Read the following passage and translate it into Chinese. The nitrogen cycle consists of a sequence of biochemical changes wherein nitrogen is used by living organisms, transformed upon death and decomposition of the organisms, and converted ultimately to its original state of oxidation. The reservoir of nitrogen for plant use is essentially that in the atmosphere, N 2 . The process of converting N 2 into forms that vascular plants can use is termed nitrogen fixation. The other major steps in the soil nitrogen cycle are: (2) mineralization, (3) nitrification, (4) immobilization, and (5) denitrification.