Atmospheric CO2 is expected to increase to between 550 ppm and 1000 ppm in the next century. CO2-induced changes in plant physiology can have ecosystem-wide implications and may alter plant-plant, plant-herbivore and plant-symbiont interactions. We examined the effects of three concentrations of CO2 (390ppm, 800ppm and 1000ppm) and two concentrations of nitrogen fertilizer (0.004gN/week vs. 0.2...