Understanding the relative contributions of aboveground and belowground processes to soil accretion and carbon density may explain carbon sequestration rates in mangroves across different coastal environmental settings. We reformulated the nutrient mangrove model (NUMAN) by improving algorithms and uncertainty analysis using literature values and site-specific observations to evaluate the relative contributions of organic and inorganic sedimentation for three mangrove sites with marked soil fertility gradients reflected by nitrogen-to-phosphorus (N:P) ratios including Shark River (N:P = 28), Rookery Bay (N:P = 54–78), and Taylor Slough (N:P = 102) in south Florida. NUMAN 2.0 considers cellulose as a refractory organic-matter sub-pool and simultaneously incorporates coarse-root inputs to soil formation. The model simulation also captures root necromass accumulation. Monte Carlo (MC) simulations (N = 1000 per site) were conducted to capture uncertainty by treating five key parameters as random variables: lignin content in fine, coarse, and large roots; inorganic sediment loading; and root biomass at the surface. With robust mass balancing of organic matter, NUMAN 2.0 generates precise predictions of surface accretion and carbon density. NUMAN 2.0 simulations estimated mean (standard deviation) soil carbon sequestration rates at 130.1 (55.4) for Shark River, 72.5 (3.7) for Rookery Bay, and 130.0 (83.9) g m-2 yr-1 for Taylor Slough, compared to field values of 123.0, 86.0, and 108.8 (8.7) g m-2 yr-1 , respectively. Simulation experiments with NUMAN 2.0 suggest that belowground organic matter dominates soil formation and carbon sequestration generally in coastal environmental settings with little allochthonous input such as carbonate settings, while wood litterfall should dominate soil organic matter in top 10 cm in estuaries, and bays.
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Above- and Below-Ground Carbon Storage of Hydrologically Altered Mangrove Wetlands in Puerto Rico after a Hurricane
Mangrove wetlands are important ecosystems, yet human development coupled with climate change threatens mangroves and their large carbon stores. This study seeks to understand the soil carbon dynamics in hydrologically altered mangrove swamps by studying aboveground biomass estimates and belowground soil carbon concentrations in mangrove swamps with high, medium, and low levels of disturbance in Cataño, Jobos Bay, and Vieques, Puerto Rico. All three sites were affected by hurricane María in 2017, one year prior to the study. As a result of being hit by the Saffir-Simpson category 4 hurricane, the low-disturbance site had almost no living mangroves left during sampling. There was no correlation between level of hydrologic alteration and carbon storage, rather different patterns emerged for each of the three sites. At the highly disturbed location, belowground carbon mass averaged 0.048 ± 0.001 g-C cm−3 which increased with increased aboveground biomass. At the moderately disturbed location, belowground carbon mass averaged 0.047 ± 0.003 g-C cm−3 and corresponded to distance from open water. At the low-disturbed location, organic carbon was consistent between all sites and inorganic carbon concentrations controlled total carbon mass which averaged 0.048 ± 0.002 g-C cm−3. These results suggest that mangroves are adaptive and resilient and have the potential to retain their carbon storage capacities despite hydrologic alterations, but mass carbon storage within mangrove forests can be spatially variable in hydrologically altered conditions.
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- Award ID(s):
- 1736093
- PAR ID:
- 10338688
- Date Published:
- Journal Name:
- Plants
- Volume:
- 10
- Issue:
- 9
- ISSN:
- 2223-7747
- Page Range / eLocation ID:
- 1965
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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