Dissertation

The Role of Host Identity in High Latitude Moss-Associated Nitrogen Fixation

Stuart, Julia M

2021

Overview

Mosses make up a significant portion of primary plant productivity in Arctic and boreal ecosystems and are important regulators of biogeochemical cycling. In addition to producing recalcitrant litter and insulating soils, mosses often host epiphytic microbes capable of fixing nitrogen (N) from the air at rates which make it the largest source of a limiting nutrient in these environments. Since the availability of N is linked to carbon (C) fixation and decomposition, the current and future rates of N2 fixation are important topics of research in an area which stores large amounts of C belowground. Past evidence indicates that host moss identity and environmental conditions can alter rates of moss-associated N2 fixation. However, past studies often focus on a limited number of species and use indirect methods to measure N2 fixation. This dissertation employs 15N2 incubations to measure rates of moss-associated fixation at sites ranging from 60° to 68° N in Alaska in both natural surveys and manipulative experiments in the field. We found that N2 fixation is almost ubiquitous among mosses and that moss identity is consistently an important predictor of associated N2 fixation rates. In subsequent analyses related to C stable isotopes and a reciprocal transplant, we also found a significant interaction between host identity and environment. The strength of the interaction term was typically host specific. As temperature and other abiotic conditions change along with climate and cause changes in moss biomass and diversity, it is critical to incorporate the interaction term into predictions of future N inputs.

• Publisher: ProQuest Dissertations & Theses
• Subject: Biogeochemistry / Ecology
• ISBN: 9798505511831