Date of Award

Summer 8-31-2020

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Forest Resources

Advisor

Daniel Hayes

Second Committee Member

Aaron Weiskittel

Third Committee Member

Ivan Fernandez

Additional Committee Members

Nathaniel Brunsell

Shawn Fraver

Abstract

The terrestrial biosphere plays an important role in the global carbon cycle, and disturbance fire and climate extreme drought have strong direct and indirect impacts on the carbon fluxes. In addition, the lateral dissolved organic carbon (DOC) flux from soils to inland waters represents an important component of the terrestrial biosphere carbon cycle.

Fires play an important role in the terrestrial biosphere carbon cycle, not only through direct carbon release but also contributing to a potential long-term storage as pyrogenic carbon (PyC). PyC is formed through fires, and because it may resist further biological and chemical degradation, is more stable in soil and sediment than original biomass. Chapter 1 presents estimates of global PyC production.

Worldwide, droughts are becoming more frequent with increasing weather extremes, resulting in substantial impacts on land-atmosphere carbon exchange. However, the patterns of carbon fluxes in response to droughts differ across biomes and time scales due to variations in the adaptation and resilience of different plant species, soil properties, and available water and nutrients. In chapter 2, I examined the biome-scale spatial patterns in the response of carbon fluxes to droughts at different time scales.

The export of dissolved organic carbon (DOC) from a watershed is a critical flux of terrestrial biosphere carbon cycles. Advanced understanding of how environmental factors drive the temporal patterns of this biogeochemical process and their relative magnitudes of impacts is necessary to accurately model and evaluate terrestrial carbon storage and fluxes. In chapter 3, I examined the impacts of environmental factors on the temporal patterns of DOC export and their relative magnitudes, as well as the autocorrelation of DOC export. The lateral flux of dissolved organic carbon (DOC) from soils to inland waters and ultimately delivered to the ocean represents a fundamental component of the global carbon cycle. To estimate the production, delivery and potential fates of DOC flux from terrestrial through aquatic ecosystems to the ocean, I developed a process-based terrestrial-aquatic DOC fluxes model (TAF-DOC), which has the ability to estimate the spatial and temporal dynamics of DOC flux through incorporating various environmental factors.

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