Canopy Effects on Rainfall Partition and Throughfall Drop Size Distribution in a Tropical Dry Forest

Abstract

The energy distribution of natural rainfall droplets at different stages of canopy development in low-latitude semi-arid environments is still understudied. We assessed relationships between canopy development, gross rainfall (P) and throughfall (TF) characteristics in a tropical dry forest (TDF) with a total of 95 events of natural rain during December 2019–July 2021, in Northeast Brazil. One disdrometer was installed in an open field to record the gross rainfall and another under the deciduous vegetation canopy to record the throughfall. At the onset of the rainy season with a low leaf density, a larger fraction of rainfall was converted into throughfall, which declines as the leaf density increases. For events higher than 3 mm, the number of TF drops was always higher than that of P and with smaller diameters, regardless of the stage of canopy development, which indicates fragmenting of the rain drops by the vegetation canopy. The insights of this study are useful to quantify the impact of canopy development stages of a TDF on the characteristics of rainfall reaching the soil forest. Since those characteristics affect the water balance and soil erosion at the hillslope scale, the information provided is crucial for water and soil management.