COS 67-5 - Belowground traits lack response to chronic nitrogen addition in tallgrass prairie

Tuesday, August 16, 2022

11:00 AM – 11:15 AM EDT

Location: 514A

Presenting Author(s)

Sarah L. Gora

Master's Student
University of North Carolina at Greensboro
Greensboro, North Carolina, United States

Slides (PDF)

Coauthor(s)

MA

Meghan L. Avolio

Assistant Professor
Johns Hopkins University
Baltimore, MD, United States
KK

Kimberly Komatsu

Senior Scientist
Smithsonian Environmental Research Center
Edgewater, MD, United States
Kevin Wilcox, PhD

Program in Ecology, University of Wyoming, United States
SK

Sally E. Koerner, PhD

Assistant Professor
University of North Carolina Greensboro
Greensboro, North Carolina, United States

Background/Question/Methods

Anthropogenic effects including nitrogen deposition are pervasive, altering nutrient limitation with cascading consequences for biodiversity and ecosystem function. Ecosystem function can be altered through changes in community composition, as well as through changes in plant traits. Functional plant traits are the mechanism that explains how changes at the organismal level lead to changes in ecosystem function. This project investigates the effect of chronic nitrogen addition on plant traits with a focus on belowground traits. Belowground traits remain underexplored due to the unique challenges of studying them, yet are critical for understanding important processes such as carbon sequestration. Specifically, this project takes advantage of three long-term and on-going nitrogen addition experiments at the Konza Long-Term Ecological Research Site in Manhattan, Kansas. We collected plant functional traits of five common plant species in the tallgrass prairie community over a six-week data collection period, having sampled each species at its peak flowering time. Here we explore how nitrogen addition affects (1) individual functional traits, (2) functional diversity, and (3) above-belowground trait tradeoffs for all five species. Understanding the relationship between plant traits and certain variables like nitrogen addition will help improve our ability to predict future response to global change drivers.

Results/Conclusions

Interestingly, we found that long-term nitrogen additions had stronger and more pervasive effects on aboveground traits with little impact on belowground traits. Of the six belowground root traits measured (SRL, Root Biomass, Maximum Root Diameter, Mean Root Diameter, Root %Carbon and Root %Nitrogen), only %N of root tissue was altered, increasing with N addition in all five species (Dichanthelium oligosanthes, Ambrosia psilostachya, Solidago missouriensis, Andropogon gerardii and Sorghastrum nutans). In contrast, all aboveground traits were responsive to N additions in at least one species. Additionally, for aboveground traits, D. oligosanthes was more responsive to N addition than the other species. When looking holistically at the suite of traits for a species in multivariate space, we saw that the nitrogen treatments caused significant differences in trait composition for D. oligosanthes and A. psilostachya, primarily driven by Plant Height while also increasing functional diversity in those same species. Significant trait correlations in A. psilostachya show tradeoffs between above and belowground traits in response to N additions but most other species did not. Overall, our results suggest that belowground traits are less responsive to chronic N addition, and that belowground function may be more resistant to N addition effects compared to aboveground functions.