Study area
The study was conducted in the Tijuca Forest, an Atlantic Forest fragment that covers the Tijuca Massif (22º55 ’and 23º00’S - 43º20’ and 43º10’W), one of the three mountainous physiographic units of the city of Rio de Janeiro and representative of the Coastal Massifs of southeastern Brazil. The Tijuca Massif a rugged relief environment, marked by the presence of rocky outcrops and abrupt slopes, reaching a maximum altitude of 1021m (Tijuca peak). The Tijuca Massif relief is the basis of the upper and middle courses of the Cachoeira River, which drains the flows from the massif to a coastal lagoon system (Tijuca Lagoon).
The local climate is Tropical Altitude (Cfa), with an annual average temperature of 22 ° C and monthly averages that vary from 25 to 19 ° C in February and June, respectively (Negreiros & Coelho Netto, 2011). The average annual rainfall varies from 2000 to 2500 mm, being able to register up to 3,300 mm in wettest and 1600 mm in the driest years.
The lithological basis is mainly formed by several gneisses and some granite intrusions which dates from the Upper Proterozoic. Latosols predominate, especially Red-Yellow ones. The soil texture on horizon A is sandy, ranging from sandy loam to loamy sand (Negreiros e Coelho Netto, 2009).
The vegetation is a typical late secondary succession of Atlantic Forest, with the presence of exotic tree species and inherent anthropic interference. The forest that is currently protected by the Tijuca National Park (3,972 ha) was recovered by reforestation actions (5.2% of the area) and the natural regeneration process (94.8%), after being almost totally deforested for coffee production until the middle of the XIX century (Drummond, 1996). Today the area has over 140 years of natural succession for the most part. The south-facing hillslopes have more lushier vegetation and less grassland due to both natural (sunny and Norwegian slopes) and land-use reasons (Dias e Coelho Netto, 2011; Oliveira et al., 1995).
We chose the southern slope of Archer Hill for the research, located at the Cachoeira River upper course and completely inserted in Tijuca National Park, where the data were collected in 04 different positions (hillslope-scale): Summit (SMT); Upper Hillslope (UHS); Lower Hillslope (LHS); and Valley Bottom (VBT) (Figure 1). The natural heterogeneity of litter accumulation and decomposition rates on the hillslope positions, exposed in (Miranda & Avelar, 2019), represented an interesting “laboratory situation” for the discussion about the DOC leaching, which led us to adopt this sample design for spatial analysis.