As previously mentioned, alpha pinene/a-pinene is one of the most commonly found oils within nature. Rosemary, eucalyptus, mint, and dill all have rather large amounts of alpha pinene within them. Evergreen trees are especially known for having high levels of the alpha pinene terpene. In fact, it is for this reason that evergreen trees have such a strong, earthy scent that we commonly refer to as pine, or piney.
Limonene is just one of what is estimated to be about 120 known terpenes within the cannabis plant, and one of what is believed to be over 100,000 terpenes throughout the world in other plants! Limonene is commonly found within citrus fruits and plants, which is where it gets its name from!