Tree diversity and the role of non‐host neighbour tree species in reducing fungal pathogen infestation

Abstract

The degree to which plant pathogen infestation occurs in a host plant is expected to be strongly influenced by the level of species diversity among neighbouring host and non-host plant species. Since pathogen infestation can negatively affect host plant performance, it can mediate the effects of local biodiversity on ecosystem functioning.We tested the effects of tree diversity and the proportion of neighbouring host and non-host species with respect to the foliar fungal pathogens of Tilia cordata and Quercus petraea in the Kreinitz tree diversity experiment in Germany. We hypothesized that fungal pathogen richness increases while infestation decreases with increasing local tree diversity. In addition, we tested whether fungal pathogen richness and infestation are dependent on the proportion of host plant species present or on the proportion of particular non-host neighbouring tree species.Leaves of the two target species were sampled across three consecutive years with visible foliar fungal pathogens on the leaf surface being identified macro- and microscopically. Effects of diversity among neighbouring trees were analysed: (i) for total fungal species richness and fungal infestation on host trees and (ii) for infestation by individual fungal species.We detected four and five fungal species on T. cordata and Q. petraea, respectively. High local tree diversity reduced (i) total fungal species richness and infestation of T. cordata and fungal infestation of Q. petraea and (ii) infestation by three host-specialized fungal pathogen species. These effects were brought about by local tree diversity and were independent of host species proportion. In general, host species proportion had almost no effect on fungal species richness and infestation. Strong effects associated with the proportion of particular non-host neighbouring tree species on fungal species richness and infestation were, however, recorded.Synthesis. For the first time, we experimentally demonstrated that for two common forestry tree species, foliar fungal pathogen richness and infestation depend on local biodiversity. Thus, local tree diversity can have positive impacts on ecosystem functioning in managed forests by decreasing the level of fungal pathogen infestation.

Species diversity of fungi on damaged branches and leaves of ashes (Fraxinus spp.) in different types of stands in Slovakia

“…Diverse forests can contribute to reduced susceptibility of trees to disease and fungal infection, and a subsequent increase in plant survival and growth (Keesing et al 2006;Hantsch et al 2014). According to Keesing et al (2006), non-host trees can reduce fungal disease risks.…”

Herbivore and pathogen effects on tree growth are additive, but mediated by tree diversity and plant traits

“…However, the positive relationship between herbivore and pathogen damage in our study became weaker with increasing tree species richness (at least the potential effects of pathogens on herbivore damage). This can be explained by the opposite effects of tree richness on herbivory and pathogen damage (see also Hantsch et al., 2014; Schuldt et al., 2010, 2015). Herbivore assemblages in our study system are dominated by generalists (Zhang et al., 2017), which can benefit from the diversity of resources available in more diverse tree communities (Lefcheck, Whalen, Davenport, Stone, & Duffy, 2013; Zhang et al., 2017).…”

“…We speculate that an evolutionarily more stable host–pathogen relationship in these tree species (e.g., because wider climatic niches allowed the persistence of these relationships during past climatic changes, or because they allow for larger and less extinction‐prone pathogen populations; Schuldt et al., 2012) might have promoted host specialization of pathogen species (Brändle & Brandl, 2001). Highly specialized pathogens can be expected to respond particularly strongly to host dilution in species‐rich plant communities (Hantsch et al., 2014). Finally, environmental constraints might play a role in determining the effects of climatic niche characteristics.…”

A Review of Processes Behind Diversity—Productivity Relationships in Forests

“…[ [115][116][117][118] Other patterns Stability of biomass production through time --Stability can be defined as the mean divided by the standard deviation of productivity for each growing period and has been attributed to three main patterns, overyielding, asynchrony of species, and species interactions. Overyielding increases stability by increasing productivity relatively more than it increases the standard deviation of productivity.…”