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Dissolved organic carbon dynamics through Atlantic rainforest compartments in Southeast Brazil
  • Felipe Miranda,
  • André Avelar
Felipe Miranda
Federal University of Rio de Janeiro
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André Avelar
Federal University of Rio de Janeiro
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Abstract

Considering the importance of dissolved organic carbon (DOC) flows for the carbon biogeochemical cycle, and a set of organic matter (OM) ecosystem services, our work aimed to analyze and discuss water DOC concentrations from different forest compartments: bulk precipitation, throughfall, soil solution, and stream water, in a mountainous rainforest in southeastern Brazil (Atlantic Forest). A hillslope-scale spatial design aimed to add to the discussion an analysis linked to the litter decomposition heterogeneity observed between different hillslope positions for DOC leaching. A temporal analysis was carried out by comparing rainfall events, which are different about their rainfall characteristics and antecedent humidity context. A dilution effect associated with rainfall intensity was observed in wet and dry depositions, being more pronounced on the dry deposition, which also showed a pre-wash effect linked to the previous rainfall-volume, with the time range of 15-days of previous rainfall as more relevant. Under-litter DOC concentrations showed no dilution or pre-wash effects. While in the throughfall there was no spatial difference in a hillslope-scale, the litter leaching showed great spatial variation, so that the intermediate stocks (and decomposition rates) of the mid-hillslope areas presented higher concentrations, which it is due to a balance between accumulation of material on the soil (little loss by microbiota respiration) and chemical rework on the material (new solubles) that favors the DOC leaching. In the soil solution, there is a tendency to decrease concentrations in depth. However, in events with greater rainfall intensity, soil packages with a higher OM incorporated can change from an adsorption environment to a desorption environment. The stream water showed, under baseflow condition, lower concentrations of DOC than observed in the bulk precipitation, highlighting the soil role for the organic carbon retention, where a high water infiltration capacity and OM decomposition efficiency may have key-role.