Semester

Fall

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Biology

Committee Chair

Dr. Edward Brzostek

Committee Co-Chair

Dr. Ember Morrissey

Committee Member

Dr. William Peterjohn

Committee Member

Dr. Justin Mathias

Abstract

Bioenergy can help mitigate climate change by providing a carbon-neutral fuel source. However, multiple challenges exist to achieving carbon neutrality including converting lignocellulosic materials to fuel and enhancing soil C sequestration during the growth of the feedstocks. To address these challenges, there have been recent efforts to genetically modify feedstocks to produce more energy dense oils that increase fuel conversion efficiency and to cultivate deep-rooted perennial feedstocks that can enhance soil C storage. However, the C consequences and efficacy of these solutions remain largely uncertain.

To examine the C consequences of enhancing oil content of bioenergy feedstocks, I examined the impact of Sugarcane litter decomposition on soil carbon (C) formation and loss and determined if the genetic modifications to produce Oilcane alter these dynamics. To do this, I traced the fate of Sugarcane and Oilcane litter in protected and unprotected soil C pools. I found that both crops led to net soil C gains dominated by an accumulation of the litter as particulate organic carbon (POC) and that the genetic modifications to Oilcane did not substantially alter soil C dynamics. To investigate the efficacy of deep-rooted perennial feedstocks to build soil C, I linked depth gradients in root biomass with microbial activity and soil C stocks down to 1 meter to determine the predictors of soil C and soil C fractions with depth. I also performed a lab experiment where I examined differences between depths in the ability of simple C inputs to prime or build soil C. In the field, I excavated quantitative 1 m deep soil pits under 20-year-old Miscanthus plots and quantified, fine root biomass, total soil C, mineral-associated organic C (MAOC), particulate organic C (POC), microbial respiration, net nitrogen cycling, and enzyme activities. In the lab, I experimentally followed the fate of 13C labeled glucose into soil C fractions at each depth. I found that soil C and MAOC declined with depth and were best predicted by fine root biomass, representing inputs, microbial respiration, representing losses, and NAG activity, representing the recycling of microbial necromass. I also found that deep soils had a greater potential to minerally stabilize new simple C inputs than shallow soils due to the C inputs having a greater stabilizing than priming effect below 50cm. Collectively, my research shows that sustainable bioenergy solutions such as lipid enhanced Oilcane and growing deep-rooted perennial feedstocks may lead to enhanced soil C.

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