Soils will be amended with selected substrates of known energy and elemental composition (Table 1), which is the basis for the turnover balancing, in selected concentrations. The substrates represent detritus (litter, necromass) and biopolymers (model substrates) of different origin and degradability. Substrates were further selected to represent compounds that require exoenzymatic transformation. Two or more of these substrates, should be used in individual projects. The overall idea of using model substrates is to compare the effect of molecular complexity and element composition vs. energetic properties on turnover of matter and energy. Isotope labelling (13C, 14C) of the proposed substrates is foreseen in order to ensure mass balancing and following metabolic pathways and spatial distribution in soil.

Table 1: Substrates and selected mixtures thereof for metabolic turnover testing.

DetritusCombustion enthalpiesaModel substrates Combustion enthalpiesa
Plant litter (Maize)-15.3 KJ g-1Cellulose
-16.3 KJ g-1
Fungal necromass
-21.5 kJ g-1Starch
-14.7 KJ g-1
Bacterial necromass
-19.8 kJ g-1 Chitin
-18.8 KJ g-1
Peptidoglycane (Murein)
a own data, and for fungal and bacterial necromass derived from Popovic (2019)


Popovic M., 2019. Thermodynamic properties of microorganisms: determination and analysis of enthalpy, entropy, and Gibbs free energy of biomass, cells and colonies of 32 microorganism species. Heliyon 5, e01950.