Peatlands are a broad range of carbon accumulating systems, including peat swamp forests, bogs, fens, and some permafrost-affected habitats. These ecosystems store over one-third of Earth’s soil carbon, are globally important sources of methane, and are unique habitats for diverse organisms. However, these systems are increasingly vulnerable to anthropogenic stressors associated with climate change and land conversion. Understanding the response of peatlands to these stressors requires an understanding of the organisms directly involved in peatland carbon transformation processes, such as fungi. Within this context, we conducted a large-scale DNA sequencing effort to characterize communities of fungi, as well as bacteria and archaea, from 180 natural and experimental peatland sites around the world. This effort was coupled with extensive measurements of abiotic site characteristics, vegetation and peat chemistry.
Results/Conclusions
Fungal communities exhibited clear global scale spatial patterning and habitat-associated structuring, including: 1) Among northern peatlands, gradients in local-scale factors (vegetation, pH, fertility and hydrology) were far stronger predictors of community composition than geographic proximity or climate. 2) At the global scale, climate emerged as the strongest predictor of fungal composition. Fungal communities in high latitude and high elevation peatlands were more similar to each other than to lowland tropical peatlands. However, vegetation, geographic distance, and peat chemistry were still significant predictors of fungal community composition. 3) Fungal operational taxonomic unit (OTU) richness was greatest between 0° and 40° latitude, and lowest towards polar regions. 4) ~90% of the OTUs did not have close matches in public databases, suggesting we recovered a large number of previously unsampled species. Our study provides evidence that a diverse, cryptic, and under-sampled group of organisms is structured both by large-scale factors (e.g., climate, geographic distance) and local biotic and abiotic peatland characteristics. However, the relative lack of geographic structuring among northern hemisphere sites suggests that a common set of fungal taxa may play an important role in carbon cycling across large areas of the Northern Hemisphere.