PARENT SESSION
Oral Session # 81: Soil Ecology II: Microorganisms and Mycorrhizae.
Presiding: SJ Hall
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 106.

Preliminary estimates of mycorrhizal biomass by region.

Cross, Alison^*,1, Treseder, Kathleen¹, Randerson, James², ¹ University of Pennsylvania, Philadelphia, PA² California Institute of Technology, Pasadena, CA

ABSTRACT- While laboratory assays address small-scale activities of mycorrhizal fungi, global biomass estimates are needed to scale up to regional and global functioning. In a literature search, mycorrhizal root colonization data were compiled from 80 published field studies in natural ecosystems, including both arbuscular mycorrhizae (AM) (as % root length) and ectomycorrhizae (ECM) (as % root tips). Global means of 3502 data points were calculated for 11 biomes dominated by AM or ECM fungi. Neither AM (40±2) nor ECM (46±10) percent colonization varied significantly by biome. We used a previously published model of hyphal architecture in conjunction with a global database of root length to calculate global mycorrhizal biomass. Moderate investment in AM biomass (6.0×10⁹ Mg, versus 13.7×10⁹ Mg for live fine roots) yields a large return in hyphal length (39.7×10¹⁵ km hyphae versus 0.88×10¹⁵ km roots). ECM biomass estimates agree with those obtained from chloroform fumigation methods. Preliminary estimates of global mycorrhizal biomass should be useful in calculating the proportion of the global C budget and C fluxes attributable to fungi.

Key words: ectomycorrhizae, arbuscular mycorrhizae, hyphal architecture