Ecological impacts of the invasive grass Sorghum halepense on native tallgrass prairie

Bacterial endophytes enhance competition by invasive plants

“…How S. halepense tolerates these high Fe 3+ concentrations is currently unknown. Our findings further emphasize the importance of the bacterial community in invaded soils on the positive feedback observed in the field on S. halepense density (Rout and Chrzanowski, 2009; Rout et al, 2013) and suggest a number of mechanisms that might explain the altered soil biogeochemical parameters observed for invaded soils in this study.…”

“…Since the decline in root to shoot ratio was similar for endophyte‐inhibited plants (EI), irrespective of N treatment, endophytic bacteria might somehow be essential for maximal rhizome production (belowground biomass), and this resource allocation is not related to bioavailable N in soil. In light of previous research that estimated rhizome growth rates of 60–90 m per year for an individual plant (McWhorter, 1981) and rhizomatous advances by S. halepense in this same field site documented at ∼0.45 m per year (Rout et al, 2013), our findings suggest that bacterial endophytes play a substantial role in resource allocation toward rhizomes and invasion persistence for this invasive grass. We do not currently know the mechanism(s) by which bacterial endophytes increase rhizome growth, but the capacity of bacteria to produce the plant‐growth‐promoting substance IAA may be an important factor.…”

Ecology and Management of Weeds in a Changing Climate

“…This would result in a much greater impact on US maize-growing regions (e.g., Midwestern USA) for this weed, which has historically had greater impacts in the southern USA [23]. In addition to this predicted increased negative impact on maize production, Sorghum halepense is also an increasing threat to native tallgrass prairie ecosystems under climate change [68]. When Sorghum halepense invades native tallgrass prairies, its rhizomatous growth allows it to advance at rates of 0.45 m year −1 in addition to the deleterious effects of its allelopathic leachates on native vegetation [68].…”

Plant and arthropod diversity in prairie restorations around Louisville, KY.

“…The dominance of the invasive Johnson grass could explain this anomaly, as exotic plants tend to exhibit greater aboveground biomass (Wilsey et al 2009). Johnson grass has very high productivity but is not as palatable as forbs or other native grasses so it would not be expected to support high diversity of arthropods (Rout et al 2013). At JMF, Johnson grass constituted 57% of the total plant cover.…”

“…In addition, the plant's more rapid growth, greater height, and larger biomass than native species effectively blocks light from reaching native species. This aggressive species can quickly turn a burgeoning, diverse prairie restoration into a virtual monoculture (Rout et al 2013). …”