Control of “blue carbon” storage by mangrove ageing: Evidence from a 66‐year chronosequence in French Guiana

Abstract

The role of mangroves in the blue carbon stock is critical and requires special focus. Mangroves are carbon-rich forests that are not in steady-state equilibrium at the decadal time scale. Over the last decades, the structure and zonation of mangroves have been largely disturbed by coastal changes and land use conversions. The amount of time since the last disturbance is a key parameter determining forest structure, but it has so far been overlooked in mangrove carbon stock projections. In particular, the carbon sequestration rates among mangrove successional ages after (re)establishment are poorly quantified and not used in large-scale estimations of the blue carbon stock. Here, it is hypothesized that ecosystem age structure significantly modulates mangrove carbon stocks. We analysed a 66-year chronosequence of the aboveground and belowground biomass and soil carbon stock of mangroves in French Guiana, and we found that in the year after forest establishment on newly formed mud banks, the aboveground, belowground and soil carbon stocks averaged 23.56 ± 7.71, 13.04 ± 3.37 and 84.26 ± 64.14 (to a depth of 1 m) Mg C/ha, respectively. The mean annual increment (MAI) in the aboveground and belowground reservoirs was 23.56 × Age and 13.20 × Age Mg C ha year , respectively, and the MAI in the soil carbon reservoir was 3.00 ± 1.80 Mg C ha year . Our results show that the plant carbon sink capacity declines with ecosystem age, while the soil carbon sequestration rate remains constant over many years. We suggest that global projections of the above- and belowground reservoirs of the carbon stock need to account for mangrove age structures, which result from historical changes in coastal morphology. Our work anticipates joint international efforts to globally quantify the multidecadal mangrove carbon balance based on the combined use of age-based parametric equations and time series of mangrove age maps at regional scales.

Jump‐starting coastal wetland restoration: a comparison of marsh and mangrove foundation species

“…Despite an area of overlap at low and medium elevations and likely changes to interactions over time, our study clearly shows that as a foundation species, Spartina provides significantly faster structural development compared to Avicennia after 18 months. Furthermore, regardless of elevation or cover metrics, SOM did not differ overtime, which is not surprising given that other studies have shown that soil development can take decades (Craft et al ; Edwards & Proffitt ; Osland et al ; Walcker et al ). The initial 18‐month period, however, is critical to prevent erosion, maintain desired elevations and hydrology, establish a plant community, and begin to ameliorate abiotic parameters that other species require before they are capable of colonizing a given location.…”

Rapid peat development beneath created, maturing mangrove forests: ecosystem changes across a 25‐yr chronosequence

“…, Walcker et al. ). The production and accumulation of refractory roots is the primary mechanism leading to peat development in mangrove forests, but benthic mat formation can also play a role: turf algae, microbial communities, and accumulated litter and detritus can also contribute to peat formation (McKee ).…”

Effects of Invasive Spartina alterniflora Loisel. and Subsequent Ecological Replacement by Sonneratia apetala Buch.-Ham. on Soil Organic Carbon Fractions and Stock

“…Mangrove structures are time and space dependent and carbon sequestration in mangrove soil can be determined by factors, such as climate and environmental conditions, vegetation community, and age of restored vegetation [8,26]. The age of mangrove is important when quantifying the multi-decadal carbon balance, owing to the fact that the carbon accumulation is more influenced by stand age than other factors [7,26,41]. Our RDA results also showed that the soil POC and TOC positively correlated with mangrove age (Figure 4).…”

“…Short-term restoration of Kandelia obovata Sheue, Liu, and Yong, a mangrove species that is native to southeastern China, did not significantly enhance the soil organic carbon (SOC) stock after 15 years [21]. However, the soil carbon accumulation and stock in mangrove ecosystems can be affected by factors, such as plant species, stand age, environmental conditions, and organic matter retention and export [5,8,14,26]. S. apetala has shown great potential in biomass accumulation and litter production when compared to the native mangroves [27,28].…”