Most plants and all animals depend on to meet their need for nitrogen.
lightning strikes
denitrifying bacteria
bacteria that break apart cellulose
nitrogen-fixing bacteria

nitrogen fixing bacteria

Explanation:

Most plants and animals are dependent on nitrogen fixing bacteria for their nitrogen requirements. As they are incapable of absorbing the atmospheric nitrogen directly. The soil bacteria traps the atmospheric nitrogen convert it into forms like ammonia, nitrates and nitrites which are readily absorbed by the plants and some soil borne animals.

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.