COMPARISON OF RESTORED TO NATURAL MANGROVE HABITAT IN FLORIDA, UNITED STATES: BELOW GROUND CARBON ACCUMULATION ON DECADAL TIMESCALES

Mangrove ecosystems are one of the Blue Carbon ecosystems, which are coastal ecosystems that pull CO₂ from the atmosphere and sequester a portion of the carbon in longer-lived, slow-circulating reservoirs such as peat soil deposits. We initiated a comparison of the belowground carbon loading and accumulation rates between adjacent restored and natural mangroves along the coast of the Gulf of Mexico in Florida, U.S.A. Typically, restored mangroves are only monitored for five years to ensure successful propagation of mangrove plants on filled and leveled ground. The sites involved in our comparative analysis were restored between 19 and 41 years ago, which enables comparison of the belowground processes on longer timescales than what is typical. Peat has accumulated at all sites, and we employ a statistical probing technique to estimate spatial uncertainty in peat carbon density and depth in study plots of equivalent low, medium, and high surface elevations. We use ²¹⁰Pb rates, carbon content, and dry bulk density to ascertain the belowground carbon accumulation rate, and we employ concurrent radiocarbon measurements in the ²¹⁰Pb-measured interval to model the downward propagation of organic carbon in these systems. This comparison serves to distinguish the best practices for mangrove restoration and carbon sequestration additionality on timescales extending beyond the typical 5 year vegetative assessment.