Plant-decomposer affinity could explain home-field advantage for decomposition in old-growth Patagonian forests

GONZALEZ-ARZAC, A; MÉNDEZ, M. SOLEDAD; AUSTIN, AT; FERNÁNDEZ, PC

Malaga

Simposio; Annual Meeting of COST Action FA1405 on Crop-Arthropod-Microorganism (CAMo) Interactions; 2016

COST Action Network

Invited SpeakerPlants interact with soil organisms in a myriad of ways, and the sum of plant-microbe and plant-arthropod interactions is a key factor in determining the formation of soil organic matter and nutrient availability in terrestrial ecosystems. One intriuging connection between plants and decomposerorganisms that has been identified is the home-field advantage for decomposition, where leaf litterof a given plant species decomposes more quickly in its home environment than in other micosites(away) independently of the litter quality or fertility of the different microsites. This phenomenon hasbeen observed in old-growth temperate Patagonian forests for three southern beech species(Nothofagus obliqua, N. nervosa and N. dombeyi), where all three species 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. Using pyrosequencing techniques, our results demonstrate that fungal and bacterial composition in the litter layer are strongly influenced by plant litter inputs, with unique microbial species associations in the litter layer of the forest floor beneath each of the three species of trees, which overall represent 42% of total microbial richness. In addition, while total macrofauna did not differ among the tree triangles, soil faunal composition was markedly distinct; of particular importance were the compositional 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 very distinct footprint of volatileorganic 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. Taken together, these results suggest that leaf litter, through volatile signals and microbial specialization can modulate the composition of the soil macro- and microfaunal community, which may contribute to the observed phenomenon of home-field advantage for litter decomposition.