Date of Award

5-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Gregory Pope

Committee Member

Jennifer Callanan

Committee Member

Joshua Galster

Abstract

Fire is a significant environmental perturbation to forests where vegetation transforms from biomass to ash, potentially releasing stored chemical elements to soils. While much research acknowledges variation in ash composition among different vegetation types (grasses, trees, shrubs and vines), less has focused on interspecific variation among trees and the elemental influx soils receive. Therefore, this research sets out to: (1) identify major, trace, and rare earth element (REE) concentrations by inductively coupled plasma mass spectroscopy (ICP-MS) in ash derived from fifteen tree species, (2) determine likely elemental enrichment to post-fire soils, and (3) assess variability in ash chemistry and color among different tree species. Traditional color assessments classify ash on a grey scale, but ash samples in this study had distinct color hues and coalesced in two groups. A significant negative correlation existed between SiO2 and CaO among all ash samples. Ash samples were more concentrated in MnO, MgO, CaO, K2O, P2O5, Ni, Cu, Zn, Sr and Ba than soil, as well as in all REE’s (La through Lu). Ash from Populus grandidentata, Betula lenta, and B. alleghaniensis had greatest enrichment in Zn and Ba while ash from Fraxinus americana had elevated Cu and Sr. This clearly shows significant chemical variability in ash, possibly derived from preferential element uptake by certain tree species to satisfy physiologic and metabolic nutrient requirements. All REE’s were 10-15 times greater in ash than soils. Little preferential uptake of any one REE exists as trees might passively sequester all these elements together, bound to essential nutrients. This research provides an important understanding of the complexities surrounding fire’s impact on biogeochemical cycling.

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