Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska

Abstract

Arctic regions are experiencing the greatest rates of climate warming on the planet and marked changes have already been observed in terrestrial arctic ecosystems. While most studies have focused on the effects of warming on arctic vegetation and nutrient cycling, little is known about how belowground communities, such as fungi root-associated, respond to warming. Here, we investigate how long-term summer warming affects ectomycorrhizal (ECM) fungal communities. We used Ion Torrent sequencing of the rDNA internal transcribed spacer 2 (ITS2) region to compare ECM fungal communities in plots with and without long-term experimental warming in both dry and moist tussock tundra. Cortinarius was the most OTU-rich genus in the moist tundra, while the most diverse genus in the dry tundra was Tomentella. On the diversity level, in the moist tundra we found significant differences in community composition, and a sharp decrease in the richness of ECM fungi due to warming. On the functional level, our results indicate that warming induces shifts in the extramatrical properties of the communities, where the species with medium-distance exploration type seem to be favored with potential implications for the mobilization of different nutrient pools in the soil. In the dry tundra, neither community richness nor community composition was significantly altered by warming, similar to what had been observed in ECM host plants. There was, however, a marginally significant increase in OTUs identified as ECM fungi with the medium-distance exploration type in the warmed plots. Linking our findings of decreasing richness with previous results of increasing ECM fungal biomass suggests that certain ECM species are favored by warming and may become more abundant, while many other species may go locally extinct due to direct or indirect effects of warming. Such compositional shifts in the community might affect nutrient cycling and soil organic C storage.

Changes in composition and abundance of functional groups of arctic fungi in response to long-term summer warming

“…Changes in communities of arctic fungal functional groups have been scarcely documented, except in ectomycorrhizal fungi [10]. The compositional differences between the warmed and control plots in all functional groups indicate that even in groups without major changes in richness, the turnover is substantial.…”

“…We extracted DNA using the Macherey–Nagel NucleoSpin-Soil kit. PCR and sequencing of the ITS2 (internal transcribed spacer 2) rDNA were done as described earlier [10–12]. We generated 4 047 811 reads using Ion 318™ Chip ().…”

Soil bacterial community and functional shifts in response to altered snowpack in moist acidic tundra of northern Alaska

“…This suggests that bacterial communities preferentially degrade microbial biomass and polysaccharide polymers and that the decomposition of more recalcitrant forms of C in Arctic soils is performed by other microorganisms such as fungi. Fungi typically play a key role in the degradation of recalcitrant organic matter by specializing in the production of oxidative enzymes (Deslippe et al, 2012;Morgado et al, 2015). The absence of bacterial genes that encode for peroxides, phenol oxidases, and laccases could also be due to the presence of tannins in the soil, which are common in the Alaskan floodplain and are produced by encroaching shrub species (DeMarco et al, 2014;Schimel et al, 1996).…”

“…It is well established that soil microbial communities may alter their composition in response to changing environmental factors such as nutrient availability, moisture, pH, temperature, and aboveground vegetation shifts (Lauber et al, 2009;Morgado et al, 2015;Semenova et al, 2015), and ecological and climate-induced changes to Arctic soil microbial community structure and function have important effects on ecosystem carbon (C) cycling and nutrient availability for plant growth (Deslippe et al, 2012;Graham et al, 2012;Waldrop et al, 2010;Zak and Kling, 2006). Because many of these environmental features are rapidly changing in Arctic tussock tundra ecosystems (Anisimov et al, 2007;Liston and Hiemstra, 2011), and because of the large amounts of C stored in Arctic soils (Hugelius et al, 2013;Ping et al, 2008;Schuur et al, 2009;Tarnocai et al, 2009), it is imperative to examine microbial responses in this system.…”

Light-driven host-symbiont interactions under hosts’ range shifts caused by global warming: A review

“…Increases in plant growth due to global warming and elevated CO 2 are welldocumented (Bazzaz, 1990). Such impacts on EMF symbionts of trees and shrubs have also been reviewed (Pickles et al, 2012;Morgado et al, 2015). In contrast, the light environment has been largely neglected in this context.…”