Carbon dynamics in a seasonally dry tropical forest

Seasonally dry tropical forests (SDTF) are a widely distributed vegetation type in the tropics, characterized by seasonal rainfall with several months of drought when they are subject to fire. This study is one of the first attempts to quantify aboveground and belowground biomass and carbon dynamics after fire, a thinning restoration treatment, and after a hurricane disturbance in a SDTF of the Yucatan Peninsula, Mexico. Total ecosystem carbon in a SDTF chronosequence ranged from 21.7 to 153.5 Mg C ha-1. Total ecosystem carbon required 50 years to recover values similar to mature forests after a fire event. I estimated that between 1.5 and 2.0 Pg C might be stored in SDTF of North and Central America. A designer ecosystem approach was used to restore a SDTF of 11 years-old after fire disturbance by using a selective vegetation thinning treatment. After four years it recreated a less dense forest, reducing the ladder fuels. In addition, it favored carbon sequestration, and hastened secondary succession toward a mature forest. Thinned plots accumulated total carbon at higher rates than the control plots (7.2 and 5.4 Mg C ha -1 y-1, respectively), and five years after the treatment, the thinned plots gained 13 Mg C ha-1 over the control plots. Hurricanes are critical disturbance events that cause evident damage on SDTF and soil respiration was measured continuously using solid-state CO2 sensors before and after hurricane Wilma. Daily mean soil respiration one year before the hurricane was 8.4 mumol CO2 m-2 s-1, but one year after the event was 10.4 mumol CO 2 m-2 s-1. Soil respiration for 365 days before the hurricane was estimated to be 9 Mg C ha-1 yr -1, while soil respiration for 365 days following the event ranged from a low estimate of 10.4 to a high of 13.7 Mg C ha-1 yr -1. The post-hurricane variations in soil respiration showed that the recovery of this process might take longer than one year. The results suggest that the recovery of soil respiration may be more sensitive to severe hurricanes than other forest soil parameters such as the recovery of forest litter biomass.