Relationship of soil ergosterol concentration and fungal biomass

Abstract

We studied the relationship between amounts of fungi and ergosterol in soil to further evaluate the use of ergosterol as an indicator of soil fungal biomass. Soils from seven sites in central Iowa were analyzed for soil ergosterol content, total fungal hyphal length (living and non-living, using calcofluor as stain), and living fungal hyphal length (using fluorescein diacetate as stain) to: 1) determine how soil ergosterol concentration correlates with total fungal hyphal length and living fungal hyphal length; and 2) determine an approximate value for ergosterol concentration in living fungal biomass present in soil. Correlation significance tests and analysis of variance indicated highly significant positive correlation between soil ergosterol content and both measures of hyphal length, but regression analysis demonstrated only a moderate degree of linear correlation between these variables (coefficients of linear correlation, r = 0.638 to 0.874). Calculated values for ergosterol concentration in living fungal biomass present in the soils examined ranged from 5 to 31 mg ergosterol g −1 living fungal biomass. Data indicate that the wide range in specific ergosterol content of living fungal biomass in soils is related to the total amount of fungal hyphae (living and non-living) in a soil. We propose a method to estimate living fungal biomass from soil ergosterol content which compensates for the variability in fungal ergosterol concentrations by accounting for this relationship. A preliminary evaluation of this approach using independent data from the literature provides support for this method, in that a high correlation ( r 2 = 0.999) between predicted and measured living fungal biomass was observed.