The vertical distribution of ericoid, ecto, and arbuscular mycorrhizae in a mixed species forest soil
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Understanding the factors affecting the spatial distribution of mycorrhizal fungi in soils is critical to understanding their impacts on forest communities. I investigated the vertical distribution, of ericoid (ERM) ecto- (ECM), arbuscular (AM), and mycorrhizal fungi in a soil at Coweeta Hydrologic Lab, Otto, N.C., and attempted to determine if this spatial distribution was correlated with N and P fraction distribution. The soil studied maintained host plants for all three mycorrhizal fungi, Rhododendron maximum (ERM), Tsuga canadensis (ECM), Liriodendron tulipifera (AM).. We utilized DNA sequencing to determine mycorrhizal fungal distribution. Sequences were identified using BLAST searches and by utilizing Maximum- Likelihood analysis. The correlation between mycorrhizal fungal distribution and N and P distribution was tested using Principal Component Analysis. The results indicate that the three mycorrhizal types are differentially distributed throughout soil horizons. ERM fungi occurred predominately in O horizons and AM fungi occurred mainly in B horizons. The majority of ECM fungi were located within the A horizon but were found in the O and B as well. ERM fungi were positively correlated with high concentrations of inorganic N and organic N and P. AM fungi were negatively correlated with inorganic and organic N, while ECM occurred throughout the range of N and P fraction distribution. I hypothesize that this fungal distribution relates to the capacity of each fungal type to utilize various soil substrates as nutrient sources. As a secondary study, I investigated the impact that different mycorrhizal types have on root system architecture. Using PCR and sequencing, I identified the different mycorrhiza occurring on roots of each of the three host species. I then used scanned images of each root fragment to determine several topological parameters including altitude, magnitude, and total exterior path-length. Comparisons of the topology of roots colonized by different mycorrhizae indicate that different ECM groups do not have a noticeable effect on the parameters measured. Other comparisons could not be made due to a lack of AM and ERM diversity on the roots tested.