The distribution of organic carbon in major components of forests located in five life zones of Venezuela

One of the major uncertainties concerning the role of tropical forests in the global carbon cycle is the lack of adequate data on the carbon content of all their components. The goal of this study was to contribute to filling this data gap by estimating the quantity of carbon in the biomass, soil and necromass for 23 long-term permanent forest plots in five life zones of Venezuela to determine how C was partitioned among these components across a range of environments. Aboveground biomass C ranged from 70 to 179 Mg ha(-1) and soil C from 125 to 257 Mg ha(-1), and they represented the two largest C components in all plots. The C in fine litter (2.4 to 5.2 Mg ha(-1)), dead wood (2.4 to 21.2 Mg ha(-1)) and roots (23.6 to 38.0 Mg ha(-1)) accounted for less than 13 % of the total C. The total amount of C among life zones ranged from 302 to 488 Mg ha(-1), and showed no clear trend with life zone. In three of the five life zones, more C was found in the dead (soil, litter, dead wood) than in the live (biomass) components (dead to live ratios of 1.3 to 2.3); the lowland moist and moist transition to dry life zones had dead to live ratios of less than one. Results from this research suggest that for most life zones, an amount equivalent to between 20 and 58% of the aboveground biomass is located in necromass and roots. These percentages coupled with reliable estimates of aboveground biomass from forest inventories enable a more complete estimation of the C content of tropical forests to be made.