Co‐occurring bunchgrasses are associated with different plant species in dry pine savannas

Abstract

Grass species are often included during restoration to reinstate feedbacks with fire. In biodiverse pine savannas of the southeastern United States, wiregrass (Aristida beyrichiana) is the preferred candidate for restoring low-intensity fires through the understory. Less common but locally co-dominant in dry pine savannas, pineywoods dropseed (Sporobolus junceus) is another bunchgrass candidate for restoration. If two bunchgrass species associate with different suites of plants in the understory, restoring both could support a twofold goal of restoring fire regimes and plant biodiversity. To guide restoration goals, we tested the hypothesis that in natural (i.e. not recently restored) dry pine savannas in North Florida where wiregrass and dropseed are co-dominant, they are associated with different understory plant species richness, occurrence, and abundance under or adjacent to their canopies. Species richness of associated plants did not differ between bunchgrass species or with distance from bunchgrass (i.e. under vs. adjacent). Some associated plant species, however, were more likely to occur and had greater abundance with one or the other bunchgrass species irrespective of distance. Our results suggest that including more than one bunchgrass species in restoration plantings could increase dry pine savanna biodiversity while also reinstating plant-fire feedbacks.

Priority effects and competitive exclusion by C4 grasses on longleaf pine savanna restoration sites

“…Our species‐specific findings are consistent with other recent studies, which have shown that different C 4 grass species have different competitive interactions and community associates. Grman et al (2021) found that in tallgrass prairies, big bluestem ( Andropogon gerardii ) had stronger competitive exclusion effects than all other C 4 grasses combined, whereas Baruzzi et al (2022) found that A. stricta and Sporobolus junceus had different suites of community associates in their immediate vicinity. In the interest of focusing on overall functional group interactions, we chose not to separate out weedy from desirable native forbs in our analysis; however, it is important to note that the ecological implications of forb abundance depend very much on the species in question.…”

“…Andropogon and Eragrostis species, being much easier to obtain and establish on disturbed sites, may be more cost‐effective and reliable alternatives to wiregrass for restoration on severely altered sites. Pineywoods dropseed ( Sporobolus junceus ) and lopsided indiangrass ( Sorghastrum secundum ) are also important grasses that co‐occur with wiregrass in many longleaf pine savannas, and have potential as restoration species (Peet 2006; Baruzzi et al 2022). However, competitive interactions and species associations vary among C 4 grass species (Grman et al 2021; Baruzzi et al 2022), presumably due to species‐specific biological differences (i.e.…”

“…Pineywoods dropseed ( Sporobolus junceus ) and lopsided indiangrass ( Sorghastrum secundum ) are also important grasses that co‐occur with wiregrass in many longleaf pine savannas, and have potential as restoration species (Peet 2006; Baruzzi et al 2022). However, competitive interactions and species associations vary among C 4 grass species (Grman et al 2021; Baruzzi et al 2022), presumably due to species‐specific biological differences (i.e. stature, flammability, and vital rates).…”

Smut fungus (Langdonia walkerae) incidence is lower in two bunchgrass species (Aristida stricta and A. beyrichiana) after fires early in the year

“…and A. beyrichiana Trin & Rupr., Poaceae) are widely distributed, endemic, warm‐season bunchgrasses that facilitate fire spread through the understory (Fill et al, 2016). Pine‐grassland ecosystems have experienced a widespread decline in the region, and groundcover reestablishment is an initial step in restoration efforts (Walker and Silletti, 2007; Baruzzi et al, 2023). For years, however, there has been concern that infection of wiregrass flowers by a smut fungus may hinder wiregrass reproduction by seeds and slow restoration efforts.…”