Carbon storage in tidal wetlands of southeast Australia

Kelleway, Jeffrey James

Carbon storage in tidal wetlands of southeast Australia

Kelleway, Jeffrey James

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Publication Type:: Thesis
Issue Date:: 2017

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Field	Value	Language
dc.contributor.author	Kelleway, Jeffrey James
dc.date.accessioned	2017-04-06T00:30:14Z
dc.date.available	2017-04-06T00:30:14Z
dc.date.issued	2017
dc.identifier.uri	http://hdl.handle.net/10453/90253
dc.description	University of Technology Sydney. Faculty of Science.	en_AU
dc.description.abstract	Saltmarshes and mangroves are among the most productive and most at risk ecosystems to the impacts of human activity and climate change, globally. Along with seagrasses, these coastal vegetated ecosystems have been termed ‘blue carbon’ habitats due to their capacity to accumulate and store C. Consequently, there is interest in the processes which govern C accumulation and storage in these ecosystems and their potential to mitigate climatic change. While previous research has indicated high C stocks and accumulation in saltmarshes, there is substantial spatial variability in saltmarsh C. An understanding of the factors behind this variability is required to better inform regional and global C management. Within the study region of southeast (SE) Australia, this thesis therefore aims to: quantify and characterise saltmarsh C stocks; determine the role of geomorphic and vegetation factors in C accumulation and storage; assess variations in quantity and character of C with sediment depth and in relation to environmental change. Analysis of sediment cores collected from 18 sites revealed mean (± SE) belowground C stocks of 164.45 ± 8.74 Mg C ha⁻¹, comparable to global values. Stocks were more than two times higher in fluvial (226.09 ± 12.37 Mg C ha⁻¹) relative to marine (104.54 ± 7.11) geomorphic sites, but did not vary between the saltmarsh vegetation structures tested. Vegetation type, however, was determined to play an important role in surface accumulation with mid- (19 month) and short-term (6 d) measures showing faster C accumulation in upper marsh rush saltmarsh relative to both succulent and grass lower marsh assemblages. Additionally, the encroachment of saltmarsh by high biomass mangrove trees and shrubs was shown to bring about substantial increases in C storage in both biomass and belowground C stocks. While there were general trends of decreasing C content with sediment profile depths, this was not always the case. The preservation of deep mangrove roots (in both contemporary saltmarsh areas as well as areas currently under mangrove encroachment) and/or remnant stable C sources (including char) were both responsible for peaks in C density down profile. This thesis improves our understanding of the processes influencing coastal wetland C storage, with implications for the prioritisation of planning policies and on-ground activities which aim to maximise the benefits from wetland protection and restoration. Such initiatives have the potential to increase overall C storage, thereby presenting a negative feedback to global warming, while also presenting other ecosystem service benefits.	en_AU
dc.format	Thesis (PhD)
dc.language.iso	en_AU	en_AU
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/90253/7/02whole.pdf
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	au.edu.uts.lib/ppc
dc.rights	info:eu-repo/semantics/openAccess
dc.subject	Wetlands.	en
dc.subject	Saltmarshes and mangroves.	en
dc.subject	Impacts of human activity and climate change on ecosystems.	en
dc.subject	‘Blue carbon’ habitats.	en
dc.subject	Climatic change.	en
dc.subject	Southeast Australia.	en
dc.subject	Wetland protection and restoration.	en
dc.title	Carbon storage in tidal wetlands of southeast Australia	en_AU
dc.type	Thesis	en_AU
utslib.copyright.status	open_access

Abstract:

Saltmarshes and mangroves are among the most productive and most at risk ecosystems to the impacts of human activity and climate change, globally. Along with seagrasses, these coastal vegetated ecosystems have been termed ‘blue carbon’ habitats due to their capacity to accumulate and store C. Consequently, there is interest in the processes which govern C accumulation and storage in these ecosystems and their potential to mitigate climatic change. While previous research has indicated high C stocks and accumulation in saltmarshes, there is substantial spatial variability in saltmarsh C. An understanding of the factors behind this variability is required to better inform regional and global C management. Within the study region of southeast (SE) Australia, this thesis therefore aims to: quantify and characterise saltmarsh C stocks; determine the role of geomorphic and vegetation factors in C accumulation and storage; assess variations in quantity and character of C with sediment depth and in relation to environmental change. Analysis of sediment cores collected from 18 sites revealed mean (± SE) belowground C stocks of 164.45 ± 8.74 Mg C ha⁻¹, comparable to global values. Stocks were more than two times higher in fluvial (226.09 ± 12.37 Mg C ha⁻¹) relative to marine (104.54 ± 7.11) geomorphic sites, but did not vary between the saltmarsh vegetation structures tested. Vegetation type, however, was determined to play an important role in surface accumulation with mid- (19 month) and short-term (6 d) measures showing faster C accumulation in upper marsh rush saltmarsh relative to both succulent and grass lower marsh assemblages. Additionally, the encroachment of saltmarsh by high biomass mangrove trees and shrubs was shown to bring about substantial increases in C storage in both biomass and belowground C stocks. While there were general trends of decreasing C content with sediment profile depths, this was not always the case. The preservation of deep mangrove roots (in both contemporary saltmarsh areas as well as areas currently under mangrove encroachment) and/or remnant stable C sources (including char) were both responsible for peaks in C density down profile. This thesis improves our understanding of the processes influencing coastal wetland C storage, with implications for the prioritisation of planning policies and on-ground activities which aim to maximise the benefits from wetland protection and restoration. Such initiatives have the potential to increase overall C storage, thereby presenting a negative feedback to global warming, while also presenting other ecosystem service benefits.

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