Rumble in the Cogongrass Jungle: Shrub Resiliency from Round 1

Cogongrass (Imperata cylindrica) is a pervasive invasive plant species across the Gulf of Mexico region and listed as the seventh worst weed in the world. Negative impacts to Gulf Coast ecosystems include agricultural disturbances, increased fire risk, and drastic declines in native plant communities. Cogongrass can form near or full monoculture patches in optimal conditions, with rapid colonization following recent disturbance events like fire where it outcompetes native species. However, the effects of newly infested Cogongrass colonizations on individual established native plants are relatively unknown. We investigated the impacts of cogongrass invasion on three native re-sprouting shrub species (Beautyberry, Yaupon Holly, and Mayberry) following a recent fire. We assessed variability in native plant height, leaf area, stem count, and diameter in relation to Cogongrass presence and percent groundcover to determine the effects of Cogongrass on shrub regeneration following fire. In addition, we measured soil moisture content and canopy cover as covariates. We hypothesized that Cogongrass will negatively impact native plant regeneration post-fire. Interestingly, we found positive relationships between shrub regeneration and cogongrass density, opposite to our prediction. Cogongrass density and soil moisture also were significantly correlated. Our data provides important information on native plant resistance to cogongrass invasion and may provide useful information for early intervention management following fire.

Gulf of Mexico Conference