Characterization, restoration, and assembly of fungal communities in lodgepole pine forests impacted by recent disturbances

• Author / Creator

  Rodriguez Ramos, Jean Carlos

• Novel disturbance regimes have impacted boreal forest with unknown consequences for belowground communities and underlying ecological processes. Soil fungi are an integral component of belowground communities and are particularly sensitive to disturbances. In the Canadian boreal forest, common overstory trees, such as lodgepole pine (Pinus contorta var. latifolia), form mutualisms with ectomycorrhizal (EcM) fungi, while many understory plants tend to associate with arbuscular mycorrhizal (AM) fungi. These fungal symbionts influence the establishment and growth of their host by mediating nutrient availability, while also interacting with saprotrophic and pathogenic fungi. The response of these different fungal guilds to individual disturbances and the response of seedlings to changes fungal communities is poorly understood. Furthermore, it is unclear what processes underlie EcM fungal community assembly and whether different disturbances affect the relative contribution of neutral and deterministic assembly processes. The objectives of this thesis are to (1) characterize soil fungal communities in lodgepole pine forests following a range of disturbances including bark beetle outbreak, wildfire, clear-cut logging, and salvage-logging, (2) test whether the disrupting soil organic matter structures fungal communities belonging to different guilds (3) determine whether soil transfers from intact (control) lodgepole pine forests into regenerating conspecific forests amend soil fungal communities and, in turn, affect the performance of pine seedlings, and (4) examine whether root-associated EcM fungi assemble at fine spatial scales based on neutral or deterministic processes across disturbances. I found that wildfire, clear-cut, and salvage-logging changes the community composition of EcM fungi and shifted the dominance from EcM to saprotrophic fungi compared to control forests. However, despite MPB outbreak declined the EcM fungal relative abundance, compared to controls, the effects were not as strong as in the other disturbances. Disruption of the soil organic layer with disturbances correlated with the decline of EcM and the increase of AM fungi. In addition, wildfire changed the community composition of pathogenic fungi but did not affect their proportion or diversity. Fungal biomass declined with the same disturbances that also disrupt the soil organic layer, specifically wildfire, clear-cut, and salvage-logging. Soil transfers from control stands did not change the composition of the resident fungal community in soils and lodgepole pine seedling roots across the disturbances. Instead, I found that the variation in the EcM fungal community was explained largely by disturbance type. Furthermore, soil transfers did not affect seedling survival or performance. For EcM fungi colonizing roots of seedlings grown in the different disturbances, a neutral model that uses species abundance in the soil metacommunity to predict their occurrence on roots predicted the abundance of 58% to 64% of root-associated EcM fungal taxa. This finding suggests that both neutral and deterministic processes are important in fine-scale assembly of EcM fungi regardless of disturbance type. I also found that the fungal communities of taxa assigned as neutral or deterministic were similar across the disturbance types. Traits, including host-specificity of EcM fungi, large production of resistant spores, and uncertain ecological roles of taxa commonly identified as EcM fungi could explain their deviations from neutrality. Collectively, these results suggest that while disturbances alter the community composition and abundance of soil fungal guilds and root-associated EcM fungi, lodgepole pine seedlings can be relatively insensitive to the in-situ variation in fungal communities across disturbances that assemble in roots largely by probabilistic dispersal from soil. Therefore, under novel disturbance regimes, soil and root-associated fungal communities can show resilience through a response diversity that may provide functions regarding seedling establishment and performance.

• Subjects / Keywords

  • soil fungi
  • forest disturbances
  • mycorrhizal fungi
  • community assembly

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-s0wr-nn61

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.