Date of Award


Degree Type


Degree Name

Departmental Honors


Wildland Resources


Aspen (Populus tremuloides) is the most widely distributed broadleaf forest tree in North America. However, aspen are declining rapidly in areas of the Intermountain West. Aspen in this area are prone to experiencing limited moisture and high temperatures. An important aspect of plant physiology when dealing with these stressors is stomatal function. Stomata control the rate of photosynthesis, therefore, the size and frequency of the stomata is likely to influence the survival of the species in this environment.

An unusual feature of aspen is the high frequency of triploidy in the southern portion of its range. Stomata! size and density differences between cytotypes have not been assessed in aspen. The purpose of this study is to evaluate the differences in stomatal length and density between diploid and triploid aspen in Utah. If stomatal differences are pronounced between cytotypes, this could be the basis of a rapid field-based test to distinguish cytotypes without laboratory analyses. To test this, I collected leaves from independent clones in Logan Canyon and Fishlake National Forest in the summers of 2013, 2014, and 2015. Using cellulose acetate impressions of the underside of the leaves, I measured the stomatal size and frequency. The results indicated that triploid aspen have larger and fewer stomata than their diploid counterparts which may influence the ploidy response to drought conditions. Understanding the complexities of the different aspen ploidy levels is essential in future forest management and predicting future vegetation changes in a changing climate.



Faculty Mentor

Karen Mock

Departmental Honors Advisor

Dave Koons