“Overdispersed spatial patterning of dominant bunchgrasses in southeastern pine savannas”

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Katherine A. Hovanes, Kyle E. Harms, Paul R. Gagnon, Jonathan A. Myers, and Bret D. Elderd (May 2018)

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Bunchgrasses are spatially overdispersed in pine savannas; this may affect population, community, and ecosystem dynamics

Muhlenbergia expansa bunchgrass tussocks one month post-burn, June 2009, Lake Ramsay Preserve, LA. (Charred black stems are Ilex glabra.)
(Credit: Jonathan A. Myers; © 2018 The University of Chicago Press)


Spatial patterning is a key natural history attribute of sessile organisms that frequently emerges from and dictates potential for interactions among organisms. We tested whether bunchgrasses, the dominant plant functional group in longleaf pine savanna groundcover communities, are non-randomly patterned by characterizing the spatial dispersion of three bunchgrass species across six sites in Louisiana and Florida. We mapped bunchgrass tussocks > 5.0-cm basal diameter in three 3×3-m plots in each site. We modeled tussocks as two-dimensional objects to analyze their spatial relationships while preserving sizes and shapes of individual tussocks. Tussocks were overdispersed (more regularly spaced than random) for all species and sites at the local interaction scale (< 0.3 m). This general pattern likely arises from a tussock-centered, distance-dependent mechanism e.g., inter-tussock competition. Non-random spatial patterns of dominant species have implications for community assembly and ecosystem function in tussock-dominated grasslands and savannas, including those characterized by extreme biodiversity.