Browsing by Author "Owers, CJ"

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    Spatial variability of coastal wetland carbon
    (Coastal & Estuarine Research Federation, 2017-12-09) Owers, CJ; Rogers, K; Mazumder, D; Woodroffe, CD
    Blue carbon ecosystems, particularly mangrove and saltmarsh, sequester more atmospheric carbon per unit area than any other natural system in the world. Variation in above and below-ground carbon storage, that relate to the expression of environmental processes across wetland landscapes, are yet to be adequately quantified. We proposed that vegetation structure was a significant control on some of the spatial variation in carbon storage, and that this was a function of the dynamic nature of vegetation change at a site. Initially vegetation structural complexity was delineated using innovative remote sensing techniques. Above-ground biomass of mangrove and saltmarsh were quantified by developing region-specific allometric relationships. Cores were extracted from wetlands on the basis of delineated vegetation complexity to characterise the variation in carbon storage within sediments to 2m depth. We found that above-ground biomass varied with vegetation structural complexity, such that tall mangrove contribute more than 65% of above-ground biomass at some sites. The influence of vegetation structure on below-ground carbon storage was only detected to a depth of 50 cm, however >50% of below-ground carbon exists below this depth. Spatial variation in below-ground carbon storage is primarily due to sedimentary factors associated with estuary evolution and geomorphic setting and the influence these factors have on vegetation distribution over the mid-late Holocene. Current approaches to carbon stock assessment, based on extrapolating mean values of carbon storage to national and global scales, oversimplify carbon stock variation and may significantly under or overestimate carbon storage. Systematic approaches to carbon stock assessments characterising carbon storage variation at various scales will provide required confidence necessary for carbon markets.
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    Spatial variation in carbon storage: a case study for Currambene Creek, NSW, Australia
    (Coastal Education and Research Foundation & Journal of Coastal Research, 2016-03-01) Owers, CJ; Rogers, K; Mazumder, D; Woodroffe, CD
    Quantifying carbon storage in coastal wetland environments is important for identifying areas of high carbon sequestration value that could be targeted for conservation. This study combines remote sensing and sediment analysis to identify spatial variation in soil carbon storage for Currambene Creek, New South Wales, Australia to establish whether vegetation structure influences soil carbon storage in the upper 30 cm. Wetland vegetation was delineated to capture structural complexity within vegetation communities using Light detection and ranging (Lidar) point cloud data and aerial imagery with an object-based image analysis approach. Sediment cores were collected and analysed for soil carbon content to quantify below-ground carbon storage across the site. The total soil carbon storage in the upper 30 cm for the wetland (59.6 ha) was estimated to be 3933 ± 444 Mg C. Tall mangrove were found to have the highest total carbon storage (1420 ± 198 Mg C), however are particularly sensitive to changes in sea-level as they are positioned lowest in the intertidal frame. Conservation efforts targeted at protecting areas of high carbon sequestration, such as the tall mangrove, will lead to a greater contribution to carbon mitigation efforts. © Coastal Education and Research Foundation, Inc. 2016
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    Temperate coastal wetland near-surface carbon storage: spatial patterns and variability
    (Elsevier B. V., 2020-04-05) Owers, CJ; Rogers, K; Mazumder, D; Woodroffe, CD
    Carbon mitigation services provided by coastal wetlands are not spatially homogeneous, nevertheless are commonly described on the basis of vegetation distribution within the intertidal zone. Distribution of mangrove and saltmarsh varies in response to frequency of tidal inundation, resulting in environmental gradients in edaphic factors that influence vegetation structure, and subsequently affect sedimentary carbon additions by vegetation and carbon losses by decomposition. Current sampling approaches and reporting do not adequately account for variability of carbon storage within a wetland, and assessments need to capture spatial variation associated with carbon storage to improve estimates of potential carbon mitigation services by natural ecosystems. This study quantifies the variation in near-surface carbon storage (i.e. upper 30 cm) across an intertidal gradient using a stratified sampling approach that recognises vegetation structure. Vegetation distribution and structure, as well as sedimentary controls on carbon content, explained variation in carbon storage. Saltmarsh near-surface carbon storage varied considerably between structural form. This was less evident for mangrove structural forms (i.e. tall, shrub, dwarf), which may be due to mangrove roots extending to depths beyond 30 cm. Sedimentary characteristics correlated with carbon content, demonstrating considerable influence on near-surface carbon storage within a wetland. The principal finding of this study was that variation within a wetland corresponds to the variation between sites. Stable carbon isotopes offer a means to identify previous vegetation contributions to sediment, associated with an earlier stage of wetland development, likely reflecting previous environmental conditions. A stratified sampling approach that recognises vegetation structure provides the capacity to account for variability of carbon within a wetland that is inadequately described by current sampling protocols. © 2020 Elsevier B.V.