Interactive comment on “ Effects of global change during the 21 st century on the nitrogen cycle ” by D

p1749 line 3, what is the meaning of “input of reactive nitrogen from human activities”, NOx emission or nitrogen fixation? Introduction: p1750 line 13, I would suggest including an introduction to the nitrogen cycle and relevant processes in the beginning. p1750 line 14, it is better to first explain what’s reactive nitrogen for policy makers.