Date of Award
2024
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Doctor of Philosophy
School
School of Science
First Supervisor
David Blake
Second Supervisor
Pierre Horwitz
Third Supervisor
Mary M. Boyce
Fourth Supervisor
Andrew Bath
Fifth Supervisor
Konrad Miotlinski
Abstract
Fire in forested catchments significantly alters organic matter fluxes and dissolved organic matter (DOM) is one of the key fluxes, which has implications for water quality. DOM is ubiquitous in aquatic ecosystems with predominant forms such as organic carbon, nitrogen, phosphorus and sulphide. Literature reports that DOM produced under fire – pyrogenic DOM (PyDOM) - is different from non-fire DOM both in terms of DOM concentration (quantity) and composition (quality). Thus, understanding natural and anthropogenic processes affecting PyDOM abundance and composition is critical for tracing its persistence and ecosystem uptake in the post-fire environment, particularly to reduce risk to water quality. The current literature rarely investigates the linkage between fire regimes – burn severity, fire intensity and fire frequency, and post-fire organic contaminants. This study undertook three different approaches to characterize PyDOM from Jarrah forest (in southwestern Australia): (i) in the laboratory by heating soil and litter of different fire histories at different temperatures followed by extracting water soluble PyDOM; (ii) in a plot-scale field experiment which included simulated rainfall and collecting runoff following two different types of fires (a wildfire and a management fire (prescribed burn)); and (iii) by sampling water in intermittent streams affected by a management fire. The laboratory and the small-scale field experiments showed that compared to high burn temperatures (500°C), low (250°C) and moderate (350°C) generated higher DOM quantity and more aromatic PyDOM. At higher burn temperatures soil generated more aromatic PyDOM than litter. In-situ plot experiments also showed prescribed burn produced higher concentration of DOM than wildfire, further supporting the lab findings where low/moderate burn severity poses a risk to water quality. However, in-situ post-fire PyDOM analysis in natural streams showed DOM to be more labile, less aromatic and low molecular weight DOM while the spike in DOM quantity was only observed briefly. While the risk of aromatic DOM generated from wildfire is well known, our results highlight risks of labile PyDOM to water quality in short-term.
DOI
10.25958/g91p-9605
Access Note
Access to this thesis is embargoed until 14th May 2026
Access to chapters 4, 5 & 6 of this thesis is not available
Recommended Citation
Tshering, K. (2024). Understanding fire transformed dissolved organic matter for water quality in forested catchments. Edith Cowan University. https://doi.org/10.25958/g91p-9605