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Rainfall, litter fall, and organic matter turnover are the major drivers of nutrient fluxes in forest ecosystems. During its passage through the forest, the quantity and chemical composition of water — which enters the forest via rainfall and clouds — changes (Parker 1983). The chemical quality of throughfall and stemflow is controlled by the intensity of rainfall, dry deposition, and soil fertility (Parker 1983; Schaefer and Reiners 1990). The few studies on litter leachate, i.e. the water percolating through the organic layer, in tropical forests indicate that the concentrations of all nutrients increase compared with rainfall and throughfall (e.g., Steinhardt 1979; Hafkenscheid 2000; Wilcke et al. 2001a). In stream water, nutrient concentrations are lower than in litter leachates, except for elements which are released by weathering (Bruijnzeel et al. 1993; McDowell 1998). [ABSTRACT FROM AUTHOR]

Rainfall in tropical mountain forests ranges between several hundreds and several thousands of millimeters per year (Cavelier et al. 1997; Bruijnzeel 2001). Many of these forests receive considerable cloud water inputs (Bruijnzeel 2001). During its passage through the forest, the quantity of the water entering the forest with rainfall and clouds changes because of increasing evaporation and transpiration during percolation through the ecosystem (Likens and Bormann 1995; Bruijnzeel 2001). An important water loss is the evaporation of water intercepted in the canopy. Measurements of interception loss of tropical mountain forests also vary over a broad range (Cavelier et al. 1997). The portion of throughfall and stemflow reaching the stream after its passage through the soil depends on water flow paths. The occurrence of rapid interflow is a frequent phenomenon on steep forested hill slopes (Mulholland et al. 1990; Bonell et al. 1998) and is mainly attributable to the high significance of macropores (Buttle and McDonald 2000). Therefore, the assessment of water and element fluxes in the soil requires the due consideration of fast interflow. [ABSTRACT FROM AUTHOR]