At a site in Watkinsville, GA, highly endophyte infected tall fescue stands has been shown to support greater soil C and N pools and altered microbial activity (Franzluebbers et al. 1999, 2005). Endophyte-produced alkaloids, by both increasing plant production and persistence during drought and reducing levels of above- and belowground herbivory and litter decomposition rates, are thought to be the primary mechanism through which soil nutrient pools are enhanced. My first graduate student, Jacob Siegrist, performed a litter decomposition experiment with alkaloid-laden, endophyte-infected (E+) and alkaloid-free, endophyte-free (E-) tall fescue material. He found that similar to other studies E+ material degraded more slowly than E- material; however, given the large differences in alkaloid quantity between the two litter types, it was surprising this statistical difference in decomposition rates wasn't larger (Siegrist et al. 2009). Jacob and postdoc, Javed Iqbal, also tested the generality of the Georgia soil nutrient pool results across a broad geographic range in the upper southeastern transition zone of the U.S. They found enhanced soil organic carbon, total nitrogen, recalcitrant particulate organic matter pools, and altered microbial biomass and communities in E+ vs. E- tall fescue stands throughout this geographic zone, suggesting that this aboveground fungal endophyte symbiosis has widespread effects on soil biology and biochemistry, and that high prevalence of the aboveground endophyte increases C sequestration capacity of tall fescue stands throughout the southeastern USA (Iqbal et al. 2012).
Postdoc, Javed Iqbal, also evaluated whether fungal endophyte presence and genotype (wild-type common toxic endophyte; AR-584, AR-542 - two novel endophytes, each producing a reduced and unique suite of alkaloids) within a single variety of tall fescue alters soil-to-atmosphere gas exchange, soil nutrient pools, soil microbial community composition, plant production and species composition, and litter decomposition. This fungal genotype project is located in Lexington, KY.