Graciela Orozco


Education: Bachelor of Science in biology and biological engineering (May 2014)

McNair Project: Temperature Impacts on Native Tallgrass Prairie Water Usage (2011)

Mentor: Stacy Hutchinson, Ph.D.

Understanding water use of the native tallgrass prairie will be critical for predicting future responses of the tallgrass prairie to climatic changes (i.e. temperature, precipitation, etc). To better understand plant water use in response to climate, a study was conducted using climatic data (temperature), reference evapotranspiration (ETr), daily calculated evapotranspiration (ETo), and soil moisture from 2001-2010 from the irrigation transects on Konza Prairie in Kansas, USA. In order to understand temperature impacts on water use, a water use coefficient was calculated using the relationship between reference ET, calculated using the modified Penman-Monteith equation, and the actual plant water use: ETc = ETx Kc x K, where Kc is the plant water use coefficient, and Ksm is the soil moisture coefficient. In fully watered sites, the plant water use coefficient is based on the relationship of ETc/ETr because K = 1.0 due to ample water. A similar method was used for unwatered sites to calculate Kc. Results from imposing the water use coefficients of fully watered and unwatered sites upon one another indicated varying responses to climate, but especially temperature. Over the growing season (June 1 to September 30), fluctuations in plant water use were in response to precipitation events and temperature. Early season precipitation (~June 1 to July 9) is the initial driver of plant water use; however, water use later in the growing season (~July 15 to August 19) is primarily a factor of temperature.