Competitive Ability of Native Grasses and Non-Native (Old World Bluestems; Bothriochloa Spp.) Grasses

Old World Bluestems (OWB), introduced from Europe and Asia in the 1920s, recently have begun to raise concerns in the Great Plains. Despite determination in the late 1950s that OWS were weedy and negatively impacted biological diversity, they were widely introduced throughout the Great Plains for agricultural purposes. Anecdotal evidence suggests that OWB exhibit invasive characteristics that promote competitive exclusion of other species. The objective of my study was to quantify the competitive abilities of two OWB species [Caucasian bluestem; Bothriochloa bladhii (Retz.) S.T. Blake [= Bothriochloa caucasia (Trin.) C.E. Hubb.], and yellow bluestem; Bothriochloa ischaemum (L.) Keng] with three native grass species [big bluestem (Andropogon gerardii Vitman), little bluestem (Schizachyrium scoparium (Michx.) Nash), and sideoats grama (Bouteloua curtipendulua (Michx.) Torr.)]. A greenhouse target-neighbor study was conducted to assess both interspecific and intraspecific competition. A total of 480 pots (4.4 liter) filled with composited soil was used with all pair-wise combinations of species (six replications). Plant growth parameters including height and tiller number were measured weekly. Biomass was measured at the end of 16 weeks by separately harvesting, drying at 60°C, and weighing (g) above-ground (vegetative and reproductive) and below-ground plant structures. Both of the OWB significantly inhibited at least one growth parameter of the three native grass species, while most of the native species did not inhibit growth of either OWB species. Growth of yellow bluestem was enhanced when grown in association with little bluestem. Based upon the results of my study of OWB competitive superiority and previous research, many of tile characteristics possessed by owe are found to be in common with known invasive species. Hence, I propose that OWB are an invasive, non-native group or grasses, which could invade and threaten the native grasslands of the Central and Southern Great Plains