Organic Carbon Stabilization Mechanisms in Mangrove Soils: A Review

Despite the recognized organic carbon (OC) sequestration potential of mangrove forests, the ongoing climate change and anthropogenic disturbances pose a great threat to these ecosystems. However, we currently lack the ability to mechanically understand and predict the consequences of such impacts, primarily because mechanisms underlying OC stabilization in these ecosystems remain elusive. Research into OC stabilization has focused on terrestrial soils and marine sediments for decades, overlooking the vegetated coastal ecosystems including mangroves. In terrestrial soils and marine sediments, it is widely accepted that OC stabilization is the integrated consequence of OM’s inherent recalcitrance, physical protection, and interactions with minerals and metals. However, related discussion is rarely done in mangrove soils, and recalcitrance of roots and high net ecosystem production (high primary production and low heterotrophic respiration) have been considered as a primary OC sequestration mechanism in mangrove peat and mineral soils, respectively. This review presents the available information on the mechanisms underlying OC stabilization in mangrove soils and highlights research questions that warrant further investigation. Primary OC stabilization mechanisms differ between mangrove peat and mineral soils. In mangrove mineral soils, physico-chemical stabilization processes are important, yet grossly understudied OC stabilization mechanisms. In mangrove peat, recalcitrance of mangrove roots and the inhibition of phenoloxidase under the anoxic condition may be the primary OC stabilization mechanisms. Salinity-induced OC immobilization likely plays a role in both type of soils. Finally, this review argues that belowground production and allochthonous inputs in mangrove forests are likely underestimated. More studies are needed to constrain C budgets to explain the enigma that mangrove OC keeps accumulating despite much higher decomposition (especially by large lateral exports) than previously considered.

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Beyond burial: lateral exchange is a significant atmospheric carbon sink in mangrove forests

Biology Letters ◽

10.1098/rsbl.2018.0200 ◽

2018 ◽

Vol 14 (7) ◽

pp. 20180200 ◽

Cited By ~ 35

Author(s):

Damien T. Maher ◽

Mitchell Call ◽

Isaac R. Santos ◽

Christian J. Sanders

Keyword(s):

Organic Carbon ◽

Dissolved Inorganic Carbon ◽

Carbon Sink ◽

Blue Carbon ◽

Mangrove Forests ◽

Carbon Framework ◽

Sequestration Potential ◽

Seagrass Ecosystems ◽

Atmospheric Carbon

The blue carbon paradigm has evolved in recognition of the high carbon storage and sequestration potential of mangrove, saltmarsh and seagrass ecosystems. However, fluxes of the potent greenhouse gases CH 4 and N 2 O, and lateral export of carbon are often overlooked within the blue carbon framework. Here, we show that the export of dissolved inorganic carbon (DIC) and alkalinity is approximately 1.7 times higher than burial as a long-term carbon sink in a subtropical mangrove system. Fluxes of methane offset burial by approximately 6%, while the nitrous oxide sink was approximately 0.5% of burial. Export of dissolved organic carbon and particulate organic carbon to the coastal zone is also significant and combined may account for an atmospheric carbon sink similar to burial. Our results indicate that the export of DIC and alkalinity results in a long-term atmospheric carbon sink and should be incorporated into the blue carbon paradigm when assessing the role of these habitats in sequestering carbon and mitigating climate change.

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Spatial Variability and Relationship of Mangrove Soil Organic Matter to Organic Carbon

Applied and Environmental Soil Science ◽

10.1155/2017/4010381 ◽

2017 ◽

Vol 2017 ◽

pp. 1-9

Author(s):

Pasicha Chaikaew ◽

Suchana Chavanich

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Spatial Variability ◽

Conversion Factor ◽

Surface Soil ◽

Mangrove Forests ◽

Mangrove Soil ◽

Subsurface Soil ◽

Mangrove Soils ◽

Relationship Of

Degradation and destruction of mangrove forests in many regions have resulted in the alteration of carbon cycling. Objectives of this study were established to answer the question regarding how much soil organic carbon (SOC) is stored in wetland soils in part of the upper northeastern Gulf of Thailand and to what extent SOC is related to organic matter (OM). A total of 29 soil samples were collected in October 2015. Soil physiochemical analyses followed the standard protocol. Spatial distributions were estimated by a kriging method. Linear regression and coefficient were used to determine the suitable conversion factor for mangrove soils. The results showed that surface soil (0–5 cm) contained higher SOC content as compared to subsurface soil (5–10 cm). Considering a depth of 10 cm, this area had a high potential to sequester carbon with a mean ± standard deviation of5.59±2.24%. The spatial variability of OM and SOC revealed that organic matter and carbon decreased with the distance from upstream areas toward the gulf. Based on the assumption that OM is 50% SOC, the conversion factor of 2 is recommended for more accuracy rather than the conventional factor of 1.724.

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Fusarium Species in Mangrove Soil in Northern Peninsular Malaysia and the Soil Physico-Chemical Properties

Microorganisms ◽

10.3390/microorganisms9030497 ◽

2021 ◽

Vol 9 (3) ◽

pp. 497

Author(s):

Wafa S. Mohamed Zubi ◽

Masratul Hawa Mohd ◽

Nik Mohd Izham Mohamed Nor ◽

Latiffah Zakaria

Keyword(s):

Plant Pathogens ◽

Soil Analysis ◽

Fusarium Species ◽

Chemical Properties ◽

Peninsular Malaysia ◽

Mangrove Forests ◽

Human Pathogens ◽

Mangrove Soil ◽

Physico Chemical ◽

Mangrove Soils

Fusarium genus comprises important saprophytic and phytopathogenic fungi and is widespread in nature. The present study reports the occurrence of Fusarium spp. in soils from two mangrove forests in northern Peninsular Malaysia and analyzed physico-chemical properties of the mangrove soil. Based on TEF-1α sequences, nine Fusarium species were identified: Fusarium solani species complex (FSSC) (n = 77), Fusarium verticillioides (n = 20), Fusarium incarnatum (n = 10), Fusarium proliferatum (n = 7), Fusarium lateritium (n = 4), Fusarium oxysporum (n = 3), Fusarium rigidiuscula (n = 2), Fusarium chlamydosporum (n = 1), and Fusarium camptoceras (n = 1); FSSC isolates were the most prevalent. Phylogenetic analysis of the combined TEF-1α and ITS sequences revealed diverse phylogenetic affinities among the FSSC isolates and potentially new phylogenetic clades of FSSC. Soil analysis showed varied carbon content, pH, soil moisture, and salinity, but not nitrogen content, between sampling locations. Regardless of the physico-chemical properties, various Fusarium species were recovered from the mangrove soils. These were likely saprophytes; however, some were well-known plant pathogens and opportunistic human pathogens. Thus, mangrove soils might serve as inoculum sources for plant and human pathogenic Fusarium species. The present study demonstrates the occurrence of various Fusarium species in the extreme environment of mangrove soil, thereby contributing to the knowledge on species diversity in Fusarium.

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Tree biomass and soil carbon stocks of a mangrove ecosystem on the Egyptian-African Red Sea coast

Fundamental and Applied Limnology / Archiv für Hydrobiologie ◽

10.1127/fal/2020/1240 ◽

2020 ◽

Vol 193 (3) ◽

pp. 239-251 ◽

Cited By ~ 2

Author(s):

Abdelwahab A. Afefe ◽

Mohamed S. Abbas ◽

Amira Sh. Soliman ◽

Abdel-Hamid A. Khedr ◽

El-Bialy E. Hatab

Keyword(s):

Carbon Sequestration ◽

Organic Carbon ◽

Carbon Content ◽

Mangrove Ecosystem ◽

Organic Carbon Content ◽

Mangrove Forests ◽

Tree Biomass ◽

Mangrove Species ◽

Carbon Sequestration Potential ◽

Sequestration Potential

Mangroves are key ecosystems in strategies addressing the mitigation of climate change through carbon storage in several countries around the world. The main objective of this study is to quantify the carbon storage (above- and below-ground) in the biomass and sediment of mangrove forests (Avicennia marina and Rhizophora mucronata), as well as to estimate the carbon sequestration potential in the Gebel Elba Protected Area along the Egyptian–African Red Sea Coast. The mean recorded soil bulk density in both mangrove species was 1.16 g cm–3, while the recorded mean soil organic carbon (SOC) content was 34.95 g C kg–1. The total mean SOC content was statistically higher in A. marina stands (39.66 g C kg–1) than in R. mucronata stands (33.15 g C kg–1 ). The total mean SOC density for A. marina and R. mucronata amounts to 40.60 kg C m–3. We recorded the carbon sequestration rate of mangrove forests in Egypt as 11.36 g C m–2 year–1 and the total carbon sequestration potential as 5.97 Gg C year–1. The average single tree biomass was notably highly variable between different mangrove species and sites, with a total average tree biomass of 164.8 and 43.7 kg tree–1 for A. marina and R. mucronata, respectively. The results show that the average total tree carbon content is 74.3 and 18.0 kg tree–1 for A. marina and R. mucronata, respectively. While the recorded tree below-ground biomass was 54.1 and 32.6 kg tree–1, and above-ground biomass was 110.7 and 11.1 kg tree–1 for A. marina and R. mucronata, respectively. The recorded average biomass per hectare of mangrove was 74997.1 and 22536.8 kg for A. marina and R. mucronata, respectively. Moreover, the average total tree carbon content per hectare was 33782.3 and 9304.7 kg for A. marina and R. mucronata, respectively. However, for Egypt mangroves (525 ha), the total organic carbon content amounts to 17.73 Gg C for biomass and 5.97 Gg C year–1 for soil, with total of 23.7 Gg C of organic carbon content storage in the mangrove ecosystem in Egypt.

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Responses of microbial activity to carbon, nitrogen, and phosphorus additions in forest mineral soils differing in organic carbon content

Biology and Fertility of Soils ◽

10.1007/s00374-021-01545-5 ◽

2021 ◽

Vol 57 (4) ◽

pp. 513-521

Author(s):

Veronika Jílková ◽

Kateřina Jandová ◽

Jaroslav Kukla

Keyword(s):

Organic Carbon ◽

Carbon Content ◽

Microbial Activity ◽

Organic Carbon Content ◽

Nitrogen And Phosphorus ◽

Mineral Soils

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The undetected loss of aged carbon from boreal mineral soils

Scientific Reports ◽

10.1038/s41598-021-85506-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Geert Hensgens ◽

Hjalmar Laudon ◽

Mark S. Johnson ◽

Martin Berggren

Keyword(s):

Organic Carbon ◽

Boreal Forest ◽

Soil C ◽

Earth Systems ◽

Nuclear Bomb ◽

C Cycle ◽

Water Extractable Organic Carbon ◽

High Lability ◽

Mineral Soils ◽

Terrestrial Biomes

AbstractThe boreal forest is among the largest terrestrial biomes on earth, storing more carbon (C) than the atmosphere. Due to rapid climatic warming and enhanced human development, the boreal region may have begun transitioning from a net C sink to a net source. This raises serious concern that old biogenic soil C can be re-introduced into the modern C cycle in near future. Combining bio-decay experiments, mixing models and the Keeling plot method, we discovered a distinct old pre-bomb organic carbon fraction with high biodegradation rate. In total, 34 ± 12% of water-extractable organic carbon (WEOC) in podzols, one of the dominating boreal soil types, consisted of aged (~ 1000 year) labile C. The omission of this aged (i.e., Δ14C depleted) WEOC fraction in earlier studies is due to the co-occurrence with Δ14C enriched modern C formed following 1950s nuclear bomb testing masking its existence. High lability of aged soil WEOC and masking effects of modern Δ14C enriched C suggests that the risk for mobilization and re-introduction of this ancient C pool into the modern C cycle has gone undetected. Our findings have important implications for earth systems models in terms of climate-carbon feedbacks and the future C balance of the boreal forest.

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