CONICET | Buscador de Institutos y Recursos Humanos

Plants interact with soil organisms in a myriad of ways, and this interaction is a key factor in determining the formation of soil organic matter and nutrient availability in terrestrial ecosystems. In old-growth temperate Patagonian forests three southern beech species (Nothofagus obliqua, N. nervosa and N. dombeyi), demonstrated faster decomposition in areas defined as ´tree triangles´ on the forest floor below an intersection of three adult trees of the same species. Our objective in this study was to explore possible mechanisms which could generate a specialized decomposer communities at the scale of single species in these tree microsites. We hypothesized that the chemical and morphological characteristics of leaf litter input, over long periods of time, could generate conditions for a specialized decomposer community, both for microbial communities and for soil macrofauna. Our results demonstrate that while total macrofauna did not differ among the tree triangles, soil faunal composition was markedly distinct. Of particular importance was the higher abundance of Coleoptera and Heteroptera in N. obliqua tree triangles. These results suggest that there may be signals that attract or repel epigeous macrofauna from these microsites, which led to an exploration of volatile signals from the leaf litter of the three plant species. We collected volatiles of unsterilized leaf litter of the three southern beech species, and analyzed their composition using a GC-MS. Surprisingly, each species has its own completely distinct footprint of volatile organic compounds (VOCs) with N. nervosa dominated by sesquiterpenes and N. dombeyi composed of aromatic derivatives and monoterpenes. Absolute abundance of VOCs showed that N. obliqua and N. nervosa were more similar, which is consistent with their phylogenetic origin. These results suggest that leaf litter, through volatile signals can modulate the composition of the soil macroand microfaunal community.