Carbon store dynamics in the structure of mangrove in the southern Pacific of Mexico

Mangroves are recognized as the wetlands with the most significant capacity to store carbon, this ability to store carbon is due to their high productivity and the low rates of organic matter decomposition. The study area is one of the Intensive Carbon Monitoring Sites (SMIC, initials in Spanish) in Mexico. In the southern coast of the Mexican Pacific, in the La Encrucijada Biosphere Reserve (REBIEN). The SMIC has an extension of 1x1 km. In this area there are eight conglomerates. Each conglomerate contains four circular-shaped secondary units of 400 m2. The inventory includes trees ≥ 2.5 cm of DBH (Diameter at breast height). Tree species, DBH, height, canopy diameter, the basal area and tree density. Tree biomass was quantified, and the carbon store was determined using the biomass-to-carbon conversion factor of 0.48. The carbon in standing dead trees was estimated using the methodology of Kauffman et al. (2012). The environmental parameters quantified: interstitial salinity, pH, temperature and flood level. Results R. mangle is the dominant species, conglomerate 2 presented the highest tree density and conglomerate 4 the lowest. Conglomerates 8 and 4 had the highest averages for DBH, basal area, height, and crown area, in contrast, the conglomerates 1, 5, and 2, had the lowest averages. In the study area, the fall of trees was the factor that most affected the aboveground (aerial) carbon content, which increased 6.91 and 3% respectively during the second and third year of monitoring. Natural mortality increased and affected mostly young trees 2.5 to 10 cm tall. Wood extraction remained constant during the three years of study. During the three years of study, conglomerate 6 presented the highest biomass averages with 210.4 Mgha-1 and carbon stores of 101.0 MgCha-1; in contrast, conglomerate 5 registered the lowest average with 124.9 Mgha-1 and 60.0 MgCha-1 . R. mangle presents the biggest store of carbon with 60.4 MgCha-1. This mangrove system registered an increase in natural mortality during the study period, which could be the result of the massive amounts of sediment the river has been carrying after the passage of Hurricane “Stan” in 2005.