Various field studies in tropical forests have indirectly demonstrated the efficiency of nutrient uptake mechanisms by epiphytic and epiphyllic organisms.  An investigation conducted by Jordan and Herrera (1981) included measuring concentrations of Calcium, Potassium, Phosphorous, Magnesium, Sulfur, and  Ammonium at the forest floor and in nearby openings in the Venezuelan Amazon for one year. The purpose of the study was to determine whether nutrient concentrations differ between throughfall (rainwater passing through the canopy) and pure rainfall. As indicated below,  several nutrients, most notably Calcium and Phosphorous, are consistently higher in rainfall throughout the year sampled, suggesting that these nutrients are absorbed within the canopy community before reaching the ground.  Another study, which measured the concentrations of phosphate (PO₄ ) and ammonium (NH₄ ) in rainfall, throughfall and  throughfall as it was coming off of pinnae from epiphyll-laden pinnae of Welfia georgii indicated that ammonium, more so than phosphate, is efficiently absorbed and retained on  leaf surfaces (Bentley 1987).  The question remaining to be answered is: Which component of the epiphyll community contributes most to the contribution of nutrients?