Mangrove Soil Carbon Burial

Soil Column Controls

Sediment accretion rate 5.0 mm/yr

Organic carbon input 0.055 g/cm³

Oxic-zone (water table) depth 12 cm

Simulation speed 25 yr/s

Core Readouts

Carbon stock (core)

0 Mg C/ha

Burial efficiency

Years modeled / core depth

0 yr · 0 cm

How it works

Each parcel of mangrove sediment is buried under fresh material at the accretion rate w (cm/yr). Its organic carbon density decays as a first-order process, but the rate constant depends on whether the parcel sits above or below the oxic/anoxic boundary at depth d_ox:

dC/dt = -k(z)·C
k(z) = k_aer   (fast, z above d_ox — oxygenated)
k(z) = k_anaer (slow, z below d_ox — waterlogged)

age a = z / w   (time since deposition)
t_ox = d_ox / w  (time spent in the oxic zone)

C(a) = C0·e^(-k_aer·a)                                  if a ≤ t_ox
C(a) = C0·e^(-k_aer·t_ox)·e^(-k_anaer·(a-t_ox))          if a > t_ox

k_aer ≈ 0.05 yr⁻¹ and k_anaer ≈ 0.002 yr⁻¹ here — roughly a 25× slowdown once burial passes the water table, matching field evidence that waterlogged, low-oxygen mangrove mud preserves organic matter far better than aerated soils. Total carbon stock is the depth integral ∫C(z)dz over the visible core; burial efficiency compares that stock to the carbon that would remain with zero decay.

Accretion rate — how fast new sediment (root debris, trapped mud) piles up; higher rates bury carbon past the oxic zone faster, before it can decompose.
Organic carbon input — the carbon density of freshly deposited sediment, set by mangrove litterfall and root productivity.
Oxic-zone depth — how deep oxygen penetrates before the anoxic, waterlogged zone begins; pneumatophores and tidal flushing control this in real marshes.

Real-world relevance: this burial-and-preservation mechanism is why mangrove soils hold some of the highest carbon densities of any ecosystem on Earth — often 500–1000+ Mg C/ha in the top metre, several times a typical tropical forest, mostly locked in soil rather than biomass.

Carbon-rich (preserved) Carbon-depleted (oxidized) Oxic / anoxic boundary

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