Atmospheric nitrogen (N) and phosphorus (P) depositions are expected to increase in the tropics as a consequence of increasing human activities in the next decades. Furthermore, a possible shortened El Niño Southern Oscillation cycle might come along with more frequent calcium (Ca) depositions on the eastern slope of the Ecuadorian Andes originating from Saharan dust. It is crucial to understand the response of the old-growth montane forest in Ecuador to increased nutrient deposition to predict the further development of this megadiverse ecosystem. This book describes the effect of experimental additions of N, P, N+P and Ca to the forest and an untreated control. The N, P and Ca concentrations and fluxes of litter leachate, mineral soil solution, throughfall and fine litterfall samples were determined. The results suggest that N, P and Ca co-limit the forest ecosystem functioning in the northern Andean montane forests.