Background: Large-diameter trees have an outsized influence on aboveground forest dynamics, composition, and structure. Although their influence on aboveground processes is well studied, their role in shaping belowground fungal communities is largely unknown. We sought to test if (H1) fungal community spatial structure matched aboveground forest structure, (H2) fungal functional guilds exhibited differential associations to aboveground tree, snag, and deadwood, and (H3) that large-diameter trees and snags have a larger influence on fungal community richness than smaller-diameter trees. We used MiSeq sequencing of fungal communities collected from soils in a spatially intensive survey in a portion of Cedar Breaks National Monument, Utah, USA. We used random forest models, to explore the spatial structure of fungal communities as they relate to explicitly mapped trees and deadwood distributed across 1.15 ha of a 15.32 ha mapped subalpine forest.
Results: We found 6,177 fungal amplicon sequence variants across 117 sequenced samples. Tree diameter, deadwood presence, and tree species identity explained more than twice as much variation (38.7% vs. 10.4%) for ectomycorrhizal composition and diversity than for the total or saprotrophic fungal communities. Species identity and distance to the nearest large-diameter tree (≥ 40.2 cm) were better predictors of fungal diversity than were the identity and distance to the nearest tree. Soil nutrients, topography, and tree species differentially influenced the composition and diversity of each fungal guild. Locally rare tree species had outsized influence on fungal community richness.
Conclusions: These results highlight that fungal guilds are differentially associated with the location, size, and species of aboveground trees. Large-diameter trees are implicated as drivers of belowground fungal diversity, particularly for ectomycorrhizal fungi.
Author ORCID Identifier
Joseph D. Birch https://orcid.org/0000-0001-8644-7345
James A. Lutz https://orcid.org/0000-0002-2560-0710
Soren Struckman https://orcid.org/0000-0002-7993-832X
Jessica Miesel https://orcid.org/0000-0001-7446-464X
Justine Karst https://orcid.org/0000-0003-0497-1552
Natural Science and Engineering Council of Canada
Utah Agricultural Experiment Station
Utah State University
Utah Agricultural Experiment Station 153, 1398 and 1423
Soil samples were taken in a ordered grid across 1.15ha and environmental DNA was extracted for amplification. The ITS2 region was amplified to identify fungal communities of each root and soil sample. Fungal sequences were quality filtered and rarefied to 90% of the minimum read abundance.
Abies bifolia, Populus tremuloides, Picea pungens, Picea engelmannii, Pinus longaeva, Pinus flexilis, Pseudotsuga menziesii
Birch, J.D., Lutz, J.A., Struckman, S., Miesel, J.R., and J. Karst. (2023). Large-diameter trees and deadwood correspond with belowground ectomycorrhizal fungal richness. Ecological Processes.
Forest Sciences | Plant Sciences
This work is licensed under a Creative Commons Attribution 4.0 License.
Birch, J. D., Lutz, J., Struckman, S., Miesel, J., & Karst, J. (2022). Data for Gridding [Data set]. Utah State University. https://doi.org/10.26078/06MV-P792
Additional FilesData_for_Gridding_Metadata.txt (5 kB)
GRID_Fungi_data.xlsx (2892 kB)