2023 Undergraduate Research Showcase

Document Type

Student Presentation

Presentation Date

4-21-2023

Faculty Sponsor

Dr. Marie-Anne de Graaff

Abstract

Biofuels from cellulosic bioenergy crops, which include perennial prairie grasses such as switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) pose as a promising potential resource to help mitigate climate change. Ecological sustainability necessitates that growing these crops for bioenergy production promotes soil carbon (C) sequestration, such that their production contributes to removing CO2 from the atmosphere. Soil C sequestration is driven by the quantity of C that plants release into soil and by the quantity of this C that is decomposed by soil microorganisms and subsequently respired back into the atmosphere. Our previous research has ascertained that the quantity of C released into soil differs between switchgrass and big bluestem, but we are uncertain about loss of this C from soil through decomposition processes. This knowledge gap makes it difficult to predict long-term soil C sequestration in these biofuel cropping systems. This project asks if there are significant differences in soil C decomposition dynamics between two grass based biofuels? We are performing a long-term controlled laboratory incubation study with soils derived from switchgrass and big bluestem bioenergy cropping systems which were collected in 2018. The field experiment was initiated in 2008 at the Fermilab National Environmental Research Park, in northeastern Illinois, USA. Soils will be homogenized by sieving, weighed (20g) into airtight incubation chambers, wetted to 60% of water holding capacity and stored in a dark environment at 20oC for 480 days. We will quantify decomposition of soil C by measuring microbial CO2 respiration on days 1, 3, 7, 15, 30, 60, 120, 240, and 480. We will be able to disentangle whether respired C was derived from switchgrass or big bluestem versus the soil C that was present in the soil prior to planting these crops, by using the natural isotopic difference between C4 plants and the soil in which they had grown for 10 years, which was reflective of C3 plants. Understanding differences in the decomposition of C derived from switchgrass and big bluestem will help us determine which one of these species will offer a more promising solution to mitigating climate change.

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