Abstract Detail


Shershen, Eric [1], Stehn, Sarah [2], Budke, Jessica [1].

Bryophyte communities change over a 12-year period along an elevational gradient in the Great Smoky Mountains National Park.

There are a number of concurrent disturbances impacting the spruce-fir zone in the Great Smoky Mountains National Park (GSMNP), including that of invasive pests (e.g., the Balsam Woolly Adelgid (BWA) (Adelges piceae)) that reduce canopy cover and ecosystem-level changes due to climate change (e.g., fluctuations in annual temperatures, stochasticity and intensity of precipitation events). These disturbances raise the question as to how understory conditions have changed over time. Bryophytes are major biodiversity contributors to the understory community of this high elevation ecosystem. This study examined if bryophyte communities have changed over time and if the observed changes were only at specific elevational zones defined by the dominant tree species present within the GSMNP. Generally, species from lower elevations are predicted to shift their distributions upwards in elevation to accommodate for their thermal optima as climate change increases average annual temperatures. Based on this, one would predict that species richness and bryophyte coverage would increase as elevation increases as more species shift upwards in elevation. I visited plots established in 2008 from a master’s thesis conducted by researcher Sarah Stehn. These plots varied in elevation and the dominant tree species present. I mirrored her study by positioning three, 20-meter transect lines across the plot and measured the coverage of every bryophyte species in each plot. This provided a direct comparison examining how bryophyte communities have changed over time. Collected specimens were identified using microscopy and deposited in the University of Tennessee Knoxville Herbarium (TENN). Species richness and coverage from 2008 and 2020 were analyzed using paired t-tests with Holm-Bonferroni corrections. Jaccard dissimilarity and beta diversity across various orders of q were also analyzed to determine if any changes in species richness were due to species turnover. I found that bryophyte species richness significantly declined across the plots, independent of elevation, and that bryophyte coverage has remained stable except at the highest elevations that are dominated by fir trees. However, when examining percent coverage on a species-by-species basis, some species significantly declined in percent cover whereas others have remained stable. None of the species significantly increased in percent cover. My results suggest that bryophytes are not responding as I initially predicted wherein higher elevations would have an increased bryophyte richness and cover. This suggests that there may be other factors impacting the bryophyte communities of the GSMNP. Future work will explore species’ physiological tolerance to drought stress to understand if stochastic precipitation events are a component driving such declines in coverage.

1 - University Of Tennessee, Ecology And Evolutionary Biology, 569 Dabney Hall, Knoxville, TN, 37996, United States
2 - National Parks Service, Denali National Park and Preserve, P.O. Box 9, Denali National Park, AK, 99755 , USA

plant ecology.

Presentation Type: Oral Paper
Number: EC03003
Abstract ID:135
Candidate for Awards:Ecological Section Best Graduate Student Paper

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