led to slightly higher annual fungal production/m2 in this stream.