Document Type

Capstone Project

Degree Name

Bachelor of Science (B.S.)


Science & Environmental Policy


he purpose of this study was to determine the feasibility and reliability of a low cost, automated instrument to measure trunk diameter change as an indicator of plant water potential in California oaks (genus: Quercus). The measurement of water potential is important for monitoring water stress and its role in oak regeneration, acorn productivity, and disease susceptibility. Several past methods for measuring eater potential were examined. A strain gage instrument was developed to measure trunk diameter change in response to the need for an automated method to measure water potential. Values from strain gage measurements were compared with xylem water potential measurements. A dead tree control was used to determine whether the strain gage is affected by daily temperature fluctuations. Results from graphed data sets depict trends that are supported by the cohesion theory of sap ascent; however, results from linear regressions do not show strong correlation between my measurements of trunk diameter change and xylem water potential. Several reasons are suggested, and further testing is recommended to determine if the lack of correlation is due to human error, calibration error, random events, or species-specific water acquisition strategies. These findings suggest, but do not confirm that our strain gage instrument may be a feasible method for providing automated data on plant water potential.


Capstone Project (B.S.) Earth Systems Science & Policy Institute