Abstract ID: 489

Fine root production in forests on contrasting soils in the Colombian Amazon

The dynamics of fine roots plays an important role in nutrient cycling, plant nutrition, and biosphere carbon. It has been hypothesized that in a gradient of increased soil resources the carbon allocated to belowground production (fine roots) decreases. To test this hypothesis we measured fine root (<2 mm) mass (FRM) and production (FRP) by two methods: 1) ingrowth cores and, 2) sequential cores during 2,2 years in two lowland forests on different soils in the Colombian Amazon. Differences of soil resources were determined by the type and the physico-chemical properties of the soil: a forest on loamy soil (Ultisol) at the Amacayacu National Park (ULT) and other on white sands (Spodosol) with lower nutrient content at the El Zafire Biological Station (SPO), located in the Forest Preserve of the Calderón River. We found that mass and production of fine roots were significantly different between forest types and soil depths (0 - 10 and 10 - 20 cm). SPO allocated more carbon to fine roots than ULT. FRP in SPO was twice (2,98 and 3,33 Mg C ha-1 year-1, method 1 and 2, respectively) as much as that in ULT (1,51 and 1,36-1,03 Mg C ha-1 year-1, method 1 and 2, respectively). Similarly, the average of FRM was higher in SPO (10,94 Mg C ha-1) than in ULT (3,04 - 3,64 Mg C ha-1). Our second hypothesis on the effect of rainfall on FRP could not be rejected: we found that FRM showed a temporal variation related to rainfall, with less production in the dry season and a substantial decrease in the extremely dry period of the year 2005. Our results suggest that soil resources play an important role in carbon allocation in these forests, and that carbon allocated to above and belowground organs is differential for loamy and sandy soils

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

Presentation Type:  Poster