As stated in Dragons: Rise of Berk's official description, there are many vines on this island and much fog. This indicates a very moist environment in order to produce so much fog, as well as a lot of vegetation, including perhaps trees and other tall plants and rock formations for vines to grow on.
Later in the graphic novel Dragonvine, the vines are revealed to be the deadly Dragonvine plant, which takes over the island when not kept in check by native Silkspanners. The island has flat areas, as well as a few mountain spires. It also has extensive underground caverns, with a Titan Wing Snaptrapper skeleton.
Dragonvine Island makes its full debut in this graphic novel. The Dragon Riders follow a scent to the island, and find a tribe of farmers about to be poisoned by encroaching dragonvines. The dragons burn away the vines. The tribesmen have settled here, after being harassed by Drago Bludvist from their native land. The farmers had chased off the Silkspanners, only to have the vines grow out of control. The Dragon Riders eventually lead the Silkspanners back, and the ecosystem of the island is quickly restored.