THE IMPACT OF DEPTH, CANE VARIETY, AND IRRIGATION TREATMENTS ON TWELVE BIOLOGICAL SOIL PARAMETERS RELATING TO CARBON STORAGE IN A HAWAIIAN OXISOL

Richardson, Daniel

THE IMPACT OF DEPTH, CANE VARIETY, AND IRRIGATION TREATMENTS ON TWELVE BIOLOGICAL SOIL PARAMETERS RELATING TO CARBON STORAGE IN A HAWAIIAN OXISOL

Files

Richardson_hawii_0085O_10650.pdf (3.18 MB)

Date

2020

Authors

Richardson, Daniel

Advisor

Crow, Susan

Department

Natural Resources and Environmental Management

Abstract

Hawai‘i has set the ambitious goals of 100% renewable energy use and carbon neutrality by 2045. Bioenergy cropping systems, depending on land management factors, have the potential to provide multiple ecosystem services addressing these challenges through the creation of renewable fuels and the potential long-term sequestration of organic carbon in the soil- the largest terrestrial carbon pool. However, the mechanisms driving long-term carbon storage are complex and not perfectly understood. Litter and root inputs undergo constant microbial transformations and soil interactions which ultimately determine how long carbon will be stored terrestrially or respired back into the atmosphere. Perennial grasses are a bioenergy option with the potential to build soil carbon stocks due to their relatively robust root networks. This study takes place on the intensively managed, former Hawai‘i Commercial and Sugar (HC&S) lands and analyzes biological soil parameters within C4 grass root profiles grown for bioenergy purposes, comparing irrigation treatments, cane variety, and four soil depths based on root distribution. Several soil parameters associated with long-term soil carbon storage were measured in this study including: inputs in the form of total organic carbon and living and dead root biomass; carbon manipulators in the form of soil microbial communities and extracellular enzymes, and; carbon quality as measured by a 90-day laboratory incubation of soils. Microbial communities, enzyme concentrations, and total organic carbon percentages decreased significantly with depth. Microbial community structure was also impacted, with surface depths showing greater abundance of fungi compared to subsoils which were almost exclusively bacterially dominated. Significantly less carbon was mineralized in the subsoil samples compared to surface soils suggesting a greater carbon storage potential as depth increases. Quantifying the mechanisms behind carbon storage and using wholistic sampling techniques (not just the plow layer) in soils located on marginal or abandoned agricultural lands in Hawai‘i have shed light on factors impacting soil carbon sequestration. Better understanding of these and other patterns may help to bring Hawai‘i closer to its goal of 100% carbon neutrality.

Keywords

Soil sciences, Agriculture, Microbiology, Enzymes, Oxisol, PLFA, Roots, Soil Carbon, Sugarcane

URI

http://hdl.handle.net/10125/69027

Extent

59 pages

Rights

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Collections

M.S. - Natural Resources and Environmental Management

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