Vegetation-environment relationships and species assemblages in three vertical strata after an intermediate-scale wind disturbance in a quercus forest

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University of Alabama Libraries

Natural disturbance is a fundamental process that exerts a strong influence in shaping forest structure, composition, and function. Canopy disturbances are often classified based on spatial extent and severity along a gradient ranging from highly localized, gap-scale events to stand-replacing or catastrophic events. The overwhelming majority of research on wind disturbance and forest response has focused on events near the two endpoints (catastrophic and gap-scale) of the disturbance classification gradient. As such, a paucity of data is available on intermediate-scale disturbances. Furthering our understanding of these events provides information on natural processes that can be used to make informed management decisions. On 20 April 2011, an EF1 tornado coupled with straight line winds affected portions of the Sipsey Wilderness in Bankhead National Forest. I subjectively established 109, 0.04 ha plots in Quercus dominated stands adjacent to the track of the tornado three growing seasons post-disturbance to quantify damage and possible effects on species assemblages in three vertical strata. Non-metric multidimensional scaling (NMS), indicator species analysis (ISA), and multi-response permutation procedures (MRPP) were used to examine vegetation-environmental relationships in each vertical stratum by species using PC-ORD v. 5.31. Species appeared to be aligned most strongly along elevation and diversity gradients and the effects of the disturbance on seedling and sapling establishment was limited because of the well-developed mid-story layer. The overstory remained dominated by Quercus and Carya spp. However, the disturbance released the shade-tolerant stems present in the understory and mid-story, thereby accelerating succession

Electronic Thesis or Dissertation
Geography, Environmental management, Conservation biology