Author ORCID Identifier

https://orcid.org/0000-0002-6454-1469

Semester

Summer

Date of Graduation

2024

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Biology

Committee Chair

Edward R Brzostek

Committee Co-Chair

Jonathan R Cumming

Committee Member

Jonathan R Cumming

Committee Member

Jennifer S Hawkins

Committee Member

Charlene N Kelly

Committee Member

Justin M Mathias

Abstract

Nutrient limitation drives forest ecosystem processes by altering net primary production, belowground (C) investments, and microbial activity. As such, the availability of essential macronutrients, such as nitrogen (N) and phosphorus (P), can severely impact plant growth, microbial decomposition, and the strength of plant-microbial interactions. However, our understanding of plant and microbe responses to changing nutrient availability, and the extent to which nutrient availability affects plant-microbe interactions, remains somewhat limited. Therefore, in this dissertation, I aimed to investigate nutrient limitation on a plant, microbe, and plant-microbe interaction level. First, to connect the phenotypic responses of nutrient-limited plants to key molecular mechanisms, I used a multi-omics approach to examine the responses of black cottonwood root and shoot transcriptomes, proteomes, and metabolomes to P deficiency. Next, to examine the susceptibility of potentially vulnerable soil C stocks to regional and global changes, I investigated the effects of removing microbial limitations on soil organic matter (SOM) decomposition in temperate forest soils after long-term N fertilization and subsequent soil C gains. Finally, to understand the responses of plant-microbial interactions to changes in nutrient availability, I compared forest stands dominated by arbuscular mycorrhizal (AM) species to forest stands dominated by ectomycorrhizal (ECM) species in their recovery from long-term N fertilization. In my first chapter, I showed that different cottonwood -omes may show either coordinated or conflicting responses to P limitation, highlighting the importance of multi-omics integration in plant nutrient stress studies. Next, I found that microbial activity remained suppressed in soils after long-term N fertilization even when N-induced limitations on decomposition, such as soil pH, plant C investments, and soil warming, were removed. Finally, I found that AM dominated stands may recover more rapidly than ECM stands after excess N inputs ceased. Given the declining rates of N-deposition and the increasing rates of nutrient limitation of both plants and soil microbes, my dissertation work linking nutrient limitation with plant and microbial traits has important implications for predicting the future of soil C stocks in Eastern temperate forests of the US.

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