You're probably thinking about Pan, but he was only associated with pastures (he was also the god of shepherds and the fertility of livestock). In Greco-Roman mythology, the trees and woods were protected by the Dryades, nymphs whose spirits were closely connected to specific trees - to the point that killing a tree could mean killing the dryad. It was a punishable offense (by men and gods) to chop down a tree without propitiating the dryads first.
I think you might be thinking of Faunus, which is the Roman counterpart to the Greek Pan, but they are only gods of the woods. There is no Greek or Roman deity associated with the concept of mischief.
In Roman mythology, the god of the woods is Silvanus. He is associated with the forests, fields, and agriculture, serving as a protector of wildlife and rural life. Silvanus is often depicted as a rustic deity, embodying the untamed aspects of nature. He is sometimes conflated with the Greek god Pan, reflecting his connection to nature and the wilderness.
Her Roman name is Diana, but her Greek name is Artemis. She is initially, in both Myths, the Goddess of Nature, but you could also call her the Goddess of Woods, if you want to get into specifics.
Pan. He was also the god of nature in general. Pan was the Greek god. His Roman counterpart was Faunus.
they roam the woods and pastures in serach of berries, leaves, clover and other vegetation
Technically, the Roman goddess Diana was the goddess of nature, as well as of fertility childbirth, wildwood, moon, forests, animals, mountains, woods, women, and the moon. She was variously known as Mother of Creatures, the Huntress or Destroyer, and Goddess of the hunt. However, other gods/goddesses often had specific realms of nature that they governed. For example(s), Ceres was goddess of corn and grain crops; Jupiter was the god of the sky, lightning, and thunder; Neptune was god of the sea and its creatures; and Mars (far from being only "god of war") was also god of spring, growth in nature, and agriculture.
Diana was the Roman goddess of the hunt and the wilderness. Her Greek counterpart was Artemis.
Diana was the Roman God who was the guardian of wild beasts, horses, and domesticated animals.
pastures, rocky terrain, savanna, grassland, marshes, but absolutely no woods. They like open sunny plains, not covered woods. Herpetologist in training, Sam A. T. Guertin
Dendron
In Greek mythology, dryads were tree nymphs. Since drysmeans "oak" in Greek, dryads were specifically nymphs of oak trees. Dryads were shy around both gods and men and only were more friendly with Artemis who was known to be a friend of the nymphs.
Faunus