The influences of lichens on soil physico-chemical properties, enzymes and microbes are species specific: Insights from South Mediterranean arid ecosystem

Despite recent advances in the ecology of lichens from a community perspective, much remains unknown at the species level particularly in arid regions. In this context, the current study investigated the differential effects of five lichen species dominating South Mediterranean arid ecosystem (Diploschistes diacapsis (Ach.) Lumbsch, Squamarina cartilaginea (With.) P. James, Fulgensia bracteata (Hoffm.) Räsenen, Psora decipiens (Hedw.) Hoffm and Endocarpon pusillum Hedw.) on soil properties as well as the importance of lichen coverage in driving these changes. Our findings revealed that thalli composition is species-specific and positively correlated to the lichen coverage. Furthermore, the influence of lichens on soil properties and its magnitude was found to be species dependent. S. cartilaginea, D. diacapsis and F. bracteata significantly reduced soil pH and increased soil water and nutrients content compared to P. decipiens and E. pusillum. All the investigated lichen species were found to increase microbial enzyme activity. In addition, our results showed that the species S. cartilaginea, D. diacapsis and F. bracteata sharply decreased the abundance of soil microbes as determined by qPCR (16S and 18S rRNA gene copy numbers). Overall, lichen coverage was found to be the key trait to drive changes in soil physico-chemical properties (soil pH, moisture, carbon and nitrogen contents) which in turn affected microbial community and activity. This research paper emphasizes the important role of lichens in arid soils and predicts that reduction of lichens coverage with climate change and land use will negatively affect soil fertility and quality.