ORIGINAL ARTICLE Resilience of Rhizopogon-Douglas-fir mycorrhizal networks 25 years after selective logging Carrie H. Van Dorp 1 & Suzanne W. Simard 2 & Daniel M. Durall 1 Received: 5 November 2019 /Accepted: 28 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Rhizopogon vesiculosus and R. vinicolor are sister fungal species; they form ectomycorrhizas exclusively with Douglas-fir roots, and they are important in forming relatively large mycorrhizal networks, but they may be vulnerable to disturbance caused by logging practices. The main objective was to determine the resilience of mycorrhizal networks 25 years following removal of large hub trees. We predicted that the targeted removal of mature trees would reduce network connectedness compared with a non-harvested neighboring forest. Rhizopogon vesiculosus was nearly absent in the non-harvested plots, whereas both species were prominent in the harvested plots. Initially, network analysis was based only on networks formed by R. vinicolor because they were well represented in both treatments. These analyses showed that the R. vinicolor-Douglas-fir MN was more densely linked in the non-harvested plots than the harvested plots. When we accounted for differences in link and node density, there was still an edge difference and a greater vulnerability to fragmentation in harvested forests than in non-harvested forests. When both Rhizopogon sister species were included in the analysis, both treatments had similar connectivity and limited vulnerability to fragmentation. This suggests that when these forests transition from a regenerating to a non-regenerating state, the Rhizopogon network will lose R. vesiculosus but will maintain link density due to the colonization with R. vinicolor. Keywords Mycorrhizal networks . Fungal genotypes . Cryptic species . Selective logging . Belowground resilience Introduction Mycorrhizas are abundant and influential symbioses in terres- trial ecosystems. Many mycorrhizal fungi associate with the roots of more than one plant species or plant individual, which results in the formation of a belowground network of plants and fungi termed a mycorrhizal network (MN). In these MNs, typically the trees are viewed as nodes and the links are where a single fungal genotype is found on two different nodes (Southworth et al. 2005). Mycorrhizal networks can be important in carbon, nutrient, and water transport between trees (Brownlee et al. 1983; Simard et al. 1997; Egerton- Warburton et al. 2007; Whiteside et al. 2019). Thus, studies have demonstrated that being connected to an MN may influ- ence plant survival (Teste and Simard 2008; van der Heijden and Horton 2009; Song et al. 2010, 2015). The morphology and genetics of some ectomycorrhizal (ECM) fungi allow us to study the MN formed between dif- ferent plant and fungal species and even between different plant and fungal individuals. For example, members of a truffle-forming ECM fungal genus, Rhizopogon, form tuber- culate mycorrhizas, which are roundish structures consisting of a proliferation of mycorrhizal roots enclosed within a thin fungal rind; they are large enough to be visible to the human eye without magnification, which allows them to be sampled individually in the field. These structures also lend themselves to have their fungal component molecularly distinguished at both the species and genotype level and their plant component molecularly distinguished at the genotype level. With respect to all species of ECM fungi, this approach allows researchers to map fungal genotypes that link different trees (Beiler et al. 2010; Hortal et al. 2012). Rhizopogon spp. also form thick Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00572-020-00968-6) contains supplementary material, which is available to authorized users. * Daniel M. Durall daniel.durall@ubc.ca 1 Biology Department, University of British Columbia, Okanagan campus, 1177 Research Road, Science Building, Kelowna, BC V1V 1V7, Canada 2 Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada Mycorrhiza https://doi.org/10.1007/s00572-020-00968-6