Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Ecology and Evolutionary Biology

First Advisor

Timothy Seastedt

Second Advisor

Pierre Johnson

Third Advisor

Kelley Simmons

Abstract

Factors that contribute to long-term persistence of restored natural areas remain largely unstudied. In Boulder, Colorado, a tallgrass prairie was mined and used as a gravel pit for 50 years before it was drilled with native grass species in 1998. The ecosystem was then allowed to revegetate without intervention. A study in 2004 investigated the sensitivity of plant community structure to nutrient manipulations. Authors of the study argued that low carbon and nitrogen levels at this site contributed to a novel, low-diversity plant community that was resistant to invasion by nonnative species. I reassessed the site in 2016 to determine whether native species persisted, and whether carbon and nitrogen content of these soils had recovered to nearby, undisturbed soil levels. Native grasses declined from 92% relative cover in 2004 to 45% in 2016. A single planted grass, Sporobolus airoides, a plant known to thrive in alkaline soils, dominated both study years. Bromus tectorum, increased its coverage by 20%, contributing to a reduction in species diversity. Soils at this site showed a nonsignificant (0.15%) increase in soil carbon in the top 10 cm of soils, suggesting that the sequestration capabilities of this ecosystem were not effective in the 12-year interval between measurements These results suggest that novel soils can produce novel vegetation communities, but initial establishment of desirable native species has been replaced by opportunistic species better adapted to current climate conditions. Restoration managers must consider the potential impact of climate variability, increasingly prevalent invasive species, and degraded soil structure to ensure the health of novel ecosystems.

Included in

Soil Science Commons

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