Watching the grass grow: Effects of habitat type, patch size, and land use on cogongrass (Imperata cylindrica (L.) Beauv.) spread on Camp Shelby training site, Mississippi.

摘要

The purpose of this research was to increase understanding of ecology and control of cogongrass (Imperata cylindrica (L.) Beauv.) to assist with management of this invasive grass. To address different aspects of cogongrass management, I examined factors that affect spread of cogongrass, effects of cogongrass on native plant communities, and use of three native species to suppress cogongrass. Relative susceptibility of pine-bluestem and pine-shrub vegetation associations to vegetative encroachment and seed dispersal of cogongrass were evaluated. Vegetative encroachment into burned and unburned areas of these two vegetation associations also was measured. Effects of infestation size on vegetative growth of cogongrass and relationships between military activity and establishment and growth of cogongrass on military firing points were investigated. I also compared frequency of cogongrass infestation and vegetative growth rates for unpaved roads with different levels of traffic and maintenance. Native plant richness, diversity, and abundance were compared between cogongrass infestations and in uninfested adjacent areas for longleaf pine-bluestem and ruderal, cleared areas. Morella cerifera (L.) Small, Chamaecrista fasciculata (Michx.) Greene, and Panicum virgatum L. were tested for their ability to suppress cogongrass re-growth after treatment with a herbicide.; Mean vegetative encroachment of cogongrass was 2 m/yr for both habitat types regardless of burning. Vegetative encroachment was more than double in burned plots compared to unburned plots. Spikelets of cogongrass consistently dispersed farther into pine-bluestem (x¯ = 17.3 m) forests compared to pine-shrub forests (x¯ = 9.4 m). Vegetative encroachment was not affected by size of infestation for cogongrass patches on firing points (x¯ 1 m/yr) (P ≥ 0.643). In areas of soil disturbance from military equipment, vegetative expansion rates of 7-10 m/yr were recorded. There was a positive relationship between military troop use and cogongrass establishment for one of the 2 years of the study (P = 0.023). Growth and establishment of cogongrass did not vary for unpaved roads with differing levels of maintenance and traffic (P ≥ 0.173). Species diversity and abundance of herbaceous vegetation was less in cogongrass infestations compared to uninfested adjacent areas. Complete suppression of cogongrass was not evident for any of three native species tested.