Organic carbon inventories in natural and restored Ecuadorian mangrove forests

Amanda G DelVecchia; John F Bruno; Larry Benninger; Marc Alperin; Ovik Banerjee; Juan de Dios Morales

doi:10.7717/peerj.388

Organic carbon inventories in natural and restored Ecuadorian mangrove forests

PeerJ. 2014 May 22:2:e388. doi: 10.7717/peerj.388. eCollection 2014.

Authors

Amanda G DelVecchia¹, John F Bruno², Larry Benninger³, Marc Alperin⁴, Ovik Banerjee¹, Juan de Dios Morales⁵

Affiliations

¹ Institute for the Environment, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA.
² Department of Biology, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA.
³ Department of Geology, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA.
⁴ Department of Marine Science, The University of North Carolina at Chapel Hill , Chapel Hill, North Carolina , USA.
⁵ Colegio de Ciencias biologicas y ambientales, Universidad San Francisco de Quito , Cumbayá, Diego de Robles y Vía Interoceánica, Quito , Ecuador.

Abstract

Mangroves can capture and store organic carbon and their protection and therefore their restoration is a component of climate change mitigation. However, there are few empirical measurements of long-term carbon storage in mangroves or of how storage varies across environmental gradients. The context dependency of this process combined with geographically limited field sampling has made it difficult to generalize regional and global rates of mangrove carbon sequestration. This has in turn hampered the inclusion of sequestration by mangroves in carbon cycle models and in carbon offset markets. The purpose of this study was to estimate the relative carbon capture and storage potential in natural and restored mangrove forests. We measured depth profiles of soil organic carbon content in 72 cores collected from six sites (three natural, two restored, and one afforested) surrounding Muisne, Ecuador. Samples up to 1 m deep were analyzed for organic matter content using loss-on-ignition and values were converted to organic carbon content using an accepted ratio of 1.72 (g/g). Results suggest that average soil carbon storage is 0.055 ± 0.002 g cm(-3) (11.3 ± 0.8% carbon content by dry mass, mean ± 1 SE) up to 1 m deep in natural sites, and 0.058 ± 0.002 g cm(-3) (8.0 ± 0.3%) in restored sites. These estimates are concordant with published global averages. Evidence of equivalent carbon stocks in restored and afforested mangrove patches emphasizes the carbon sink potential for reestablished mangrove systems. We found no relationship between sediment carbon storage and aboveground biomass, forest structure, or within-patch location. Our results demonstrate the long-term carbon storage potential of natural mangroves, high effectiveness of mangrove restoration and afforestation, a lack of predictability in carbon storage strictly based on aboveground parameters, and the need to establish standardized protocol for quantifying mangrove sediment carbon stocks.

Keywords: Aquaculture; Blue carbon; Carbon sequestration; Carbon storage; Loss-on-ignition; Mangroves.

Grants and funding

Research was funded in part by a Summer Undergraduate Research Fellowship from the Office for Undergraduate Research at the University of North Carolina at Chapel Hill, and a Watts-Hill Award from the Institute for the Environment at the University of North Carolina at Chapel Hill. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.