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Abstract:Throughfall has been widely studied in forests but there is a scarcity of studies that focus on the spatial variability and temporal stability of throughfall in eucalyptus plantations. We examined throughfall in a daily basis in a 2Ð5-year eucalyptus plantation in southeastern Brazil using three sample arrangements: (1) close to tree trunks (CT) and in the central point between trunks (BT), (2) four-radial layout centred in tree trunk and (3) eight-radial layout. Throughfall was spatially non-uniform and varied according to the spatial monitoring arrangement: accumulated throughfall/precipitation ratio of 146% (CT) and 85% (BT) in arrangement 1, mean throughfall of 88% in arrangement 2, 84% (hilltop) and 85% (side slope) in arrangement 3. The highest throughfall values, spatial variability and persistence of dry and wet conditions were found close to eucalyptus trunks. Often accumulated throughfall close to trunks exceeded rainfall, especially for long-duration rainfall >5 mm. The 'funnel effect' was consistently observed in all three arrangements and we speculate that the high throughfall concentration and temporal stability are related to canopy structures of eucalyptus.

Brazil has the 6 th greatest planted forest area in the world and more than 3.7 million hectares of Eucalyptus. Although, still exists lots of questions related to environmental impacts of this activity, specially focused on hydrological alterations. Since late 1990´s landscape mosaic of middle Paraíba do Sul river valley has been rapidly modified by spreading of Eucalyptus patches in substitution to cattle grazing grasslands. Our current research interests are driven to understand the role played by Eucalyptus controlling the hillslope, headwater basins and main rivers hydrology and erosion and explain how these changes may affect the regional landscape system. Sesmaria experimental basin is composed of four monitoring stations in the main rivers (Feio, Formoso, São João e Sesmaria rivers) and also in four headwater basins with different spacing and management to observe water discharge and quality (turbidity and electrical conductivity). Ground water level, tensiometry and road erosion are also going to be monitored in the headwater bains. Precipitation has been measured in eight different positions to avoid analysis errors related to spatial variability of rainfall.

A Serra do Mar apresenta ainda um dos maiores remanescentes contínuos de Mata Atlântica sendo caracterizada ao mesmo tempo pela recorrência dos movimentos de massa associados às chuvas intensas. No desastre da região serrana (RJ), mais de 3.600 deslizamentos foram defl agrados, dos quais 24,6% ocorreram em coberturas de gramíneas, enquanto 54,8% ocorreram em coberturas de fl orestas. Esse trabalho teve como objetivo analisar a infl uência dessas vegetações no controle da umidade do solo para o entendimento da defl agração dos deslizamentos nas chuvas intensas. Duas encostas foram selecionadas em Nova Friburgo (RJ) para o monitoramento da precipitação, interceptação e sucção nas profundidades de 5, 20, 50, 100, 150 e 220 cm, que também foram analisadas em relação a biomassa e comprimento de raízes grossas (> 2 mm) e fi nas (< 2 mm) e em relação as propriedades físicas do solo (granulometria, estabilidade de agregados e porosidade). Os resultados demonstraram diferenças expressivas de biomassa e comprimento de raízes grossas entre a fl oresta (1785,0 g.m-3 e 40,1 m.m-3) e a gramínea (121,2 g.m-3 e 6,4 m.m-3). A biomassa de raízes fi nas foi parecida entre as vegetações, porém na gramínea foram encontradas até 100 cm, enquanto na fl oresta até 200 cm. Em Informações sobre o Artigo Recebido (