Plant litter decomposition and microbial characteristics in volcanic soils (Mt Etna, Sicily) at different stages of development

Soils at different developmental stages weresampled from eight sites on the slopes of Mt Etna, Sicily(Italy) and characterized for total C, microbial biomass andmicrobial respiration. The values of these parameters weregreatest for the most developed soils, but differences inrecent management and site characteristics limited analysisof trends with soil development across the eight sites. Thedecomposition kinetics of both intact leaf litter and thewater-insoluble fraction of leaf litter from three commonspecies on Etna [Etnean broom(Genista aetnensis), Europeanchestnut (Castanea sativa), and Corsican pine (Pinus nigra)]were determined in four of the soils (the two with thesmallest and the two with the largest organic C contents) in alaboratory experiment over 168 days to test two hypotheses.First, that the readily mineralized fraction of added plant C isgreater when the plant material decomposes in welldevelopedsoils compared to less developed soils, andsecond, that the microbial communities in less developedsoils are less efficient at mineralizing C from low qualityplant residues. The first hypothesis held for Genista andPinus litter, but not Castanea litter. The second hypothesiswas supported for the Castanea and Pinus litter, but not forthe Genista litter. Thus, the general applicability of thehypotheses was dependent on the precise source andcharacteristics of the litter