Boreal peatlands occupy 3% of the earth’s land area, yet store 13-30% of the earth’s terrestrial carbon. As northern areas are disproportionately affected by climate change, hydrologic and vegetation community changes have been documented in boreal ecosystems. However, little research has examined the effects of hydrologic and vegetative changes on peatland microbial communities, the main drivers of carbon cycling in wetlands. The goal of this study was to document changes to the microbial community in peat and plant rhizospheres of a northern rich fen under long-term water table manipulations (control, lowered, raised). Rhizosphere bacterial, archaeal, and fungal communities of four main plant functional groups (PFGs) –Calamagrostis spp., Carex atherodes, Equisetum fluviatile, and Comarum palustre—were gathered to examine how shifts in dominant PFG would affect the overall microbial community of the peatland. DNA was extracted and purified from 0.5 grams of ground peat or fine roots from each of the three water table treatments. Samples underwent library preparation and community amplicon sequencing on an Illumina MiSeq platform using primers targeting bacteria, archaea, and fungi. Bioinformatic processing was conducted with the Quantitative Insights into Microbial Ecology (QIIME) pipeline.
Results/Conclusions
Bacterial and fungal communities differed between PFG and long-term changes in hydrology. The bacterial genus Geobacter, capable of iron reduction and organic compound oxidation, had a greater presence in rhizosphere communities than in the bulk peat and highest relative abundance in the raised water table treatment. Sedges and horsetails had a high relative abundance of the bacterial family Gallionellaceae, species of which are associated with iron oxidation and carbon cycling. Methanogenic archaeal genus Methanobacterium was associated with the roots of sedge, grass, and horsetail but not cinquefoil roots, and had the highest relative abundance in the raised water table treatment. Fungal alpha diversity was affected by water table in the cinquefoil (lowest diversity in raised water table) and horsetail (lowest in lowered water table) rhizospheres. Interestingly, cinquefoil appears to be plagued by disease and parasites of both bacterial and fungal origin, present in the disturbed (lowered, raised) plots. The results from this experiment demonstrate how climate change-driven vegetation and hydrology shifts could affect plant-microbe relationships, and highlight the potential link between carbon cycling and iron in northern fens. Further research will be needed to understand how peatland species will respond to climate change, and implications for the global carbon balance.