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.