Patterns and carbon accumulation in the inland water-land palm ecotone (morichal) across the Orinoco lowlands, South America

摘要

We examined the carbon dynamic across the inland water-land palm ecotones (morichals) of the Orinoco lowlands to increase comprehension of their potential for accumulating global carbon. Ecotone biomass was quantified for ecotones representing the flat-floored valley type with sparse woody vegetation and the V-shaped valley type with closed woody vegetation. The soil organic carbon (SOC) was linearly ordinated in a double logarithmic plot by the rank-ordering technique. The plot showed that there was an inflection point corresponding to the two sets of ecotones in flat-floored and V-shaped valley type. On average, a smaller proportion of the SOC in the ecotones was stored in the V-shaped than in the flat-floored valley type. As a result, the fractal dimension for the two ecotone groups was 1.27 and 2.67, respectively. The seasonal trend of above- and below-ground phytomass in the flat-floored and V-shaped valley type showed a temporal increase. However, the seasonal increment was only significant for the flat floored valley during the second annual course. The net primary productivity (NPP) of ecotone in flood-prone and stream bed areas in the flat-floored valley type was 340-837 and 2,438 g C m(-2) year(-1), respectively. The NPP value for the stream bed in the flat-floored valley type exceeds the NPP of those reported for a wide range of ecotones. Depending on the annual hydrological dynamic, the ecotone of the flood-prone area ranged from carbon steady-state store-house to carbon sink.