The effect of fertilization on the below-ground diversity and community composition of ectomycorrhizal fungi associated with western hemlock (Tsuga heterophylla)

Abstract

Fertilization typically reduces ectomycorrhizal diversity shortly after its application but less is known about its longer-term influence on fungal species. Long-term effects are important in forests where fertilizer is rarely applied. We compared fungal species composition in western hemlock control plots with plots last fertilized 7 years ago with nitrogen (N) or nitrogen plus phosphorus (N + P). The N + P fertilization had a significant lingering effect, increasing the tree size and foliar P content of the western hemlocks. From ectomycorrhizal roots of 24-year-old trees from northern Vancouver Island, Canada, we identified fungi from 12 samples per treatment, by amplifying, cloning, and sequencing fungal ribosomal DNA fragments, placing sequences with 97% or more identity in the same operational taxonomic unit (OTU). Diversity was high across treatments; we detected 77 fungal OTUs, 52 from ectomycorrhizal genera, among 922 clone sequences. The five most frequent OTUs were similar in abundance across treatments. Only 19 OTUs matched any of the 197 previously reported ectomycorrhizal species of western hemlock. Species composition but not diversity in nitrogen plus phosphorus plots differed significantly from control or nitrogen plots. Two Cortinarius OTUs were indicator species for nitrogen plus phosphorus plots and presence of Cortinarius cinnamomeus was correlated with control or nitrogen plots. After 7 years, fertilization history had made no detectable difference in ectomycorrhizal fungal diversity, but long-lasting changes in environment resulting from fertilization had a lingering effect on fungal ectomycorrhizal species composition.

Ectomycorrhizal community structure and function in interior spruce forests of British Columbia under long term fertilization

“…The responses of ectomycorrhizas to nitrogen fertilization are known to be variable. Some studies report no changes to ECM fungal species richness, evenness or diversity indices in coniferous forests (Fransson et al, 2000;Peter et al, 2001;Berch et al, 2009;Wright et al, 2009), while others report significant reductions in diversity indices (Frey et al, 2004) or richness (Lilleskov et al, 2002;Berch et al, 2006). At the pine sites within the Maximum Productivity Study, 10-12 years of annual fertilization decreased ECM roots by 40% (albeit at a higher rate of application than tested here), and ECM fungal richness also decreased (Jones et al, 2012).…”

“…Studies of mixed fertilizer application are fewer and tend to be of short duration, but report lower ECM fungal species richness, percent root length colonized, mycelium production or total sporocarp biomass, in response to fertilization (Baum and Makeschin, 2000;Nilsson and Wallander, 2003;Berch et al, 2006). Shifts in ECM fungal community structure have also been observed, including a reduction or elimination of some dominant ECM fungal taxa (Berch et al, 2006;Wright et al, 2009). These shifts may impact the nutrient cycling capacity of forest soils, as nitrogen fertilizers select against ECM fungi with enhanced abilities to attack N-containing biomolecules (Lilleskov et al, 2011 and references therein).…”

Mixotrophy of Platanthera minor, an orchid associated with ectomycorrhiza‐forming Ceratobasidiaceae fungi

“…As Ceratobasidiaceae are generally recognized as nonECM fungi, their detection in ectomycorrhiza may have been considered as contamination by saprobic or endophytic fungi in many previous studies -but see Rosling et al (2003), Wright et al (2009) andCollier &Bidartondo (2009) for detection of ECM colonized by Ceratobasidiaceae. Unfortunately, Ceratobasidiaceae do not form conspicuous fruit bodies that would confirm the ECM vs saprobic status of the various clades of this family by assessment of their 13 C and 15 N abundance (Trudell et al, 2004).…”

Ectomycorrhizae and tree seedling nitrogen nutrition in forest restoration

“…Sarg.) (Wright et al 2009). When fertilization occurs annually, however, ECM fungal species composition or richness (Fransson et al 2000;Jones et al 2012), colonization or both (Berch et al 2006) are negatively affected.…”