Abstract

Water fluxes in the subsurface of forested and agricultural ecosystems vary spatially across wide ranges because of several interconnected phenomena. On the one hand, subsurface environments are often highly heterogeneous. On the other hand, infiltration water is often distributed unevenly due to aboveground interception and redistribution of rainfall by the plant canopy. These phenomena have important hydro-ecological consequences because they significantly affect groundwater recharge and nutrient leaching. Field experiments involving subsurface lysimeters and tensiometers were performed to quantify the spatial distribution of fluxes in an Andisol under a banana plant (Musa acuminata Colla). Wick lysimeters were installed at a depth of 70 cm at several locations with respect to the banana stem to measure the spatial distribution of subsurface water fluxes. Collected experimental data were simulated using the HYDRUS software package, which numerically solves the Richards equation describing three-dimensional variably saturated water flow in the subsurface. Spatially distributed drainage fluxes were well reproduced with the numerical model. Due to the impact of stemflow, drainage volumes under the banana stem were up to six times higher than in the row downstream from the stem, as well as between rows, as these areas were sheltered from direct rainfall by the banana leaves and received only throughfall.

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