Dissolved organic carbon dynamics through Atlantic rainforest
compartments in Southeast Brazil
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.