Soils in transition: dynamics and functioning of fungi

Abstract

The focus of this thesis is on the dynamics and functions of saprotrophic soil fungi during conversion from an arable land into a natural ecosystem (heathland) and to asses their effects on soil ecosystem processes. Chapter 2 describes that fungal biomass in abandoned arable land is not increasing for at least 3 decades to the level of a natural ecosystem. Opportunistic fungi showed to be responsible for the decomposition processes, and these fungi are stimulated by large sizes of nitrogen-rich substrate buried in soil (Chapter 4& 5). Chapter 3 presents that no large amounts of phosphorus seem to leach into deeper soil layers after land abandonment. In Chapter 6 it is shown that the establishment of Calluna vulgaris in a recently abandoned arable land can be due to a fast colonization of Calluna immediately after abandonment and the reduction of microbial nitrogen mineralization, in combination with the colonization of Calluna roots by ericoid mycorrhizal fungi. In Chapter 7 it is concluded that an increase in fungal biomass in ex-arable soils can be of interest for soil ecosystem restoration and this may be triggered by the introduction of large particles of recalcitrant organic matter together with sufficient fungal biomass.