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Woody plant encroachment has occurred in tallgrass prairie due to reduced fire frequency, climate change, and urbanization. One woody plant in particular, Cornus drummondii, a clonal shrub that forms monospecific stands has increased in abundance and cover to alter site ecohydrology. Because climate change predictions include hotter and drier conditions, competition for water among plant growth forms is likely to increase. During clonal expansion of C. drummondii individuals, we hypothesize that the larger islands will have increased water use because of higher levels of transpiration compared to the smaller islands, complicating landscape estimates of water flux. Our study site was the Konza Prairie Biological Station within a four-year burned watershed where 6 C. drummondii islands of varying sizes were chosen. Within each island, 5 ramets were chosen equidistant from the outer edge of the island to the center where leaf-level physiological data were measured bi-weekly during the summer of 2015. Ecosystem data from an adjacent Ameriflux tower was used for a scaling analysis between the leaf-level and watershed measurements. During the study no differences between predawn and midday leaf-water potentials were found between and among the varying island sizes. Net photosynthesis, stomatal conductance, day and nighttime transpiration measurements were generally higher in the small islands versus the medium and large islands. Interestingly, we also found that the outer most ramets of the islands had higher leaf-level measurements compared to the ramets within the island which had no differences. The small and large islands also had higher LAI values than the medium sized islands. These results facilitate creation of simpler models for scaling water fluxes from individual shrub islands to watersheds that are encroached with C. drummondii. Additionally, these results improve our ability to predict changes in water budgets between woody encroached grasslands versus unencroached grasslands.