Nitrates are reduced back into nitrogen in the soil by a process called denitrification. This process is performed by bacteria like Pseudomonas denitrificans, etc.

Sleeping under a tree is not advisable at night, since photosynthesis does not occur, oxygen is not being produced by the trees. In addition to this, the trees continue respiring thereby causing the amount of carbon dioxide to be increased and the amount of oxygen to be reduced.