Changes in fungal community composition during permafrost thawing

Background/Question/Methods

Fungi, major components of the soil microbial community, are involved in a wide range of activities including carbon turnover, symbiotic associations with plants, and as pathogens. How global warming, with the associated thawing of permafrost soils, would affect this community and its activities is currently unknown. Samples (107) taken from several soil layers at 7 different plots that encompassed areas of minimal, moderate, and extensive permafrost thawing in the Alaska Range (Eight Mile Watershed) were analyzed by a functional gene based fungal chip (FungiChip) containing 6291 probes, covering ~7100 sequences, for 91 key genes involved in biogeochemical cycling (S, N, P, Fe), carbon degradation, virulence, and major biomolecule synthesis.

Results/Conclusions

A range of 705 to 2509 sequences were detected per sample. Though detrended correspondence analysis (DCA) did not show any significant difference of fungal compositions caused by the three thawing intensities across all soil depths, non-parametric multivariate statistical tests (anosim, adonis and MRPP) showed that fungal community composition differed significantly (p<0.05) between minor and moderate thawing sites at all depths, between minor and extensive thawing sites in surface and middle layers, and between moderate and extensive thawing sites in the middle layers. Community composition did not differ significantly among the other comparable layers.    A significantly lower fungal community diversity, based on Shannon Index, was observed in moderately thawed samples at all depths, compared to samples that experienced minor thawing. While there was significant recovery in the surface and middle, but not deep, layers in extensively thawed samples, diversity still did not return the level seen in the minor thawed samples.  These results show that thawing has a significant and lasting effect upon the permafrost fungal community and give us a hint of what will likely occur over the next several decades in arctic soils due to the continued effects of global warming.