Abstract
The 2, 4, 6, 8, 10, 12 and 30-year restored mangroves were studied through non-destructive method by measuring their stem diameter and tree height. Two allometric references: (a) stem diameter (D<sub>30</sub>) and (b) combined quadratic stem diameter and tree height (D<sub>30</sub><sup>2</sup>H) were used to estimate aboveground and belowground vegetation carbon stocks. The soil samples were collected from different depth and analysed in laboratory for soil carbon. The objective of this study was to estimate ecosystem carbon stocks of restored mangroves and its sequestration. The growth of restored mangroves induced an increase of tree biomass and a corresponding increase in vegetation carbon stocks from 3.7 MgC ha<sup>-1</sup> at 2-year to 136.8 MgC ha<sup>-1</sup> at 30-years. However, soil carbon stocks among restored mangrove plots spread randomly and didn't follow the sequence of mangrove tree ages. Average (2-30 years) mangrove ecosystem carbon in Northern Sumatra estimated by D<sub>30</sub><sup>2</sup>H allometry (362.0 MgC ha<sup>-1</sup>) was higher than that estimated by D<sub>30</sub> allometry (344.1 MgC ha<sup>-1</sup>). This higher trend was also followed by its carbon sequestration with values of 41.1 MgCO<sub>2</sub>e ha<sup>-1</sup> yr<sup>-1</sup> estimated by D<sub>30</sub><sup>2</sup>H allometry and 31.5 MgCO<sub>2</sub>e ha<sup>-1</sup> yr<sup>-1</sup> estimated by D<sub>30</sub> allometry. It is concluded that the values of ecosystem carbon stock of restored mangroves and its sequestration estimated by combined quadratic stem diameter and tree height (D<sub>30</sub><sup>2</sup>H) are higher than if it is estimated by stem diameter (D<sub>30</sub>). The D<sub>30</sub><sup>2</sup>H value is higher because this allometry calculates the volume of the tree stem, while D<sub>30</sub> allometry only calculates the surface of the stem. The range values of average ecosystem carbon sequestration of this study may be better used as a reference for Afforestation, Reforestation and Re-vegetation (ARR) verification than what has been used as default/conservative values.
Highlights
The concentration of CO2 in atmosphere is predicted to rise by 40 ppm (from 370 ppm in 2000 to 410 ppm in 2025 (IPCC, 2001). [1] In his presentation at the World Blue Carbon Conference in Jakarta mentioned that the CO2 concentration in atmosphere was detected around 400 ppm in 2015 and is predicted to continue increasing to 425 ppm by 2025
The growth of stem diameter in this study was higher than Rhizophora mangle stem (0.33 cm yr-1) growing at exposed sea tides in Braganca Peninsula, Northern Brazil [7] in which the stem diameter growth was only 0.12 cm yr-1 when a monthly rainfall
Belowground vegetation carbon stocks of 2-30 year restored mangroves estimated by D30 and D302H allometries increased with increasing age of trees (Annex 7), with exception of the 6-year (9.5 MgC ha-1) is less than the 4-years (10.1 MgC ha-1)
Summary
The concentration of CO2 in atmosphere is predicted to rise by 40 ppm (from 370 ppm in 2000 to 410 ppm in 2025 (IPCC, 2001). [1] In his presentation at the World Blue Carbon Conference in Jakarta mentioned that the CO2 concentration in atmosphere was detected around 400 ppm in 2015 and is predicted to continue increasing to 425 ppm by 2025. The objective of this study was to estimate ecosystem carbon stocks of serial age restored mangroves and its sequestration that estimated by two different allometries.
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