Ectomycorrhizal fungal mycelia turnover in a longleaf pine forest

Abstract

Elucidation of the patterns and controls of carbon (C) flow and nitrogen (N) cycling in forests has been hindered by a poor understanding of ectomycorrhizal fungal mycelia (EFM) dynamics. In this study, EFM standing biomass (based on soil ergosterol concentrations), production (based on ergosterol accrual in ingrowth cores), and turnover rate (the quotient of annual production and average standing biomass estimates) were assessed in a 25-yr-old longleaf pine (Pinus palustris) plantation where C flow was manipulated by foliar scorching and N fertilization for 5 yr before study initiation. In the controls, EFM standing biomass was 30 ± 7 g m-2, production was 279 ± 63 g m-2 yr-1, and turnover rate was 10 ± 3 times yr-1. The scorched × fertilized treatment had significantly higher EFM standing biomass (38 ± 8 g m-2), significantly lower production (205 ± 28 g m-2 yr-1), and a trend of decreased turnover rate (6 ± 1 times yr-1). The EFM turnover estimates, which are among the first reported for natural systems, indicate that EFM are a dynamic component of ecosystems, and that conventional assessments have probably underestimated the role of EFM in C flow and nutrient cycling.