Date of Award

2025

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Forest Science (PhD)

Administrative Home Department

College of Forest Resources and Environmental Science

Advisor 1

Andrew Burton

Committee Member 1

Carsten Külheim

Committee Member 2

Amy Marcerelli

Committee Member 3

Erika Hersch-Green

Abstract

Sequestration of carbon (C) in forests means that the C is stored in the ecosystem and not emitted to the atmosphere, thus slowing the accumulation of greenhouse gases and mitigating the acceleration of manmade climate change. Quantifying the pools and fluxes of C in forests is therefore of considerable interest to landowners, policy makers, and scientists.

Decomposition is an ecological process central to the movement of C through ecosystems. This dissertation uses several techniques to help determine the factors influencing the speed of decomposition and long-term fate of decomposed plant material. In Chapter Two, phospholipid fatty acid analysis was used to assess microorganism populations in soils from experimental forest plots heavily amended by simulated anthropogenic nitrogen (N) deposition. Decomposition rates in the forests were suppressed during active N loading due to the alteration of the soil microbial community (Propson et al. 2024). Measurements made after three years of recovery following cessation of N loading found gradual recovery of microorganisms and their associated ecosystem processes. Chapters Three and Four detail my work on the FACE Wood Decomposition Experiment (FWDE), a long-term project that measured decomposition of three log species placed in nine forest sites across the continental United States. Fungal communities in logs from one site were measured to look for patterns in fungal species distribution or assemblages. No significant differences were found in fungal communities by species or orientation of logs after eleven years of decomposition, indicating a possible stronger influence of physical location than wood chemistry at advanced stages of decay. I further examined the movement of log C into soil via a unique 13C signature present in the decomposing logs. Soil samples from beneath and beside the logs to a depth of 50 cm were taken. I found that decomposing coarse woody debris (CWD) contributes measurably to the overall soil C stocks with 0.5% to nearly 40% of log C residing in mineral soil after ten years, and that the patterns and residence time of C from wood depended upon climate, soil texture, and specific log attributes. Sites with higher mean annual temperature and precipitation had faster log decomposition, but also less C storage in soils. Colder and dryer sites showed more C retained in intact wood on the surface as well as in soils beneath the dead logs. Soils with a high percentage of sand retained less log C than those with more silt and clay. Horizontal logs contributed more C to the soil than upright snags, and larger logs naturally decayed more slowly than small ones, slowing their inputs to the soil. Together, this dissertation sheds light on the process of decomposition and the long-term influences of dead wood on soil C sequestration.

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

Download

Available for download on Thursday, July 30, 2026

Share

COinS