Undergraduate Honors Theses

Thesis Defended

Fall 2018

Document Type


Type of Thesis

Departmental Honors


Ecology and Evolutionary Biology

First Advisor

Katharine Suding

Second Advisor

Heidi Souder

Third Advisor

Barbara Demmig-Adams


Changes in precipitation patterns paired with exotic species invasion pose a threat to grassland biodiversity and ecosystem functions. To understand how Front Range plants will respond to projected precipitation changes, we designed an experiment to simulate spring (March-May) and summer (June-August) drought on 17 common, functionally diverse prairie plant species. Our common garden experiment was conducted in Boulder, Colorado from February 2018 to August 2018. Plants were individually sown and monitored weekly for emergence and flowering timing. Extreme precipitation significantly impacted plant survival in different life stages depending on the timing of precipitation manipulation. Spring drought decreased emergence likelihood by 54% (p = 0.0399) and wet spring significantly increased emergence likelihood by 169.6% (p = 0.0416). A wetter spring also significantly increased the likelihood of plant survival after germination when effects were aggregated across the 17 species. The transition from seed to seedling was the most pronounced bottleneck in a species reaching recruitment (becoming a mature member of a population), which suggests the need for increased care of native plants seeds during years of early drought.