The production and decomposition of litter in mangroves plays a significant role in the nutrient and organic carbon cycles. These can be highly variable both spatially and temporally as a result of numerous factors including tidal range, forest type, abundance and type of herbivorous fauna, temperature, and microbial activity. Mangroves also play an important role in blue carbon sequestration, with their status as carbon sinks crucial in mitigating against greenhouse gas-induced climate change. Blue carbon is a term used to describe the carbon captured by oceans and coastal ecosystems. We review and discuss the current available knowledge regarding sources of organic matter (OM) in mangroves as well as the roles of benthic macrofauna, water and microbial activity in the decomposition of OM in order to gain a better understanding of the decompositional processes that take place. Macrofauna break down and bury litter, thereby improving litter quality, in turn increasing decomposition rates via leaching and microbial activity. Microbial decomposition in mangroves is slow as a result of phenolic concentrations in the litter. A buildup of phenolic compounds inhibits microbial activity leading to the accumulation of OM in mangroves. Although knowledge has improved, there are still gaps in the information available and we still have an incomplete picture of the decompositional process in mangroves, and in particular the formation of blue carbon stores, necessitating further research.
Purpose of ReviewDespite covering only 3% of the land surface, peatlands represent the largest terrestrial organic carbon stock on the planet and continue to act as a carbon sink. Managing ecosystems to reduce greenhouse gas (GHG) emissions and protect carbon stocks provide nature-based climate solutions that can play an important role in emission reduction strategies, particularly over the next decade. This review provides an overview of peatland management pathways that can contribute to natural climate solutions and compiles regional and global estimates for the size of potential GHG emission reductions. Recent FindingsDegraded peatlands may account for 5% of current anthropogenic GHG emissions and therefore reducing emissions through rewetting and restoration offer substantial emission reductions. However, as a majority of peatland remains intact, particularly in boreal and subarctic regions, protection from future development is also an important peatland management pathway. Literature compilation indicates a global potential for peatland nature-based climate solutions of 1.1 to 2.6 Gt CO2e yr -1 in 2030.
Article (refereed) -postprintRhymes, J.; Jones, L.; Wallace, H.; Jones, T.G.; Dunn, C.; Fenner, N. 2016. Small changes in water levels and groundwater nutrients alter nitrogen and carbon processing in dune slack soils.Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner.© 2016 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This version available http://nora.nerc.ac.uk/514381/ NERC has developed NORA to enable users to access research outputs wholly or partially funded by NERC. Copyright and other rights for material on this site are retained by the rights owners. Users should read the terms and conditions of use of this material at http://nora.nerc.ac.uk/policies.html#access NOTICE: this is the author's version of a work that was accepted for publication in Soil Biology and Biochemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Soil Biology and Biochemistry (2016), 99. 28-35. 10.1016/j.soilbio.2016 www.elsevier.com/ 1 This is an author-created version of the article:Rhymes, J., Jones, L., Wallace, H., Jones, T.G., Dunn, C., Fenner, N. (2016). Small changes in water levels and groundwater nutrients alter nitrogen and carbon processing in dune slack soils. Soil Biology and Biochemistry 99, 28-35. http://dx.doi.org/10.1016/j.soilbio.2016.04.018 The published version can be found at:http://www.sciencedirect.com/science/article/pii/S0038071716300554Small changes in water levels and groundwater nutrients alter nitrogen and carbon processing in dune slack soils abstraction and from eutrophication. The biological effects caused by the interactions of these pressures are poorly understood, particularly on soil processes. We used a mesocosm experiment and laboratory assays to study the impact of lowered water tables, groundwater nitrogen contamination, and their synergistic effects on soil microbial processes and greenhouse gas emissions. This study showed that just a 10 cm decrease in water table depth led to a reduction in denitrification and to a corresponding increase in soil nitrogen content. Meanwhile N2O emissions occurred for longer durations within dune slack soils subject to higher concentrations of groundwater nitrogen contamination. The results from extracellular enzyme assays suggest that decomposition rates increase within drier soils shown by the increase in β-glucosidase activity, with further sensitivity to groundwater nitrogen contamination shown by the increase in phenol oxidase activity. Dune slack soils with a 10 cm lower water table had signific...
Northern peatlands store 455 Pg of carbon-a third of the entire global carbon store. Carbon accumulates because phenolic inhibitors slow the rate of decomposition to below that of photosynthetic production. The disproportionate importance of phenolics in peatlands is related to the unique properties of waterlogged peat soils suppressing the activity of phenol oxidase; one of the few enzymes capable of breaking these inhibitors down. This permits accumulation of phenolic compounds that are potent inhibitors of hydrolase enzymes-major agents in the breakdown of organic matter. In our study we investigate the importance of molecular weight of natural phenolic inhibitors on microbial decomposition in peat. We found the higher the molecular weight, of a phenolic compound, the greater its inhibitory effect on the breakdown of organic matter.
Northern peatlands are substantial carbon sinks because organic matter in peat is highly stable due to the low rate of decomposition. Waterlogged anaerobic conditions induce accumulation of Sphagnum-derived phenolic compounds that inhibit peat organic matter decomposition, a mechanism referred to as the “enzymic latch”. Recent studies have predicted that the water table in northern peatlands may become unstable. We observed that such unstable water table levels can impede the development of Sphagnum mosses. In this study, we determined the effects of low and high frequency water table fluctuation regimes on Sphagnum growth and peat organic matter decomposition, by conducting a year-long mesocosm experiment. In addition, we conducted a molecular analysis to examine changes in abundance of fungal community which may play a key role in the decomposition of organic matter in peatlands. We found that rapid water table fluctuation inhibited the growth of Sphagnum due to fungal infection but stimulated decomposition of organic matter that may dramatically destabilize peatland carbon storage. Increased pH, induced by the fluctuation, may contribute to the enhanced activity of hydrolases in peat. We demonstrated that the water table fluctuation in peatlands impeded Sphagnum growth and accelerates decomposition due to fungal proliferation. Thus, we suggested that understanding the microbial community in the northern peatlands is essential for elucidating the possible changes in carbon cycle of peatland under the changing world.
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