Nitrogen decreases and precipitation increases ectomycorrhizal extramatrical mycelia production in a longleaf pine forest

Stephanie E. Sims
Joseph J. Hendricks
Robert J. Mitchell
Kevin A. Kuehn, University of Southern Mississippi


The rates and controls of ectomycorrhizal fungal production were assessed in a 22-year-old longleaf pine (Pines palustris Mill.) plantation using a complete factorial design that included two foliar scorching (control and 95% plus needle scorch) and two nitrogen (N) fertilization (control and 5 g N m(-2) year(-1)) treatments during an annual assessment. Ectomycorrhizal fungi production comprised of extramatrical mycelia, Hartig nets and mantles on fine root tips, and sporocarps was estimated to be 49 g m(-2) year(-1) in the control treatment plots. Extramatrical mycelia accounted for approximately 95% of the total mycorrhizal production estimate. Mycorrhizal production rates did not vary significantly among sample periods throughout the annual assessment (p=0.1366). In addition, reduction in foliar leaf area via experimental scorching treatments did not influence mycorrhizal production (p=0.9374), suggesting that stored carbon (C) may decouple the linkage between current photosynthate production and ectomycorrhizal fungi dynamics in this forest type. Nitrogen fertilization had a negative effect, whereas precipitation had a positive effect on mycorrhizal fungi production (p=0.0292; r(2)=0.42). These results support the widely speculated but poorly documented supposition that mycorrhizal fungi are a large and dynamic component of C flow and nutrient cycling dynamics in forest ecosystems.