Nature Mode is a state acheived by Jonny 2x4 and Plank. This is a sensory technique which allows the user to "see" events in nature, which allows him to cover a wide range of the Earth's surface area. However, if the fighting is taking place in a man-made structure, such as the Gravity Machine, he can't sense anything until the fighting exits that area.
Interestingly, Plank also exhibits effects that he and Jonny share. The outline of Plank's eyes changes to orange, while his "pupils" become green. Jonny's eyes change to a green color while his eyes become rimmed in brown. This is influenced from the Sage Mode seen in the second part of Naruto.
It is unknown if this is simply a hereditary abilitiy or if anyone with a strong bond with nature just as Jonny's can use it. It is however shown that Jonny has some form of talent with the form, as he was able to greatly advance it's capabilities as the Revenge Saga went on, heightening it's effects so he could even begin to visualize the Mechas.
The user of the form actualy does gain a fair boost in power, but as only non-fighters like Jonny and Plank are shown using the form it is unknown how this would allow anyone to fair in battle.
- Jonny 2x4