CONCLUSIONS
The urban matrix character where forest fragments (Tijuca Forest) are inserted conditions anthropogenic DOC inputs by wet and dry depositions and stochastic causes. These can generate some input peaks, mainly due to wet deposition. Temporal variations (between-event) in rainfall and throughfall DOC concentrations are controlled by precipitation intensity and antecedent rainfall (15-days) producing dilution and prewash effects, respectively. The rainfall canopy-through percolate presented DOC increases with very spatially punctual control so that spatial variations in the hillslope-scale (between hillslope positions) are not significant.
Litter above ground is the main source compartment of DOC to inside soil and its DOC leaching reflects the balance between synthesis and decomposition of OM in the local ecosystem in a non-linear tendency. In an increasing litter decomposition rates gradient on the downhill way, typical of these mountainous rainforests, mid-hillslope areas stand out with higher DOC leaching due to a favorable balance between OM accumulation above ground (DOC source) and OM degradation (new solubles). Our results demonstrated the absence of dilution and prewash effects litter leaching so that the DOC concentrations in this compartment were independent of the antecedent rainfall and the rainfall intensity and volume.
A high soil-water infiltration capacity is responsible for maintaining low DOC concentrations in the stream water, given the opportunities of MO sorption to soil particles. Even under a high productivity environment with shallow and sandy soils, in baseflow condition (after stormflow), the stream water presented lower values compared to the bulk precipitation, which highlights the role of soils in the retention of OM and maintenance of the quality of water resources. In this sense, the efficiency of OM mineralization by providing new sorption sites seems to be a prominent factor in this ecosystem service provided by soils concerning the water quality.