Multi-trophic frameworks that capture the links between above as well as belowground community dynamics are lacking and thus are a challenge in ecological research. Such are especially relevant today, where research is increasingly needed to understand the influence of rapid climate change in the structure of ecosystems worldwide as well as the biotic communities living in them. We studied an ongoing invasion of non-native lodgepole pines into an non-forested plateau in alpine Patagonia. This particular invasion setting allows us to observe community wide responses to predicted global change events, such as for example range expansions. We ask how the magnitude of effects differ between above-belowground communities and between biotic and abiotic conditions. Moreover, we search to establish above-belowground casual relationships amongst biotic and abiotic effects. We hypothesize that pines invaders will significantly modify their surrounding abiotic environment, with a higher magnitude of belowground abiotic effects such as increasing soil carbon, water content and available nitrogen. We also hypothesize that pines affect first and with higher magnitude to native plant-soil microbial belowground interactions, thus creating distinct networks topologies. We sampled aboveground plant and arthropod communities. We also quantified belowground plant soil-microbial root multitrophic interactions using high throughput DNA sequencing. We analyzed the multitrophic responses of above-belowground communities in terms of richness, composition, and biotic interactions. We calculated effect sizes relative to pine-free control areas. Causality between pine-induced above-belowground effects was established using structural equation modelling.
Results/Conclusions
We suggest that pines trigger bottom-up controls that can modulate aboveground multitrophic community structure. Pines alter aboveground abiotic conditions such as reducing soil temperature, and increasing litter. Belowground, pines increase the heterogeneity of available soil nitrogen and reduce available phosphorus. We found that pines influence local multitrophic communities and their above-belowground effects are entangled. Aboveground pines homogenize community composition, drive changes in plant relative cover. Additionally, functional shifts in leaf morphology were observed for certain plant species. Belowground, pines drive an increasing generalism of plant-soil microbial interactions. As such, plant-soil microbiome networks can rewire their interactions in response to the pines, however, network structural changes rather responded to the interaction effects of changes in soil chemistry with changes in plant spatial composition. Finally, we show that an increasing understanding of the ecological dynamics between multi-trophic taxa as well as the abiotic environment can greatly enhance our capacity towards better predict community level biodiversity responses in global change scenarios.