Abstract
The arctic tundra is undergoing climate-driven changes and there are serious concerns related to the future of arctic biodiversity and altered ecological processes under possible climate change scenarios. Arctic land surface temperatures and precipitation are predicted to increase further, likely causing major transformation in terrestrial ecosystems. As a response to increasing temperatures, shifts in vegetation and soil fungal communities have already been observed. Little is known, however, how long-term experimental warming coupled with increased snow depth influence the trajectories of soil fungal communities in different tundra types. We compared edaphic variables and fungal community composition in experimental plots simulating the expected increase in summer warming and winter snow depth, based on DNA metabarcoding data. Fungal communities in the sampled dry and moist acidic tundra communities differed greatly, with tundra type explaining ca. one-third of compositional variation. Furthermore, dry and moist tundra appear to have different trajectories in response to climate change. Specifically, while both warming and increased snow depth had significant effects on fungal community composition and edaphic variables in dry tundra, the effect of increased snow was greater. However, in moist tundra, fungal communities mainly were affected by summer warming, while increased snow depth had a smaller effect and only on some functional groups. In dry tundra, microorganisms generally are limited by moisture in the summer and extremely low temperatures in winter, which is in agreement with the stronger effect of increased snow depth relative to warming. On the contrary, moist tundra soils generally are saturated with water, remain cold year-round and show relatively small seasonal fluctuations in temperature. The greater observed effect of warming on fungi in moist tundra may be explained by the narrower temperature optimum compared to those in dry tundra.
Highlights
The arctic tundra is being transformed by a wide range of climate-driven processes and there are serious concerns related to the future of arctic biodiversity because of the threats represented by climate change (Wookey, 2007)
Total fungal richness was similar in all dry tundra sites, with a non-significant increase in S and SW treatments relative to the control, while all experimental manipulations resulted in a clear decrease in fungal richness in the moist tundra, only the combined SW treatment was statistically different from the control (Figure 1)
Root-associated non-mycorrhizal fungi showed highest richness in moist control plots and decreased in all treatment plots, with significant difference observed between control and the SW and S treatments, while richness values were uniformly low for all treatments in the dry tundra
Summary
The arctic tundra is being transformed by a wide range of climate-driven processes and there are serious concerns related to the future of arctic biodiversity because of the threats represented by climate change (Wookey, 2007). In addition to the profound consequences for arctic biota, nutrient cycling in the Arctic is of paramount importance for global change (Tarnocai et al, 2009). The arctic tundra occupies an area of 8 million km and stores a great portion of the Earth’s soil carbon (C) that is critically important in global C cycles and climate feedback (Callaghan et al, 2004; Tarnocai et al, 2009). Due to retreating sea ice, arctic land surface temperatures have increased and will continue to increase, causing major changes in terrestrial ecosystems (Kaufman et al, 2009). Pronounced increase in arctic precipitation is predicted due to increased local surface evaporation of the Arctic Ocean, as well as greater moisture inflow from lower latitudes (Kattsov and Walsh, 2000; Stocker et al, 2013; Bintaja and Selten, 2014). Because most of the precipitation falls as snow, deeper snow is expected in many parts of the Arctic (Bintaja and Selten, 2014)
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