Fungal communities can influence the productivity, composition, and survival of trees through cycling nutrients, providing resources, and altering pathogens. Thus, shifts in fungal communities could impact forests by altering interactions between trees and their environments. Fungal community composition may be shaped by stochastic and deterministic processes such as dispersal-limitation, environmental filtering, and partner specificity between trees and fungi. For tree species with large geographic ranges, we expect fungal assembly processes to change with environmental variation across the range of the tree partner. Due to specificity between trees and symbiotic fungi, we expect deterministic to outweigh stochastic processes in root compared with soil fungi. As some tree species have exceptional longevity, we also expected tree age to influence fungal community assembly.

We surveyed fungi in four stands of Pseudotsuga menziesii with tree ages up to 800 years along an 1,800 km north-south transect. We sampled roots and soil around 12 P. menziesii in each stand, aged the trees, and sequenced fungal rDNA to determine composition and richness from which we calculated the relative role of deterministic and stochastic assembly processes. We used null models to evaluate the relative importance of deterministic variable and homogenizing selection, and stochastic dispersal-limitation, drift, and homogenizing dispersal in fungal community assembly.

We detected 7,280 amplicon sequence variants with 5,270 associated with soil, 3,887 with roots and 1,877 found across both roots and soils. Deterministic processes dominated root and soil fungal communities at all sites except one where stochastic processes (i.e., dispersal-limitation and drift) controlled root-fungi. Despite the dominance of determinism in fungal community assembly, the proportion of processes differed by site. Assembly processes did not vary with tree age.

Taken together, we suggest that the local environment, water limitation, and partner-preference between trees and their associated fungi, influence fungal community composition across the range of P. menziesii. We conclude that while fungal communities occurring near P. menziesii are dominated by homogenizing selection, the role of neutral processes still has minor influence on community assembly and may be important in shaping spatially isolated communities and those with strong gradients of fungal diversity.

Author ORCID Identifier

Joseph D. Birch

James A. Lutz

Justine Karst

Document Type




File Format

.xlsx, .csv

Publication Date



Natural Science and Engineering Council of Canada

Utah Agricultural Experiment Station


Utah State University


Trees were cored and tree-rings measured to estimate the age of each tree. Soil and root samples were taken around P. menziesii 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.

Scientfic Names

Pseudotsuga menziesii

Referenced by

Birch, J. D., Lutz, J. A., Karst, J. 2022. Dancing with Douglas-fir: Determinism dominates fungal community assembly processes. Journal of Ecology.

Start Date


End Date



54.6° N, 124.3° W ; 50.8° N, 120.3° W ; 41.6° N 112.0° W ; 37.6° N, 112.8° W



Code Lists

Please see README


Research was performed under National Park Service research permits CEBR-2014-SCI-0001, CEBR-2015-SCI-0001, CEBR-2016-SCI-0001, CEBR-2017-SCI-0001, CEBR-2018-SCI-0001, and CEBR-2019-SCI-0001 for study CEBR-00016 and permits CEBR-2018-SCI-0002 and CEBR-2019-SCI-0002 for study CEBR-00020


Forest Sciences


Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.




Additional Files

PSME_Tree_Fungi_data.xlsx (2855 kB)
MD5: 65756c53e6eca2e21f7a320b03f2eeab

TreesSheet_PSME_Tree_Fungi_data.csv (3 kB)
MD5: f3ebe5ce16f6a9fefe3a60790a037daf

SequenceSheet_PSME_Tree_Fungi_data.csv (3865 kB)
MD5: 35181026b8d02011ea8fcc9c6bd3cc07

MetadataSheet_PSME_Tree_Fungi_data.csv (1 kB)
MD5: 4b6a6fc13a46192c2b0ea416fba7a15d

README_Birch.txt (6 kB)
MD5: 802D087f20115667cbc3e2df9ccdc7a16