Description:

Thunderstorms contribute to the nitrogen cycle primarily through lightning-induced nitrogen fixation.

Explanation:

Lightning-induced nitrogen fixation: The intense energy from lightning breaks the strong bonds of nitrogen gas (N₂) in the atmosphere. This allows nitrogen atoms to combine with oxygen to form nitrogen oxides (NO and NO₂).

These nitrogen oxides dissolve in rainwater and form nitrates (NO₃⁻), which fall to the ground with precipitation.

Plants absorb these nitrates from the soil, incorporating them into proteins and other vital compounds—thus entering the nitrogen cycle.

Not related:

Oceanic upwelling involves the movement of nutrient-rich water to the surface but does not relate to thunderstorms.

Lunar gravity affects tides but has no role in the nitrogen cycle.