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Climate change effects on soil carbon dynamics: CO2 flux from water-repellent and fire-affected soils / CARMEN SANCHEZ-GARCIA

Swansea University Author: CARMEN, SANCHEZ-GARCIA

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DOI (Published version): 10.23889/SUthesis.57470

Abstract

Climate change is increasing the frequency and intensity of droughts and this is expected to enhance the development of soil water repellency: a very common property of both dry and fire-affected soils. In some regions climate change is also increasing the occurrence and severity of wildfires. Large...

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Published: Swansea 2021
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Urbanek, Emilia ; Doerr, Stefan
URI: https://cronfa.swan.ac.uk/Record/cronfa57470
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Abstract: Climate change is increasing the frequency and intensity of droughts and this is expected to enhance the development of soil water repellency: a very common property of both dry and fire-affected soils. In some regions climate change is also increasing the occurrence and severity of wildfires. Large pulses of CO2 flux from soil to the atmosphere caused by heavy rainfall events (i.e. the Birch effect) can contribute substantially to annual C emissions from soils. However, the effect of the first rainfall after a drought on water-repellent soils and the first post-fire rainfall event on soil CO2 flux remain poorly understood. To address these knowledge gaps this research focuses on: i) investigating the effects of soil water repellency on the CO2 pulse after wetting; ii) improving understanding of the effects of vegetation fires on post-fire soil CO2 flux; and iii) studying the role of ash produced naturally during vegetation fires in post-fire soil CO2 flux. The results from this research clearly indicate that water repellency is a key controller of the CO2 pulse following the wetting of dry and fire-affected soils. Both the amount of water and the increase in soil water content after wetting are used as indicators of the magnitude of the Birch effect, but this research suggests that their application in water-repellent soils should be re-evaluated. The findings presented here challenge the conceptual notion that the Birch effect is comprised of one large pulse of CO2 and highlights the need to incorporate high-frequency observations during the period following wetting to capture the entire CO2 response to wetting. The results from this thesis suggest that ash is a key player in post-fire C fluxes and should be considered in post-fire C investigations in order to make realistic predictions of the impacts of vegetation fires on C dynamics.
Item Description: A selection of third party content is redacted or is partially redacted from this thesis due to copyright restrictions.ORCiD identifier https://orcid.org/0000-0001-6753-243X
Keywords: soil, carbon, climate change, water repellency, hydrophobicity, wildfire, ash, drying-wetting, Birch effect, CO2 pulse
College: College of Science