This portrait is called "The Pic-nic" by Thomas Cole in 1846.
Variety: The artist provided a lot of different points of interests to focus on.
Rule of Space: The portrait has horizontal lines but its not in the center. There is also many different objects that makes the eye move. Also the prominent objects are not in the middle of the portrait but is off to the left.
Lines: In addition to having horizontal lines; the portrait also has diagonal lines. For example, the trees are not completely vertical but they're bending in different directions.
Color: The artists used different variations of the color green (monochromatic).
Repetition: The repetition of the trees.
Unity: Although there are many different shapes and sizes in the portrait over it gives you a sense that overall the entire portrait is complete.