Date of Award

December 2019

Degree Name

Master of Science (MS)

Department

Biology

Advisor(s)

Douglas Frank

Second Advisor

Jason Fridley

Keywords

Ecology, Invasion, Microbial Activity, N Cycling

Subject Categories

Life Sciences

Abstract

Invasive woody plants are often strong competitors that can have large effects on ecosystem function. While there is evidence that Northeastern invasive species can increase nitrogen cycling in monocultures, little is known about how invasive plants alter biogeochemistry in the field. I hypothesized that the high-quality leaf and root litter of invaders would enhance the quality of soil organic matter, leading to greater belowground microbial activity and faster rates of nitrogen mineralization. In the summer of 2017, I conducted a field survey of invasive and native understory shrubs to see how invasive woody plants influence microbial activity in central New York temperate forests. I selected 105 shrubs and trees and took soil cores from directly below each plant and around each plant canopy; the latter used to account for site effects on soil properties. Inorganic N pools were measured by extracting fresh soil with KCl, and potential C and N mineralization rates were determined with 10-day laboratory incubations. Soil percent C and N, pH, and root biomass were also measured for each soil sample. I then used linear mixed models to determine the effect of nativity on each of these soil traits, with nativity, soil core location (below vs. around) and plant height as fixed effects. I used least squares regression models to determine their effects on potential rates of mineralized N and respired C. Contrary to my hypothesis, I found that invaders did not significantly alter any of the measured soil traits. Instead, root biomass and pH were better predictors of potential respired C and mineralized N. This suggests that plant quantity, not quality, controls available C and N pools, and plants that create more roots are able to better stimulate microbial activity regardless of nativity. Thus, understory invaders do not appear to alter soil biogeochemistry in the context of a native dominated overstory.

Access

Open Access

Included in

Life Sciences Commons

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