Girdling: effects of carbon-13 concentrations and biomass in mycorrhizal fungi.

Abstract

Our study examined the effects of girdling trees on both the total biomass and the stable carbon -13 isotope concentrations of mycorrhizal fungi. In order to conduct this research we used two test sites, the FASET (Forest Accelerated Succession ExperimenT) and the reference plot. During the spring of 2008, in the FASET forest plot all Bigtooth Aspen and Birch trees were girdled, which in turn kills the trees. We used mesh bags to monitor the growth of fungi one year after the girdling process. After the bags were collected we separated the fungi and analyzed them. We found no significant correlation between biomass of the two plots, as well as no variation in carbon-13 levels. In hopes of explaining this inconclusive evidence we looked at tree specific biomass to see if species had any effect on total biomass. The results showed that only Red Maple demonstrated higher levels of biomass between reference and FASET plots. One explanation for these results could be the intermingling of tree roots below ground, which would allow for the mutualistic mycorrhizal fungi to transfer to other tree roots without loss of biomass. Future studies that could be done include monitoring hyphal growth closer to the date of girdling to ensure that population size of fungi are representative of the new growth after girdling. In addition we would like to measure carbon-13 concentrations in the flowering bodies of the fungi precisely after the trees are girdled.