CONICET | Buscador de Institutos y Recursos Humanos

Nitrogen limits plant growth in almost all terrestrial ecosystems. However, nitrogen fertilization experiments in water-limited ecosystems showed contradictory results. Our objective was to quantify plant growth response to N addition and to assess changes in this response along a precipitation gradient. The specific questions that guided our study were: 1. Does nitrogen limit plant growth in water-limited ecosystems?, and how large is the effect overall? 2. Is plant response to N addition similar in arid, semiarid and subhumid ecosystems? 3. How does plant response to N addition change along temperature gradient? 4. Are vegetation responses of grass-dominated sites similar as those of shrub-dominated sites?, and 5. How do fertilizer type (i.e. urea vs. ammonium nitrate) and doses affect plant responses? To answer these questions, we conducted a meta-analysis which offers formal statistical methods for comparing and integrating results of previously published N-fertilization studies. Mean effects were estimated as the response ratio, the ratio of biomass measured in fertilized to control treatments (relative yield). We assessed changes in mean effects along mean annual precipitation (MAP), mean annual temperature (MAT), latitude, primary production, and the rate of N addition