Effects of environmental factors and leaf chemistry on leaf litter colonization by fungi in a Mediterranean shrubland

Estimation of litter colonization by fungi, using ergosterol, an indicator of fungal biomass, is a reliable way to describe the process of leaf litter decomposition. This litter colonization by fungi is regulated both by exogenous or environmental factors, and endogenous factors, i.e. litter chemistry. In this work, we have examined the effects of some of these factors on litter fungal colonization in a Mediterranean ecosystem, by determining ergosterol content of Quercus coccifera leaf litter. Environmental factors have been studied through the fertility of the soil, by comparing plots amended with two rates of compost and plots without amendment. Results indicated that (i) compost had a significant effect on soil fertility but did not increase ergosterol content of leaf litter and (ii) soil humidity improved leaf litter colonization by fungi. Endogenous factors have been studied through measurements of total phenolic and ergosterol concentrations of seven shrub species leaf litter. We have shown (i) a negative significant correlation between total phenolic compounds and ergosterol concentrations of leaf litter and (ii) a positive significant correlation between total phenolic compound concentrations in green leaves and in leaf litter. We conclude that, in this Mediterranean shrub ecosystem, leaf litter colonization by fungi is controlled by soil moisture and plant leaf litter quality.