Compost effect on bacterial and fungal colonization of kermes oak leaf litter in a terrestrial Mediterranean ecosystem

Abstract Mediterranean soils are generally low in organic matter and have a low water holding capacity. Moreover, recurrent fires are common in Mediterranean regions and increase the deterioration of these soils. Soil properties and ecosystem resilience after fire could be improved by amendment with compost, which is a source of organic matter and nutrients. A way to determine ecosystem integrity is to study leaf litter breakdown, which is a vital process in the functioning of terrestrial ecosystems and involves fungi and bacteria. In this study, we determined fungal and bacterial biomass associated with decomposing oak leaves ( Quercus coccifera L.) in a burnt shrub amended ecosystem during 1.5 years. Three treatments were studied: control, 50 t ha −1 and 100 t ha −1 of co-composted sewage sludge and green wastes. Bacterial biomass was not affected, although moisture, N and P concentrations in litter were increased by the amendment. However, fungal biomass was depressed on plots amended with 100 t ha −1 , and negatively correlated to exchangeable P. For all treatments, both types of microorganisms followed marked seasonal dynamics, with peaks of biomass during the wet periods of the year.