Root-Associated Ectomycorrhizal Fungi Shared by Various Boreal Forest Seedlings Naturally Regenerating after a Fire in Interior Alaska and Correlation of Different Fungi with Host Growth Responses

Abstract

The role of common mycorrhizal networks (CMNs) in postfire boreal forest successional trajectories is unknown. We investigated this issue by sampling a 50-m by 40-m area of naturally regenerating black spruce (Picea mariana), trembling aspen (Populus tremuloides), and paper birch (Betula papyrifera) seedlings at various distances from alder (Alnus viridis subsp. crispa), a nitrogen-fixing shrub, 5 years after wildfire in an Alaskan interior boreal forest. Shoot biomasses and stem diameters of 4-year-old seedlings were recorded, and the fungal community associated with ectomycorrhizal (ECM) root tips from each seedling was profiled using molecular techniques. We found distinct assemblages of fungi associated with alder compared with those associated with the other tree species, making the formation of CMNs between them unlikely. However, among the spruce, aspen, and birch seedlings, there were many shared fungi (including members of the Pezoloma ericae [Hymenoscyphus ericae] species aggregate, Thelephora terrestris, and Russula spp.), raising the possibility that these regenerating seedlings may form interspecies CMNs. Distance between samples did not influence how similar ECM root tip-associated fungal communities were, and of the fungal groups identified, only one of them was more likely to be shared between seedlings that were closer together, suggesting that the majority of fungi surveyed did not have a clumped distribution across the small scale of this study. The presence of some fungal ribotypes was associated with larger or smaller seedlings, suggesting that these fungi may play a role in the promotion or inhibition of seedling growth. The fungal ribotypes associated with larger seedlings were different between spruce, aspen, and birch, suggesting differential impacts of some host-fungus combinations. One may speculate that wildfire-induced shifts in a given soil fungal community could result in variation in the growth response of different plant species after fire and a shift in regenerating vegetation.In Alaska and adjacent boreal forest regions, the frequency, severity, and extent of fires are increasing due to climatic changes, and this trend is expected to continue and intensify in the future (14,26). Major tree species found in developing postfire forests in interior Alaska include black spruce (Picea mariana), white spruce (Picea glauca), trembling aspen (Populus tremuloides), and paper birch (Betula papyrifera). Plant dispersal and physiological responses to soil, site, climatic factors, and other species will certainly influence which plant species survive and thrive in a given area. However, a likely influence that has only recently been given attention is the role of soil fungi in mediating these plant responses.Despite their importance to the functioning of ecosystems, microorganisms are rarely explicitly considered in individual ecosystem or global process models; the interactions of soil microbes with plants are similarly ignored or are considered a "black box"(45). It is widely known that e...

Low host specificity of root‐associated fungi at an Arctic site

“…; Bent et al . ). CMNs may be of particular importance for seedling establishment under stressful conditions (Bingham & Simard ).…”

Fungal Community Shifts in Structure and Function across a Boreal Forest Fire Chronosequence

“…However, only a few studies have investigated whether these changes in the microbial community persist over long periods of time. There are large numbers of studies using nonmolecular methods to investigate the effects of fire on fungal communities, from boreal to Mediterranean areas (21)(22)(23)(24)(25). Studies examining the recovery of fungal components of the soil microbial communities in boreal forests are lacking (26,27).…”

Post-fire Successions of Vegetation and Pinus koraiensis Ectomycorrhizal Communities in Korean Pine–Broadleaf Forests of the Central Sikhote-Alin

“…The regrowth of only two age categories of Korean pine (1-5 years old and 7-10 years old) is present on the fire site, while seedstalking trees have remained at its border. Under the new conditions initiated by fire a certain fungal community is formed which may affect the growth processes and lead to a shift in succession by the symbiosis with particular species or a number of species, as shown by the studies (Visser, 1995;Nara, 2006;Bent et al, 2011). Mycorrhization of pine seedlings is possible both with fungal spores resistant to fire and from the surviving climax species of trees that are able to develop shared mycorrhizal networks.…”

“…Thanks to mycorrhiza a plant benefits in availability of nutrients and resistance to pathogens, which is reflected in its growth and development (Smith and Read, 2008). In this regard, one of the most important factors in the study of regenerative successions of communities is the mycorrhization of seedlings of the host plant and its impact on the direction of development of the ecosystem (Grogan et al, 2000;Guariguata and Ostertag, 2001;Nara, 2006;Ishida et al, 2007;Bent et al, 2011;Peay et al, 2011).…”