An improved method for measuring the production, mortality and decomposition of extramatrical mycelia of ectomycorrhizal fungi in forests

The production and mortality of extramatrical mycelia (EMM) of ectomycorrhizal fungi are poorly quantified despite their importance in soil carbon cycling in forests. Ingrowth bag/core methods are the most widely used but can not accurately assess temporal changes in EMM production and mortality, resulting in great uncertainty in annual estimates. A modified method using two mathematical models (Biomarker and Algebraic models) is proposed to quantify EMM production, mortality and decomposition over differing time periods by integrating EMM decomposition dynamics with ingrowth core/bag data. In the Biomarker model, EMM biomass and EMM total mass (sum of necromass and biomass) are assumed to be known by using chemical biomarkers as proxies. In the Algebraic model, only the total mass is known and the biomass is calculated using an algebraic method. Model application in a loblolly pine plantation showed that mean monthly EMM production, mortality and decomposition estimates among three time periods ranged from 10.1 to 16.0 kg ha−1, 6.6-15.0 kg ha−1, and 1.4-6.1 kg ha−1, respectively, when using the Biomarker model, while these estimates ranged from 24.8 to 35.7 kg ha−1, 15.5-22.8 kg ha−1, and 5.7-9.8 kg ha−1, respectively, when using the Algebraic model, demonstrating the importance of assessing temporal changes. Model validation indicated that EMM estimates were more reliable for short-term compared to long-term incubation (184 vs. 322 days). Our method could improve EMM estimation by accurately assessing temporal changes in EMM production, mortality and decomposition in forests.