Effect of permafrost thaw on plant and soil fungal community in a boreal forest: Does fungal community change mediate plant productivity response?

Abstract

Permafrost thaw is leading to rapid shifts in boreal ecosystem function. Permafrost thaw affects soil carbon turnover through changes in soil hydrology; however, the biotic mechanisms regulating plant community response remain elusive. Here, we measured the response of fungal community composition and soil nutrient content in an intact permafrost plateau forest soil and an adjacent thermokarst bog and evaluated their potential to mediate shifts in plant composition. We used barcoded amplicon targeting ITS2 and 28S rRNA genes to determine fungal community composition. Next, we used the soils from the permafrost plateau and the thermokarst bog as soil inoculum in a greenhouse experiment to measure whether shifts in fungal community and soil water level regulate plant productivity and composition. Overall, we found that fungal community composition differed significantly between the thawed and intact permafrost sites, but soil nutrient content did not. Relative abundance of mycorrhizal fungal taxa decreased while relative abundance of putative fungal pathogens increased with permafrost thaw. In the greenhouse, we found that ecto‐ and arbuscular‐associated host plants had higher productivity in permafrost‐intact soils relative to thawed soils. However, productivity of non‐mycorrhizal tussock grass was more affected by soil water levels than soil communities. Synthesis. Our results suggest that fungal communities are crucial in mediating plant community response to permafrost thaws inducing hydrology changes.

Arctic riparian shrub expansion indicates a shift from streams gaining water to those that lose flow

“…Other studies of permafrost degradation have shown that plant communities are a stronger predictor for soil microbial communities (and their function) than soil physical and chemical factors 53 . Conversely, soil microbial communities (fungi) have been shown to affect plant community composition and biomass after permafrost thaw 65 . This has led to the suggestion that plant growth and composition could be directly linked with microbial composition through the process of coevolution 53 .…”

Soil disturbance affects plant growth via soil microbial community shifts

“…These results were similar to a study performed on boreal plant species using microbial inoculums from thermokarst bogs (disturbed soils) and permafrost plateaus (undisturbed soil). Schütte et al (2019) showed that bog blueberry and marsh-cinquefoil ( Potentilla palustris ) grew significantly worse when inoculated with soil microbes from thermokarst bogs than when inoculated by permafrost plateau soil microbes.…”

“…Recent research has turned to exploring the effects of climate change on microbial communities residing in soil and permafrost (Jansson and Hofmockel, 2018). As permafrost thaws and soil disturbance events occur, microbial communities undergo shifts in membership composition and biomass, as well as in functional diversity (Schuur et al, 2015; Mackelprang et al, 2011; Schütte et al, 2019). As these smaller scale changes develop, it is important that we build a better understanding of how microbial communities in northern latitude soils affect larger scale processes such as plant growth.…”

“…The atmospheric release of carbon trapped in soils following permafrost thaw is mediated by soil bacterial and fungal respiration. These organisms have been surviving in the active layer and frozen soil below for millennia, either frozen or respiring at extremely low rates, using the frozen organic matter as an energy source (Schütte et al, 2019; Tripathi et al, 2018). As the permafrost thaws, soil microbes exit dormancy and microbial communities gain access to large pools of previously frozen carbon and nutrients (Burkert et al, 2019).…”

Biogeochemical Response to Vegetation and Hydrologic Change in an Alaskan Boreal Fen Ecosystem

“…Since mycorrhizal communities can obtain their carbon from host plants, it is thought that their enzyme systems focus more on nutrient mining rather than carbon uptake (Treseder et al 2007;Hobbie et al 2013;Lindahl and Tunlid 2015). Mycorrhizal associates of Comarum palustris have been documented (Schütte et al 2019), along with several other plants of the family Rosaceae and genus Comarum (Kytoviita and Ruotsalainen 2007;Sudová and Vosátka 2008). If such mycorrhizal fungi were associated with the cinquefoil rhizospheres in this experiment, this may explain the slowed decomposition (Gadgil and Gadgil 1975;Wiedermann et al 2017).…”