Abstract ID: 492

Total Net Primary Production in Forests on Contrasting Soils in Colombian Amazon: Does Belowground offset lower aboveground production in poorer soils?

Recent studies have suggested that wood productivity shows a positive relationship with soil fertility throughout the Amazon basin and that carbon allocation between above and belowground organs changes with soil fertility. To test whether the higher belowground production - BGP - in poorer soils offsets the higher aboveground production - AGP - in more fertile soils, we measured the aboveground (growth rate of stems DBH≥10 cm and litterfall) and belowground production (fine roots) of forests in the Colombian Amazon during two years in three permanent plots: two of them are located on clay soils of the Pebas formation (Amacayacu National Natural Park) and the third one on white sands (called Varillal or Caatinga) on the Guiana Shield (Zafire Biological Station, Forest Reserve of the River Calderón). Wood productivity showed lower rates in the forest on the Guiana Shield than in forests on the Pebas formation (1,32 and 3,84 Mg C ha-1 year-1, respectively). Litterfall showed the same pattern: 2,67 vs. 3,76 Mg C ha-1 year-1, respectively. Therefore, AGP totaled 3,99 in forests on white sands and 7,35 Mg C ha-1 year-1 in forests on clay soils. Fine root production showed the opposite pattern: varied between 2,94 and 3,33 Mg C ha-1 year-1 in white sands, and between 1,36 and 1,51 Mg C ha-1 year-1 in clay soils. Total net primary production - NPP - (below plus aboveground) totaled 7,12 and 8,78 Mg C ha-1 year-1, respectively. Our results show that carbon allocation differs between AGP and BGP in the two forests, with higher BGP in forests on white sands than on clay soils and the opposite for AGP. Our results also suggest that BGP is an important component of NPP and carbon balance in forests; overlooking this compartment might produce biased estimations of forest carbon dynamics

Session:  Carbon - Forest dynamics, natural disturbance, and recovery. (A)

Presentation Type:  Oral