Princeton Grand Challenge Interns, Summer 2011

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From June through August 2011 the Caylor Lab in Kenya hosted three undergraduate interns from the Princeton Environmental Institute’s Grand Challenges Internship Program – Kathleen Ryan, Hannah Safford, and Alice Suh. The interns advanced our research in three areas: rainfall patterns, soil vapor isotopes, and vegetation monitoring.

Intern Kathleen compiled all of the rainfall data for Mpala Research Centre (the record is now continuous for the past 40 years), and calibrated each of the active rainfall gauges. She also initiated a long-term project of using atmospheric back-trajectories from NOAA’s HYSPLIT model ( to help interpret the isotope signatures of rain samples that we have been collecting since 2008. The rainfall database will be available to all Mpala researchers, and the back-trajectory analysis will be presented at the Isoscapes conference at Purdue University, September 2011.

Hannah put together an experiment to monitor the soil vapor isotope signal during a soil drying event for comparison with the corresponding liquid isotope values. This work helps to refine our understanding of isotope fractionation during evaporation from the soil, and the experimental setup serves as a prototype for a continuous soil vapor monitoring system to be installed at our flux tower.

Alice developed a non-destructive biomass monitoring technique and performed a comparison of instrumentation for leaf-level photosynthesis and plant water potential measurements. The water potential comparison showed good agreement between the somewhat cumbersome “pressure bomb” technique and the much more portable WP4T dew point potentiometer. The latter will help in our monitoring of water stress and the effect of water potential on the transpiration water vapor isotope signature.

Overall, we had a very productive summer, and it was a pleasure to host these three young scholars.