Influences of nitrogen deposition and soil warming on saprophytic fungal community structure, fungal growth, and litter decomposition

Background/Question/Methods

How global change will impact microbial community composition remains poorly understood.  However, because microbes are important drivers of biogeochemical cycles, anthropogenically mediated changes in communities may have strong impacts on ecosystem function.  Saprophytic fungi are a diverse group of species and primarily responsible for decomposition in temperate forest systems, yet relatively little is known about the factors, including global changes such as increased nitrogen deposition and soil worming, that influence fungal decomposer community assembly.  Here we focus on results from the first year of a multi-year litterbag/decomposition experiment using long-term experimental N addition (with a control, low and high N treatment) and soil warming plots (with a control and elevated 5^oC treatment) in a northeastern hardwood forest.  We examined the saprophytic fungal community structure, fungal growth rate, and decomposition of tree litter from 95 litter bags harvested after 1 year in the field.  Using a combination of metagenomics, culturing and sequencing, and laboratory growth experiment techniques we tested the influence of increased nitrogen deposition and soil warming on fungal communities and ecosystem function. 

Results/Conclusions

In our study we found 4 major patterns.  1) Fungal community composition in elevated nitrogen deposition and soil warming plots were significantly different from the control plots.  2)  Decomposition rate varied significantly between treatment and control plots in both experiments. 3) The community composition  strongly correlated with decomposition and C/N ratio of the litter it was isolated from.  4)  There were significant differences in growth rate of the same fungal species cultured from litter collected in all three nitrogen treatments.  Our results increase understanding of the ecology and evolution of saprophytic fungi in a global change context, and add to what is known about the biodiversity of decomposer fungi.  In addition, our results show that global change may not only be changing which fungi are found within and environment, but also may be influencing the evolution of some fungal species as well.