Effects of vegetation and disturbance on fungal communities in the western Cascades of Oregon

The use of high throughput molecular methods that allow for the study of bacterial communities in environmental samples is commonplace in microbial ecology. Until recently, fungal community ecology has focused on isolation, collection of sporocarps, or collection of ectomycorrhizal roots. The techniques used to extract and amplify DNA from environmental samples are relatively new to the world of fungal community ecology. Many fungi are difficult to isolate. Collection and identification of sporocarps and root tips is time-consuming. Sporocarp production may vary from year-to-year. Here, we present three studies using length heterogeneity PCR (LH-PCR) with the general fungal primers ITS1-F and ITS4 for the internal transcribed spacer region of rRNA to examine changes in fungal community composition in response to changes in vegetation, and disturbance events. In the first study, we used LH-PCR to examine differences in fungal community composition along transects from the forest to the meadow sites at two sites in the western Cascades of Oregon. We found dramatic differences in fungal community composition due to vegetation type and found an intermediate community in the transition zone between meadow and forest. In the second and third studies, we used LH-PCR to identify treatment effects in two manipulative experiments. In both studies, LH-PCR allowed us to observe the changes in community dynamics and identify some of the factors involved in community changes following disturbance. In the second study, we found that fungal succession occurred rapidly when cores were transferred to new environments. We also found evidence that succession occurred more slowly when roots were excluded. In the third study, we used bacterial primers in addition to the fungal ITS primers. We found that presence of live roots rather than either aboveground litter inputs or seasonal differences in sampling times were the greatest determinant of both fungal and bacterial communities at the Detritus Input and Removal Treatment plots 6 years after initiation.