Thirty-Year Repeat Measures of Mangrove Above- and Below-Ground Biomass Reveals Unexpectedly High Carbon Sequestration
Mangrove ecosystems store large quantities of organic carbon for long periods of time. This study explores organic carbon stock change through the first comparative study of radiometric analysis and repeat field measures over a multi-decadal period in a mangrove system. Examining one tall gallery forest of Avicennia marina, and an adjacent interior scrub mangrove of mixed Avicennia marina and Aegiceras corniculatum, radiometric analysis estimated a soil organic carbon accumulation rate of 4.3 ± 0.6 Mg C ha−1 y−1 in the tall gallery forest and 2.2 ± 0.5 Mg C ha−1 y−1 in a stunted mangrove. Repeat measures of root carbon separated by 30 years estimated an increase of 5.06 Mg C ha−1 y−1 in the tall forest and 6.63 Mg C ha−1 y−1 in the stunted forest—suggesting an underestimate of carbon accumulation by radiometric dating of 15% and 67% in the tall and stunted forest, respectively. A higher carbon stock in the interior forest was attributed to root mass increase, associated with landward mangrove encroachment. Extrapolated to the entire region of NSW we estimate that mangrove encroachment has contributed at least about 1.8 Tg C sequestration over the 70 years for which this has been observed in New South Wales, Australia.
Keywordsblue carbon mangrove stock change organic carbon
We thank Jennifer Van Holsten and Sabika Maizma at the Australian Nuclear Science and Technology Organisation (ANSTO) for their assistance with the radiometric analysis. Nicole Cormier made valuable comments on an earlier draft of the manuscript. The analysis was funded by an ANSTO research grant and AINSE Honours award to KL. Figure 8 incorporates content from Christine Thurbur IAN Image Library (ian.umces.edu), used with permission.
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