Plant-fungal interactions are important drivers of plant establishment and survival. Positive feedbacks, such as mutualistic interactions between plants and fungi, allow thriving of both partners. In contrast, negative feedbacks, especially the presence of fungal pathogens, can cause seed decay or hinder seedling survival. Lab experiments have revealed the relative importance of positive and negative feedbacks of plant-fungal interactions, but quantification across environmental gradients in the field has been challenging so far. Recent advances in high throughput sequencing may help to overcome these challenges and allow for a rapid and efficient sampling of soil fungi. In this study, we used high throughput sequencing to test how plant-associated fungi affect seedling establishment and survival of Swiss stone pine (Pinus cembra). We transplanted pine seeds across and beyond the elevational distribution of the species (1850-2250 m a.s.l.) in the Swiss Alps and monitored seedling establishment and survival over two years (2014-2016). We measured environmental factors (i.e. canopy openness, temperature, soil moisture, vegetation cover, distance to conspecific trees) and recorded mycorrhizal and pathogenic fungi using DNA metabarcoding of soils.
Results/Conclusions
Our results show that early seedling establishment was only significantly affected by environmental conditions (e.g., canopy openness, temperature). In contrast, distance to conspecific trees and the presence of a pathogenic fungus had significant effects on seedling survival. We conclude that high throughput sequencing can be a promising tool to unravel plant-fungal feedbacks in field studies. Understanding these relationships is important if we wanted to project potential range shifts of plants under climate change.