Bouteloua gracilis competition with Salsola iberica in Shortgrass Prairie Rangelands



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Invasive annual species are a major concern in rangelands, especially in areas such as the shortgrass prairie, where patches of bare soil are common. Competition between blue grama (Bouteloua gracilis), a dominant grass, and various invasive species has been studied with regard to nutrient availability and temperature regimes, but very few studies have been conducted focusing on weed density. This thesis reports on research exploring the effect of Russian thistle (Salsola iberica) density on B. gracilis biomass in the Southern Great Plains Shortgrass Prairie. This relationship was explored via a glasshouse experiment and a field experiment. Density ratios of B. gracilis to S. iberica were 1:0, 1:1, 1:2, 1:3, 1:4, and 0:1 individuals of B. gracilis to S. iberica, respectively. In the glasshouse study, S. iberica presence reduced B. gracilis biomass from 12.13g to 2.31g-2.80g, while varying density had no effect. Salsola iberica also displayed higher intraspecific competition than interspecific. In the field study, neither S. iberica presence nor density affected B. gracilis biomass. However, B. gracilis reduced average individual S. iberica biomass by 65.9%. In addition, S. iberica did not display intraspecific competition. Future research should continue to study the effect of S. iberica density on B. gracilis to identify the S. iberica density level at which B. gracilis is affected and should focus on S. iberica establishment and dispersion cycles in B. gracilis dominant rangelands on a landscape scale.



Bouteloua gracilis, Blue grama grass, Salsola iberica, Russian thistle, Competition, Density, Rangeland, High Plains, Shortgrass prairie, Glasshouse, Field study