Factors regulating carbon sinks in mangrove ecosystems

Area of Science:

• Ecology
• Biogeochemistry
• Climate Science

Background:

• Mangroves are vital carbon sinks, yet factors controlling their carbon storage remain poorly understood, especially in subtropical regions.
• Subtropical mangroves' carbon budgets are complex, influenced by vegetation, environmental conditions, and decomposition rates.

Purpose of the Study:

• To quantify carbon budgets for subtropical (Kandelia obovata) and tropical (Avicennia marina) mangroves in Taiwan.
• To identify key factors regulating carbon storage and flux within these mangrove ecosystems.

Main Methods:

• Field measurements of biomass, production, litterfall, detrital export, and decomposition from 2011-2014.
• Principal component analysis to assess the influence of site conditions versus tree species.
• Stable isotope analysis to trace organic matter sources.

Main Results:

• Net production (NP) rates were high due to tree density, exceeding global averages.
• Rapid decomposition (72%-91%) and high organic carbon export and respiration rates were observed.
• Low carbon burial rates (3%-12% of NP) indicate decomposition significantly limits sediment carbon storage.
• External organic matter input from rivers/waters contributed more to carbon sinks than mangrove production.

Conclusions:

• Environmental conditions, rather than tree species, primarily drive carbon processes in these mangroves.
• Rapid decomposition and high export limit long-term carbon burial in mangrove sediments.
• External organic matter sources play a crucial role in mangrove carbon sequestration, often exceeding in-situ production.