Comparing soil carbon pools and carbon gas fluxes in coastal forested wetlands and flooded grasslands in Veracruz, Mexico

Abstract

Wetlands play an important role in carbon cycling. Perturbation of these ecosystems by human activities causes changes in the soil carbon storage and carbon gaseous emissions. These changes might have important repercussions for global warming. The aim of this study was to investigate whether the conversion of freshwater forested wetlands (FW) to flooded grasslands (FGL) has affected soil carbon cycling. Soil carbon pools and soil organic carbon (SOC) fractions (water-soluble carbon (WSC), hot-water-soluble carbon (HWSC), and HCl/HF soluble carbon (HCl/HF-SC)) were compared between FW and FGL. Additionally, the seasonal dynamic of methane (CH₄) and carbon dioxide (CO₂) fluxes were monitored in both ecosystems located in the coastal plain of Veracruz State Mexico. In FW, soil organic matter (SOM) concentrations were significantly (P ≤ 0.05) higher than FGL. Soil bulk density (BD) was slightly higher in FGL than FW but it was not significantly different (P ≥ 0.05). The average of WSC and HWSC in FW were not significantly (P ≤ 0.05) different. Total carbon pools (44 cm deep) were not significantly different (P = 0.735). During the dry season, CO₂ fluxes (26.38 ± 4.45 g m⁻² d⁻¹) in FGL were significantly higher (P = 0.023) than in FW (14.36 ± 5.77 g m⁻² d⁻¹). During the rainy and windy seasons, both CH₄ and CO₂ fluxes were significantly higher (P = 0.000 and P = 0.001) in FGL compared with FW. It was concluded that converting FW to FGL causes loss of SOC and increases carbon gaseous fluxes.

Keywords:

• carbon cycle
• global warming
• land-use change
• soil organic carbon
• tropical freshwater wetlands
• ecosystem services

Acknowledgements

Funding for this work was provided by the Mexican National Council for Science and Technology – CONACYT – through Sector fund CONACYT-SEMARNAT Grant # 107887 and the Basic Science Grant # 081942. The authors thank Alejandro Hernández, Monserrat Vidal, J. Alejandro Marín, and Carmelo Maximiliano for their help in the field work. We are also grateful to the local guides who accompanied us throughout the field work: Tomas León Rodríguez and Eduardo Lauranchet.