Undergraduate Honors Theses

Thesis Defended

Spring 2019

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Environmental Studies

First Advisor

Bill Bowman

Second Advisor

Eve Hinckley

Third Advisor

Dale Miller

Abstract

Invasive species are increasing in abundance globally and have had detrimental effects on ecosystems by altering nutrient cycling and harming native biodiversity. Generally, high-elevation alpine ecosystems are believed to be the least invaded global biomes. One particularly problematic invasive in the American West is Bromus tectorum, commonly known as Cheatgrass, which is an aggressive competitor and can displace native species. While there is a plethora of research concerning its invasive range in the Great Basin, few studies have addressed what inhibits growth at its high elevation range margin. An earlier study showed that while increased temperatures and N deposition increased growth in montane soils, it had no effect on plants grown in alpine soils. Instead, soil type was implicated as the likely the filter preventing alpine establishment of Bromus tectorum. I expanded on this hypothesis by conducting a greenhouse experiment that grew Bromus tectorum seeds in soils collected from four different montane sites and four different alpine soils on the Front Range in the Rocky Mountains of Colorado. It was found that aboveground, belowground, and total biomasses were higher in montane soils compared to alpine. Higher root:shoot ratios were also found in alpine soils relative to montane soils, suggesting a soil factor was responsible for the lower growth. Soil pH was found to be significantly more acidic in alpine soils. While soil pH is a plausible soil characteristic preventing alpine invasion, it is likely a combination of a multitude of factors including both abiotic and biotic interactions. Further research is needed to understand invasive plant-soil interactions at high elevations to determine the factors that influence invasion, especially with altered temperature and precipitation regimes in a changing climate.

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