Graduation Year


Graduation Month


Document Type


Degree Name

Bachelor of Science

School or Department

Biological Sciences, Division of


Biology – Ecology and Organismal Biology

Faculty Mentor

Ragan M. Callaway

Faculty Mentor Department

Biological Sciences, Division of


Nitrogen, resource pulses, competition, native, invasive, interaction

Subject Categories

Other Plant Sciences | Terrestrial and Aquatic Ecology


Variation in the timing and size of resource fluctuations can influence how plants grow, allocate biomass, and reproduce. Resources are sometimes made available in relatively continuous, reliable pulses while other times they are temporally separated and unpredictable. Native and invasive plant species are thought to respond differently to resource fluctuations, or pulses, which can influence competitive outcomes. The “Fluctuating Resource Hypothesis” predicts that resource fluctuations benefit invasive species more than native species, potentially because many invaders are highly effective at rapidly capturing resources. In a field setting, we examined the effects of varying nitrogen pulses on competition between exotic invasive and native species that are common in the intermountain prairie. We planted pairs of two native and two invasive plant species alone and in competition, and these groups of species received one of three treatments: no nitrogen at all (control), one large pulse of nitrogen (0.31 g N), or three smaller pulses equaling the total amount of nitrogen in the large pulse. The total amount of nitrogen added in the treatments was quite small in an attempt to mimic what these plants would be more likely to experience in nature. Invasives competitively suppressed natives regardless of the pulse treatment. Conversely, natives did not influence invasives and there was no effect of nitrogen addition or pulses on natives or invasives. Our results provide relatively limited insight into the impact of nitrogen pulses on plant interactions because the total amount added was low, and did not stimulate growth relative to controls. However, in that context we did not find evidence for any influence of fluctuating resources on the growth or competitive interactions of invasive or native plants.

Honors College Research Project




© Copyright 2017 Nicolas Matallana, Mandy L. Slate, and Ragan M. Callaway