Do Aerial Nitrogen Depositions Affect Fungal and Bacterial Communities of Oak Leaves?

Abstract

The amount of nitrogen (N) deposition onto forests has globally increased and is expected to double by 2050, mostly because of fertilizer production and fossil fuel burning. Several studies have already investigated the effects of N depositions in forest soils, highlighting negative consequences on plant biodiversity and the associated biota. Nevertheless, the impact of N aerial inputs deposited directly on the tree canopy is still unexplored. This study aimed to investigate the influence of increased N deposition on the leaf-associated fungal and bacterial communities in a temperate forest dominated by Sessile oak [Quercus petraea (Matt.) Liebl.]. The study area was located in the Monticolo forest (South Tyrol, Italy), where an ecosystem experiment simulating an increased N deposition has been established. The results highlighted that N deposition affected the fungal beta-diversity and bacterial alpha-diversity without affecting leaf total N and C contents. We found several indicator genera of both fertilized and natural conditions within bacteria and fungi, suggesting a highly specific response to altered N inputs. Moreover, we found an increase of symbiotrophic fungi in N-treated, samples which are commonly represented by lichen-forming mycobionts. Overall, our results indicated that N-deposition, by increasing the level of bioavailable nutrients in leaves, could directly influence the bacterial and fungal community diversity.

Amorpha canescens and Andropogon gerardii Recruit Comparable Foliar Fungal Communities Across the Steep Precipitation Gradient in Kansas

“…Substrate nitrogen content may affect fungal growth rate, and some evidence suggests a correlation between foliar fungal communities and foliar nitrogen content in northeastern Kansas (Jumpponen and Jones 2010). Similarly, fungal communities respond to available nitrogen; atmospheric nitrogen deposition can increase fungal community diversity and functional groups in prairie soil and on deciduous tree leaves (Borruso et al 2021; Lekberg et al 2021). Because A. canescens is an N-fixing species, and A. gerardii is a grass, they would differ in N content and their C:N ratios in our areas of study and thus, in quality as a resource for fungal communities (Thomas and Asakawa 1993).…”

“…These diverse plant communities host hyperdiverse fungal communities reflective of the plant diversity (Peršoh 2015) and lead to compounding diversity across trophic levels. Such diverse fungal communities can occur at the scale of plant leaves (e.g., Dea et al 2022), as well as vary with nutrient quality within plants (Borruso et al 2021;Lekberg et al 2021). One example of a unique fungal community is that of the phyllosphere fungi.…”